master of science (m.s.) in fisheries biology and genetics

MORPHOLOGICAL CHARACTERIZATION OF TWO CUCHIA-

Monopterus cuchia (Hamilton, 1822) AND Ophisternon bengalense

(McClelland, 1844) FOUND IN INLAND WATER OF BANGLADESH

A Thesis

By

Examination Roll No. 10 Fish FBG JD 14 M Registration No. 36963

Session: 2010-2011 Semester: July-December, 2011

MASTER OF SCIENCE (M.S.) IN

FISHERIES BIOLOGY AND GENETICS

DEPARTMENT OF FISHERIES BIOLOGY AND GENETICS BANGLADESH AGRICULTURAL UNIVERSITY

MYMENSINGH

November 2011

MORPHOLOGICAL CHARACTERIZATION OF TWO CUCHIA -



A Thesis

By



Submitted to the Department of Fisheries Biology and Genetics Bangladesh Agricultural University, Mymensingh

in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE (M.S.)

IN FISHERIES BIOLOGY AND GENETICS

DEPARTMENT OF FISHERIES BIOLOGY AND GENETICS

BANGLADESH AGRICULTURAL UNIVERSITY MYMENSINGH

November 2011

MORPHOLOGICAL CHARACTERIZATION OF TWO CUCHIA -



A Thesis

By



Approved as to the style and contents by

...……………………………………... …...….………………………

Prof. Dr. Mostafa Ali Reza Hossain Prof. Dr. Md. Samsul Alam Supervisor Co-Supervisor

………………………….. Dr. Zakir Hossain

Chairman

Examination Committee and

Head, Department of Fisheries Biology and Genetics Bangladesh Agricultural University

Mymensingh

November 2011

ACKNOWLEDGEMENTS

All the praises and thanks to almighty God, who enabled the author with His enormous

blessings to complete the research work and thesis for the degree of Master of Science in the

discipline of Fisheries Biology and Genetics in due time.

The author sincerely expresses deepest sense of gratitude and immense indebtedness, profound

regard, deep sense of respect to her respected teacher and research supervisor Dr. Mostafa Ali

Reza Hossain, Professor, Department of Fisheries Biology and Genetics, Bangladesh

Agricultural University, Mymensingh for his unconditional love, scholastic guidance,

continuous suggestion, constant inspiration and sincere supervision of her research work. His

regular advice and valuable supervision helped the author to complete the thesis.

The author greatly indebted to her co-supervisor Dr. Md. Samsul Alam, Professor, Department

of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh, for his

valuable suggestions, constructive direction, affectionate encouragement, and kind cooperation

in performing the research activities precisely.

The author pleasure to expresses her heartiest gratefulness to Dr. Zakir Hossain, Head,

Department of Fisheries Biology and Genetics, Bangladesh Agricultural University,

Mymensingh, for his inspiration, valuable suggestions and generous help during the period of the

experiment.

The author is proud to acknowledge her gratefulness and boundless gratitude to her honourable

teachers of the Department of Fisheries Biology and Genetics, especially Professor Dr. Md.

Fazlul Awal Mollah, Professor Dr. Md. Rafiqul Islam Sarder, Professor Dr. Md. Mukhlesur

Rahman Khan, Associate Professor Dr. Md. Sadiqul Islam, Assistant Professor Dr. Mohd. Golam

Quader Khan and Lecturer Mr. A. K. Shakur Ahmed for their constant inspiration, generous help

and illuminating suggestions in many ways for completing the research work and preparation of

the thesis.

The author wishes to express her deepest sense of respect to all the teachers of the Faculty of

Fisheries, Bangladesh Agricultural University, Mymensingh, for their valuable teaching,

suggestion and encouragement during her study period at the University.

The author also expresses her honest and heartfelt gratitude and special thanks to her respected

teachers of Faculty of Fisheries, Hajee Mohammad Danesh Science and Technology University,

Dinajpur for their help, affectionate encouragement, cordial feelings, brilliant advice and fruitful

suggestions and kind co-operation at every step to complete her B. Sc. Fisheries (Hons.) degree.

The author expresses her cheerful acknowledgement to her well wisher and elder brother Dr. Md.

Nahiduzzaman, Ex PhD fellow, Department of Fisheries Biology and Genetics, BAU,

Mymensingh for his continuous encouragement and kind cooperation throughout the period of

the research work and preparation of the thesis. The author is also grateful to elder brother

Pankoz Kumar Roy, Department of Fisheries Biology and Genetics, BAU, Mymensingh for his

affectionate encouragement, continuous help and kind co-operation during the research period

and completion of the thesis.

The author offers her sincere thanks to Anis bhai, Jakaria bhai and other laboratory attendants of

the Department of Fisheries Biology and Genetics, BAU, Mymensingh for their active

cooperation and overall assistance during the whole study period.

The author expresses her cordial thanks and gratitude to all of her sweet surroundings and

beloved friends and well wishers specially Krishna, Shipra, Munmun, Nishu, Shamole, Maya,

Konica, Munni, Imran, Shuvo, Himel, Rakhi, Kollol, Wahed, Naznin, Shilpi, Tonusree, Momo,

Suma, Lipi and all other friends for their kind cooperation and inspiration throughout the study

period and research work.

Finally, the author would like to acknowledge with great regards and pleasure, deepest sense of

gratitude and immense indebtness to her beloved parents Rajendra Nath Roy and Shikha Rani

Roy, dear elder brothers and sisters especially Tapan, Dhananjoy and Nondita, beloved nephew

Kabya and other relatives for their blessing, countless sacrifice and endless inspiration

throughout her life. The deepest and most sincere appreciation is also due to her late grandfather

and grandmother and all other well-wishers for their endless patience, sacrifice, encouragement

which made everything possible in her life.

November 2011 The Author

CONTENTS

CHAPTER TITLE PAGES

ACKNOWLEDGEMENTS

iv-v

CONTENTS vi-vii

LIST OF TABLES viii-ix

LIST OF FIGURES x-xi

ABSTRACT xii

I INTRODUCTION 1-9

1.1 Importance of Fisheries in Bangladesh 1 1.2 Description of two eels and distribution 2-5

1.3 Global importance 5 1.4 Importance in Bangladesh context 6-7 1.5 Aquaculture potential 8 1.6 Justification of the study 8-9

1.7 Objectives 9

II REVIEW OF LITERATURE 10-20

III MATERIALS AND METHODS 21-27

3.1. Collection of sample 21

3.2. Rearing of sample 22

3.3. Measurement of morphometric and meristic characters

3.3.1 Morphometric characters

3.3.2 Meristic characters

22-25

22-24

24-25

3.4. Land mark distances of the species 25

3.5. Dissection of the species 25

3.6. Statistical analyses 26-27

CONTENTS (Contd.)

CHAPTER TITLE PAGES

IV RESULTS 28-46

4.1 Length and body weight of M. cuchia and O.

bengalense and their sexing pattern 28

4.2 Physical characteristics 29-33

4.3 Meristic characters 34

4.4 Morphological and landmark differences 35-46

V DISCUSSION 47-53

VI SUMMARY AND CONCLUSION 54-56

REFERENCES 57-65

LIST OF TABLES

TABLE TITLE PAGES

3.1. The morphometric characters measured

22-23

3.2. The meristic characters of eels 24

4.1

Length and weight of M. cuchia and O.

bengalense and their sexing pattern (SD =

standard deviation, n = number of fish) and the

range

28-29

4.2 Comparison of meristic counts between M. cuchia

and O. bengalense (Mann-Whitney U) (minimum

and maximum values are in parenthesis)

34

4.3

Comparison of adjusted morphological and

landmark measurements between sexes of M.

cuchia (Mean ± SD)

35-37

4.4 Comparison of adjusted morphological and

landmark measurements between sexes of O.

bengalense (Mean ± SD) (Independent samples t-

test)

37-38

4.5 Means and standard deviation of adjusted

morphological data for M. cuchia and O.

bengalense (t-test for difference before and after

adjustment of the variables)

39 -40

4.6

Univariate statistics (ANOVA) testing difference

between M. cuchia and O. bengalense (df1=1;

df2=47)

41-42

LIST OF TABLES (Contd.)

TABLE TITLE PAGES

4.7

Contribution of morphometric and truss

measurements of M. cuchia and O. bengalense to

the canonical functions

43

4.8 Correct classifications of individuals M. cuchia

(collected from Mymensingh and Dinajpur) and

O. bengalense (collected from Satkhira and

Bagerhat) into their original population (leave-

one-out-classification)

46

LIST OF FIGURES

FIGURE TITLE PAGES

1.1. Photograph of the mud eel, Monopterus cuchia

(Hamilton,1822)

2

1.2.

Photograph of the swamp eel, Ophisternon

bengalense (McClelland, 1844)

4

3.1. Map of Bangladesh showing sampling sites of M.

cuchia and O. bengalense.

21

3.2. Morphometric measurement

24

3.3 Six landmarks determining 8 distances on eel body 25

4.1

Body colour (ventral view-left and dorsal view-

right) of M. cuchia

29

4.2 Body colour (ventral view-left and dorsal view-

right) of O. bengalense

30

4.3 Head shape of M. cuchia

30

4.4 Head shape of O. bengalense

30

4.5 Head shape (ventral side) of M. cuchia 31

4.6 Head shape (ventral side) O. bengalense 31

4.7 Lines present beside lateral line in M. cuchia (left)

and no line present in O. bengalense (right)

31

4.8

Tail shape of M. cuchia (left) and O. bengalense

(right)

32

LIST OF FIGURES (Contd.)

