The determination of maturity stages in male elasmobranchs
Published online on 19. April 2013
The determination of maturity stages in male elasmobranchs (Chondrichthyes) using a segmented regression of clasper length on total length
Angel Manuel Segura, Andrés Conrado Milessi, Rodolfo Vögler, Felipe Galvan-Magaña, Vito Muggeo
ABSTRACT:
A novel statistical method for estimating the stages of maturity in male sharks and skates based on a segmented regression (SRM) is proposed. We hypothesise that this method is able to find the transition points in the three-phase relationship between total length (TL) and clasper length (CL). We applied an SRM to TL-CL data of nine species, from large pelagic sharks (e.g., Carcharhinus falciformis) to small coastal skates (e.g., Rioraja agassizi), captured in the Southwestern Atlantic and Northeastern Pacific. As expected, a segmented regression detected two breakpoints, defining three maturity stages (immature, maturing and mature), in six out of nine species. For three species, it was not possible to find two breakpoints due to incomplete sampling of TL. This novel method is non-invasive, it is applicable to previously collected data, is easy to use and provides a reliable tool for increasing our understanding of elasmobranch reproductive strategies.
Canadian Journal of Fisheries and Aquatic Sciences, 10.1139/cjfas-2012-0545