Demographic analysis of the shortfin mako shark, Isurus oxyrinchus, in the Northwest Pacific using a two-sex stage-based matrix model

Abstract

Most demographic models are single sex, and assume both sexes have the same vital rates. However, many species, including the shortfin mako shark, are sexually dimorphic in vital rates, which suggests the need for two-sex models. In this study, a two-sex stage-structured matrix model was constructed to estimate shortfin mako shark demography and population dynamics. Monte Carlo simulations were used to evaluate the impact of uncertainties on the estimate of population growth rate. The number of shortfin mako sharks is found to be dropping under current conditions, but will stabilize if size-limit management is implemented. The simulations indicated that population growth rate estimates are mainly influenced by the uncertainty related to survival rate and fecundity. The effects of uncertainty regarding the age at maturity and longevity were found to be relatively minor. Future research should focus on obtaining estimates of natural mortality and reproductive traits for this species to improve the accuracy of demographic estimates.

Insights into the life history and ecology of a large shortfin mako shark Isurus oxyrinchus captured in southern California

“…oxyrinchus females (280 cm total length, L T ; Joung & Hsu, ) is often difficult because these specimens are typically less prevalent, harder to capture, unable to be held in captivity and, unlike the great white shark Carcharodon carcharias (L. 1758), they do not form known aggregations. Despite the importance of large females to the reproductive potential of the population (Tsai et al , ), very little basic information about mature female I . oxyrinchus is available, particularly with regard to morphometrics, reproductive biology, foraging ecology, contaminant loads and age and growth.…”

Impact of biology knowledge on the conservation and management of large pelagic sharks

“…This Leslie matrix model was applied only to females. To evaluate sex-dependent effects on the population growth rate, a stage- and sex-based matrix population model for the shortfin mako shark was developed and explored using a stochastic simulation with the uncertainty of life history parameters 49 . The effect of the mating system on the population growth rate of the shortfin mako shark was also evaluated using a two-sex stage-structured matrix population model with different mating systems 50 .…”

Development and testing of a Bayesian population model for the bigeye thresher shark, Alopias superciliosus, in an area subset of the western North Pacific

“…In this assessment, a Bayesian analysis for the bigeye thresher is presented based on best avail- On the other hand, conventional stock assessment methods, such as surplus production and stock-recruitment models, have seldom been applied to examine shark population dynamics. Instead, per-recruit models and demographic methods are often employed to assess the stock status of elasmobranchs because sufficient catch, effort and abundance index data are often not available (Hisano, Connolly, & Robbins, 2011;Tribuzio & Kruse, 2011;Tsai, Liu, Punt, & Sun, 2015;Tsai, Sun, Punt, & Liu, 2014). The greatest advantage of demographic methods is the simplicity of their data requirements.…”