FIGURE TITLE

PAGES

4.9

Gill arch of M. cuchia (left) and O. bengalense

(right)

32

4.10

Mouth gape of M. cuchia (left) and O. bengalense

(right)

33

4.11

Teeth of M. cuchia (left) and O. bengalense (right)

33

4.12

Fat like organ in the stomach of O.bengalense

33

4 .13

Sample centroids of discriminant function scores

based on morphometric and truss measurements

(1. M. cuchia (collected from Mymensingh), 2. M.

cuchia (collected from Dinajpur), 3. O. bengalense

(collected from Satkhira), and 4. O. bengalense

(collected from Bagerhat)

44

4.14 Dendrogram based on morphometric characters

and landmark distances - 1. M. cuchia

(Mymensingh), 2. M. cuchia (Dinajpur), 3. O.

bengalense (Satkhira) and 4. O. bengalense

(Bagerhat)

45

ABSTRACT Morphometric comparison was carried out to evaluate the population status of two eels-

Monopterus cuchia and Ophisternon bengalense collected from four different stocks.

Morphometric, truss measurements and meristic characters from thirty two M. cuchia

(collected from Mymensingh and Dinajpur), seventeen O. bengalense (from Bagerhat and

Satkhira) were analyzed. The mean number of line below head were significantly (Mann-

Whitney U test; z= -6.091; P<0.001) different between two species out of five meristic

characters. Significant differences were observed in eleven morphometric characters Pre

dorsal length (PDL), Post dorsal length (PoDL), Post anal length (PoAL), Head length

(HL), Snout length (SnL), Upper jaw length (UJL), Lower jaw length (LJL), Head width

(HW), Pre orbital length (PrOrL), Least body diameter (LBD) and Highest body diameter

(HBD) and one truss measurement (3-5) between two species in varying degrees. Plotting

discriminant function DF1 and DF2 showed a clear differentiation between the species as

well as between the stocks for both morphometric and landmark measurements. For both

morphometric and landmark measurements, the first and second DF accounted 64.8%

and 33.2% of among group variability, explaining 98% of total group variability. A

dendrogram based on morphometric and landmark distance data shows the populations of

both the species constructed one cluster and further divided into two distinct sub-clusters.

M. cuchia collected from Mymensingh and from Dinajpur constructed one sub-cluster

and O. bengalense collected from Satkhira and from Bagerhat constructed another sub-

cluster based on the Distance of squared Euclidean dissimilarity. A correct classification

of individuals into their original population from leave-one-out-classification varied

between 93.3% and 94.1% by discriminant analysis and 95.9% of individuals could be

classified in their correct priori grouping. Morphological characterization could be used

effectively to know the population structure and taxonomic status. Both eels have high

commercial value with domestic and overseas demand and their biodiversity should be

conserved and should be brought under aquaculture to save them from extinction.

CHAPTER I

INTRODUCTION

INTRODUCTION

1.1. Importance of Fisheries in Bangladesh

Bangladesh is a country of rivers, rivulets and tributaries. These water bodies are abound

in fishery resources. Fisheries sector has been playing a significant role from time of

immemorial in Bangladesh. Around 58% of animal protein is being supplied by the

commercially important fisheries organisms to the people of Bangladesh (DoF 2010).

Bangladesh is one of the richest countries of the world considering the availability of

fisheries resources but annual fish production is still a lesser amount than the demand of

the people. Bangladesh earns second highest foreign currency from fisheries sector by

exporting fisheries products. Also considering product sources, fisheries sector is found

to be the highest export earning sources because of fisheries products are completely of

native sources. According to Department of Fisheries (DoF 2010), fisheries sector

contributed 3.74% to GDP and 22.23% of total agricultural production of Bangladesh.

Besides, fisheries sector contributes 2.70% to the country’s total export earnings in 2009-

10 fiscal years.

Fisheries and aquaculture play a major role in nutrition, employment and foreign

exchange earnings with about 12 million people are associated with the fisheries sector,

of which 1.4 million people rely exclusively on fisheries related activities (DoF 2010).

The country's main exportable product is frozen shrimp/prawn, live fish, frozen fish, dry

fish, salted and dehydrated fish, turtles, tortoises, crab, eels, shark and other fishes (DOF

2010).

The mud eel, Monopterus cuchia and the swamp eel, Ophisternon bengalense are the

recent export item in Bangladesh and play a vital role for earning foreign currencies.

Both species are locally known as cuchia and are the important species considering their

medicinal value as because their blood contain highest amount of hemoglobin.

1.2. Description of two eels and distribution

Classification of M. cuchia [ Kingdom Animalia

Phylum Chordata

Sub-phylum Vertebrata

Class Osteichthyes

Subclass Actinopterygii

Infraclass Acanthopterygii

Superorder Teleostei

Order Synbranchiformes

Sub-order Synbranchoidei

Family Synbranchidae

Genus Monopterus

Species Monopterus cuchia

(Hamilton of 1822)

The mud eel, Monopterus cuchia is a freshwater air breathing fish, locally known as

cuchia (Fig.1.1). They are capable of dispersal overland, and able to survive for long

periods out of water. M.cuchia is commonly found in the freshwater of Bangladesh,

Pakistan, Northern and Northeastern India and Nepal (Jingran and Talwar 1991).

Fig .1.1. Photograph of Mud eel, Monopterus cuchia (Hamilton of 1822)

They have high fecundity, and are protogynous hermaphrodite. Once, indigenous mud eel

- M. cuchia was abundant throughout Bangladesh. They were available in plenty in mud

holes in shallow “beels” and “boro” paddy field particularly in greater Sylhet,

Mymensingh and Tangail Districts (Rahman 2005). Now-a-days this fish is hardly found

in the open water system due to over exploitation and various ecological changes in its

natural habitat. Therefore, IUCN-Bangladesh (2000) enlisted M. cuchia as a vulnerable

species in Bangladesh. The fisheries resources are under severe threat due to sediment in

the downstream of the river system which reduces the rate of water flow and changing

aquatic ecosystems, human interventions through construction of flood control

embankments, drainage structures and sluice gates, conversion of inundated land to

cropland and indiscriminate destructive fishing practices and use of pesticides (Hossain et

al. 2009). Pollution from domestic, industrial and agrochemicals wastes and run off have

resulted in threat of a considerable amount of aquatic biota in all stretches in the open

water system.

Classification of O. bengalense

Kingdom Animalia

Phylum Chordata

Sub-phylum Vertebrata

Class Osteichthyes

Subclass Actinopterygii

Infraclass Acanthopterygii

Superorder Teleostei

Order Synbranchiformes

Sub order Synbranchoidei

Family Synbranchidae

Genus Ophisternon

Species Ophisternon bengalense

(McClelland of 1844)

The swamp eel also known as Bengal eel, Ophisternon bengalense is a freshwater,

demersal and brackish water eel (Fig. 1.2). It is distributed in India, Sri Lanka, Indonesia,

Philippines and New Guinea. Adults inhabit both fresh and brackish waters of rivers and

swamps or near the river mouth. They found mainly in thick vegetation of muddy, still

water bodies, such as lagoons, swamps, canals and rice fields. This fish species prefers

estuarine or tidal areas and they also live in soft bottom sediments in quiet, well vegetated

backwaters of brackish estuaries and nearby swamps, usually in burrows.

Fig. 1.2. Photograph of swamp eel, Ophisternon bengalens (McClelland of 1844)

The male guards and builds nest or burrow. This species moult their body sometimes.

Their sexing pattern is mostly unknown. Their skin is so much thin and when they moult,

they become very aggressive. Because of its taste O. bengalense is a fish of high demand

to the tribal people of Bangladesh and people of China, Hong Kong, Thailand, Vietnam,

Malaysia, Japan and Indonesia.

1.3. Global importance

Eels are considered as a nutritious and tasty fish species and it is also a valued medicinal

species in oriental region. Raising eels is presumed a low-cost enterprise to farmers. It is

easy to do and achieves more profit than some other small size fish-culture activities

(IIRR et al. 2001; Lu et al. 2005). In recent years, the rice field eel culture has been

increased strongly in some areas of Vietnam. They are consumed mainly by domestic

market and some consumed by export markets.

Globally eel production was expected to grow by thrice between 1985 and 1992 which

representing an increase of about 58% (ADCP 1995). World aquaculture production of

freshwater eels has increased over the past decade and is currently around 2,33,000

MT/year which valued at over US$975 million (FAO 2005; FAO/UN 2005). A

significant commercial eel fishery exists in various countries like Australia, Thailand,

Malaysia, Japan, Korea, USA, China, Italy, Greece, Egypt, Singapore, Cambodia and

Taiwan (ADCP 1995; Hicks and McCaughan 1997; August and Hicks 2006) consisting a

great available export market (Ishak 1994; Moriarty and Dekker 1997; Jessop 2000). The

rapid expansion of eel farming in Japan since the middle of the 19th century aroused

considerable interest in intensive farming of eel and eel culture enterprises have

developed in a number of countries in Europe, especially Italy, Germany, Netherlands

and France. In Asia, Taiwan has become a major exporter of cultured eels to Japan and

European markets.

1.4. Importance in Bangladesh context

Shrimp, Bangladesh’s main aquatic export item facing grave environmental, socio-

political and socio-economic consequences have resulted in the wake of its expansion

which jeopardized the livelihoods of millions, particularly the most vulnerable women

and children (Mazid 2002). Concurrently, crab is gaining an important position of

immense prospects. However, eels, a recent export item, though, have not yet been given

any attention of its culture and collection could be considered as an alternative option for

poor peoples. Collection from the wild to meet growing export demand and lack of

aquaculture of this species could be the major concern for biodiversity loss in

Bangladesh. However, considering the increasing demand in the international markets

(Usui 1991; VAC 1999; FAO 2005) eel fishery has been gaining popularity among the

coastal community of greater Khulna and Chittagong regions as well as greater

Mymenshing, Shylet and Comilla region. Five species of eel, Monopterus cuchia,

Anguilla bengalensis, Ophisternon bengalense, Pisodonophis boro and Pisodonophis

cancrivorus (Chowdhury et al. 1980; FRSS 1984 and BOBP 1985) are available in

Bangladesh, in which, M. cuchia, P. boro and O. bengalense are presently being exported

to Japan, Korea, Hong Kong, Thailand, China and Taiwan from Bangladesh. Mud eel

collecting from wild is exported in a large quantity to China and other Asian countries

and no fry production and culture is practiced yet. On the other hand, plenty of works on

reproductive physiology, neuroendocrine mechanism of reproduction, fry production and

aquaculture of its close relative from the same genus (swamp eel, M. albus) have already

been done in many countries and intensive aquaculture of eels have been practiced for its

high market value (Chen and Fernald 2008; Fu and Zhengfeng 2009; Khanh and Ngan

2010; Wang 2010; Jun 2010; Chu et al. 2011).

