An exploratory analysis to identify reproductive strategies of billfishes

Abstract

This contribution is aimed to the identification of reproductive patterns of billfishes, which is in turn a key issue supporting management and conservation policies. Information reported in the literature on features of reproductive processes of billfishes was examined with a Principal Components Analysis (PCA) to identify groups of species with similar reproductive strategies. PCA was applied based in a correlation matrix and the significances (p<0.05) of the factors and loadings of the variables were used as criteria for the identification of reproductive patterns. In general, four groups were found. The first group consists of Tetrapturus albidus and T. audax, which are characterised by rapid growth, an early age at first maturity with respect to maximum age (T/Tmax) and high values of reproductive variables (e.g., Spawning Duration (Sd), Spawning Frequency (Sf), Annual Fecundity (AF) and Relative Fecundity (RF). A second group consists of T. belone, T. georgii and T. pfluegeri, which present rapid growth, high Tm/Tmax ratios and Batch Fecundity (BF) values and low Sd values. Another group consists of the genera Makaira and Xiphias, which present low Lm/Lmax ratios and high values for AF, RF, Sf and BF. The last group consists of species of the genus Istiophorus, which present the lowest AF values and the highest RF and BF values. In billfishes, the reproductive pattern is strongly influenced by the growth process and the age at which a species reaches sexual maturity relative to its maximum age. The observed differences in reproductive variables result from adaptive mechanisms that allow species greater reproductive success in the epipelagic environment.