The largest to the south?: Assessment of the latitudinal variation in Mustelus schmitti (Chondrichthyes: Carcharhiniforms: Triakidae), an endemic coastal shark of the Southwest Atlantic Ocean

Abstract

Relative growth and life history traits along latitudinal gradients have been widely examined in bony fishes, but chondrichthyans have received less attention. The present work focuses on testing whether southern distributed individuals of Mustelus schmitti sharks are larger and will mature at larger sizes than northern distributed individuals. We also show that intraspecific variation follows the latitudinal pattern and that body shape proportions are not altered by latitudinal distribution. The specimens come from two areas 1200 km apart [Puerto Quequén (PQ) and Ria Deseado (Deseado estuary) (PD)], which implies 9 degrees of latitudinal difference. For PQ, four allometric variables related to the trunk of the body showed secondary sexual dimorphism, while for PD this dimorphism was observed in a single variable. The females of PQ presented with a higher relative growth of the trunk than the females of PD. Males, by contrast, did not present a characteristic growth pattern that could differentiate specimens between the two areas. Specimens of both sexes in PD reached a larger average total length at first maturity (P < .05) than those in PQ