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This study aimed to investigate the effects of stocking density on Litopenaeus vannamei at the nursery phase in low-salinity biofloc system. Post-larvae of L. vannmei were cultured for 28 days at 2000, 4000 and 6000 shrimp m-3, and the water quality, plankton composition and growth performance were evaluated. The water quality variables remained within the ideal range for the shrimp culture, and only total suspended solids showed a significant difference between treatments -- the highest stocking density has increased the levels of total suspended solids. In regarding to zooplankton structure, the Protozoa group had the greatest diversity regardless of treatment, and also the greatest abundance (> 66%). For phytoplankton structure, Bacillariophyta (Navicula sp. and Cyclotella sp.) was the dominant class in phytoplankton structure throughout the culture, although a Cyanobacteria bloom has reported at the end of the cultivation at 2000 shrimp m-3. At the end of cultivation, the shrimp yield (0.133 ± 0.028 kg m-3) was significantly higher in the 6,000 shrimp m-3. In contrast, the shrimp survival was significantly higher in the lowest stocking density (71.66 ± 10.36%). Our findings suggest that a density of 6,000 shrimp m-3 should be used under these conditions, but an economic feasibility study should be considered in the future. [ABSTRACT FROM AUTHOR]

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Several studies conducted in Brazilian oceanic islands have generated many results of great significance for the understanding of these ecosystems. However, most of these studies have been restricted to shallow waters, not going beyond 200 m depth. In this work, seven exploratory deep-water fishing surveys were carried out with bottom traps at Saint Peter and Saint Paul Archipelago, between 2012 and 2014, at depths ranging from 300 to 700 m. During these surveys the presence of a deep-sea crab, identified as Chaceon gordonae was recorded, with 458 specimens being caught. Of the sampled specimens, 252 were males and 206 were females. The carapace length (CL) of sampled crabs measured, on the average, 110.81 ± 14.52 mm for males and 102.00 ± 16.55 mm for females. In general, the β1 parameter of the length-weight relationship indicates a positive allometric growth. A comparison of linear regression between the carapace length and right chela length and width for males suggested a morphological maturity of 108.90 and 110.10 mm CL, respectively, whereas the regression between carapace length and abdomen width in females indicated a size at morphological maturity of 84.00 mm CL. [ABSTRACT FROM AUTHOR]

In order to know the morphological variations of Goyazana castelnaui, we conducted an ontogenetic study from the first crab stage to the adult stage using geometric morphometry. We studied 36 females, 43 males and 162 juveniles collected in the Pajeú River, Brazil. We photographed crabs' carapace, pleon and right cheliped with they arranged parallel to the plane, afterwards landmarks and semi-landmarks were strategically distributed in the images. Through principal components analysis, we observed that the variation occurred mainly in the frontal and posterior region of the carapace. The pleon presented marked variations in the posterior and anterolateral region, while chelipeds presented greater variations at the base of the fixed finger. The canonical variation between sexes and between juveniles and adults (p<0.05) varied significantly. Correct allocations obtained by discriminant analysis (p<0.05) varied between 89.3% and 100.0%. The carapace shows a constant dimorphism along the ontogenetic trajectory, and both sexes reach similar centroid sizes (p>0.05). While the pleon and the cheliped, both sexes are similar when juvenile, diverging along the trajectory and reaching different centroid sizes (p<0.05). Females have a larger pleon and males a larger cheliped, corroborating the monophyletic theory of Brachyura.