GROWTH OF BIGEYE TUNA (THUNNUS OBESUS) IN THE EASTERN ATLANTIC OCEAN FROM TAGGING-RECAPTURE DATA AND OTOLITH READINGS

Growth of bigeye tuna (Thunnus obesus) in the eastern Atlantic Ocean is studied from (1) 625 bigeye tagged and recaptured with a fork length (FL) range 37-124 cm, (2) otoliths collected on 108 bigeye in Dakar from which 83 were use to validate the growth ring deposit by oxytetracyclin antibiotic injection, and (3) otoliths from 147 bigeye collected in Abidjan. For otoliths, the sizes of Dakar bigeye range from 37 cm to 112 cm FL (almost all juveniles), those from Abidjan from 29 cm to 190 cm (juveniles and adults). Growth curves obtained from the two different sets of data are similar so all data are combined to give a single growth curve for bigeye with K=0.180 yr , L∞ = 217.3 cm and t0 = -0.709 year. The interest of this approach is the confirmation of the daily rate for ring deposit on otoliths and the use of both tagging and otoliths’ reading to estimate growth parameters.