Biological and reproductive characteristics of the Patagonian smoothhoundMustelus schmitti(Chondrichthyes, Triakidae) as documented from an artisanal fishery in Uruguay

Abstract

The use of a highly selective fishing gear is the main reason for mature individual dominance in the Patagonian smoothhound (Mustelus schmitti Springer, 1939) artisanal fishery in Punta del Diablo, Uruguay. Differences in length–weight relationships (LWR) and size at 50% maturity (L50) within its distribution were also expected. A total of 696 M. schmitti specimens (281 females; 415 males) were examined between July 2005 and October 2006. Length-frequency distribution (LFD) presented a peak at 660 mm total length (L) in both sexes, with females significantly larger in size than males. LWR was W = 1.36E−7 × L3.51 for females and W = 5.12E−6 × L2.93 in males. Of the captured females, 67% were mature, whereas 85% of captured males were mature. The smallest mature females and males were 455 and 495 mm L, respectively; largest immature females and males were 680 and 670 mm L. L50 and the confidence intervals (CI) were 597 mm (577–616) and 566 mm (553–580) for females and males, respectively. These figures are similar to those obtained from other populations in the area (34–41° S), although the L50 values were different from the Uruguayan outer shelf and populations further south. Fecundity ranged from 1 to 14 embryos per female (average = 6; SD = 3) and was positively correlated with female L. The results were compared with previous works comprising most of this species’ latitudinal distribution. This is the first research showing results of M. schmitti bottom-fixed gill-net artisanal fisheries. Different from industrial catches, this type of gear results in catches composed mainly of mature individuals (>80%), thus constituting an adequate scenario for sustainability of this endangered resource.