Fitness of generalised maturity scales for elasmobranchs with a practical example of the angelshark Squatina squatina.

Abstract

Improvements related to nomenclature, criteria, uniformity and standardization of macroscopic generalised sexual maturity scales for elasmobranchs are presented, based on data from the angelshark Squatina squatina. Individuals of angelshark were sampled from incidental captures of the artisanal fishery in the island of Gran Canaria (Canary Islands, Central-East Atlantic). The male reproductive tract consists of paired testes, epididymides, ductus deferens, seminal vesicles and claspers. The female reproductive tract consists of paired ovaries, ostia, and oviducts. Macroscopic condition indices of key organs from the reproductive tract can elucidate five maturity phases in males and females respectively: juvenile, subadult, developing, active / gravid and spent / post-partum. Conflicts to adopt the sexual development of this species to recent proposed generalised maturity scales for viviparous elasmobranchs are useful to enhance the scales. Emphasize is made in comprehensive and unambiguous criteria of macroscopic condition indices while maintaining uniformity in nomenclature with other studies.