trawl fishery of juvenile fishes and its impact on fish stock credit seminar jitendra
TRANSCRIPT
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Major Advisor : Dr. S. Benakappa
Presented by:Jitendra Kumar
ID No. MFK 1109Department of Fisheries Resources and Management
Credit seminar presentation
Trawl Fishery of Juvenile Fishes and its Impact on
Fish Stock
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Introduction
Terminology/ Definition
Results and Discussion
Impact Studies
Conclusion
OUTLINE
Methodology
References
Paper Presentation
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• Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats….
• The boats that are used for trawling are called trawlers or draggers
• The net that is used for trawling is called a trawl
• In Karnataka, bottom trawling was first introduced by the Japanese trawler M.S. Maru in 1961. (Kurup et al., 1987)
Trawling
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• There are about 28 fish landing centres in the state. – Mangalore and Malpe in South Karnataka– Karwar in the north are main landing centres
• Mangalore and Malpe fisheries harbours account for more than 53% of the total marine fish landings and 43% of trawl fisheries of Karnataka.
• The main types of fishing are by – Purse-seine,– Trawling and – Gill netting
Cont..
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• The use of the term “L V F” varies from country to country
• One category of LVF are those not used for direct human consumption, which may be either landed and discarded at the sea itself.
L V F
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“Fish that have a low commercial value by virtue of their low quality, small size or low consumer preference –
or used for livestock/fish, either directly or through reduction to fish meal/oil”.
• The term “low-value fish” is preferred to “trash fish”.
• Trash fishes not only include non-commercial species, but also commercial species that are below minimum landing size (MLS) or less profitable species owing to market conditions.
TRASH FISH
FAO, 2012
APFIC, 2005
Catchpole et al.,2005
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• An estimated 3.83 lakh t of bycatch valued at Rs. 192 crores was landed which form 27.8% of the total trawl catch.
At Mangalore: – An estimated 25,067 t of LVB valued at Rs. 25 crores was
landed by multiday trawlers (MDF) at Mangalore Fisheries Harbour.
CMFRI, 2011
Landing of LVB
The high demand for trash fish has been the major reason for increased landing.
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T1 T2 T3 T4 T5 T6 T7 T8 T9 T100
2000
4000
6000
8000
10000
12000
Total (Kg)Trash fish
A case study at Mangalore landing center, Sep-Oct- 2012
T= Trawler No.
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• The definition, “juveniles are young fish, mostly similar in form to
adult but not yet sexually mature” by Hubbs (1943).
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size.
Juvenile
holds appropriate criteria for distinguishing juveniles of tropical fishes and it is used in the present study.
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Catch of Juveniles (t) in trawlers along Karnataka in 2001 and 2002
SDFYear Total catch Juveniles catch %2001 31729 5205 16.52002 38880 5969 17.2
MDFYear Total catch Juveniles catch %2001 71207 15283 22.62002 70414 20947 25.1
Zacharia, et at., 2006
At Mangalore, highest percentage of juvenile fishes by weight in bycatch was of Nemipterus spp. (4,023 t) which results in an annual revenue loss of Rs.16.5 crores.
The economic loss due to discards of juvenile fishes by trawlers at Calicut is an estimated Rs.6.6 crores.
Estimations of Low value/Trash fish production in Asia-Pacific (tonnes)
Country Low value/trash
fish
% of total catch
Dominant gear Year of estimation
Bangladesh 71 000 17% Gill nets (48%)Non-mechanised set bags (42%)
2001-2002
China 5 316 000 38% Trawl 2001
India 271 000 10-20% Trawl 2003
Viet Nam 933 183 36% Trawl 2001
FAO 2005, 12
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Category I
Adult
Juvenile
Category II
Adult in other gear
Juvenile in trawler
Category III
But there is no adult catch
Juvenile in trawler
Categories
Materials and Methods
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Study Location
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Results and discussion
108 species of finfishes
4 species of cephalopods
12 species of shrimps
At Mangalore and Malpe,
Category III: Epinephelus species especially E. diacanthusin which “protogyny” was reported
Category I: Thread fin breams, Soles, Ribbonfishes, Scianids, Carangids and Pomfrets
Category II: Seerfishes, Indian mackerel and oil sardines
Among the important species
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Important groups of juveniles
• Groupers, • Thread fin breams,• Soles, • Ribbon fishes, • Scianids,• Carangids,• Pomfrets, • Seer fishes• Indian mackerel
Nemipterus mesoprion was more
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Category I
N. mesoprionJuvenile :- 42% by No.
22% by wt. TC- 13,386 t JC- 2,914 tJuveniles %:-
Dec (96%)Nov (86%)
Jan to April:- 50% - 69%.
Finfishes:
N. japonicus Juvenile :- 35% by No.
12% by wt. TC- 5,780 t JC- 696 tJuveniles %:-
March (58%)Feb, Dec and Jan
53%, 47% and 42%, respectively
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In sole, Cynoglossus macrostomus
Juvenile :- 35% by No. 26% by wt.
TC- 4,599 t JC- 1,119 tJuveniles %:-
Feb (63%). Jan, April and Sep
60%, 58%, and 49%, respectively
In whitefish, Lactarius lactarius,
Juvenile :- 35% by No. 18% by wt.
TC- 553 t JC- 97 tJuveniles %:-
June 64%, Aug and Sep,
61% and 56%, respectively.
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Juvenile :- 5% by No. 1% by wt.
TC- 25,471 t JC- 341 t
Juveniles %:- Jan, Feb and March,
~12%.
Juvenile :- 15% by No. 5% by wt.