Cuchia is an important fish for the livelihoods of Adivasi people in terms of both for

home consumption and trade. However, the availability of the eel has been drastically

reduced over the years. Several factors contributed to this, while the main two factors are

the destruction of natural habitat and over harvesting. The natural habitats of cuchia has

been destructed by variety of ways like horizontal expansion of agriculture and

aquaculture, destructive hunting methods, use of chemicals, fertilizer and pesticide,

infrastructure development etc. On the other hand, harvesting of cuchia has been

increased with the increase of population, which is further influenced by the international

demand and trade of cuchia. Many of poor Adivasi people harvest and sell cuchia as a

full-time or part-time profession.

In this background, increase in production of cuchia through restoring and protecting

natural habitats on sustainable harvesting may be a good option improving livelihoods of

Adivasi people. In addition, most of the mainstream people of Bangladesh do not eat

cuchia and considered cuchia production as an advantage only to the Adivasi people.

Seeing the potential, a few donor has funded project to increase production of cuchia in

small suitable private owned resources involving poor Adivasi people along with owners

in culturing cuchia and improvement of habitats. However, lack of knowledge and

information on cuchia culture technique in such natural environments was found to be an

important constrain.

Since there is very little culture for freshwater eels, it is necessary to develop a scientific

eel culture system. Advanced aquaculture is not possible without proper understanding of

the various biological factors of fishes such as morphological study, food and feeding

habit, hematology, reproductive biology and optimum growth and water quality

parameters which are responsible directly for the production of biomass in a water body.

1.5. Aquaculture potential

Aquaculture is a part of art and part of science. As time goes on, we understand more

about where this division lies and the science of aquaculture continues to mature

enhancing our understanding of the complexities that ensure profitable production of a

given species. Freshwater eels are generally available in open water resources such as

rivers, beels (relatively large waterbodies with static water in the Ganga-Brahmaputra

flood plains of Bangladesh), haors (wetlands in the northeastern part of Bangladesh

which are a bowl or saucer shaped shallow depressions), baors (oxbow lakes, found

mostly in moribund deltas as in northeastern Bangladesh), canals, floodplains and

estuaries. Comparatively shallow and small ponds, ditches, tanks or cisterns also could be

utilized to culture freshwater eels as they tolerate various adverse conditions such as low

oxygen levels, high temperature and shallow water. However, the eel aquaculture

industry in Bangladesh is completely absent, only capture based fishery practice are

performed. Both freshwater and saltwater eels of Bangladesh could be grown for

international market. Hence, Bangladesh has great opportunity to develop eel farming

industry and to enter European and Asian markets, if proper attempt could be taken. Although some laboratory-scale progress have been made in maturing and fertilizing the

eggs of some species of eels, it has not yet been studied in response to the whole

morphological characterization of eel.

1.6. Justification of the study

Study of the morphological characters is a prerequisite for domestication and culture of

any animals either aquatic or territorial. Now a days, two cuchia are only caught from

wild to meet up the increasing demand in the international market. As a result, the

biodiversity of both of the species is already in danger. It is essential to develop

sustainable aquaculture technology to save the species and take the advantage of export

market. It is also necessary to develop the breeding technologies for both for the species

for mass seed production for the sustainable eel aquaculture. The initiatives for the

development of these technologies are in infancy in Bangladesh. The urgent need is

detailed phenotypical study for both the species which is essential for domestication and

development of breeding technologies.

To better understand and document morphological variation in two eels M. cuchia and O.

bengalense, their head and body shape and color pattern, their whole physical

characteristics and comparison between them is essential. Populations in close

geographic proximity may represent separate introductions of genetically distinct forms

thus has significant management implications. Few attempts have been taken to study of

larval rearing and reproductive biology of eels in Bangladesh but to our knowledge,

comparison of their morphological characteristics so far is not studied. Therefore, the

present study was conducted to characterize and compare the two eels M. cuchia and O.

bengalense.

1.7. Objectives:

In this experiment, the following objectives have been outlined:

• To characterize phenotype of two eel species- M. cuchia and O.

Bengalense;

• To study the physical characteristics of body;

• To determine the relationship among morphometric and meristic characteristics;

and

• Comparison the two species with their physical characteristics.

CHAPTER II

REVIEW OF LITERATURE

REVIEW OF LITERATURE

The purpose of this chapter is to review previous studies, opinions and observations of

experts which are related to the present study. Comprehensive and systematic reviews of

previous research works provide a strong base for carrying out any scientific research. A

reference to the previous work provides guidelines for not only to frame study

hypothesis, methodology to be adopted, future areas of research to be covered but also

substantiate or repudiate research out come with possible reason. Few published works

related to morphological characterization between Monopterus cuchia and Ophisternon

bengalense and some related literature on different fish have been reviewed and

presented followings:

Darlina et al. (2011) investigated Mackerel (Scombridae; Rastrelliger) are small

commercially important pelagic fish found in tropical regions. They serve as a cheap

source of animal protein and are commonly used as live bait. By using a truss

morphometric protocol and RAPD analysis, there examined morphological and genetic

variation among 77 individual mackerel that were caught using long lines and gillnets at

11 locations along the west coast of Peninsular Malaysia. Nineteen morphometric traits

were evaluated and genetic information was estimated using five 10-base RAPD random

primers. Morphometric discriminant function analysis revealed a single group of

Rastrelliger brachysoma can be found along the west coast of Peninsular Malaysia. They

found that the head-related characters and those from the anterior part of the body of

Rastrelliger spp significantly contribute to stock assessment of this population. RAPD

analysis showed a trend similar to that of the morphometric analysis, suggesting a genetic

component to the observed phenotypic differentiation. These data will be useful for

developing conservation strategies for these species.

Mekkawy et al. (2011) reported the morphometric and meristic characteristics of

Cephalopholis argus, Cephalopholis miniata and Variola louti. The type of allometry of

the morphometric traditional as well as truss characters in terms of size and shape were

determined. The morphometric indices exhibited a great variability in their behavior

among the three Epinepheline species studied and in turn different mode of growth of

such species. However the only indices to be size-free are PRVFL/SL, DEVOFL/SL,

DEDCFL/SL VDOL/HL, VEAOFL/HL, AEVCFL/HL and AEDCFL/HL for the three

Epinepheline species considered. The clustering of the allometric growth was considered

as a taxonomic tool in fishes. The inter and intra-specific relationship between the three

Epinepheline species were also evaluated on further patterns of size and shape using

standard DFA and cluster analysis.

Roesma and Santoso (2011) reported that morphological divergences among three

sympatric populations of Silver Shark minnow (Cyprinidae: Osteochilus hasseltii) in

West Sumatra. Silver shark minnow (Osteochilus hasseltii) named by local people as

Asang is one of potential Cyprinid fish species found in several different ecosystems in

West Sumatra. The differences of habitat types and another ecological factor among

populations may have significant influences on variation and differentiation of

morphological characters of this species. In order to elucidate the pattern of

morphological divergence, meristic and morphometric characters of O. hasselti in

Singkarak and Dibawah Lake and adjoining river were compared. Phenogram based on

cluster analysis showed specific morphological divergence among populations. There

were 23 characters significantly different among all compared populations, the highest

degree of differentiation was found between Singkarak and Dibawah Lake population (22

characters significantly different) and the most similar population were Singkarak Lake

and Ombilin an outlet river of lake (only six characters significantly different).

Hossain et al. (2010) reported Landmark-based morphometric and meristic variations of

the endangered carp, kalibaus Labeo calbasu, from stocks of two isolated rivers, the

Jamuna and Halda, and a hatchery Landmark-based morphometric were examined to

evaluate the population status of the endangered carp, kalibaus L. calbasu, collected from

2 isolated rivers (the Jamuna and Halda) and a hatchery. Morphometric characters along

with truss network measurements and meristic counts were applied. Significant

differences were observed in four (maximum body height, pre-orbital length, peduncle

length, and maxillary barbell length) of 12 morphometric measurements, two (pectoral

fin rays and scales above the lateral line) of 9 meristic counts, and four (8 to 9, 3 to 10, 2

to 10, and 1 to 11) of 22 truss network measurements among the stocks. The dendrogram

based on morphometric and truss distance data placed the Jamuna and hatchery in 1

cluster and the Halda in another cluster, and the distance between the Halda and hatchery

populations was the highest.

Erguden et al. (2009) reported that morphometric and meristic analyses of chub mackerel

Scomber japonicus were used to discriminate stocks throughout the Black, Marmara,

Aegean, and northeastern Mediterranean Seas. Morphometric and Meristic analyses

showed a similar pattern of differentiation between S. japonicus stocks and revealed a

clear discreteness of two groups, northeastern Mediterranean (Antalya Bay–Iskenderun

Bay) and the northern group, including the Aegean, Marmara, and Black Seas. Hossain et al. (2009) describe the morphometric, meristic characteristics and threatening

factors for the critically endangered species Puntius sarana (Hamilton 1822) in the lower

part of Ganges River, northwestern Bangladesh. A total of 87 specimens ranging from

9.30-21.70 mm TL (total length) and 10.05-189.25 g body weight (BW) were used for the

studies of the morphometric and meristic characteristics. The necessary data and

information were collected through the interview or survey on >120 fishers and >80 fish

farmers from March 2006 to December 2007. The results indicated that the populations

are declining due to over-exploitation, pollution and environmental degradation, spread

of disease, uncontrolled introduction of exotic fish, and lack of proper management. This

study also suggested the measures for the conservation of the remnant isolated population

of P. sarana in the Ganges river and nearby areas.

Neves et al. (2009) carried out experiment on to morphologically characterization and

classified the stages of gonad development in different Nile tilapia strains (Oreochromis

niloticus).

