ABSTRACT. The aim of the present study was to determine the size at sexual maturity in the freshwater crab Dilocarcinus pagei Stimpson, 1861, from a population located in Mendonça, state of São Paulo, Brazil. The crabs were sampled monthly (July 2005 to June 2007, at Barra Mansa reservoir. The specimens were captured manually or in sieves passed through the aquatic vegetation. The crabs were captured and separated by sex based on morphology of the pleon and on the number of pleopods. The following dimensions were measured: carapace width (CW); carapace length (CL); propodus length (PL); and abdomen width (AW). The morphological analysis of the gonads was used to identify and categorize individuals according to their stage of development. The morphological maturity was estimated based on the analysis of relative growth based on the allometric equation y = ax b . The gonadal maturity was based on the morphology of the gonads by the method CW 50 which indicates the size at which 50% of the individuals in the population showed gonads morphologically mature to reproduction. The biometric relationships that best demonstrated the different patterns of growth for the juvenile and adult stages were CW vs. PL for males and CW vs. AW for females (p<0.001). Based on these relationships, the estimated value to morphological sexual maturity was 21.5 mm (CW) in males and 19.7 mm (CW) in females. The determination of the size at sexual maturity and the adjustment of the data based on the logistic curve (CW 50 ) resulted in a size of 38.2 mm for males and 39.4 mm for females (CW). Based on the data obtained for sexual maturity for D. pagei, we can estimate a minimum size for capture of 40 mm (CW). This minimum size allows at least half of the population to reproduce and retains the juveniles and a portion of the adults in the population.KEYWORDS. Allometric growth, gonadal maturity, morphological maturity, reproduction. Os caranguejos foram separados por sexo, de acordo com a morfologia do abdome e pleópodos. As dimensões mensuradas foram: largura da carapaça (LC); comprimento da carapaça (CC); comprimento do própodo (CP) e largura do abdome (LA). Além disso, análise morfológica das gônadas foram realizadas e caracterizadas em relação ao estágio de desenvolvimento. A maturidade morfológica foi estimada com base no estudo do crescimento relativo, esta análise é baseada na equação alométrica y = ax b e a maturidade gonadal através da morfologia das gônadas, utilizando o método LC 50 indicando o tamanho em que 50% dos indivíduos encontram-se com gônadas desenvolvidas para a reprodução. As relações biométricas que melhor indicaram os diferentes padrões de crescimento das fases jovem e adulta foram LCxCP para os machos e LCxAB para fêmeas (p<0,001). Baseado nessas relações, o valor estimado para a maturidade sexual morfológica em machos foi de 21,5 mm (LC) e de 19,7 mm de (LC) para fêmeas. Na determinação da maturidade sexual gonadal, o ajuste da curva logística (LC 50 ) resultou em um tamanho de 38,2 mm para os machos e 39,4 mm para...

This study aimed to analyze the carcino-bycatch of seabob shrimp (Xiphopenaeus kroyeri) in Macaé/RJ, a region influenced by the Cabo Frio upwelling. Samples were collected monthly with a shrimp fishing boat, from July/2010 to June/2011. The carcino-group bycatch was represented by 15 families, 24 genera and 30 species. The families with the highest number of species were Portunidae (7) and Penaeidae (5), representing 23.33% and 16.66% of the total catch, respectively. For each seabob shrimp captured, 2.94 bycatch individuals were caught on average, with the largest discrepant values in summer (1: 4.82) and autumn (1: 5.76). The main components of this carcinofauna (Artemesia longinaris and Pleoticus muelleri) are species with increasing importance as a fishery resource in the region due to their abundance, and need to be continuously studied over diverse aspects of population biology, aiming to improve conservation actions.

The seabob shrimp Xiphopenaeus kroyeri ranks third in commercial importance among fisheries in southeastern Brazil. An important management question is whether the same offseason can be applied to different regions. The population dynamics of the seabob shrimp was compared in two regions of southeastern Brazil: Macaé, state of Rio de Janeiro and Ubatuba, state of São Paulo. All demographic categories of shrimp in the Macaé region were larger than those in the Ubatuba region. Lower temperatures and greater longevities in the Macaé region may account for this difference in size from Ubatuba. In Macaé, number of reproductive females and juveniles correlated with organic-matter content. In Ubatuba, only chlorophyll-a showed a correlation with reproductive females. The reproductive period and recruitment were correlated in both populations. The difference in environmental factors between these regions, resulting of the Cabo Frio upwelling, although they are located close together, directly influences the population dynamics of X. kroyeri. The Cabo Frio upwelling may be acting as a physical barrier, preventing gene flow and differentiating the seabob shrimp stocks in the two regions. These data suggest that different offseason periods for different regions could increase the sustainability of shrimp harvesting along the Brazilian coast.

ABSTRACT.Regions affected by upwelling show environmental characteristics that may change the distribution of the species. This study evaluated the influence of environmental factors on the spatiotemporal distribution of two caridean shrimps, Nematopalaemon schmitti and Exhippolysmata oplophoroides, in a region of the Brazilian coast affected by Cabo Frio upwelling. Shrimps were collected monthly from July 2010 through June 2011 off Macaé off the northern coast of Rio de Janeiro State, at six locations: three at 5 m, and the other three at 15 m depth. Shrimp abundance was compared among seasons and sampling sites. Nematopalaemon schmitti (n = 1200) was more abundant at 5 m depth while E. oplophoroides (n = 2176) occurred predominately at 15 m. There were significant seasonal fluctuations in the distribution of the species in the region, resulting from variation in bottom temperature. The presence of the South Atlantic Central Water (SACW) favors the decrease in the abundance of N. schmitti and highest abundance of E. oplophoroides. The abundance of E. oplophoroides and the percentage of organic matter were significantly and positively correlated. The organic matter content in the sediment and water temperature was among the most important variables affecting seasonal distribution of the species. The distinct environmental characteristic between the bathymetric regions were a determinant factor in their spatial distribution.

In crustaceans, successful reproductive processes, such as the transition from juvenile to adult, exhibit important morphological changes that can be detected by analyzing relative growth. This study describes the relative growth of body structures in Nematopalaemon schmitti and its secondary sexual characteristics, and also estimates the morphological sexual maturity of this species in a region influenced by upwelling. The carapace length (CL), second pleuron length (PlL), cheliped carpus length (CaL), cheliped propodus length (PrL) and the length of appendix masculina (AML) of the shrimp were measured. The relationships that best demonstrated the changes in allometric coefficient between demographic categories were AML vs. CL for males, and PlL vs. CL for females. The estimated CL for morphological sexual maturity in males was 8.51 mm and 9.30 in females. Our results showed the appendix masculine and the second pleuron were secondary sexual characteristics that play roles in reaching the morphological sexual maturity necessary for reproductive success and to assure the life cycle of this species.