We tested the substrate colour preference and its effect on the specific growth rate (SGR), food intake and feeding efficiency (FE) of the shrimp Litopenaeus vannamei (Boone, 1931). Preference was tested in 50 cm diameter circular tanks divided into 4 lateral compartments, each filled with 2 cm depth of fine-grain, coloured sand (yellow, blue, green and red). The respective walls of each tank were also kept with the same colour, using coloured paper. Tanks were fiUed with 10 1 of water (salinity of 4) and illuminated with fluorescent light (n = 35). Tanks with natural sand (without a specific colour) were used as controls (n = 6). Thirty-five shrimps were observed individually for three days at 7, 10, 13 and 16 h, for 20 min each time. Visit frequency to each compartment was registered every 2 min. Shrimps did not show any preference for a specific colour substrate for the first two days, however, there was higher preference for the yellow and red substrates on the third day. Control shrimps did not show preference for any compartment. To test the effects of substrate colour on feeding rate and growth, 25 shrimps were isolated for 60 days in a 15-1 aquahum covered with coloured paper on the walls and filled with 2 cm of coloured substrate (yellow, blue, green, red and natural sand, n = 5 for each colour). Shrimps were fed daily and uneaten food removed and recorded. Shrimps were weighed every 10 days. Feeding rate was higher in the red environment than in blue or green environments, and ra was also higher for red than for blue shrimps group. SGR was higher in red and yellow environments. These results suggest that yellow and red substrate enhance the shrimps' visual perception and food detection, and thus supports the finding that these substrate colours can improve FE and SGR of cultivated shrimps. RESUMOTestamos a preferencia por coloraçâo do substrato e seus efeitos sobre a taxa de crescimento específico (SRG), ingestao alimentar e eficiencia alimentar (FE) do camarao Litopenaeus

The trophic structure of fishes is associated with the habitat diversity and food availability along the river continuum (Miranda et al., 2019), where the input of detritus and sediments increases from the source to the mouth, with coarse organic matter (source) being replaced by fine organic matter (mouth), as described in the river continuum concept (Vannote et al., 1980). The regulation of fluvial systems through dams, isolated or in cascades along the main river and its tributaries, causes changes in water flow patterns, transforming lotic habitats into lentic habitats (Santos et al., 2020) and modifying detritus, sediment and nutrient transport to the lower

We investigated the population dynamics of the spider crab Libinia ferreirae, focusing on the frequency distribution of individuals in size classes, sex ratio and the action of environmental variables (temperature, salinity, texture and organic matter content in the sediment) on reproduction and recruitment. Monthly collections were made in the Ubatuba region from January 1998 to December 2000. A total of 222 individuals were collected, including 123 juveniles (males and females), 43 adult males, 25 non-ovigerous adult females and 31 ovigerous females. Unlike most adult brachyurans, there was no significant size difference between sexes, and sexual dimorphism seems to be a varying characteristic for this crab genus. The reproductive period and recruitment were continuous with peaks that could be related to water mass dynamics and higher food availability in the Ubatuba region. In addition, our results increase knowledge about part of the life cycle of L. ferreirae, which could be useful for comparative studies.

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