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 - [email protected]
Introduction
The 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 methods
From 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. 1 – Technical characteristics of standard trammel net, “tramaglino” (small mesh size
trammel net) and gillnet used by the artisanal fleet of Livorno (PA = Polyammide)
"Tramaglino"
Standard trammel net
Inner panel
Stretched
Heigth Lenght N. meshes
mesh size
(m)
(m)
width
(mm)
3.3
90
3000
60-70
Outer panel
Stretched
Heigth Lenght N. meshes
mesh size
(m)
(m)
width
(mm)
1.8
90
500
320-360
Netting yarn
(denier)
Headline
Total
Leadline
Hanging number Diameter
(g/m)
Material
of floats
ratio
(mm)
210/6
0.45
Netting yarn
(denier)
Hanging
ratio
210/12
0.53
55
4
PA
Inner panel
Stretched
Heigth Lenght N. meshes
mesh size
(m)
(m)
width
(mm)
2.8
65
4000
40-45
Outer panel
120
Heigth Lenght N. meshes
(m)
(m)
width
1.4
65
Netting yarn
(denier)
Headline
Total
Leadline
Hanging number Diameter
(g/m)
Material
of floats
ratio
(mm)
210/8
0.36
Stretched
mesh size
(mm)
Netting yarn
(denier)
Hanging
ratio
260-300
210/12
0.58
400
65
5
PA
120
Gillnet
Panel
Headline
Stretched
Heigth Lenght N. meshes
mesh size
(m)
(m)
width
(mm)
4.1
45
2000
80-85
Diameter of the
filament
(mm)
0.25
Total
Leadline
Hanging number Diameter
(g/m)
Material
of floats
ratio
(mm)
0.27
33
4
PA
120
Results and discussion
A 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 1.54.0 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 smallsized species, reflecting the composition of the epibenthic communities inhabiting the exploited fishing grounds.
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. 2 – Faunistic list of the species caught with the three different gears (G = Gillnet; STN = Standard trammel net;
SSTN = “Tramaglino”).
STN
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
SSTN
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
G TAXA
FISHES
Psetta 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
MOLLUSCS
Acanthocardia spp.
STN
SSTN
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
G
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
TAXA
MOLLUSCS
Acanthocardia 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
CRUSTACEANS
Carcinus 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)
STN
*
*
*
*
*
SSTN
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
SSTN
G
*
ECHINODERMS
Astropecten 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)
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
Tab. 3 – The most important species in biomass, according to the different
fractions of the catch, by gear.
*
*
*
*
*
STN
TAXA
CNIDARIANS
Alcyonium palmatum Pallas, 1766
*
*
*
*
*
*
*
G
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
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
Solea vulgaris
Trachurus mediterraneus
Hexaplex trunculus
Diplodus annularis
Mullus barbatus
Mullus surmuletus
Solea vulgaris
Mugil cephalus
Raja asterias
Pagurus alatus
Pagurus excavatus
Liocarcinus vernalis
Dardanus arrosor
Marthasterias glacialis
Holoturia tubulosa
Dardanus arrosor
Aporrhais pespelecani
Medorippe lanata
*
*
*
*
*
*
*
BY CATCH
TAXA
FISHES
Alosa 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)
DISCARD OF
COMMERCIAL
SPECIES
DISCARD OF
NONCOMMERCIAL
SPECIES
*
References
1. 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.