Dynamics of ENSO events in the Indian ocean: To what extent would recruitment and catchability of tropical tunas be affected ?
Le Blanc, J.-L.
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In this paper, the authors explore functional relationships between environmental fluctuations and some key parameters used in stock assessment such as recruitment and catchability. Yellowfin tuna (Thunnus albacares) is taken as an example but the concepts developed in this study could be widened to other tropical tunas. The French purse seine data-set is used to estimate a recruitment index from adjusted CPUE of age 0 fishes, and the effect of the environment on catchability is assessed using CPUE of age 3 fishes which provide the bulk of adult catches. The ACE algorithm is used to describe a non-linear relationship between the recruitment and the turbulence (wind speed cubed). There is a detrimental effect of an increasing turbulence on recruitment. The optimal transformation of this simple regression explains more than 25 % of the variance of recruitment. The analogy, with the fundamental triad and the optimal environmental window that explain the variability of small pelagic fish p.....