From plentiful to critically endangered: Demographic evidence of the artisanal fisheries impact on the smalltail shark (Carcharhinus porosus) from Northern Brazil.

The smalltail shark, Carcharhinus porosus, was the most abundant elasmobranch species in fisheries off Brazil's northern coast (BNC) in the 1980s, but its population has been declining since the 1990s. For this reason, a demographic analysis is necessary to determine the extent of this decline and the fishing effect on the BNC's population. Therefore, we performed a stochastic demographic analysis of the population in the BNC, and considered its global center of abundance. Smalltail shark specimens (n = 937) were collected with gillnets in Maranhão state, eastern BNC, in the 1980s with sizes ranging between 29.6 and 120.0 cm total length. Most of the individuals (90.6%) caught were juveniles (< 6 years-old), and the mortality and exploitation rates showed that the species was overexploited (92.3% above the fishing mortality corresponding to the population equilibrium threshold). The smalltail shark's biological characteristics, such as slow growth and low fecundity, demonstrate that it is one of the least resilient species among similar sized coastal sharks in the region. All these factors yielded an annual decrease of 28% in the intrinsic population growth rate, resulting in a population decline of more than 90% in only 10 years, and much higher for the current period. This set of features comprising fishing recruitment occurring upon juveniles, overfishing, and intrinsically low resilience make the population unable to sustain fishing pressure and severely hamper biological recruitment, thus causing this drastic population decline. Furthermore, several local extinctions for this species in the northeastern and southeastern regions of Brazil highlight its concerning conservation scenario. Therefore, since similar fisheries characteristics occur throughout its distribution range, C. porosus fits the criteria E of the IUCN Red List for a critically endangered species and urgent conservation measures are needed to prevent its extinction in the near future.

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

Increasing fishing effort has caused declines in shark populations worldwide. Understanding biological and ecological characteristics of sharks is essential to effectively implement management measures, but to fully understand drivers of fishing pressure social factors must be considered through multidisciplinary and integrated approaches. The present study aimed to use fisher and trader knowledge to describe the shark catch and product supply chain in Northeastern Brazil, and evaluate perceptions regarding the regional conservation status of shark species. Non-systematic observations and structured individual interviews were conducted with experienced fishers and traders. The demand and economic value of shark fins has reportedly decreased over the last 10 years while the shark meat trade has increased slightly, including a small increase in the average price per kilogram of meat. Several threatened shark species were reportedly often captured off shore and traded at local markets. This reported and observed harvest breaches current Brazilian environmental laws. Fishing communities are aware of population declines of several shark species, but rarely take action to avoid capture of sharks. The continuing capture of sharks is mainly due to a lack of knowledge of environmental laws, lack of enforcement by responsible authorities, and difficulties encountered by fishers in finding alternative income streams. National and regional conservation measures are immediately required to reduce overfishing on shark populations in Northeastern Brazil. Social and economic improvements for poor fishing communities must also be implemented to achieve sustainable fisheries.

Feeding habits of the blue shark (Prionace glauca) off the coast of Brazil / Habito alimentar do tubarão-azul (Prionace glauca) da costa do Brasil

Stomachs from 222 blue sharks collected along the Brazilian coast were analyzed - 116 from the northeastern region and 106 from the southern region. A total of 51 prey taxa were identified. The most important prey items in the southern region were Mysticeti whales, teleosteans, the gempylid Ruvettus pretiosus and the nomeid Arioma bondi. Cephalopods were more diverse, with dominance of vertical migrants Histioteuthis spp., Cranchiidae and the epipelagic octopus Ocythoe tuberculata. In the northeastern region, blue sharks consumed mainly teleosteans, including the alepisaurid Alepisaurus ferox and the gempylid Gempylus serpens. Among cephalopods, Histioteuthis spp. and the epipelagic octopus Tremoctopus violaceus were the dominant items. Predation upon schooling prey was occasional, as observed on Arioma bondi. Birds also were consumed in both regions; Puffinus gravis was the fifth most frequent item in the northeastern region. During the reproductive migration cycle, blue sharks likely prey in the thermocline, which is deeper in the northeastern region and closer to the surface in the southern region.

Estômagos de 222 tubarões-azuis coletados ao longo da costa brasileira foram analisados, sendo 116 da região nordeste e 106 da região sul. Um total de 51 táxons de presas foram identificados. Os itens mais importantes na região sul foram baleias Mysticeti, teleósteos, o peixe gempilídeo Ruvettus pretiosus e o nomeídeo Arioma bondi. Cefalópodes foram mais diversos, com preferência pelas espécies migradoras verticais Histioteuthis spp., Cranchiidae e o polvo epipelágico Ocythoe tuberculata. Na região nordeste, o tubarão-azul consumiu principalmente teleósteos, incluindo o peixe alepisaurídeo Alepisaurus ferox e o gempilídeo Gempylus serpens. Entre os cefalópodes, Histioteuthis spp. e o polvo epipelágico Tremoctopus violaceus foram os itens principais. Predação sobre cardumes foi ocasional, como observada para Arioma bondi. Aves também foram consumidas em ambas as regiões. Puffinus gravis foi o quinto item mais freqüente na região nordeste. Durante o ciclo migratório reprodutivo, o tubarão-azul costuma predar nas adjacências da termoclina, que é mais profunda na região nordeste e mais perto da superfície na região sul.

