Evaluation of the Blue Crab Callinectes sapidus Rathbun, 1896 Bycatch in Artisanal Fisheries in Southern Brazil

ABSTRACT We evaluated the incidental catch of the blue crab in artisanal fisheries through the analysis of sex ratio, catch per unit effort, net positioning, and size in which the capture probability was 50% (P50). The specimens were collected from 2011 to 2013 in the estuary of Patos Lagoon, southern Brazil. The analysis showed a higher occurrence of males. Variations in the catch per unit effort showed greatest abundance values close to the mouth of the estuary. Catch per unit effort was similar when comparing fishing seasons and net positions. P50 indicated a low selectivity of the nets since it varied between studied areas but stayed below the size at first maturity. Catches indicated a greater effort on males, since females migrated to spawn in the ocean area adjacent to the estuary during the fishing period studied. The spatial variation of the catch per unit effort showed heterogeneity in fishing catches. Thus, optimal management of the resource should consider the particularities of each area.

Bioecology of the crab Ucides cordatus (Crustacea, Decapoda) in mangroves influenced by the Amazon River, Brazil / Bioecologia do caranguejo Ucides cordatus (Crustacea, Decapoda) em manguezais influenciados pelo Rio Amazonas, Brasil

The mangrove crab (Ucides cordatus) is a valuable fishery resource, overfished along the Brazilian coast. This study aimed to obtain bioecological data on this crab along the coast of the State of Amapá. Six bimonthly samplings were conducted between December 2008 and January 2010. Transects were used to estimate the density (burrows m-2) and population abundance (individuals m-2). All the animals were subjected to biometrics, with females being classified according to their stage of gonadal maturation. The mean density (1.09 burrows m-2) and abundance (0.31 individuals m-2) were influenced by the climate with the highest values in summer (1.17 burrows m-2 and 0.34 individuals m-2). The male to female ratio was 1.38:1 showing significant difference in the proportion of sexes. The individuals showed sexual dimorphism, with linear measurements significantly higher in males. The sampled animals also had larger carapace length and width (CL and CW) compared to crabs studied in other Brazilian states. There was a positive relationship between CW and CL and individual weight (IW) and CW for males (R² = 0.83 and 0.90) and females (R² = 0.79 and 0.84). The growth was negative allometric (CL increases to a lesser extent than CW) for both sexes. The highest frequency of ovigerous females (78%) and in maturation stage IV (38%) occurred in the CW size class between 59.8 and 67.5 mm. The peak of mature females occurred in May and August, showing a reproductive period different from those in other Brazilian states.

O caranguejo-uçá (Ucides cordatus) é um valioso recurso pesqueiro, sobreexplorado ao longo do litoral brasileiro. O objetivo deste trabalho foi obter dados bioecológicos deste caranguejo em toda a costa do Estado do Amapá. Foram realizadas seis coletas de frequência bimensal, compreendidas entre os meses de dezembro de 2008 a janeiro de 2010. Por meio de transectos foram estimadas a densidade (tocas m-2) e a abundância (indivíduos m-2) populacional. Todos os animais foram submetidos à biometria, sendo somente as fêmeas, classificadas quanto ao estágio de maturação gonadal. A densidade (1,09 tocas m-2) e a abundância (0,31 indivíduos m-2) foram influenciadas pelo clima, sendo os maiores valores observados durante o verão (1,17 tocas m-2 e 0,34 indivíduos m-2). A razão sexual foi de 1,38M:1F, mostrando diferença significativa entre a proporção de sexos. Os indivíduos apresentaram dimorfometria sexual, com medidas lineares significativamente superiores nos machos. Os animais coletados também apresentaram maior comprimento e largura de cefalotórax (CC e LC), quando comparados aos caranguejos estudados em outros estados brasileiros. Houve relação tanto entre LC e CC, como entre peso individual (PI) e LC para machos (R² = 0,83 e 0,90) e fêmeas (R² = 0,79 e 0,84). O crescimento foi alométrico negativo (menor crescimento de CC em relação à LC) para ambos os sexos. A maior frequência de fêmeas ovígeras (78%) e no estágio IV de maturação (38%) pertenciam à classe de tamanho de LC 59,8 - 67,5 mm. O maior pico de fêmeas maduras ocorreu nos meses de maio e agosto, mostrando um período reprodutivo diferente de outros estados do Brasil.

Reproductive cycle of Tagelus plebeius (Mollusca: Bivalvia) in the estuary of the Cachoeira River, Ilhéus, Bahia, Brazil / Ciclo reprodutivo de Tagelus plebeius (Mollusca: Bivalvia) no estuário do Rio Cachoeira, Ilhéus-Bahia, Brasil

This study characterized the reproductive cycle of the stout razor clam Tagelus plebeius in the estuary of the Cachoeira River, Ilhéus, Bahia, northeastern Brazil. Samples of 20 animals per collection were taken biweekly from August 2005 to August 2006. The 480 specimens were measured on the antero-posterior axis (length) and then removed from the shell. After macroscopic analysis, the gonads were fixed in Davidson's solution, processed by routine histology and stained by Harris hematoxylin and eosin. The gonads of both males and females appeared milky white, without sexual dimorphism. Microscopic analyses indicated a M: F ratio of 1.06: 1 and continuous reproduction of T. plebeius in the region. The period from August to October showed the most intense spawning. This study provides another example of continuous reproduction of bivalves in tropical waters, and because this species is a heavily exploited fishery resource in the region, it draws attention to the need for a management plan aimed at reducing harvests.

Neste estudo, objetivou-se caracterizar o ciclo reprodutivo de Tagelus plebeius na região estuarina do Rio Cachoeira, Ilhéus-Bahia. As amostragens, 20 animais/coleta, foram feitas quinzenalmente, entre agosto de 2005 e agosto de 2006. Os 480 animais, depois de medidos quanto ao seu eixo ântero-posterior (comprimento), foram removidos da concha e, após análise macroscópica, as gônadas foram fixadas em solução de Davidson, processadas por técnica rotineira de histologia e coradas com hematoxilina de Harris e eosina. As gônadas de machos e fêmeas apresentaram aspecto branco leitoso e não houve dimorfismo sexual. As análises microscópicas evidenciaram razão sexual M:F de 1,06:1 e reprodução contínua de T. plebeius na região. O período entre agosto e outubro foi caracterizado como o de maior eliminação de gametas. O estudo fornece outro exemplo de reprodução contínua de bivalves em regiões tropicais e, por ser um recurso pesqueiro intensamente explorado na região, chama a atenção para a criação de um plano de manejo que vise à redução de sua coleta.