Catch composition of set nets used by the small-scale fishery of Livorno (eastern Ligurian Sea)

M. Sbrana(1), B. Francesconi(2), I. Rossetti(2), P. Sartor(1), S. De Ranieri(1)

(1) Centro Interuniversitario di Biologia Marina ed Ecologia Applicata - Viale N. Sauro, 4 - 57128 - Livorno, Italy(2) Aplysia p.s.c.r.l.- Via delle Viole, 1 - 57124 - Livorno, Italy - aplysia1@libero.it

IntroductionThe small-scale fishery is an important sector of the Livorno fleet; this activity is carried out with different types of set nets, used in seasonal succession according to the main target species and the availability of resources (1, 2). This paper describes the catch composition of these gears, paying particular attention on discards, an important information for an ecological-based management (3). This work was performed in the framework of a project funded by the Italian Ministero delle Politiche Agricole e Forestali (2). Material and methodsFrom January 1999 to December 2000, 49 observations onboard of commercial vessels of the artisanal fleet of Livorno were carried out, considering three types of set nets: standard trammel nets (60-70 mm stretched mesh size of inner panel), trammel nets of smaller mesh sizes (40-45 mm, stretched), locally called “tramaglino” and gillnets (80-85 mm, stretched) (Tab. 1). The composition of the catch, discards included, was studied without interference in the usual fishing procedures of the crew, especially concerning the sorting operations. For each haul the catch was divided in: target species, retained by-catch, discard of commercial and non-commercial species (3). Discard was determined to the lowest taxonomic level; total weight was recorded for each species caught. Catch per unit of effort (cpue) was estimated, standardising the collected data as kg/5000 m of net per hour of hauling.

Tab. 2 – Faunistic list of the species caught with the three different gears (G = Gillnet; STN = Standard trammel net; SSTN = “Tramaglino”).

Results and discussionA total of 68 species were caught with gillnets (45 fishes, 11 molluscs, 10 crustaceans and 2 echinoderms), 95 with standard trammel nets (59 fishes, 13 molluscs, 19 crustaceans and 4 echinoderms), and 111 with “tramaglino” (69 fishes, 10 molluscs, 21 crustaceans, 1 cnidarian and 10 echinoderms) (Tab. 2). In terms of weight, the majority of the total catch was composed of commercial species (target species + retained by catch), especially for trammel nets (69 to 84%) and “tramaglino” (91 to 94%), while this percentage was lower for gillnets (51 to 92%). For the latter, noticeable amounts of discards were recorded in summer and autumn (5.0 and 3.1 kg/5000m/h, representing 49 and 34% of the total catch, respectively) (Fig. 1).Table 3 shows the main species per catch category and gear studied. The target species of trammel nets (Sepia officinalis, Solea vulgaris and Lithognathus mormyrus) accounted for 19-42% of the total catch, those of “tramaglino” (Mullus barbatus, Mullus surmuletus and S. officinalis) from 35 to 45% and that of gillnets (S. vulgaris) from 22 to 37%. Retained by-catch also had an important contribution, with generally higher cpues than those for the target species (from 2.1 to 5.2 kg/5000m/h compared to 1.5-4.0 kg/5000m/h of the target species, Fig. 1). Important species of this fraction, both in terms of weight and commercial value, were Raja asterias, Umbrina cirrosa, Pagellus erythrinus, Octopus vulgaris and Squilla mantis. Discards, in terms of weight, were mostly composed of commercial species (77 to 97% of total discards) and dominated by fishes, often represented by damaged and unmarketable specimens. Non-commercial species discarded were mostly represented by small-sized species, reflecting the composition of the epibenthic communities inhabiting the exploited fishing grounds.