Age and growth of Spanish mackerel (Scomberomorus brasiliensis) off the northeastern coast of Brazil

Age and growth of the Spanish mackerel (Scomberomorus brasiliensis) caught off northeastern Brazil were determined. A total of 831 otoliths were examined - 296 from males (12 - 75 cm FL), 212 from females (11.5 - 72 cm FL) and 323 from specimens of undetermined sex (12.4 - 75 cm FL). There was a high percentage of juveniles in the catches, resulting mainly from the use of gillnets. Marginal increment analysis of the otoliths indicated that the shortest distances from the last ring to the edge occurred from November to May, laying down just one ring annually. One to eight rings were found, with specimen lengths ranging from 11.5 to 75.8 cm. The Schunute model was used to determine what model was best fit the data, demonstrating that the specialized von Bertalanffy growth equation is the most appropriate. Curves were established for males (L∞ = 79.52 cm, K = 0.189, t0 = -0.384 year) and females (L∞ = 109.18 cm, K = 0.114, t0 = -0.414 year), which resulted in distinct growth patterns between sexes. Based on the parameters estimated for the sexes separately, males have an approximate longevity of 15.5 years, whereas female longevity is 25.9 years. Specimens between 2 and 6 years of age represented 86 percent (n = 5,290) of the catch composition, characterizing the species as a catchable stock in the region. The present study updates essential information for assessing the stock of this important resource, for which the last growth studies in the region were carried out approximately thirty years ago.(AU)

Foram determinados a idade e o crescimento da serra (Scomberomorus brasiliensis) capturada na região nordeste do Brasil. Um total de 831 otólitos foi examinado, sendo 296 machos (12 - 75 cm FL), 212 fêmeas (11,5 - 72 cm FL) e 323 exemplares com sexo indeterminado (12,4 - 75 cm FL). Um alto percentual de exemplares jovens foi verificado nas capturas, principalmente pela utilização de redes de emalhar. A análise do incremento marginal nos otólitos indicou que as menores distâncias do último anel a borda ocorrem nos meses de novembro a maio, marcando apenas um anel anualmente. Foram encontrados de 1 a 8 anéis, com comprimentos de 11,5 a 75,8 cm FL. O modelo de Schunute foi utilizado, a fim de verificar qual modelo melhor se ajustava aos dados, demonstrando que a equação de crescimento de von Bertalanffy especializada é a mais indicada. Curvas foram estabelecidas para machos (L∞ = 79,52 cm, K = 0,189, t0 = -0,384) e fêmeas (L∞ = 109,18 cm, K = 0,114 e t0 = -0,414), resultando em um padrão distinto de crescimento entre sexos. De acordo com os parâmetros estimados para sexos separadamente, machos apresentam longevidade aproximada de 15,5 anos e fêmeas de 25,9 anos. Exemplares entre 2 e 6 anos de idade representaram 86 por cento (n = 5.290) da composição das capturas, caracterizando o estoque capturável da espécie na região. O presente estudo atualiza informações essenciais para avaliação do estado de exploração desse importante recurso, cujo último estudo de crescimento na região foi realizado aproximadamente há 30 anos atrás.(AU)

Total mercury in the night shark, Carcharhinus signatus in the western equatorial Atlantic Ocean

O mercúrio (Hg) é o único metal que comprovadamente biomagnifica através da cadeia alimentar, e sendo assim, espécies de peixes predadores tendem a apresentar altas concentrações deste metal. Porções de tecido muscular de C. signatus coletados na região oeste equatorial do oceano Atlântico foram submetidas a extração ácida e tiveram a concentração de mercúrio determinada com acessório gerador de vapor a frio acoplado a um ICP-AES. A concentração média de Hg apresentou valores acima do limite máximo permissível para consumo humano estabelecido pela legislação brasileira (1000 µg.kg-1 de peso úmido). Conseqüentemente, um consumo médio de 0,1 kg.dia-1 de C. signatus resultaria numa ingestão media de 174,2 µg de Hg, mais de cinco vezes o consumo máximo de 30 µg.dia-1 estabelecido pela Organizacao Munidal da Saúde. Dentro das classes de tamanho analisadas, o comprimento total não pode ser utilizado como indicador do grau de contaminação por mercúrio em C. signatus. Ainda, o sexo não pode ser considerado um fator determinante na acumulação total de mercúrio em C. signatus.