Besides its extreme climate conditions, the Caatinga (a type of tropical seasonal forest) hosts an impressive faunal and floristic biodiversity. In the last 50 years there has been a considerable increase in the number of studies in the area. Here we aimed to present a review of these studies, focusing on four main fields: vertebrate ecology, plant ecology, human ecology, and ethnobiology. Furthermore, we identify directions for future research. We hope that the present paper will help defining actions and strategies for the conservation of the biological diversity of the Caatinga.

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A 42-day trial was conducted to evaluate the effects of a low-salinity biofloc system with different stocking densities on water quality and zootechnical performance of Nile tilapia fingerlings (10 g/L). Four treatments were tested at different densities: 500 fish/m³, 750 fish/m³, 1,000 fish/m³ and 1,250 fish/m³, all in triplicate. Fingerlings of Oreochromis niloticus (initial mean weight of 1.17 ± 0.05 g) were stocked in twelve experimental black-plastic tanks (40 L) with no water exchange during the experimental period. Molasses was added daily to the system at 30% of the amount of feed, and fish were given four daily rations of a formulated feed composed of 36% crude protein and 9% lipids. Water quality variables (dissolved oxygen, pH, salinity, TAN, NO2, NO3 and PO43) did not demonstrate significant differences between the treatments. However, significant influences (α ≤ 0.05) of the stocking densities were observed for total suspended solids, settleable solids, final weight, yield, and protein efficiency ratio. The results showed survival over 96%, final weight values between 12 and 18 g, yield between 9.49 and 15.27 kg/m3, water consumption of 52 to 101 L/kg fish, and total time of settling chambers between 238 and 305 h/kg fish. These results indicate a negative effect of stocking density on final weight, survival, alkalinity, NO2, PO43 and water consumption, and a positive effect on yield in Nile tilapia fingerling culture (1-20 g) in a low-salinity biofloc system with densities up to 1000 fish/m³.

Effect of the addition of diatoms (Navicula spp.) and rotifers (Brachionus plicatilis) on water quality and growth of the Litopenaeus vannamei postlarvae reared in a biofloc system Abstract The aim of this study was to evaluate the effect of the addition of Navicula spp. and Brachionus plicatilis on water quality and growth of postlarvae shrimp Litopenaeus vannamei reared in a biofloc system. Four treatments were considered: a control (biofloc system -BFT); BFT with the addition of Navicula spp. (BFT-N); BFT with the addition of Brachionus plicatilis (BFT-B) and BFT with the addition of Navicula spp. and Brachionus plicatilis (BFT-NB), each in triplicate. Shrimp (16.2 AE 0.03 mg) were stocked at a density of 2500 shrimp m À3 and plankton were added on days 1, 5, 10, 15, 20, 25 and 30 at a density of 5 9 10 4 cells mL À1 (Navicula spp.) and 30 organisms L À1 (Brachionus plicatilis). The shrimp were fed a formulated feed in four daily rations composed of 40% crude protein and 8% lipids. Significant differences between treatments were observed for final weight, yield, feed conversion ratio, specific growth rate, protein efficiency ratio and protein content of the shrimp. The combined plankton addition of Navicula spp. and B. plicatilis had better performance parameters, indicating their benefit as natural food sources for postlarvae L. vannamei in biofloc systems.

Measurements of gill dimensions were carried out on two ecologically distinct active rheophilic teleost species, the curvina Plagioscion squamosissimus and the curimbatá Prochilodus scrofa, and were analysed in relation to body mass according to the equation Y=aW b . The gill respiratory areas of P. squamosissimus and P. scrofa were large as expected for active fish and increased with increasing body mass (b=0·70 and 0·72, respectively) showing no significant difference between them. However, the large respiratory area of both species was realized in a different way revealing an adaptation to the plasticity of head components related to feeding habits. Consequently, significant differences were found between the number and average length of gill filaments and the bilateral area of secondary lamellae. The respiratory area of P. scrofa was due mainly to larger bilateral surface area of the secondary lamellae and its growth coefficient (b=0·51) that was significantly higher (P<0·05) than that found for P. squamosissimus (b=0·36). The frequency of secondary lamellae mm 1 of filament was similar in both species (22 2 on one side of gill filament). The dimensions of gill components and the respiratory area of these species suggest a complex interaction between head form, and feeding habits related to the functional morphology of the gills to meet the oxygen requirements of each species. 1998 The Fisheries Society of the British Isles

The functioning of systems arranged in cascades of reservoirs can be explained by the Cascading Reservoir Continuum Concept, providing a theoretical framework for addressing ecological processes. In this context, this study tested the following hypotheses: (i) the benthic macroinvertebrate assemblage shows a nested distribution along a reservoir cascade; and (ii) local factors explain the structure of the benthic assemblage in every reservoir along the cascade. Macroinvertebrates play essential role in aquatic systems, especially due to recycling and, in reservoirs, as important links in every food chain. Sampling was conducted quarterly between October 2006 and September 2010 in six reservoirs located in the São Francisco River, Brazil. The benthic macroinvertebrate assemblage showed nested distribution in the reservoirs, indicating that a loss of species occurs along the cascade. Each reservoir presented a different set of variables that explained the distribution of macroinvertebrates, showing the importance of local factors determining the composition and distribution of benthic assemblages in the reservoirs. Therefore, there is a clear interaction between the position of a reservoir along a cascade and the macroinvertebrate assemblages, which indicate the importance of considering this pattern during the decision-making process of constructing new dams on rivers already regulated.