Pollar et al. (2007) stated that the population structure of the Tor tambroides was

investigated with morphometric data (i.e. morphometric measurement and truss

measurement). A morphometric analysis was conducted to compare specimens from

three waterfalls: Sunanta, Nan Chong Fa and Wang Muang waterfalls at Khao Nan

National Park, Nakhon Si Thammarat and Southern Thailand. The results of stepwise

discriminant analysis on seven morphometric variables and 21 truss variables per

individual were the same as from a neural network. Fish from three waterfalls were

separated into three groups based on their morphometric measurements. The

morphometric data shows that the nerual network model performed better than the

stepwise discriminant analysis.

Urra et al (2007) analyzed morphometric differentiate Adelomelon ancilla and

Odontocymbiola magellanica (Caenograstropoda: Volutidae) of southern Chile. The

volutid snails Adelomelon ancilla and Odontocymbiola magellanica are of economic

importance to the fishery of Chile’s southern zone. These species were direct developers,

which made them very sensitive to localized catches but there were no fishery regulations

to control their catches. Although these sympatric species might be distinguished by their

radular morphology, their external characteristics (used in field recognition) were so

similar that they wee confusedly lumped under the common name of “piquilhue” snail

and registered as A. ancilla in the fisheries national statistics. With the aim of

identifying external population characters which could facilitate discrimination between

taxa, common samples of piquilhue snails were taken and separated into 330 A. ancilla

and 54 O. magellanica using identification guides. The radular morphology, and shell

and body characteristics of these 2 species were evaluated through traditional and

landmark-based geometric morphometric methods. The results revealed that the species

could not be distinguished by meristic traits (number of whorls and columella folds) or by

the thickness or weight of their shells, but they did exhibit significant differences in shell

shape and body weight. Adelomelon ancilla had a fusiform shell shape (a small aperture

and a high-spired shell) that accommodated a smaller body mass than that of O.

magellanica, which had a globose shape (a larger aperture and a low-spired shell). The

external differences found by traditional and geometric analyses are sufficient to

discriminate between the 2 species, which would be useful in establishing proper

fisheries statistics and adequate management strategies.

Turan et al. (2006) studied the genetic and morphological variation of Pomatomus

saltatrix were studied based on morphometric and meristic analyses of samples collected

throughout the Black Seas, Marmara, Aegean and eastern Mediterranean Seas. In

discriminant function analysis, plotting first and second discriminant functions explained

61% and 77% of the between-group variation for morphometric and meristic analyses

respectively, and indicated existence of three morphologically differentiated groups of P.

saltatrix.

Turan (2004) investigated that Morphologic differentiation among stocks of

Mediterranean horse mackerel, Trachurus mediterraneus, throughout the Black,

Marmara, Aegean and Eastern Mediterranean Seas, was investigated using morphometric

and meristic characters. Discriminant function analysis of both morphometric and

meristic characters suggested that there is restricted migration of mackerel among the

adjacent seas. Overlapping of four Black sea samples on the discriminant space in

morphometric and meristic characters suggested that there is one self-recruiting

population in the area. The Marmara sea samples were the most isolated samples from all

others for both morphometric and meristic characters, which may indicate existence of a

distinguishable mackerel stock in the area. The sample from the Aegean Sea was grouped

with one geographically close Mediterranean sample based on morphometrics and

separated from all other Mediterranean samples based on meristic characters, suggesting

some degree of intermingling between these areas. Examination of the contribution of

each morphometric variable to canonical functions indicated that differences among

samples seemed to be associated with the anterior part of the body. In meristic analyses,

highest contributions to canonical functions were associated with the number of gill

rakers and pectoral fin rays.

Turan and Erguden (2004) worked with Liza abu stocks from the Orontes, Euphrates and

Tigris rivers to know the genetic and morphometric structure. Simultaneously, allozyme

electrophoresis for genetic comparison and the truss network system for morphometric

comparison were applied to the same sample set. They observed highly significant

morphological differences between the 3 L. abu stocks. In discriminant function analyses,

plotting discriminant functions revealed high isolation of the 3 stocks and the Tigris stock

was very isolated from the other two stocks. The pattern of phenotypic discreteness

suggests a direct relationship between the extent of phenotypic divergence and

geographic separation. A 5 enzyme system (ICD, PGM, ME, MDH and G3PDH)

composed of 6 loci was used to determine genetic comparison. However, genetic data do

not support the detected morphometric variations. They concluded that major limitation

of morphological characters at the intra-specific level is that phenotypic variation is not

directly under genetic control but is subjected to environmental modification.

Turan et al. (2004) investigated the status of populations of anchovies in Turkish

terrestrial waters was preliminarily investigated using morphometric characters with the

truss network system. Samples were taken from the main fishing areas of each sea,

comprising the central (Sinop) and eastern (Trabzon) Black Sea, the Aegean Sea (Uzmir)

and the eastern Mediterranean (Uskenderun). Plotting discriminant functions 1 and 2,

explaining 93% of between-group variability, revealed a high degree of dissimilarity

among the anchovy samples, indicating that the anchovies in each sea represent different

aggregations. The overall random assignment of individuals into their original group was

high (80%). Pairwise comparisons using multivariate analysis of variance (MANOVA)

showed highly significant differences between all the samples (P<0.001). Univariate

analysis of variance (ANOVA) revealed significant differences with varying degrees

between the means of the 4 samples for 16 out of 25 standardized morphometric

measurements. Principal components analysis (PCA) indicated that the observed

differences were mainly from the measurements taken from the head.

Doherty and McCarthy (2004) illustrated the monomorphic character of the two

populations despite differences in growth and size between the ‘stunted’, slower-growing

Lough Eske fish and the ‘normal’, faster -growing Lough Mask fish. The results are

discussed in the context of other systems where sympatric morphs have been described.

Differences in body size and growth rate appear to reflect the trophic status and the

productivity of the two lakes. The results confirmed earlier findings, which were based on

dietary analysis and analysis of metazoan parasites of both Irish populations of Arctic

charr.

For better understanding of phylogenetic diversity and evolution of PGH alpha in fish,

Han-Yu San and Yu-Yuh Lin (2002) have cloned cDNAs for PGH alpha subunits from

swamp eels, Monopterus albus and Ophisternon bengalense, two members of the Order

Synbranchiformes, Suborder Synbranchoidei, Family Synbranchidae.

Narejo et al. (2001) reported that variations in the haematological parameters of the

freshwater mud eel, Monopterus cuchia (Hamilton) with respect to sex and season.

Nakamura (2001) stated that Meristic and morphometric characters of local populations

of fluvial Japanese charr, Salvelinus leucomaenis, which had been isolated above dams

and a waterfall, were compared between river systems (Naka and Tone rivers, central

Japan) and among the tributaries of the Naka River (Ashinagasawa, Akasawa,

Ushirosawa and Moto-okashirasawa streams). Between the river systems, there was a

significant difference in the mean number of dorsal fin rays, pyloric caeca, white spots

under the lateral line and the proportion of the diameter of the white spots to the diameter

of the pupil, respectively. On the other hand, among the tributaries within a river system,

a significant difference was occurred in the mean number of anal fin rays, pored scales on

the lateral line, gill rackers, vertebrae, pyloric caeca, white spots under the lateral line,

white spots on the surface of the gill covers and the proportion of the diameter of the

white spots to the diameter of the pupil, respectively. A dendrogram based on data of the

meristic and morphometric characters showed that the population of the Tone River was

included within the variation detected among the tributary populations of the Naka River.

Meristic and morphometric characters of Japanese charr varied not only between river

systems but also among tributaries within a river system.

Turan and Basusta (2000) evaluated the degree of differentiation among populations of

twaite shad, Alosa fallax nilotica, in Turkish territorial waters with the truss

morphometric system using Discriminant Function (DFA) and Principal Component

Analyses (PCA). Approximately 40 individuals were collected from each sea to represent

regions. In DFA, the proportion of correctly classified Eastern Mediterranean sea sample

to their original group was highest (90%) with a high overall random assignment of

individuals into their original population (78%). Plotting discriminant function 1 (DF1)

and discriminant function 2 (DF2) explained 100% of total between group variability and

clearly discriminated Eastern Mediterranean sea sample from the Baltic and Aegean sea

samples, which were over plotted. This finding was also supported in multivariate

analysis of variance. PCA revealed that the observed differences were mainly from

posterior morphometric measurements of the fish. The patterns of morphological

differentiation suggested that there is limited exchange of individuals among areas to

homogenize populations phenotypically from the Black and Aegean seas to Eastern

Mediterranean sea.

Turan (1999) identified intraspecific units or stocks of a species with unique

morphological characters enable a better management of these subunits of species and

ensure perpetuations of the resources. Multivariate morphometry has been commonly

used to investigate the discreteness and interrelationships of stocks within a species.

Different types of body measurements have been traditionally used to charecterise stocks.

As an alternative, a new system of morphometric measurements called The Truss

Network System has been increasingly used for stock identification. In this review a

computer-originated approach to the collection and analysis of morphometric

characteristics of stocks is described.

Hunt (1992) reported the relationships between otolith dimensions and fish size for six

demersal and two pelagic species. Otolith morphometric observations included length

for all species examined and weight ,width, volume, cross - sectional area and

location of the focal point for the selected species.

Swain et al. (1991) used the truss system in the identification of hatchery and wild

populations of Coho salmon (Oncorhynchus kisutch). They found significant

morphometric variation. They commented that the variation was attributed to an effect of

the rearing environment rather than genetic differences between the hatchery or wild

stocks.

Henault M. and Fortin R. (1989) compared the meristic and morphometric phenotypes of

the spring-spawning stock of ciscoes (Coregonus artedii) from lac des Ecorces with those

of fall-spawning stocks from the same drainage basin. Meristic and morphometric

phenotypes of the spring-spawning stock of ciscoes (Coregonus artedii) from lac des

Ecorces were compared with those of fall-spawning stocks from the same drainage basin.

