This study evaluated the salinity tolerance of the macroalga Ulva ohnoi cultivated in a biofloc system over a 14-day period. Five salinity treatments (10, 15, 20, 25, and 30‰) were tested, using 40-L tanks. Algae were acclimated to the target salinities before the cultivation phase and stocked at the density of 2 g∙L-1. Water quality parameters (ammonia, nitrite, nitrate, orthophosphate, alkalinity, and pH), biomass gain, daily growth rate, phenolic compounds, chlorophyll, and carotenoids were evaluated. Water quality remained within acceptable ranges across treatments, although alkalinity showed significant differences. Complete mortality of U. ohnoi was observed at 10‰, and reduced growth was recorded at 15‰. In contrast, salinities of 20, 25, and 30‰ supported higher biomass gains and daily growth rates, with no significant differences in antioxidant compound concentrations among these treatments. Growth was significantly higher at salinities of 20–30‰, with biomass gains of 318–400 g and daily growth rates of 5.4–6.4% day-1, whereas at 15‰ biomass gain reached only ~111 g and growth rate ~1.2% day-1. These findings highlight the potential of U. ohnoi for integration into low-salinity biofloc systems and multitrophic aquaculture strategies, contributing to sustainable aquaculture practices by recycling nutrients and producing valuable biomass.

The aim of this study was to evaluate the performance of Penaeus vannamei and Oreochromis niloticus in an integrated multi-trophic system with biofloc technology using different strategies. Two treatments were developed: TC (chemoautotrophic) and TH (heterotrophic). The TC treatment started 46 days before stocking the animals, with inorganic fertilization. In the TH treatment, organic fertilization was carried out after stocking the animals. Four hundred shrimp∙m-2 (1.00 ± 0.04 g) and 45 tilapia fry∙m-3 (25 ± 0.50 g) were stocked for 86 days. Water quality parameters such as temperature, oxygen, and pH were monitored daily. Total ammonia, nitrite, nitrate, phosphate, total suspended solids, and settleable solids were monitored twice a week. Prior fertilization in the chemoautotrophic treatment avoided high concentrations of nitrogen compounds in the system, due to the prior establishment of bacteria, compared to the heterotrophic treatment. The increase in nitrogen compounds in heterotrophic treatment led to higher water use, reduction in feed and consequently lower shrimp growth performance compared to the chemoautotrophic system. Tilapia’s growth was not affected. Therefore, the use of prior fertilization in chemoautotrophic treatment allowed for a higher final weight, yield of shrimp, and greater environmental sustainability.

This study evaluated the effects of astaxanthin from Haematococcus pluvialis on coloration, antioxidant activity, and growth performance in Cryptocentrus cinctus. Three dietary treatments were formulated with increasing astaxanthin concentrations: A0 (0%—control), A10 (0.01% of the total dry diet), and A15 (0.015% of the total dry diet). Astaxanthin supplementation significantly enhanced skin pigmentation, with A15 fish exhibiting a distinct yellow coloration (R = 144.75; G = 122.9; B = 48.5). Catalase activity was also the highest in the A15 group (25 UCAT mg-1), suggesting improved antioxidant capacity. Zootechnical performance improved with astaxanthin inclusion, as A15 fish demonstrated greater weight gain (0.44 g), length gain (7.93 mm), and a lower feed conversion ratio (1.10). Overall, dietary supplementation with 0.015% astaxanthin from H. pluvialis enhanced pigmentation, antioxidant response, and growth efficiency in C. cinctus, representing the first report of carotenoid supplementation for this species.

Gastropods of the genus Pomacea are exploited for food in different parts of the world. Pomacea dolioides has recently received attention on its stocking density and meat characteristics, remaining a gap on the effects of calcium in its cultivation. The present study evaluated the influence of calcium dissolved in water on the culture of the gastropod P. dolioides considering the growth, weight, survival, ultrastructure, and shell regeneration time. Juveniles were distributed into six treatments with different concentrations of Ca2+. The calcium dissolved in water was essential, as gastropod did not survive for more than 40 days without calcium. Also it showed greater growth and fattening with 60 mg*L-1 of CaSO4 or more, in addition to a thicker shell with two layers of crystals. The calcium carbonate content in the shells was significantly higher in the treatment with 80 mg*L-1 of CaSO4. The regeneration time did not differ between treatments. Based on these results, it was concluded that the calcium dissolved in the water influences the culture of the gastropod P. dolioides in relation to the length, inorganic and organic weight and calcium of the snail, and 80 mg*L-1 of CaSO4 is the ideal concentration to culture species.

Laetacara dorsigera is a fish species that has excellent potential for ornamental fish farming. The present study aimed to evaluate the effect of stocking density on its growth in two experiments, with three treatments and four repetitions, lasting 45 days each. The first experiment used 0.25, 0.50, and 0.75 fish L-1, and the second used the best density found in the first experiment, plus densities of 0.30 and 0.40 fish L-1. The measured zootechnical parameters were survival rate, mean total lengths, and mean initial and final weights, as well as relative growth, specific growth, and weight gain rates. A significant difference was observed in the first experiment for the final length (18.7 and 17.5 mm, in the densities of 0.25 and 0.50 fish L-1, respectively), relative growth rate percent, and specific growth rate weight% (0.25 fish L-1) and survival (0.50 fish L-1). In the second experiment, there was no significant difference for the densities tested. The density of 0.50 fish L-1 is the most viable, due to the greater final survival achieved and no significant difference for the other parameters analyzed.