Tab. 1 – Technical characteristics of standard trammel net, “tramaglino” (small mesh size trammel net) and gillnet used by the artisanal fleet of Livorno (PA = Polyammide)

References1. Sbrana M., Reale B., Rossetti I. and Sartor P., 2002. Fishing grounds of the target species exploited by the artisanal fleet of Livorno (eastern Ligurian sea). Biol. Mar. Medit., 9(2): 804-807.2. Fabi G. and Sbrana M., 2002. Attrezzi della piccola pesca utilizzati in funzione della successione stagionale e dell’eco-etologia delle specie ittiche in due aree costiere (Tirreno settentrionale e Medio Adriatico). Ministero delle Politiche Agricole e Forestali, Final report: 159 pp. 3. Alverson D.L., Freeberg M.H., Pope J.G. and Murawski S.A., 1994. A global assessment of fisheries bycatch and discards. FAO Fish. Tech. Pap., 339: 233 pp.

Fig. 1 – Seasonal catches per unit of effort (mean cpue) of set nets used by the artisanal fleet of Livorno. T = Target species; R = Retained by catch; CD = Discard of commercial species; NCD = Discard of non-commercial species.

Tab. 3 – The most important species in biomass, according to the different fractions of the catch, by gear.

4.1 45 2000 80-85 0.25 0.27 33 4 PA 120

Headline

Diameter (mm)

MaterialHeigth

(m)Lenght

(m)N. meshes

width

Panel

Hanging ratio

Stretched mesh size

(mm)

Diameter of the filament

(mm)

Leadline (g/m)

Total number of floats

Gillnet

3.3 90 3000 60-70 210/6 0.45 55 4 PA 120

1.8 90 500 320-360 210/12 0.53

Inner panelTotal

number of floats

HeadlineLeadline

(g/m)Heigth

(m)Lenght

(m)N. meshes

widthHanging

ratio

N. meshes width

Hanging ratio

Stretched mesh size

(mm)

Stretched mesh size

(mm)

Standard trammel net

Netting yarn (denier)

Netting yarn (denier)

Diameter (mm)

Material

Outer panel

Heigth (m)

Lenght (m)

2.8 65 4000 40-45 210/8 0.36 65 5 PA 120

1.4 65 400 260-300 210/12 0.58

Inner panelTotal

number of floats

Headline

Leadline (g/m)

Heigth (m)

Lenght (m)

N. meshes width

Hanging ratio

Diameter (mm)

Netting yarn (denier)

Netting yarn (denier)

Material

Outer panel

Heigth (m)

Lenght (m)

N. meshes width

Hanging ratio

Stretched mesh size

(mm)

Stretched mesh size

(mm)

"Tramaglino"

SPRINGSUMMERAUTUMNWINTER

STANDARD TRAMMEL NET

0

2

4

6

"TRAMAGLINO"

0

2

4

6

GILLNET

0

2

4

6

T R CD NCD

TAXA STN SSTN GFISHESAlosa fallax (Lacépède, 1803) *Anthias anthias (Linnaeus, 1758) *Apogon imberbis (Linnaeus, 1758) *Arnoglossus laterna (Walbaum, 1792) * *Aspitrigla cuculus (Linnaeus, 1758) *Aspitrigla obscura (Linnaeus, 1764) * *Balistes carolinensis Gmelin, 1789 * *Boops boops (Linnaeus, 1758) * *Blennius ocellaris Linnaeus, 1758 *Bothus p. podas (Delaroche, 1809) * * *Chromis chromis (Linnaeus, 1758) *Citharus linguatula (Linnaeus, 1758) * *Conger conger (Linnaeus, 1758) * *Coris julis (Linnaeus, 1758) *Dasyatis pastinaca (Linnaeus, 1758) *Dentex dentex (Linnaeus, 1758) * *Dicentrarchus labrax (Linnaeus, 1758) * *Diplodus annularis (Linnaeus, 1758) * * *Diplodus puntazzo (Cetti, 1777) * * *Diplodus s. sargus (Linnaeus, 1758) * * *Diplodus vulgaris (Geoffroy Saint-Hilaire, 1817) * * *Engraulis encrasicolus (Linnaeus, 1758) * * *Eutrigla gurnardus (Linnaeus, 1758) *Hippocampus hippocampus (Linnaeus, 1758) * *Hippocampus ramulosus Leach, 1814 *Labrus bimaculatus Linnaeus, 1758 *Labrus merula Linnaeus, 1758 *Labrus viridis Linnaeus, 1758 *Lepidorhombus bosci (Risso, 1810) *Lichia amia (Linnaeus, 1758) *Lithognathus mormyrus (Linnaeus, 1758) * *Liza aurata (Risso, 1810) * *Merluccius merluccius (Linnaeus, 1758) * * *Microchirus variegatus (Donovan, 1808) * *Micromesistius potassou (Risso, 1826) *Mugil cephalus Linnaeus, 1758 * *Mugilidae unid. *Mullus barbatus (Linnaeus, 1758) * * *Mullus surmuletus (Linnaeus, 1758) * * *Myliobatis aquila (Linnaeus, 1758) *Oblada melanura (Linnaeus, 1758) *Pagellus acarne (Risso, 1826) * * *Pagellus erythrinus (Linnaeus, 1758) * * *Pagrus pagrus (Linnaeus, 1758) * *Phycis phycis (Linnaeus, 1758) *Pomatomus saltator (Linnaeus, 1758) *

