Resumen

TORREJON-MAGALLANES, Josymar et al. Estimation and temporal variability in size at gonad maturity of Chub Mackerel (Scomber japonicus peruanus) in the Peruvian littoral. Rev. peru biol. [online]. 2017, vol.24, n.4, pp.391-400. ISSN 1727-9933.  http://dx.doi.org/10.15381/rpb.v24i4.13741.

The values of size-at-gonad maturity (L₅₀) of chub mackerel (Scomber japonicus peruanus) were estimated for the years 1994 - 2017 in the Peruvian littoral. The analysis was performed for the period November - March where the highest reproductive activity occurs. The proportion of mature females was ftted using a logistic binary model, through generalized linear mixed models (MLGM), which assumes random effects associated with the periods. The GLMM, with fixed effects estimated a L₅₀ of 24.8 cm of fork length (FL) (24.69 cm - 24.9 cm), while with changes between periods, with random effects, L₅₀ ranged between 20.4 cm and 27.0 cm FL. It was observed that an increase in temperature caused the decrease of the L₅₀ in the years 1997 - 1999 and 2015 - 2016, which coincides with El Niño events. A positive correlation was found between the L₅₀ and spawning biomass, so changes in L₅₀ may be a density-dependent effect. There was no trend in the L₅₀ series, so there would be no effect of the fishing mortality (F) on the L₅₀. However, we think that the decrease in the L₅₀ in relation to a low population density and mainly an increase in F should be given as a long-term effect and not in isolated events as our results showed.

Palabras clave : Chub mackerel; size-at-gonad maturity; temporary changes; generalized linear mixed models; random effects.

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