Stock Structure of the Gulf Hake Urophycis cirrata (Teleostei: Phycidae) in South-Western Atlantic Using Otolith Shape and Elemental Analyses

Abstract

Urophycis cirrata is an important demersal fish species targeted by Brazilian industrial fisheries. With high exploitation rates, its stock(s) is(are) currently deemed fully exploited or overexploited. While basic ecological information, such as length at first maturity, exists, knowledge of its population structure is limited. A sub-sample of 90 sagittal otoliths of U. cirrata juveniles (300–411 mm total length) collected during the Program for Assessment of the Sustainable Potential of Living Resources in the Exclusive Economic Zone (REVIZEE) in 2001/2002 was analyzed. Samples came from the outer continental shelf and upper slope of the southeast-south Brazilian coast, divided into three regions: northern (Cabo São Tomé to São Sebastião), central (São Sebastião to Cabo Santa Marta Grande), and southern (Cabo Santa Marta Grande to Chuí). Otolith shape (elliptic Fourier descriptors) and elemental (element:Ca) signatures were examined using univariate (ANOVA, Tukey) and multivariate (MANOVA, LDFA) statistical methods. An overall reclassification success rate of 86% was achieved using both signatures. However, individuals from the three regions were not fully separable, indicating a single, albeit not homogeneous, population unit for fisheries management. As fish stocks are dynamic, contemporary studies should be conducted to verify whether this population structure persists.

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