TAXA STN SSTN GFISHESPsetta maxima (Linnaeus, 1758) *Raja asterias Delaroche, 1809 * *Raja clavata Linnaeus, 1758 *Raja miraletus Linnaeus, 1758 * *Sarda sarda (Bloch, 1793) *Sardina pilchardus (Walbaum, 1792) * *Sardinella aurita Valenciennes, 1847 * *Sarpa salpa (Linnaeus, 1758) * * *Sciaena umbra Linnaeus, 1758 * *Scomber scombrus Linnaeus, 1758 * *Scophthalmus rhombus (Linnaeus, 1758) * * *Scorpaena notata Rafinesque, 1810 * * *Scorpaena porcus Linnaeus, 1758 * * *Scorpaena scrofa Linnaeus, 1758 * * *Scyliorhinus canicula (Linnaeus, 1758) *Seriola dumerili (Risso, 1810) * * *Serranus cabrilla (Linnaeus, 1758) * * *Serranus hepatus (Linnaeus, 1758) * *Serranus scriba (Linnaeus, 1758) * *Solea lascaris (Risso, 1810) * * *Solea vulgaris Quensel, 1806 * * *Sparus auratus Linnaeus, 1758 * *Sphyrena sphyrena (Linnaeus, 1758) * * *Spicara flexuosa Rafinesque, 1810 * * *Spicara maena (Linnaeus, 1758) *Spicara smaris (Linnaeus, 1758) *Spondyliosoma cantharus (Linnaeus, 1758) * * *Stromateus fiatola Linnaeus, 1758 *Symphodus mediterraneus (Linnaeus, 1758) *Symphodus roissali (Risso, 1810) *Symphodus tinca (Linnaeus, 1758) * *Synodus saurus (Linnaeus, 1758) *Torpedo marmorata Risso, 1758 *Torpedo torpedo (Linnaeus, 1758) * *Trachinus araneus Cuvier, 1829 * *Trachurus mediterraneus (Steindachner, 1868) * *Trachurus trachurus (Linnaeus, 1758) * * *Trachynotus ovatus (Linnaeus, 1758) *Trigla lucerna Linnaeus, 1758 * * *Trigloporus lastoviza (Brunnich, 1768) * * *Trisopterus m. capelanus (Lecépède, 1800) * *Umbrina cirrosa (Linnaeus, 1758) * *Uranoscopus scaber Linnaeus, 1758 * * *Zeus faber Linnaeus, 1758 * *MOLLUSCSAcanthocardia spp. * * *

