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Estimation of age and growth and mortality parameters of the sea cucumber Isostichopus fuscus (Ludwig, 1875) and implications for the management of its fishery in the Galapagos Marine Reserve

Abstract:

The fishery of the sea cucumber Isostichopus fuscus was the most important one in the early 2000s in the Galapagos Marine Reserve. Its overexploitation leads to its total closure from 2016 to 2021. At the end of this period, if the co-management system of the Galapagos Marine Reserve decides to open this fishery, a total allowed catch must be established using the methodology of Wolff, Schuhbauer, and Castrejón (2012). The objective of this paper is to evaluate this methodology and improve the total allowed catch calculation. We replicated Wolff et al.‘s methodology that uses the Cadima equation of Maximum Sustainable Yield (in Troadec, 1977). We determined the age and growth parameters of I. fuscus to estimate total mortality and improved the calculation of the area of fishing and habitat of this species in Galapagos to estimate its abundance. We found inconsistences in Wolff et al.‘s estimations of mortality and abundance and we recommend that the Maximum Sustainable Yield be used not as the total allowed catch, but as a limit reference point for this fishery. We propose, instead, to use a dynamic abundance model that is capable of estimating a variety of reference points, including the fishing mortality for optimal fishing that is recommended to use to establish a total allowed catch. In addition, for the first time, the age and growth parameters of I. fuscus for Galapagos and the eastern-central region of the Pacific Ocean are determined (L∞ = 42.5 cm; K = 0.21/year).