This study aimed to evaluate the effect of different levels of omega-3 polyunsaturated fatty acids (n-3 PUFA) in the diet of Sardinella brasiliensis on their hematological parameters. A total of 375 fish were distributed in 15 experimental units to evaluate the effects of the diet on their blood for 45 days. The levels of n-3 PUFA added in the diet were 0, 0.3, 0.6, 0.9, and 1.2% of the lipid fraction. These values represent the total percentage of n-3 PUFA in the lipid fraction of the diet, and 0% n-3 PUFA was used as the negative control. Five fish from each experimental unit were sampled at the end of the experiment for hematological analysis, and the parameters measured include the total number of erythrocytes, hematocrit percentage, hemoglobin and glucose concentration and differential leukocyte count. Higher numbers of circulating eosinophils were observed in fish fed 0.3% and 1.2% n-3 PUFA. Although no significant differences were observed in several of the parameters, the results demonstrate that the health of the sardines was not affected by the addition of n-3 PUFA in their diet. It should be emphasized that this is the first study with emphasis on the blood analysis of S. brasiliensis.

This study reports the occurrence of the invasive clam Corbicula fluminea at three locations in the state of Amazonas, Brazil: Saracá Lake (Silves), Macurany Lake (Parintins), and the Amazon River (Itacoatiara). Specimens were collected from exposed sediments and shallow marginal areas during the dry season. Abundance varied among sites, with 952 valves recorded in Macurany Lake, 78 in Saracá Lake, and 56 in the Amazon River. Valve lengths ranged from 3.00 to 22.88 mm, indicating different size classes. These records expand the known distribution of C. fluminea in the Amazon and suggest recent colonization or drought-related mortality, particularly in lentic environments. Hydrological connectivity between lakes and the Amazon River during the seasonal flood pulse may facilitate dispersal and establishment of the species. Because C. fluminea can alter sediment structure, reduce primary production, and compete with native bivalves, its occurrence in a region with limited malacological surveys raises ecological concerns. These records provide essential baseline information for monitoring programs and support preventive management actions to limit the spread of this invasive species throughout the Amazon basin.