TAXA STN SSTN GMOLLUSCSAcanthocardia tuberculata (Linnaues, 1758) *Aporrhais pespelecani (Linnaeus, 1758) * *Bolinus brandaris (Linnaeus, 1758) * * *Bolma rugosa (Linnaeus, 1767) * *Buccinulum corneum (Linnaeus, 1758) *Cerithium vulgatum Bruguiere, 1792 *Hexaplex trunculus (Linnaeus, 1758) * * *Galeodea echinophora (Linnaeus, 1758) * *Loligo vulgaris Lamarck, 1798 *Mytilus galloprovincialis Lamarck, 1819 *Nassarius mutabilis (Linnaeus, 1758) * *Natica stercusmuscarum (Gmelin, 1791) *Octopus defilippi Verany, 1851 *Octopus vulgaris Cuvier, 1797 * * *Sepia officinalis Linnaeus, 1758 * * *Solecurtus strigilatus (Linnaeus, 1758) *Solen marginatus Pulteney, 1799 *Turritella communis Risso, 1826 * *

CRUSTACEANSCarcinus aestuarii Nardo, 1847 *Corystes cassivelaunus (Pennant, 1777) *Dardanus arrosor (Herbst, 1796) * * *Diogenes pugilator (Roux, 1829) * *Erynome aspera (Pennant, 1777) *Galathea strigosa (Linnaeus, 1761) *Goneplax rhomboides (Linnaeus, 1758) * * *Ilia nucleus (Linnaeus, 1758) * *Inachus comunissimus Rizza, 1839 * *Liocarcinus vernalis (Risso, 1827) * * *Macropipus tuberculatus (Roux, 1830) *Macropodia rostrata (Linnaeus, 1761) *Maja crispata (Risso, 1827) * *Maja squinado (Herbst, 1788) *Medorippe lanata (Linnaeus, 1767) * * *Munida intermedia A. Milne Edwards & Bouvier, 1899 *Pagurus alatus Fabricius, 1775 * * *Pagurus cuanensis Bell, 1845 * *Pagurus excavatus (Herbst, 1791) * * *Pagurus prideaux Leach, 1815 * *Palinurus elephas (Fabricius, 1787) * *Parthenope macrochelos (Herbst, 1790) * * *Penaeus keraturus (Forsskal, 1775) *Pisa armata (Latreille, 1803) * *Scyllarus arctus (Linnaeus, 1758) *Squilla mantis (Linnaeus, 1758) * * *

TAXA STN SSTN GCNIDARIANSAlcyonium palmatum Pallas, 1766 *

ECHINODERMSAstropecten bispinosus (Otto, 1823) * * *Astropecten i. pentacanthus (Delle Chiaje, 1825) * *Echinaster sepositus (Retzius, 1783) *Holothuria tubulosa Gmelin, 1788 * *Marthasterias glacialis (Linnaeus, 1758) *Holoturoidaea unid. *Paracentrotus lividus (Lamarck, 1816) * *Spatangus purpureus (O. F. Muller, 1776) *Sphaerechinus granularis (Lamarck, 1816) * *Stichopus regalis (Cuvier, 1817) *Stylocidaris affinis (Philippi, 1845) *

STANDARD TRAMMEL NET

“TRAMAGLINO” GILLNET

TARGET SPECIES

Lithognathus mormyrus Solea vulgaris

Sepia officinalis

Mullus surmuletus Mullus barbatus Sepia officinalis

Solea vulgaris

RETAINED BY CATCH

Raja asterias Squilla mantis

Umbrina cirrosa

Octopus vulgaris Diplodus annularis Pagellus erythrinus

Raja asterias Trigla lucerna Squilla mantis

DISCARD OF COMMERCIAL

SPECIES

Solea vulgaris Trachurus mediterraneus

Hexaplex trunculus

Diplodus annularis Mullus barbatus

Mullus surmuletus

Solea vulgaris Mugil cephalus Raja asterias

BY

CA

TC

H

DISCARD OF NON-

COMMERCIAL SPECIES

Pagurus alatus Pagurus excavatus

Liocarcinus vernalis

Dardanus arrosor Marthasterias glacialis

Holoturia tubulosa

Dardanus arrosor Aporrhais pespelecani

Medorippe lanata

37th

CIE

SM

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arce

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a, 7

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Jun

e 20

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