The spring spawners show almost complete non overlap in gill rakers compared with fall

spawners (averages of 42.7 and 50.5 respectively). This large gap could indicate

genotypic differences between these stocks. Spring spawners also show smaller numbers

of lateral line scales and of dorsal and anal fin rays, which might be related to higher

incubation temperatures. Based on the comparison of conventional and truss network

measures, discriminant analyses performed separately on males and females showed that

the head and cephalic structures are smaller in spring ciscoes; their thoracic region is also

longer and their caudal peduncle narrower and shorter. A principal components analysis

showed that the few fall-spawning ciscoes captured in lac des Ecorces do not differ from

the fall spawners occurring upriver: the spring-spawning population would thus be

allopatric.

Vascularization of the pectoral fin and capacity of larval respiratory organs were also

studied by Munshi et al. (1989) for Monopterus cuchia. Observations on breeding habits

and larval development were also provided for the Asian synbranchids Monopterus albus

(Wu and Liu 1942), M. cuchia (Banerji et al. 1981), and Ophisternon bengalense

(Rangarajan and Jacob 1960). [[[[

Ojeda (1986) reported the morphological characterization of the alimentary tract of

Antarctic fishes and its relation to feeding habits. Morphological and morphometric

characteristics of the alimentary tract in 22 species of carnivorous antarctic fishes were

studied. It is shown that all of these species have similar, well-developed Y-shaped

stomachs with generally thick (0.5–1.0 mm) walls. The relative stomach lengths are also

similar, ranging from 9.8 to 22.2% of body length. Relative intestine lengths, a

characteristic frequently used as an indicator of the kind of food eaten by a species, are

also remarkably similar among most species (31 to 67%). Notothenia gibberifrons, a

conspicuous benthos feeder, has a significantly longer intestine (91%), probably as an

adaptation to the quantity of undigestible material (mud) incorporated with its faunal

prey. These values fit within or below the limits (60–150$) of relative intestine length

described in the literature for carnivorous fishes. The number of pyloric caecae is in

general relatively low and fairly constant in each species. It is concluded that the

morphological features studied could represent similar adaptations of these antarctic

fishes to a similar carnivorous diet.

The biometric analysis, including meristic and morphometric characters, has been

adopted by many authors to identify and relate different fish races and/or populations

(Khalil et al. 1984; Mekkawy 1995; Mekkawy et al. 2002, Turan 2004 and Ali and

McNoon 2010). This trend in biometric analysis reflects its validity in stock identification

in different fisheries of the world.

Few studies on morphological variation within different fish species have been reported

(Prakash and Verma 1982; Hoque and Rahman 1985; Kohinoor et al.1995; Azadi and

Naser 1996). Sex related morphological variation have also been reported by Islam et al.

http://www.springerlink.com/content/?Author=F.+Patricio+Ojeda�


http://scialert.net/fulltext/?doi=jbs.2011.10.21&org=11#704710_ja�







1983. Unfortunately no published information on morphometric studies of freshwater

mud eels is available.

The morphological variations have been used as a basic tool in separating population of

species (Seymour 1959; Anthony and Bayer 1968). For the proper identification of fish, it

is essential to study its morphometric characters. The review of literature indicates that

there are two types of freshwater mud eels Monopterus cuchia and Monopterus albus and

three species of baim Mastacembelus armatus, Mastacembelus pancalus, Mastacembelus

aculeatus of similar colour, shape, size and characters are available in different water

bodies of Bangladesh (Rahman 1989; Jhingran and Talwar 1991). It is therefore essential

to determine whether the fish samples of Monopterus cuchia and Ophisternon bengalense

handled during the course of present investigation belonged to a single homogenous

population or not.

CHAPTER III

MATERIALS AND METHOD

2

2

2 2

MATERIALS AND METHODS 3.1. Collection of sample Monopterus cuchia sample were collected from two places of Bangladesh, Dinajpur and

Mymensingh and Ophisternon bengalense were collected from two places, Satkhira and

Bagerhat (Fig. 3.1).

Fig. 3.1. Map of Bangladesh showing sampling sites of M. cuchia & O. bengalense.

3.2. Rearing of sample Two fish species (total thirty two M. cuchia and seventeen O. bengalense from four

areas) were reared in two tanks at the Mini Hatchery under the Faculty of Fisheries,

Bangladesh Agricultural University and Mymensingh. The fishes were reared with

intensive care, maintaining appropriate water quality and fed with live earthworm and

tubifex twice a day. Small parts of bamboos were in place for their shelter.

3.3. Measurement of morphometric and meristic characters

3.3.1. Morphometric characters Twenty six morphometric characters and body weights of the fish were measured with an

accuracy of 0.05 mm and 1.0 g, respectively (Table 3.1.) A total of nine meristic

characters (Table 3.2) were analyzed. Six landmarks determining eight distances were

measured on the fish body (Fig. 3.2).

Table 3.1. The morphometric characters measured

Characters Description

1. Total length (TL)

2. Pre dorsal length (PDL)

3. Post dorsal length (PoDL)

4. Pre anal length (PAL)

5. Post anal length (PoAL)

6. Length of lateral line (LAL)

7. Head length (HL)

8. Snout length (SnL)

Distance from the tip of the snout to the

longest caudal fin ray

Distance from the snout tip to the anterior

base of the dorsal fin

Distance from anterior base of the dorsal fin

to last part of the caudal fin

Distance from the tip of the snout to the anal

base

Distance from the anal base to the last part of

the anal fin

Distance from the first base to the last base of

lateral line

Distance from the tip of the snout to the

posterior margin of the opercula

Distance from tip of mouth to nostril

9. Upper jaw length (UJL)

10. Lower jaw length (LJL)

11. Mouth gape (MG)

12. Eye diameter (ED)

13. Head depth (HD)

14. Head width (HW)

15. Pre orbital length (POL)

16. Post orbital length (PoOrL)

17. Greatest body depth (GBD)

18. Least body depth (LBD)

19. Greatest width of body

(GWB)

20. Highest body diameter

(HBD)

21. Width of body at vent

(WBV)

22. Depth of body at vent

(DBV)

23. Distance between vent and

commencement of dorsal fin

(DBCB)

24. Intestine length (IL)

25. Fat length (FL)

26. Length beside lateral line

(LBLL)

Length of upper jaw

Length of lower jaw

Length of mouth gape

Diameter of eye

Depth of head

Width of head

Distance from tip of mouth to anterior base of

eye

Distance from posterior base of eye to last

hard part of head

Greatest body depth of the body

Least body depth of the body

Width of body at greatest part

Diameter of the highest body part

At vent base width of the upper part of the

body

Depth of body at vent base

Distance between at vent base to dorsal fin

base

Length of intestine

Length of fatlike structure which attached

with the intestine

Length beside lateral line

TL LLL LLLL

LLL LLLL

LLL

LL

22

2

2222

222 22

WLV

GWL

The fat length (fat like structure with small blackish dot shown attached with intestine)

was measured only in case of Ophisternon bengalense, which only present in this species.

In case of Monopterus cuchia four lines were present beside lateral lines which were

measured. Figure 3.2 shows the morphometric measurement. The measurement were

done in the way in both species.

Fig. 3.2. Morphometric measurements of cuchia.

3.3.2.Meristic characters

Table 3.2. The meristic characters of eels

Characters Description

1. Body line The number of line present in the body

2. Line below head The number of line below head

3. Teeth The number of teeth at both in the upper and lower jaw

4. Gill raker The number of gill rakers

Five meristic characters were analyzed and measured (Table 3.2). The characters were-

No. of line in body, No. of line below head, No. of teeth in both the upper jaw and lower

jaw and No. of gill rakers. No. of gill raker were same for both species, but in case of

Ophisternon bengalense teeth were very small so it was not possible to count the teeth for

this species.

3.4. Land mark distances of the species

The truss network system described for fish body morphometrics (Hossain et al. 2010)

was used to construct a network on fish body, 6 landmarks determining 8 distances were

produced and measured as illustrated in Fig. 3.3. Each landmark was obtained by placing

the fish on a graph paper and then the landmark points were detected with colored

pointers. Finally the distances on the graph paper were measured using vernier calipers.

Fig. 3.3. Six landmarks determining 8 distances on eel body.

3.5. Dissection of the species: After measurement of morphometric, meristic and landmark distances, the fish were

dissected using scissors and tweezers. Intestine of the fish were cleaned with tap water

and were measured. The sex pattern was observed, head was dissected and the gill rakers

were observed and both upper jaw and lower jaw were cut and the teeth were counted.

3.6. Statistical analyses Sexes were determined by macroscopic examination of the respective gonads and this

subset was used to test hypothesis of no sexual dimorphism in morphometric, landmark

distance and meristic characters of both the species. Sexual variation was analyzed using

independent sample t-tests.

A multivariate discriminant analysis was used for morphometric data to identify the

combination of variables that best separate both the species. Prior to the analysis, size

effects from the data set were eliminated. Variations were attributed to body shape

differences, and not to the relative size of the fish. In the present study, there were

significant linear correlations among all measured characters and the total length of the

fish. Therefore, it was necessary to remove size-dependent variation for all the characters.

1

2

3 4

5

6

An allometric formula given by Elliott et al. (1995) with slight modification was used to

remove the size effect from the data set.

Madj = M (Ls / Lo) b

Where M: Original measurement, Madj: Size adjusted measurement, Lo: Total length of

fish, and Ls: Overall mean of total length for all fish from all samples. Parameter b was

estimated for each character from the observed data as the slope of the regression of log

M on log Lo, using all fish in all groups. The efficiency of size adjustment

transformations was assessed by testing the significance of the correlation between

transformed variable and total length.

Efficiency of the allometric formula in removing size effect from the data was justified

by using correlation between total length and the adjusted morphological, meristic

characters and landmark distances. Total length were excluded first and not transformed

because using this parameter as standard all other parameters were standardized. After

the allometric transformation, the correlation results revealed that all of the meristic

variables studied were free from the influence of size.

