In order to assess the latitudinal variability in growth of the eastern
Atlantic skipjack (Katsuwonus pelamis), conventional tagging data collected by the International Commission of the Conservation of Atlantic Tunas (ICCAT) since the 1960s are reanalyzed using a modified version of the von Bertalanffy-Fabens
growth model. An analysis of the latitudinal patterns of recaptures showed
that the lowest mixing rate between northern and southern regions was
evidenced at 10° N Latitude. Since it is theoretically admitted that
growth parameters L∞ and K are negatively correlated, we
substituted L∞ into the growth equation model by a simple
bioenergetic function of K fitted from existing studies on skipjack growth
parameters. The likelihood for the meta-analysis of growth is combined with
the likelihoods from the two regional tagging data with the aim of
estimating simultaneously K in both areas and to transfer adequately
uncertainties associated with the different data sets. From this study, it
was showed that fish inhabiting waters south of 10° N latitude can be
expected to grow generally larger but at slower rate than in the North
(L∞ = 112.34 cm vs. 89.38 cm, and K = 0.14 vs. 0.38, respectively).
Our results are consistent with the range of growth estimates obtained in
the Atlantic Ocean and in different parts of the World's oceans. In
contrast, the estimates of L∞ and K done in the Senegalese region
in the 1980s within the framework of the Skipjack Year Program, and
traditionally applied by ICCAT, are not supported by the present study. The
findings concerning the phenotypic plasticity exhibited by growth of
skipjack among latitudinal regions suggest potential differences in fish
population productivity and consequently imply that non-conventional stock
assessment methods such as catch-at size/growth transition matrix per
region could be used to assess the responses of skipjack to exploitation.