Population structure of nurse sharks, Ginglymostoma cirratum (Orectolobiformes), caught off Ceará State, Brazil, south-western Equatorial Atlantic

Abstract

The nurse shark, Ginglymostoma cirratum, is considered an endangered species in Brazil and its capture by fisheries forbidden. Despite such legislation, nurse sharks continue to be caught as these laws are unenforced and fisheries are not monitored. The goal of the present study was to describe the population structure of nurse sharks caught off Ceará State, north-eastern Brazil, based on the following aspects: abundance and size, sex-ratio, fisheries incidence and seasonality of captures. Landings were monitored weekly during a two-year period. A total of 189 specimens were recorded. Total length (TL) varied between 73 and 274 cm. The male-female ratio did not differ significantly (1.19C:1F). TL of individuals landed as carcasses was estimated based on interdorsal length. The following equation was obtained for males and females: TL ¼ 12.606ID + 14.24 (R 2 ¼ 0.9505). Most of the landed sharks were juveniles (86.2%). No seasonal pattern of abundance and TL variation was observed. Management of this fishery is required in order to prevent localized over-fishing of nurse sharks.

Analysis of the supply chain and conservation status of sharks (Elasmobranchii: Superorder Selachimorpha) based on fisher knowledge

“…cirratum a highly abundant species and difficult to avoid capturing throughout the rainy season. This differs from patterns found in other Brazilian regions, where the species is now rare [ 54 , 57 ] and seasonal variation in abundance has not been observed [ 58 ]. Based on Almeida et al [ 36 ], strong winds and rough seas during the dry season reduce fishing effort on Maranhão’s coast, which could explain reduced capture of G .…”

Necrophagy of a nurse shark (Ginglymostoma cirratum) by tiger sharks (Galeocerdo cuvier)

“…Fishing is not permitted in the Fernando de Noronha Marine Park and therefore we assume that the nurse shark was not hooked at the moment of the attack by tiger sharks. In any event, illegal fishing occurs along the Brazilian coast (Santander-Neto et al 2011) and thus, it is not an excluded possibility. A straight cut on the upper lobe of the caudal fin is seen in the video and in one of the examined photographs and suggests an artificially cut-off tail by a sharp instrument.…”

Sharks and rays caught by a small‐scale fisheries in the western equatorial Atlantic

“…The former is Data Deficient and requires more information about fisheries and biological aspects, and the latter is one of the most endangered shark groups (Dulvy et al, 2014). Santander-Neto, Shinozaki-Mendes, et al, 2011), its conservation status in Brazil was changed from Endangered (Brasil, 2004) to Vulnerable (Brasil, 2014). More effort should be directed to evaluating the biology and population status of the elasmobranch species recorded in the present-study in order to generate data that could be applied to management policies before any further decline trend becomes evident.…”