Study on the sampling of catch species composition and size distribution in the purse seine fisheries

Obtaining accurate estimates of species and size composition of tuna catches is essential in order to provide accurate scientific advices for management of tuna resources. Experience has shown that this requires dedicated sampling programs, particularly when species are difficult to identify except by a
trained observers (Fonteneau 1975, Báez et al. 2019). For the Atlantic and Indian ocean, species composition and size distribution of tuna targeted species (skipjack, yellowfin and bigeye) are estimated from the T3 methodology, developed by IRD and IEO (Pallarés and Hallier 1997, Pallarés and Petit
1998). The efficiency of this data processing depends on the quality of the sampling data (Duparc et al. 2018, Herrera and Baez 2019). Recent results (Duparc et al. 2018, 2019a, 2019b) pointed out the importance of the sampling at landing for the assessment of the species composition that lead to the final estimation of PS catches for several CPCs (EU-SP, EU-FR, EU-IT, SYC).