Abstract We estimated the growth parameters of the spider crab, Libinia ferreirae (age, asymptotic size and growth rate) using the von Bertalanffy growth equation model. We obtained nine cohorts for female carapace asymptotic width (CW∞) = 64.32 mm, growth coefficient (day-1) (k) = 0.0027 e t0= 0.77 days) and seven for males (CW∞ = 81.93 mm, k= 0.0021 e t0= 0.49 days). The longevity for males was higher than that for females, estimated 2,156 days (5.91 years) and 1,706 days (4.68 years), respectively. The growth curves for males and females differed (F = 34.67 e p < 0.001). Males reached gonadal maturity before morphometric maturity and occurred at 8.8 and 16.6 months of life, respectively. Females reach gonad and morphometric maturity synchronously and this was estimated to occur at about 11.42 months of life. These crabs invest a great amount of energy in growth during a brief period of their development until reaching the terminal moult. This growth strategy would bring less wear to the organism and consequently a greater longevity.

Abstract We estimated the growth patterns, age at the onset of sexual maturity, longevity, and natural mortality of the snapping shrimp Alpheus brasileiro Anker, 2012. The sampling occurred monthly from April 2015 to March 2016 in the estuarine intertidal zone of Cananéia, São Paulo, Brazil. To estimate the growth parameters, all cohorts were adjusted to the Bertalanffy growth model. Longevity was estimated by the inverse growth equation. Natural mortality was calculated following the decrease in abundance over time of each cohort. We obtained the following estimates: CL∞ = 9.49 mm, k = 0.0077 day-1 (1.64 year-1), t0 = - 0.7628 for males, and CL∞ = 9.31 mm, k = 0.0095 day-1 (1.32 year-1), t0 = 0.0374 for females. The estimated age at the onset of morphological sexual maturity was 94 and 74 days for males and females, respectively. Females take 89 days to reach functional maturity, and have a higher mortality (4.35 year-1) than males (3.67 year-1). We rejected the hypothesis that males and females of A. brasileiro have the same growth patterns, longevity, mortality and, reaches sexual maturity at the same age. Our results suggest that physiological aspects and energy allocation strategies modulate the growth, longevity, and mortality of these snapping shrimps.

Abstract Xiphopenaeus kroyeri (Heller, 1862) is the third most common species caught by fishing boats in the state of São Paulo, Brazil and production of this shrimp in the Cananéia region located on the southern coast of this state ranks second in the nation. The aim of this study was to investigate the temporal variation of the total biomass and size of X. kroyeri and analyze this variation against environmental factors in order to suggest some information about the best periods to fish this species. Samples were caught monthly from four sampling stations in Cananéia between July 2012 and June 2014 using a fishing boat equipped with otter-trawl nets. Temperature and salinity were monitored using a multiparameter probe, and sediment samples were also taken using a Van Veen-type gripper for particle size analysis. The shrimp were weighed, quantified, and carapace length was measured (mm). In general, the highest total biomass values were recorded when the fishery was closed in the southeast and south regions, and the highest catch of smaller individuals was also observed during this period. In contrast, in November 2013 the fishing is permitted and high biomass composed of large individuals was observed. The monthly biomass showed a positive relationship with sediment texture, because this species prefers very fine sediments to burrow as a defense against predators.