The degree of similarity among samples in the overall analysis and relative importance of

each measurement for group separation were assessed by discriminant function analysis

(DFA) with cross validation. Population centroids with 95% confidence ellipses derived

from the DFA were used to visualize relationships among the individuals of groups. A

dendrogram of the populations based on the morphometric and landmark distances data

was drawn by the unweighted pair group (UPGMA) cluster analysis. Univariate analysis

of variance (ANOVA) and independent sample t-test were carried out to test the

significance of morphological differences. Comparison of meristic characters was done

using non parametric Mann-Whitney U test. Resulting DFAs were examined for the

extent of classification between two stocks and between stocks. In addition, a “leave-one-

out cross-validation” was performed on each DFA as a testing procedure. All statistical

analyses were done using SPSS v 11.5.

CHAPTER IV

RESULTS

RESULTS

4.1. Length and body weight of M. cuchia and O. bengalense and their sexing

pattern

Morphometric, truss measurements and meristic characters from thirty two M. cuchia and

seventeen O. bengalense were analyzed in this experiment. Their sex patterns were found

to be heterosexual i.e. male and female in both the species. There were nineteen males

(59.4%) and thirteen females (40.6%) in M. cuchia and five males (29.4%) and twelve

females (70.6%) in O. bengalense (Table 4.1). The average length and weight of M.

cuchia were 62.74±6.84 cm and 547.03±271.48 g respectively. On the other hand the

average length and weight of O. bengalense were 53.12±5.27 cm and 161.76±33.21 g

respectively. The sex and location wise length and weight of M. cuchia and O.

bengalense are presented in the Table 4.1. Table 4.1. Length and weight of M. cuchia and O. bengalense and their sexing pattern (SD

= standard deviation, n = number of fish) and the range

Species Sex Location of

samples

n Mean total

length ± SD

(cm)

Mean weight ±

SD (g)

M. cuchia F 1 4 70.15±4.45

(66-74)

825±28.87

(800-850)

M 13 67.9±2.14

(62-71)

771.54±118.99

(500-900)

F 2 9 58.82±2.69

(52-61)

281.11±68.23

(150-300)

M 6 55.5±4.07

(52-63)

274.17±74.39

(215-400)

O. bengalense

F

3

6

53.02±2.60

(48-55)

158.33±20.41

(150-200)

M 2 100±0

(48-48)

47.6±0

(100-100)

F

4 6

53.72±5.96

(46-63)

175±27.39

(150-200)

M 3 55.83±8.60

(48-63)

183.33±28.89

(150-200)

M: Male; F: Female; 1. Mymensingh 2. Dinajpur 3. Satkhira and 4. Bagerhat

4.2. Physical characteristics

Body description

The body is cylindrically elongated. The body colour of M. cuchia is brownish dark with

numerous small black and yellowish blotches. Body is triangular in shaped. The skin is

very thick and rough looking. The dorsal part of body is dark brownish and ventral part is

yellow brownish. All over the body, numerous black blotches are present (Fig. 4.1).

Fig. 4.1. Body colour (ventral view-left and dorsal view-right) of M. cuchia.

The body of O. bengalense is rounded and elongated. The body colour is lightly red

brownish with very little minute light blackish spot all over the body. The whole body is

more or less smooth. The dorsal part of the body is somewhat dark reddish brown. The

ventral part is whitish red. The skin of body is somewhat transparent with light zigzag

starting slightly far of chest (approximately 5 cm far) the line are more dominant in dead

fish (Fig. 4.2).

Fig. 4.2. Body colour (ventral view-left and dorsal view-right) of O. bengalense.

The head shape of M. cuchia is triangular. Middle part of the head is slightly straight.

Numerous lines and black blotches are also present on the head. Eyes are small and

visible through a translucent layer of skin. Mouth part is blunt shape. Upper jaw is very

long due to large head size (Fig. 4.3).

Fig.4.3. Head shape of M. cuchia.

The head in O. bengalense is short and rounded. Mouth part is sharp. At the upper part of

jaw there are two small barbells. Eyes are protractile and no line is present as M. cuchia.

The middle part of the head is anteriorly rounded. Upper jaw is not long due to short head

size (Fig. 4.4).

Fig. 4.4. Head shape of O. bengalense.

At ventral part of head there are various lines arranged in ‘V’ liked shape. More

than 22-28 lines are arranged here. The lines end near to the lower jaw. In the M. cuchia

two sides of the head look swollen because of respiratory sac (Fig. 4.5).

Fig.4.5. Head shape (ventral side) of M.cuchia.

In the ventral part of O. bengalense there are around 10 lines arranged in crescent shape.

Lines finally end near the lower jaw (Fig. 4.6). The two sides of the head are not swollen.

Fig. 4.6. Head shape (ventral side) O. bengalense.

There are four lines present beside the lateral line in M.cuchia.There is no line present

beside lateral line in O. bengalense (Fig. 4.7)

Fig. 4.7. Lines present beside lateral line in M. cuchia (left) and no line present in O.

bengalense (right).

The last part of the tail of M. cuchia is blunt shaped. The dorsal and anal fin are

rudimentary i.e. they are not dominant. The dorsal fin is originated slightly away from the

dorsal part from the anus (Fig. 4.8).

Fig. 4.8. Tail shape of M. cuchia (left) and O. bengalense (right)

The last part of the tail of O. bengalense is sometwhat a sharp structure. The dorsal and

anal fins are more dominant than M. cuchia. The dorsal fin is slightly before position

from the anus (Fig. 4.8).

The gill arch is spiral and arranged in fibre-like fashion in M. cuchia and O. bengalense

respectively (Fig. 4.9). The mouth gape is broader in M. cuchia than in O. bengalense

(Fig. 4.10).

Fig. 4.9. Gill arch of M. cuchia (left) and O. bengalense (right).

Fig. 4.10. Mouth gape of M. cuchia (left) and O. bengalense (right).

The teeth of M. cuchia are relatively large and are countable while the teeth of O.

bengalense are very small in size and are not countable (Fig. 4.11).

Fig. 4.11: Teeth of M. cuchia (left) and O. bengalense (right).

In the stomach of M. cuchia, no other structure is attached with intestine. In case of O.

bengalense a long fat like structure is attached with intestine (Fig. 4.12)

Fig. 4.12: Fat like organ in the stomach of O.bengalense.

4.3. Meristic characters Efficiency of the allometric formula in removing size effect from the data was justified

by using correlation between total length and the adjusted meristic character. Total length

were excluded first and not transformed because using this parameter as standard all

other parameters were standardized. After the allometric transformation, the correlation

results revealed that all of the meristic variables studied were free from the influence of

size.

The mean number of line in body, number of line below head, number of teeth (upper

jaw), number of teeth (lower jaw) and number of gill racker were 6.0±0, 21.94±2.06,

17.47±2.97, 26.66±4.57 and 8.0±0 respectively in M. cuchia. Whereas the mean number

of line below head and gill racker was 10.21±0.631 and 8.0±0, respectively in O.

bengalense (Table 4.2). The mean number of line below head were significantly (Mann-

Whitney U test; z= -6.091; P<0.001) different between the two species (Table 4.2).

Table 4.2. Comparison of meristic counts between M. cuchia and O. bengalense (Mann-

Whitney U) (minimum and maximum values are in parenthesis)

Meristic characters M. cuchia O. bengalense Z-statistic Significance

No. of line in body

No. of line below head

6.0±0

(6-6)

21.94±2.06

(20-27)

-

10.21±0.631

(10-12)

-

-6.091

-

0***

No. of teeth (upper jaw) 17.47±2.97

(13-24)

- - -

No. of teeth (lower jaw) 26.66±4.57

(17-36)

- - -

No. of gill racker 8.0±0

(8-8)

8.0±0

(8-8)

0 1.0

***P<0.001

4.4. Morphological and landmark differences As for meristic characters are concerned none of the characters were found to be

significantly correlated (P<0.05) with total length, indicating that size effects had been

removed from the morphometric and landmark variates.

Sexes were determined by macroscopic examination of the respective gonads and this

subset was used to test hypothesis of no sexual dimorphosim in morphometric and

meristic characters of both the species. No meristic heterogeneity was observed among

the sexes in both the species.

Among the thirty five transformed morphometric (27 characters) and truss measurements

(8 characters) of M. cuchia, two morphometric measurements (Eye diameter, t = -2.34;

P<0.05 and Pre orbital length, t = -2.12; P<0.05) and one truss measurement (4-6, t =

2.09; P<0.05) were found significantly different among the sexes of M. cuchia (Table

4.3). Therefore, those characteristics were excluded for further analyses.

Table 4.3. Comparison of adjusted morphological and landmark measurements between

sexes of M. cuchia (Mean ± SD)

Characters

Sexes t-statistic Significance

or

Probability M F

Morphological characters

Pre dorsal length 47.43±5.16 47.02±2.68 0.26 0.795

Post dorsal length 13.57±1.68 13.10±1.70 0.76 0.453

Pre anal length 44.40±1.11 45.22±1.27 -1.94 0.062

Post anal length 14.15±2.22 13.87±1.30 0.41 0.681

Length of lateral line 53.84±3.30 55.24±1.19 -1.46 0.155

Head length 4.12±0.69 4.18±0.26 -0.32 0.755

Snout length 1.18±0.16 1.21±0.21 -0.44 0.666

Upper jaw length 2.42±0.21 2.52±0.33 -1.00 0.325

Lower jaw length 2.38±0.26 2.48±0.43 -0.78 0.443

Mouth gap 1.85±0.46 1.84±0.42 0.08 0.937

Eye diameter 0.50±0.12 0.60±0.14 -2.34 0.026*

Head depth 2.03±0.20 2.03±0.30 0.02 0.988

Head width 2.10±0.15 2.19±0.20 -1.47 0.153

Pre orbital length 1.00±0.16 1.21±0.37 -2.12 0.042*

Post orbital length 2.93±0.34 2.91±0.23 0.21 0.837

Greatest body depth 2.52±0.33 2.46±0.35 0.48 0.636

Least body depth 2.04±0.13 2.01±0.15 0.63 0.536

Greatest width of body depth 1.99±0.20 2.09±0.17 -1.58 0.125

Highest body diameter 7.96±0.70 8.17±0.68 -0.86 0.399

Width of body at vent 1.43±0.34 1.60±1.07 -0.63 0.534

Depth of body at vent 2.27±1.05 2.10±0.39 0.58 0.568

Distance between vent and


2.30±0.74

2.26±0.42 0.17 0.866

Intestine length 18.54±3.29 17.82±4.79 0.51 0.617

Length beside lateral line-1 3.64±0.89 3.82±0.61 -0.62 0.541


Length beside lateral line-3 3.87±1.25 3.60±0.90 0.66 0.512


Landmark distances

1-2 4.06±0.50 4.24±0.50 -1.01 0.319

1-3 4.23±0.43 4.20±0.46 0.19 0.849

2-3 2.45±0.54 2.41±0.41 0.19 0.849

2-4 40.75±2.38 40.83±3.60 -0.08 0.938

3-5 42.41±2.34 42.05±2.08 0.45 0.658

4-5 2.50±0.81 2.27±0.46 0.93 0.360

5-6 13.17±1.49 12.84±1.94 0.54 0.590

4-6 14.57±1.02 13.83±0.89 2.09 0.045*

M: Male; F: Female

*P<0.05

Among the thirty two transformed morphometric (24 characters) and truss measurements

(8 characters) of O. bengalense, two morphometric measurements (Lower jaw length, t =

2.73; P<0.05 and Eye diameter, t= -2.24; P<0.05) were found significantly different

among the sexes (Table 4.4.). Therefore, those characteristics were excluded for

discriminant analyses for both the species. None of the truss measurements were found

significantly different between sexes of O. bengalense.