TC- 2,559 t JC- 118 t
Juveniles %:- Jan (48%)
Oct (38%) and Nov (19%).
In ribbonfish, Trichiurus lepturus In carangid, Decapterus russelli
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Shellfishes:
In shrimp, Metapenaeus dobsoni
Juvenile :- 15% by No. 8% by wt. (64 t)
Juveniles %:- Dec (49%)Jan (10%) and March (9%).
In M. monoceros,
Juvenile :- 7% by No. 2% by wt. (61
t)Juveniles %:- May 22%.
Juvenile :- 6% by No. 2% by wt. (20 t)
Juveniles %:- Feb (16%)
In Solenocera choprai
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In cuttle fish, Sepia pharaonis
Juvenile :- 13% by No. 2% by wt.
TC- 6,165 t JC- 123 t
Juveniles %:- March (33%) followed by Feb
(32%) and May (26%).
In squid, Loligo duvaucelli
Juvenile :- 20% by No. 3% by wt.
TC- 6,698 t JC- 201 t
Juveniles %:- April (58%) and another peak was observed in Oct (30%).
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Category II
Seerfish, Scomberomorus commerson
Juvenile :- 16% by wt. TC- 183 t JC- 183 tJuveniles %:- all the months 100% of the
catch comprised of juveniles.
Catch was highest in March (26%) followed by Feb, Sep, Dec and Jan with
18%, 13%, 10% and 9%, respectively.
Muthiah & Pillai (2003) stated that out of 11.61 t million S. commerson landed by trawlers, only less than 1% get a chance to reproduce once before they were caught.
In Indian mackerel and oil sardine, influence of juvenile fishery in trawl was found to be negligible when compared with total landing from the coast.
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Category III
In Epinephelus diacanthus
All the fishes caught were immature females
TC- 3,646 t JC- 3,573t98% wt 99% No.Big fishes were rarely caught, which were
not available for maturity studies
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Impact Studies
Category I
• The juvenile fishery is damaging the adult catch in trawl itself.
Category II• The losses are occurring in gears other than
trawls, which are the major gear for those fishery.
Category III
• The impact is to be studied in wide geological platform where no data is available on the adult fishery from the area of fishing of juveniles
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An example in the first category, N. mesoprion catch was analyzed and results are given in tables
Yield in 2006: 13,347 t value of ` 1,258 lakh
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The resulting yield is 14,293 t with an increase in weight of 7% and an increase in value of 23% ( ` 286 lakh).
If the fishing mortality upto a size of MSM is reduced to zero
The increased percentage for value reflects the increased value realized for bigger sized fishes.
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In the second category, where adults are caught by gears other than trawls, S. commerson
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Yield from gillnet and trawl during 2006 was 1,287 t value of ` 1,390 lakh
If the trawl is not catching the juveniles of seerfishes(if fishing mortality zero),
the projected yield in gillnet is 1541 t weight of 20% value of 29% (406 lakh rupees).
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• Its is often argued in tropical multispecies trawl fisheries, It is impossible to make policies for avoiding juvenile catches.
• However, by incorporating the knowledge about temporal and spatial
juvenile abundance data, it is possible to formulate policies to reduce juvenile fishery.
• From the landing data, it is possible for us to identify the peak months of juvenile exploitation.
• Trawlers - equipped with geographical positioning systems
• These policies can be implemented under responsible fisheries guidelines, so as to minimize the damages occurring to the commercial fishery due to juvenile exploitation.
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Dan Watson devised a system based on a series of escape rings for fish – which can be fitted to a fisherman's trawler net
won a prestigious international award for creating a "humane" net to make fishing more sustainable by preventing small fish
Designed by: Dan Watson Thursday 8 Nov 2 01 2
Source: www.guardian.co.uk/environment/2012/nov/08/humane-fishing-net-dyson-award
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Fishing net with emergency exits
The net is designed to make commercial fishing more sustainable by reducing the number of non-target and juvenile fish picked up by trawlers,
Watson explained to the BBC that about 20 rings are needed per net, costing a total of around $790 (£500). ` ~ 43000
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APFIC. 2005. Regional workshop on Low value and “trash fish” in the Asia-Pacific region. Asia-Pacific Fishery Commission. pp 1-6
CMFRI. 2010-11. CMFRI annual report 2010-2011: pp 41-43.DINESHBABU, A. P. AND RADHAKRISHNAN, E.V., 2009. Trawl fishery of juvenile
fishes along Mangalore- Malpe coast of Karnataka and its impact on fish stock, Asian Fish. Sci. 22: 491-500.
DINESHBABU, A. P., THOMAS, S. AND RADHAKRISHNAN, E. V., 2012. Spatio-temporal analysis and impact assessment of trawl by catch of Karnataka to suggest operation based fishery management options, Indian J. Fish., 59(2): 27-38.
FAO. 2012. The state of world Fisheries and Aquaculture. FAO, Fisheries and Aquaculture Department. Rome, pp 194-196.
KURUP, K. N., NAIR, G. K. K., ANNAM, V. P., KANT, A., BEENA, M. R., AND KHAMBADKAR, L. 1987. An appraisal of the marine fisheries of Karnataka and Goa. CMFRI Sp. Publ., 36: 1-104.
ZACHARIA, P. U., KRISHNAKUMAR, P. K., DURGEKAR, R. N., KRISHNAN, A. A., AND MUTHIAH, C. 2006. Assessment of bycatch and discards associated with bottom trawling along Karnataka coast, India. School of Industrial Fisheries, Cochin University of Science & Technology, Cochin. pp: 434-445.
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