Length at maturity of two pelagic sharks (Isurus paucus and Carcharhinus longimanus) found off northern Cuba

Abstract

Many shark species show regional structure and seasonal movements, complicating the gathering of life history data needed for fisheries management. Length-at-maturity is a relatively straightforward trait to quantify through the sampling of fisheries landings and is of great value for stock assessment. We report here on the median size at maturity for the longfin mako (Isurus paucus) and the oceanic whitetip shark (Carcharhinus longimanus), two important pelagic sharks caught by the small-scale longline fishery operating off northwest Cuba. We determined the maturity stages for 118 longfin makos and 84 oceanic whitetip sharks, based on the development of internal and external organs. A binary logistic regression was applied to estimate model coefficients necessary to describe proportion mature at size and determine L50 and the steepness of the model (φ). For the longfin mako, the parameters of logistic models for males were L50 = 215 cm TL (CI: 210–220 cm TL), φ = 4.46 (CI: 2.30–8.64) and for females L50 = 230 cm TL (CI: 220–239 cm TL), φ = 9.79 (CI: 5.15–18.62). For the oceanic whitetip shark, the parameters for males were L50 = 203 cm TL (CI: 186–220 cm TL), φ = 14.59 (CI: 6.74–31.58) and for females L50 = 199 cm TL (CI: 187–211 cm TL), φ = 7.48 (CI: 2.56–21.8). The parameters presented here contribute to stock assessment and management measures for global conservation of these transboundary, highly vulnerable species of pelagic sharks.