One morphological character, fat length of O. bengalense was not found in M. cuchia and

four morphological characters (Length beside lateral line 1, 2, 3 and 4) in M. cuchia were

not found in O. bengalense, therefore, those characters were not included for

discriminannt analyses or to determine the difference between the species.

Table 4.4. Comparison of adjusted morphological and landmark measurements between

sexes of O. bengalense (Mean ± SD) (Independent samples t-test)

Characters

Sexes

t-statistic Significance M F

Morphological characters

Pre dorsal length 45.12±4.02 44.72±2.56 0.25 0.808

post dorsal length 16.14±1.65 16.10±1.19 0.06 0.954

Pre anal length 43.40±0.84 43.78±0.53 -1.14 0.271

post anal length 15.48±0.84 15.13±0.58 0.99 0.336

Length of lateral line 54.09±0.46 54.00±0.68 0.27 0.789

Head length 3.76±0.23 3.81±0.33 -0.34 0.741

Snout length 0.96±0.24 1.08±0.17 -1.14 0.271

Upper jaw length 2.29±0.24 2.10±0.16 1.93 0.072

Lower jaw length 2.21±0.21 1.88±0.24 2.73 0.015*

Mouth gap 1.81±0.21 1.50±0.39 1.67 0.116

Eye diameter 0.43±0.05 0.56±0.13 -2.24 0.041*

Head depth 1.94±0.19 2.15±0.25 -1.62 0.127

Head width 1.86±0.21 2.03±0.33 -1.06 0.306

Pre orbital length 0.85±0.25 0.76±0.18 0.87 0.399

Post orbital length 3.00±0.23 3.02±0.20 -0.18 0.861

Greatest body depth 2.16±0.19 2.36±0.43 -0.97 0.346

Least body depth 1.86±0.49 1.80±0.40 0.26 0.802

Greatest width of body depth 1.77±0.33 2.06±0.33 -1.64 0.123

Highest body diameter 7.59±1.11 7.45±0.91 0.28 0.782

Width of body at vent 1.24±0.26 1.36±0.41 -0.62 0.542

Depth of body at vent 1.85±0.37 1.96±0.29 -0.66 0.521

Distance between vent and


2.31±0.52

2.41±0.27 -0.50 0.623

Intestine length 19.79±0.37 21.17±1.64 -1.83 0.087

Fat length 24.33±2.78 25.87±1.16 -1.66 0.118

Landmark distances

1-2 4.36±0.32 4.17±0.24 1.34 0.201

1-3 4.28±0.37 4.22±0.32 0.35 0.729

2-3 2.36±0.31 2.44±0.27 -0.49 0.633

2-4 42.38±5.91 40.06±4.30 0.91 0.378

3-5 39.42±3.99 38.18±2.64 0.77 0.456

4-5 2.33±0.32 2.68±0.31 -2.12 0.051

5-6 16.59±1.53 15.99±1.46 0.75 0.463

4-6 15.94±1.05 15.17±1.17 1.26 0.226

M: Male; F: Female

*P<0.05

Table 4.5. Means and standard deviation of adjusted morphological data for M. cuchia and

O. bengalense (t-test for difference before and after adjustment of the variables)

Characters M. cuchia O. bengalense t-

statistic Significance

PDL 47.26±4.28 44.84±2.92 2.09 0.042*

PoDL 13.38±1.68 16.12±1.28 -5.86 0***

PAL 44.73±1.23 43.66±0.63 3.35 0.002**

PoAL 14.03±1.88 15.23±0.65 -2.53 0.015*

LAL 54.41±2.71 54.02±0.61 0.58 0.568

HL 4.14±0.55 3.80±0.30 2.39 0.021*

SnL 1.20±0.18 1.05±0.20 2.71 0.009**

UJL 2.46±0.27 2.16±0.20 4.15 0***

MG 1.84±0.44 1.59±0.37 2.02 0.049*

HD 2.03±0.24 2.09±0.25 -0.83 0.411

HW 2.14±0.17 1.98±0.30 2.34 0.023*

PoOrl 2.92±0.29 3.02±0.20 -1.19 0.242

GBD 2.50±0.33 2.30±0.38 1.90 0.064

LBD 2.03±0.14 1.82±0.41 2.72 0.009**

GWD 2.03±0.19 1.97±0.35 0.74 0.465

HBD 8.04±0.69 7.49±0.94 2.35 0.023*

WBV 1.50±0.72 1.33±0.37 0.93 0.356

DBV 2.20±0.84 1.92±0.31 1.31 0.195

DBCB 2.29±0.62 2.38±0.35 -0.56 0.578

IL 18.24±3.91 20.76±1.52 -2.55 0.014*

1-2 4.14±0.50 4.23±0.27 -0.69 0.491

1-3 4.22±0.44 4.24±0.32 -0.16 0.878

2-3 2.43±0.48 2.42±0.27 0.15 0.884

2-4 40.78±2.88 40.74±4.75 0.03 0.974

3-5 42.27±2.21 38.54±3.02 4.94 0***

4-5 2.41±0.69 2.58±0.35 -0.93 0.355

5-6 13.03±1.67 16.17±1.46 -6.53 0***

*P<0.05; **P<0.01; ***P<0.001

Independent sample t test showed that fourteen morphometric characters Pre dorsal

length (PDL), t test = 2.09; P<0.05; Pre anal length (PAL), t test = 3.35; P<0.01; Post

dorsal length (PoDL), t test = -5.86; P<0.001; Post anal length (PoAL), t test = -2.53;

P<0.05; Head length (HL), t test = 2.39; P<0.05; Snout length (SnL), t test = 2.71;

P<0.01; Upper jaw length (UJL) t test = 4.15; P<0.001; Mouth gape (MG), t test = 2.02;

P<0.05; Head width (HW) t test = 2.34; P<0.05; Least body depth (LBD), t test= 2.72;

P<0.01; Highest body diameter (HBD) t test = 2.35; P<0.05; Intestine length (IL) t test =

2.55; P<0.05 and two truss measurement 3-5, t test = 4.94; P<0.001; 5-6, t test = -6.53;

P<0.001 revealed a significant variation between two species in varying degrees (Table

4.5). Length of lateral line (LAL), t test = 0.58; P=0.568; Head depth (HD), t test= -0.83;

P=0.411; Post orbital length (PoOrL) t test = -1.19; P=0.242; Greatest body depth

(GBD), t test = 1.90; P=0.064; Greatest width of body depth (GWD), t test =0.74;

P=0.465; Width of body at vent (WBV), t test = 0.93; P=0.356; Depth of body at vent

(DBV), t test =1.31; P=0.195; Distance between vent and commencement of dorsal fin

(DBCB), t test = -0.56; P=0.578 and five truss measurement 1-2, t test = -0.69; P=0.491;

1-3, t test= -0.16; P=0.878, 2-3, t test =0.15; P=0.884, 2-4, t test =0.03; P=0.974, 4-5, t

test = -0.93; P=0.355 did not varied significantly between two species (Table 4.5).

Univariate statistics (ANOVA) showed that tweleve morphometric characters (PDL, F=

4.352; P<0.05; PoDL, F=34.289; P<0.001; PoAL, F= 6.404; P<0.05; HL, F=5.707;

P<0.05; SnL, F=7.326; P<0.01; UJL, F=17.219; P<0.001; MG, F=4.089; P<0.05; HW,

F=5.491; P<0.05; LBD, F=7.406; P<0.01; HBD, F=5.539; P<0.05; IL, F=6.485;

P<0.05) and two truss measurement (3-5, F=24.392; P<0.001; 5-6, F=42.58; P<0.001)

revealed a significant variation between two species in varying degrees (Table 4.6). eight

morphometric characters (LAL, F=0.331; P=0.568; HD, F=0.687; P=0.411; PrOrL,

F=1.405; P=0.242; GWD, F=0.543; P=0.465; WBV, F=0.867; P=0.356; GBD, F=3.603;

P=0.064; DBV, F=1.726; P=0.195; DBCB, F=0.314; P=0.578) and five truss

measurements (1-2, F=0.481; P=0.491; 1-3, F=0.024; P=0.878; 2-3, F=0.021; P=0.884;

2-4, F=0.001; P=0.974; 4-5, F=0.871; P=0.355 did not varied significantly between two

species (Table 4.6).

