Ariz-Tellería, F.J. (Francisco Javier)

Delgado-de-Molina-Acevedo, A. (Alicia)

Santana-Fernández, J.C. (José Carlos)

Sotillo, B.

This document presents several results obtained in the ABYSS project whose main aim is to
study the possible relationship between the catch rate of juvenile bigeye and the depth of the
purse seine net in order to implement the most suitable management measures using the results
obtained. The project was undertaken between June 2008 and April 2010. Temperature and
depth loggers were deployed in the nets of 11 tuna purse seiners operating under the Spanish
flag in the Atlantic, Indian and Pacific Oceans. 1648 sets were analyzed, which provided 61933
tons of tropical tuna: yellowfin (Thunnus albacares, Bonnaterre, 1788), skipjack (Katsuwonus
pelamis, Linnaeus, 1758) and bigeye (Thunnus obesus, Lowe, 1839). The depth of the nets used
ranged from 220 to 309 metres and the fishing depths reached varied between 65 and 226
metres. This means that the percentage of mean depth vis-à-vis net size was 56.73% (range
between 20% and 83%). The speed of the falling net varied between 0.1 and 0.2 metres per
second. In addition to the analysis of the catches estimated by the skipper, the study was made
using specific composition data of the catch corrected by multi-species sampling. On this
assumption, the analysis was reduced to 400 sets with 17230 tons of catch. No differential
bathymetric distribution was observed between the three species in any of the oceans and in
either of the two analyses undertaken (with and without specific correction).This document presents several results obtained in the ABYSS project whose main aim is to
study the possible relationship between the catch rate of juvenile bigeye and the depth of the
purse seine net in order to implement the most suitable management measures using the results
obtained. The project was undertaken between June 2008 and April 2010. Temperature and
depth loggers were deployed in the nets of 11 tuna purse seiners operating under the Spanish
flag in the Atlantic, Indian and Pacific Oceans. 1648 sets were analyzed, which provided 61933
tons of tropical tuna: yellowfin (Thunnus albacares, Bonnaterre, 1788), skipjack (Katsuwonus
pelamis, Linnaeus, 1758) and bigeye (Thunnus obesus, Lowe, 1839). The depth of the nets used
ranged from 220 to 309 metres and the fishing depths reached varied between 65 and 226
metres. This means that the percentage of mean depth vis-à-vis net size was 56.73% (range
between 20% and 83%). The speed of the falling net varied between 0.1 and 0.2 metres per
second. In addition to the analysis of the catches estimated by the skipper, the study was made
using specific composition data of the catch corrected by multi-species sampling. On this
assumption, the analysis was reduced to 400 sets with 17230 tons of catch. No differential
bathymetric distribution was observed between the three species in any of the oceans and in
either of the two analyses undertaken (with and without specific correction).

Repositorio Institucional Digital del IEO

Analysis of the catch rate of juvenile bigeye (Thunnus obesus, Lowe 1839) depending on the depth of the purse seine net used by the tropical fleet.

This document presents several results obtained in the ABYSS project whose main aim is to
study the possible relationship between the catch rate of juvenile bigeye and the depth of the
purse seine net in order to implement the most suitable management measures using the results
obtained. The project was undertaken between June 2008 and April 2010. Temperature and
depth loggers were deployed in the nets of 11 tuna purse seiners operating under the Spanish
flag in the Atlantic, Indian and Pacific Oceans. 1648 sets were analyzed, which provided 61933
tons of tropical tuna: yellowfin (Thunnus albacares, Bonnaterre, 1788), skipjack (Katsuwonus
pelamis, Linnaeus, 1758) and bigeye (Thunnus obesus, Lowe, 1839). The depth of the nets used
ranged from 220 to 309 metres and the fishing depths reached varied between 65 and 226
metres. This means that the percentage of mean depth vis-à-vis net size was 56.73% (range
between 20% and 83%). The speed of the falling net varied between 0.1 and 0.2 metres per
second. In addition to the analysis of the catches estimated by the skipper, the study was made
using specific composition data of the catch corrected by multi-species sampling. On this
assumption, the analysis was reduced to 400 sets with 17230 tons of catch. No differential
bathymetric distribution was observed between the three species in any of the oceans and in
either of the two analyses undertaken (with and without specific correction).This document presents several results obtained in the ABYSS project whose main aim is to
study the possible relationship between the catch rate of juvenile bigeye and the depth of the
purse seine net in order to implement the most suitable management measures using the results
obtained. The project was undertaken between June 2008 and April 2010. Temperature and
depth loggers were deployed in the nets of 11 tuna purse seiners operating under the Spanish
flag in the Atlantic, Indian and Pacific Oceans. 1648 sets were analyzed, which provided 61933
tons of tropical tuna: yellowfin (Thunnus albacares, Bonnaterre, 1788), skipjack (Katsuwonus
pelamis, Linnaeus, 1758) and bigeye (Thunnus obesus, Lowe, 1839). The depth of the nets used
ranged from 220 to 309 metres and the fishing depths reached varied between 65 and 226
metres. This means that the percentage of mean depth vis-à-vis net size was 56.73% (range
between 20% and 83%). The speed of the falling net varied between 0.1 and 0.2 metres per
second. In addition to the analysis of the catches estimated by the skipper, the study was made
using specific composition data of the catch corrected by multi-species sampling. On this
assumption, the analysis was reduced to 400 sets with 17230 tons of catch. No differential
bathymetric distribution was observed between the three species in any of the oceans and in
either of the two analyses undertaken (with and without specific correction)

Analysis of the catch rate of juvenile bigeye (Thunnus obesus, Lowe 1839) depending on the depth of the purse seine net used by the tropical fleet.

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