Acronym Albacore
Category
Fisheries
Title Gruppo di studio ed elementi di base per la gestione dei grandi pelagici - Study group and basic elements for the management of large pelagics Programme National Programme
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source National Coordinator Franco Andaloro Coordinator email franco.andaloro@isprambiente.it
Coordinator institution
ISPRA - Italian National Institute for Environmental Protection and Research (Italy)
Institutions involved
NA
Start year 2004 End year 2006 Funding (€) € NA Website NA Summary The albacore (Thunnus alalunga, Bonnaterre,1788) is an epi-mesopelagic fish belonging, together with the bluefin tuna (Thunnus thynnus) and the swordfish (Xiphias gladius), to the species of direct concern to ICCAT. The albacore fishery represents one of the most widespread alieutic activities in the Tyrrhenian and Ionian sea, involving about 500 fishing vessels. The objective of the present study, conducted in a three year period (2004-2006), in the ambit of the "Study group on large pelagics", was to implement the knowledge on the fishing activity and the population consistency of the albacore in the southern Tyrrhenian, to study the feeding habits of this species and to improve the knowledge on the diet of the swordfish and bluefin tuna, in order to identify possible overlap mechanisms within the pelagic ecosystem. The census of the fishing fleet conducted in the northern Sicilian area, between Messina and Cefalù has detected 13 fishing harbours (89 fishing vessels). The survey has highlighted a seasonal fishing activity conducted between April and November by means of longlines and several types of fishing nets. The catch data survey was carried out in Lipari which, in the area, has the larger fleet (36 vessels). The results showed that CPUEs were highly variable both with gear type and season; long-lines had, mostly during autumn, a by-catch of swordfish juveniles while the other fishing gears showed a by-catch of tuna during spring and summer. The study of the albacore feeding habits was carried out on 189 specimens (480-910 mm FL) between, caught by professional fishing vessels or by experimental fishing surveys. A total of 3698 prey items were identified. The data analysis highlighted the dominance in terms of weight of teleosts (%P = 73%), while cephalopods were the most important prey category according to percentage abundance (68%). Crustaceans, thaliaceans (salpidae) and coelenterates (siphonophora) were also recorded. The family Paralepididae was the most represented among teleosts. The multivariate statistical analyses (MDS) did not show any seasonal and size-related significant variability of its diet. The Levins index was equal to 0.10 according to biomass data, indicating a limited trophic niche width and confirming the albacore as a specialist predator of teleostean Paralepidids. In order to study the trophic overlap in the study area, the diet of the swordfish was studied on a sample of 101 individuals (645-2070 mm LFJL). The results, in accordance with literature data, confirmed that although teleosts were the predominant group in terms of biomass, cephalopods were the most frequent category in the stomach contents. Moreover, data stressed the relevance of Todarodes sagittatus in its diet, followed by Illex coindettii. The MDS did not underline differences in the diet of specimens belonging to different size classes. Low values of the Levins index indicated a specialist diet, dominated by cephalopods (Theutoidea) and teleosts (Perciformes). The Schoener index, calculated on a total of 49 prey categories present in the diet of X. gladius e T. alalunga, indicated no trophic competition between these two species in the Tyrrhenian area. The study of the diet of bluefin tuna juveniles was conducted on 91 specimens (180- 480 mm FL), caught in the southern Tyrrhenian. The results showed a diet based on teleosts, followed by cephalopods and crustaceans, as also reported in other studies in the area. Twenty-one albacore stomachs coming from the Ionian sea, nine bluefin tuna adults caught with longlines in the Ionian sea and ten bluefin tuna adults caught in the Tyrrhenian were provided by the other operational units and then analysed. The results were of limited significance due to the sample meagreness.
Goals:
(1) To implement the knowledge on the fishing activity and the population consistency of the albacore in the southern Tyrrhenian; (2) To study the feeding habits of this species; (3) To improve the knowledge on the diet of the swordfish and bluefin tuna, in order to identify possible overlap mechanisms within the pelagic ecosystem.
Keywords
Fish;
Fish habitat;
Catch;
Tuna;
Environmental impact;
Passive gears;
Longline fishing;
Diets;
Bycatch;
Marine Region
48
South Tyrrhenian Sea (GSA 10)
1
Marine Region Map