Table 4.6. Univariate statistics (ANOVA) testing difference between M. cuchia and O.

bengalense (df1=1; df2=47)

Characters Wilks' Lambda F Significance

PDL 0.915 4.352 0.042*

PoDL 0.578 34.289 0***

PAL 0.807 11.216 0.002**

PoAL 0.88 6.404 0.015*

LAL 0.993 0.331 0.568

HL 0.892 5.707 0.021*

SnL 0.865 7.326 0.009**

UJL 0.732 17.219 0***

MG 0.92 4.089 0.049*

HD 0.986 0.687 0.411

HW 0.895 5.491 0.023*

PoOrL 0.971 1.405 0.242

GBD 0.929 3.603 0.064

LBD 0.864 7.406 0.009**

GWD 0.989 0.543 0.465

HBD 0.895 5.539 0.023*

WBV 0.982 0.867 0.356

DBV 0.965 1.726 0.195

DBCB 0.993 0.314 0.578

IL 0.879 6.485 0.014*

1-2 0.99 0.481 0.491

1-3 0.999 0.024 0.878

2-3 1 0.021 0.884

2-4 1 0.001 0.974

3-5 0.658 24.392 0***

4-5 0.982 0.871 0.355

5-6 0.525 42.58 0***

*P<0.05; **P<0.01; ***P<0.001

First three canonical discriminant functions were used in the analysis. Pooled within-

groups correlations between discriminant variables and DFs revealed that four

morphometric characters (PoDL, UJL, PAL and IL) and two landmark distances (5-6 and

3-5) contributed to the first DF and three morphometric characters (HW, LBD and MG) contributed second DF and six morphometric characters (HL, HBD, PoAL, SnL, PDL

and LAL) contributed to the third DF (Table 4.7) implying that these characters are the

most important in the description of population characteristics.

Table 4.7. Contribution of morphometric and truss measurements of M. cuchia and O.

bengalense to the canonical functions

Characters Function

DF1 DF2 DF3

5-6 -0.614* 0.093 0.204

PoDL -0.430* 0.122 -0.113

3-5 0.332* -0.084 0.176

UJL 0.309* -0.072 -0.069

PAL 0.223* 0.032 0.133

IL -0.195* -0.042 0.089

HW 0.167 -0.459* -0.022

LBD 0.145 -0.348* 0.335

MG 0.198 0.212* -0.199

HL 0.084 -0.016 0.700*

HBD 0.104 -0.169 .410*

PoAL -0.132 -0.007 -0.360*

SnL 0.251 0.143 -0.263*

PDL 0.115 -0.077 0.179*

LAL 0.063 0.039 -0.178*

Eigenvalue 6.59 3.37 0.21

% of Variance 64.8 33.2 2.0

Variables ordered by absolute size of correlation within function. * Largest absolute correlation

between each variable and any discriminant function. Plotting Discriminant function DF1 and DF2 showed a clear differentiation between the

species as well as between the stocks for both morphometric and landmark

measurements. For both morphometric and landmark measurements the first and second

DF accounted 64.8% and 33.2% of among group variability, explaining 98% of total

group variability. All the populations were clearly separated from each other in the

discriminant space (Fig. 4.13). This suggested that there was limited intermingling among

populations and the populations of the species were separated (Fig. 4.13).

Fig. 4.13. Sample centroids of discriminant function scores based on morphometric and truss

measurements -1. M. cuchia (Mymensingh), 2. M. cuchia (Dinajpur), 3. O. bengalense

(Satkhira), and 4. O. bengalense (Bagerhat).

A dendrogram based on morphometric and landmark distance data was shown for the

populations of both the species constructed one cluster and further divided into two

distinct sub-clusters. M. cuchia collected from Mymensingh and M. cuchia collected

from Dinajpur constructed one sub-cluster and O. bengalense collected from Satkhira and

O. bengalense collected from Bagerhat constructed another sub-cluster based on the

Distance of squared Euclidean dissimilarity (Fig. 4.14).

Distance of squared Euclidean dissimilarity

0 5 10 15 20 25

+---------+---------+---------+---------+---------+

3

4

1

2

Fig. 4.14. Dendrogram based on morphometric characters and landmark distances - 1. M. cuchia

(Mymensingh), 2. M. cuchia (Dinajpur), 3. O. bengalense (Satkhira), and 4. O.

bengalense (Bagerhat). A correct classification of individuals into their original population from leave-one-out-

classification varied between 93.3% and 94.1% by discriminant analysis and 95.9% of

individuals could be classified in their correct priori grouping (Table 4.8). The proportion

correctly classifies M. cuchia (collected from Dinajpur) into the corresponding original

group was the highest (93.3%) (Table 4.8).

Table 4.8. Correct classifications of individuals M. cuchia (collected from Mymensingh and

Dinajpur) and O. bengalense (collected from Satkhira and Bagerhat) into their original

population (leave-one-out-classification)

Population

Predicted Group Membership Total

1 2 3 4

Original Count 1 16 0 1 0 17

2 1 14 0 0 15

3 0 0 8 0 8

4 0 0 0 9 9

% 1 94.1 0 5.9 0 100

2 6.7 93.3 0 0 100

3 0 0 100 0 100

4 0 0 0 100 100

1. M. cuchia (Mymensingh), 2. M. cuchia (Dinajpur), 3. O. bengalense (Satkhira) and 4. O. bengalense

(Bagerhat))

CHAPTER VI

SUMMARY AND CONCLUSION

SUMMARY AND CONCLUSION Eels, a recent export item, though, have not yet been given any attention on its culture

and collection could be the only option to meet the export demand. Hence, Bangladesh

has great opportunity to develop eel farming industry and to enter in wider Asian and

European market if proper attempt could be taken. Domestication is the first step to bring

eels under aquaculture. Knowing morphological characters is also a prerequisite for

breeding in captivity. The morphological difference may be explained by the relationship

between geographical distance and differences in environmental adaptation over the

geographical distances.

This study was designed to investigate regional and population variations in

morphological traits in a natural environment of two similar eels - M. cuchia and O.

bengalense collected from four areas of Bangladesh. A simple design was constructed to

analyze the morphological, morphometric and meristic characters of two species. The

whole physical appearances were analyzed which help in specific identification of the

species. On the other hand, the length and weight are measured. The average length and

weight of M. cuchia were 62.74±6.84 cm and 547.03±271.48 g respectively and

53.12±5.27 cm and 161.76±33.21 g respectively for O. bengalense.

There were minor sex-dependent morphological differences detected in the present study.

The mean number of line below head were significantly (Mann-Whitney U test; z = -

6.091; P<0.001) different between two species. In M. cuchia, two morphometric

measurements Eye diameter, t = -2.34; P<0.05 and Pre orbital length, t = -2.12; P<0.05

and one truss measurement (4-6) t = 2.09; P<0.05 were found significantly different and

O. bengalense, six morphometric measurements Lower jaw length, t = 2.73; P<0.05 and

Eye diameter, t = -2.24; P<0.05 were found significantly different among the sexes of O.

bengalense.

For both sexes of two species, adjusted morphological data were analyzed and

Independent sample t test showed that fourteen morphometric characters, Pre dorsal

length (PDL), t test = 2.09; P<0.05; Pre anal length (PAL), t test = 3.35; P<0.01; Post

dorsal length (PoDL), t test = -5.86; P<0.001; Post anal length (PoAL), t test = -2.53;

P<0.05; Head length (HL), t test = 2.39; P<0.05; Snout length (SnL), t test = 2.71;

P<0.01; Upper jaw length (UJL) t test = 4.15; P<0.001; Mouth gape (MG), t test = 2.02;

P<0.05; Head width (HW) t test = 2.34; P<0.05; Least body depth (LBD), t test = 2.72;

P<0.01; Highest body diameter (HBD) t test = 2.35; P<0.05; Intestine length (IL) t test =

2.55; P<0.05 and two truss measurement (3-5), t test = 4.94; P<0.001; 5-6, t test = -

6.53; P<0.001 revealed a significant variation between two species in varying degrees.

For better understanding of differences of between M. cuchia and O. bengalense

univariate statistics (ANOVA) showed that eleven morphometric characters Pre dorsal

length (PDL), P<0.05; Post dorsal length (PoDL), P<0.001; Post anal length (PoAL);

P<0.05; Head length (HL); P<0.05; Snout length (SnL); P<0.01; Upper jaw length

(UJL); P<0.001; Lower jaw length (LJL); P<0.001; Head width (HW); P<0.05; Pre

orbital length (PrOrL); P<0.001; Least body depth (LBD); P<0.01; Highest body

diameter (HBD); P<0.05 and one truss measurement (3-5); P<0.001 revealed a

significant variation between two species in varying degrees.

Major differences in morphological traits between M. cuchia and O. bengalense are

determined by discriminant function analysis. For both morphometric and landmark

measurements the first and second DF accounted 64.8% and 33.2% of among group

variability. By this discriminant analysis it was clear that the population were limited

intermingling separated among population. A dendrogram based on morphometric and

landmark distance showing the population is distinctly distanced. In this study, we found

two distantly related fish species – distinguished at the level of population structure –

exhibited two types of body shape where M. cuchia is cylindrically elongated and O.

bengalense is round elongated. Many differences were found among the species from

head to tail. Differences also occur in meristic measurement such as there are no lines

present beside lateral line of O. bengalense but there are few in M. cuchia. Numbers of

line below head were arranging by distinctly different shape and varies also in number.

Other major morphological differences are found in eye, head shape, body shape,

distance between vent and commencement of dorsal fin. Minor differences were also

found all over the body of both of the species, O. bengalense at the upper lip has two

little barbells and mouth gape was much broader in M. cuchia fat like structure attached

with intestine in O. bengalense was one of the major characters of the species. The whole

measurement of the morphological character of both the species indicates that they are

morphologically separated from each other.

The present study dealt with the population structure of two cuchia from a phenotypical

point of view to determine the morphometric among the stocks. It revealed the

differences of morphological characteristics between two species. This has major

implications in understanding morphological diversity among population.The result

indicates differences in population and can be very important for further taxonomic and

genetic studies to know the exact population structure.

The results of the study are useful as baseline information of cuchia populations for

further studies. In both aquaculture and open-water management, it is essential to select

stocks with better features. More research especially genetic studies and investigations of

the impacts of geo-environmental factors is needed for conservation and mass seed

production of selected stocks to pave the way to saving the two valuable eel species from

extinction.

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