Lifespan and population dynamics of the endemic South American shrimp Artemesia longinaris (Crustacea: Penaeidae) in southeastern Brazil.

The present study investigated the growth, longevity and reproductive dynamics of Artemesia longinaris in the southeastern coast of Brazil over a two-year period. Monthly collections were conducted in Ubatuba and Caraguatatuba using a shrimp fishing boat equipped with "double-rig" nets. Each region was divided into 7 sampling stations up to 35 m deep. Size frequency distributions, growth, longevity, sex ratio, and abundance of individuals in each demographic class, were compared. The relationship between abiotic factors and abundance of each demographic class was assessed using a Canonical Correlation Analysis. A total of 64,641 individuals were collected (6,928 measured) with an estimated longevity of 1.30 (Ubatuba) and 1.14 (Caraguatatuba) years for females and 1.03 years for males in both regions. There was a statistically significant bias in sex ratio toward females (Chi-squared test, p < 0.05) in both regions. The Canonical Correlation Analysis resulted in a canonical correlation coefficient of 0.31 (p = 0.00002). Salinity and temperature showed high correlation mainly with the presence of reproductive females. In general, this demographic class was most common in conditions of low temperature and high salinity. These findings, as well as other studies carried out in colder regions with the same species, are consistent with classical latitudinal paradigm.

Annual, seasonal and spatial abundance of the seabob shrimp Xiphopenaeus kroyeri (Decapoda, Penaeidae) off the Southeastern coast of Brazil.

We investigated the influence of environmental factors in spatial and temporal distribution of the seabob shrimp Xiphopenaeus kroyeri in Santos Bay and São Vicente Estuary, state of São Paulo, Brazil. Monthly samples were obtained, from May 2008 through April 2010, from four locations in the estuary and four in the bay. No individual was collected in the estuary and this was attributed to the low salinity means recorded in this environment. We collected 109,153 individuals in the bay and there was no difference in abundance between the two years comprised by the study period. The similarity in spatial distribution can be related to sediment grain size that in all sampling locations showed great amount of very fine sand. The largest amount of reproductive females was obtained in early 2010, when temperature was high, and this could have increased the juvenile recruitment in April 2010. According to our results, the distribution of X. kroyeri in the study area is influenced by temperature, which is related to reproduction, and salinity, limiting the entrance of individuals in the estuarine region.

Diel variation in abundance and size of the seabob shrimp Xiphopenaeus kroyeri (Crustacea, Penaeoidea) in the Ubatuba region, Southeastern Brazil.

The objective of the present study was to analyze diel variation in the abundance and size of the seabob shrimp Xiphopenaeus kroyeri in the Ubatuba region, state of São Paulo, during the year 2000. In each season of the year, collections were made in the day and at night on 9 transects at depths ranging from 2 to 40 m. The estimated shrimp amount was of 28,878 individuals. Although the catch rate was higher during the day (15,853 shrimp), this did not differ significantly from the catch at night (13,025). The catch rate was higher in daytime on most transects, but was higher at night at locations where fine and very fine sand predominated. The majority of juveniles were caught during the day. The mean size (CL) was 14.43 +/- 4.02 mm for day and 14.82 +/- 4.28 mm for night samples, and the difference was significant (Student's t-test, df = 2, 429, t = 2.27, p = 0.02). The largest individuals were caught during the night. None of the three models that have been proposed in the literature to account for differences in the diurnal catch pattern of penaeid species can be applied to X. kroyeri. Our results provide evidence that sediment type not only influenced the catch rate in the analyzed periods, but also determined which models might fit the behavior of this species.

Diel variation in abundance and size of the seabob shrimp Xiphopenaeus kroyeri (Crustacea, Penaeoidea) in the Ubatuba region, Southeastern Brazil

The objective of the present study was to analyze diel variation in the abundance and size of the seabob shrimp Xiphopenaeus kroyeri in the Ubatuba region, state of São Paulo, during the year 2000. In each season of the year, collections were made in the day and at night on 9 transects at depths ranging from 2 to 40 m. The estimated shrimp amount was of 28,878 individuals. Although the catch rate was higher during the day (15,853 shrimp), this did not differ significantly from the catch at night (13,025). The catch rate was higher in daytime on most transects, but was higher at night at locations where fine and very fine sand predominated. The majority of juveniles were caught during the day. The mean size (CL) was 14.43 ± 4.02 mm for day and 14.82 ± 4.28 mm for night samples, and the difference was significant (Student's t-test, df = 2, 429, t = 2.27, p = 0.02). The largest individuals were caught during the night. None of the three models that have been proposed in the literature to account for differences in the diurnal catch pattern of penaeid species can be applied to X. kroyeri. Our results provide evidence that sediment type not only influenced the catch rate in the analyzed periods, but also determined which models might fit the behavior of this species.

O objetivo do presente estudo foi analisar a variação diuturna na abundância e no tamanho do camarão sete-barbas Xiphopenaeus kroyeri na região de Ubatuba/São Paulo, durante o ano 2000. Em cada estação do ano, as coletas foram realizadas no período diurno e noturno, em 9 transectos localizados nas profundidades de 2 a 40 m. Um total de 28.878 camarões foi obtido e apesar da maior taxa de captura observada durante o dia (15.853 camarões), não houve diferença significativa em relação ao período noturno (13.025). Na maioria dos tran-sectos houve também uma maior taxa de captura de camarões durante o dia, no entanto, verificou-se que em locais com sedimentos com predominância de areia fina e muito fina, houve uma captura no período noturno. Já em relação aos juvenis, a maioria dos indivíduos foi amostrada durante o dia. Em consideração ao tamanho (CC) médio, obteve-se o valor de 14,43 ± 4,02 mm durante o dia e 14,82 ± 4,28 mm durante a noite, com significativa diferença (Student's t-test, df = 2.429, t = 2,27, p = 0,02). Verificou-se também que os maiores indivíduos foram capturados no período noturno. Um único modelo dos três propostos na literatura para as espécies de peneídeos quanto ao padrão de captura diuturna não pode ser aplicado ao X. kroyeri. Nossos resultados evidenciaram que tipo de sedimento não somente influenciou na taxa de captura entre os períodos analisados como determinou os modelos em que esta pode ser incluída.