O estudo avaliou o crescimento muscular e o desempenho de alevinos de tilápia-do-Nilo alimentados com uma dieta restrita combinada com fitoplâncton em viveiros fertilizados. Quatro tratamentos foram testados: 100% da ração diária, 100% da ração em dias alternados, 50% da ração diária + fertilização e 50% da ração em dias alternados + fertilização. Os peixes foram estocados a uma densidade de 19 peixes/m² e alimentados com uma dieta contendo 45% de proteína bruta. Os viveiros foram fertilizados semanalmente com superfosfato e sulfato de amônio, e os parâmetros da água foram monitorados. O crescimento, a morfometria e as análises histológicas dos músculos dorsal e caudal foram realizados nos dias 0, 30 e 60. O tratamento com 50% da ração diária + fertilização apresentou ganho de peso, curva de crescimento e comprimento final similares ao grupo alimentado com 100% da ração diária. O crescimento muscular por hiperplasia e hipertrofia foi significativamente maior (p < 0,05) no grupo com 50% de ração diária + fertilização, promovendo comunidades diversificadas de fitoplâncton, especialmente Chlorophyceae, Bacillariophyceae e Cyanobacteria. Esses resultados indicam que a restrição alimentar a 50% do peso corporal com fertilização semanal mantém o desenvolvimento dos peixes, reduz custos com ração e favorece o crescimento muscular, além de promover a diversidade de fitoplâncton nos viveiros.

This study evaluated the effects of dietary supplementation with citral on growth performance and intestinal parameters, and specific activity of the digestive enzymes of Sardinella brasiliensis. 240 juvenile S. brasiliensis were randomly distributed in a recirculating aquaculture system (RAS) composed of 12 circular tanks of 150 L (n = 20 per tank). A diet without citral addition (control) and three diets containing different levels of citral inclusion (0.5, 1.0 and 2.0 mL kg*feed–1) were used in the fish feeding management during 20 days. The indexes of zootechnical performance, survival, weight gain, specific growth rate, feed conversion and condition factor of the fish were verified, as well as digestive enzymes and histological analysis. A significant positive relationship was found between citral supplementation and fish survival. In the specific activity of digestive enzymes, dietary citral supplementation at 2.0 mL* kg feed–1 increased lipase and amylase activity. Citral supplementation positively influenced the number of villi and intestinal crypt depth. Furthermore, the inclusion of citral at 0.5 mL kg*feed–1 increased the intestine diameter of the fish. The results of the experiment suggest that the addition of citral as an additive in the diet of S. brasiliensis improved the survival of fish.

This study analyzed the spatial and seasonal distribution of piranha species and their respective diets. Samples were collected monthly from August 2020 to July 2021 using various types of fishing gear in different sections of the river. Limnological data were also analyzed to assess correlations with the distribution of piranha species. A total of 326 fish were identified, encompassing nine species and three genera. The most abundant species were Serrasalmus rhombeus (N = 155), Pygocentrus nattereri (N = 89), and Serrasalmus spilopleura (N = 23), which were found in the headwaters, intermediate section and river mouth, respectively. The stomach contents of 56 piranhas were analyzed and revealed that 55.35% of the stomachs were full and 44.65% were empty. The results indicated that fish remains were the most relevant food items at all the collection points. The results demonstrated spatial effects among the fish communities in the headwaters, intermediate section and river mouth, along with variations in water levels, with differences between high- and low-water periods. The redundancy analysis indicated significant effects for temperature, but not for other water parameters. It can be concluded that the piranha populations of the São Miguel River are distributed according to the water levels and the different sections of the river, though they utilize the same type of food resource.

Snappers’ domestication for reproductive purposes is a first step to allow future offering of high quality, more sustainable fish products, generating ecological advantages to the marine ecosystem such as the reduction on the pressure of current stocks. The dog snapper Lutjanus jocu is a very important species with very little information on its capability for domestication. For that reason, dog snappers were collected in the coastal area and maintained in laboratory to verify their capacity to be domesticated and achieve reproductive success. A specific protocol was designed for their maintenance in recirculating aquaculture systems and is presented in the methods section. The domestication of wild specimens until they achieved reproductive success and produced viable eggs in captivity took approximately 2.5 years. Spawning events produced an average of about 25,000 eggs, or about 2,100 eggs·kg-1 of broodstock, with an average of three events per week. During new and full moon, the viability of eggs was higher, showing a strong influence of the lunar cycle in their reproduction. Spawning activities only happened during the night, and embryo development took about 535 degree-hours. Our results concluded that the dog snapper L. jocu can be conditioned in captivity for reproductive purposes, with consistent production of eggs in a weekly basis, enabling the possibility of a large-scale production to help reduce the pressure on the natural stocks.

This study aimed to evaluate environmental suitability scenarios for fish farms in Santa Catarina, Brazil, applying the rules regarding suitability and occupation in Permanent Preservation Areas (PPAs) of the current Forest Code. Rural properties (n=15) with commercial aquaculture were selected to verify the occupation scenarios in PPAs. The suitability analysis was based on the legal regulations that guide the activity’s licensing process, later with the inclusion of public databases that make up this environmental policy. From the suitability maps per property in different scenarios, in the most restrictive rule, 93.3% of the properties analyzed presented environmental liabilities due to occupation in PPAs. Based on the least restrictive rule, 80% of the rural properties presented environmental liabilities. Considering the ideal scenario, in which PPA occupation is absent, 6% of the fish farms were identified; in the less restrictive scenario, 16%; and in the restrictive scenario, 78% of the fish farms. In conclusion, legal uncertainty surrounding the application of the NFC in the Atlantic Forest biome can be an obstacle to the regularization of environmental processes in fish farming. However, is possible and feasible in both scenarios, only for occupation profiles III and IV is it more particular to continue with the activity, considering the minimum recomposition rule.