This study examined the effect of potential probiotic bacteria on growth and survival of the tilapia Oreochromis niloticus, under high density and suboptimum temperature. Presumptive Bacillus and lactic acid bacteria (LAB) were isolated from tilapia and from their culture system and were characterized for haemolytic and enzymatic activity, and antagonism against Vibrio. Selected strains were included in the diet of juvenile tilapia and evaluated during a 134‐day assay. The experiment was conducted with four treatments: (1) fish fed with commercial feed plus Dry Oil®; (2) fish fed with commercial feed plus LAB; (3) fish with bacilli in water; (4) fish with a mixture of treatments 2 and 3. Tilapias in all treatments, including bacteria, grew significantly better than fish fed with commercial feed plus Dry Oil® (control group). Survival was similar in all treatments. The physicochemical parameters of the culture system were maintained within the optimal ranges for the species, with the exception of temperature (19.9–24.82 °C). Animals fed diet supplemented with bacilli and LAB had good survival and the best growth performance, suggesting that bacteria are appropriate growth‐stimulating additives in tilapia cultivation.

Red jumbo tilapia and M. americanum prawns were placed in 1000 L units in polyculture at three different densities of tilapia (4/5, 9/5 and 14/5 m 2 ; tilapia/prawn) during 112 days with initial weight of 6.5 ± 2.8 g for tilapia and 25.9 ± 8.5 g for prawn. Prawn (0/5 m 2) and tilapia (4/0, 9/0 and 14/0 m 2) controls were included. Tanks were maintained outdoors and under shade. Total weight gain (WG), daily individual weight gain (DWG), specific growth rate (SGR), survival, production of gross mass and food conversion ratios (FCR), ammonia, nitrite and nitrate, and chlorophyll a were measured in all units. Only prawn weight gain was significantly higher in polyculture. For tilapia, the highest survival at the end of the trial was 94% and the lowest was 75%, while prawns had final survival rates from 43% to 86%. No statistical differences were observed in weight increase among treatments at p ≤ 0.05.

Length-weight relationships, morpho-physiological index and blood biochemical parameters are frequently used to determine the health status of wild and cultured fish. Between December 2013 and July 2015, a total of 123 yellow snappers (L. argentiventris) were captured with gillnets in the Macapule Lagoon and blood samples were taken. All the blood biochemical parameter varied significantly among sampling seasons. The total proteins, triglycerides, and cholesterol values were significantly highs in December 2013 (cold season). We found significant differences intra and inter-correlations between morpho-physiological and blood biochemical parameters in bout seasons. The equation parameters (a & b) of the length-weight relationship in each of the seasons indicated that the growth of yellow snapper showed important variations over time between year 1 and year 2. Among the morpho-physiological index, only the Hepatosomatic Index (HIS) and Gastric Repletion Index (GRI) varied significantly among the seasons (P<0.01); and they were positively correlated with water temperature. In conclusion, the morpho-physiological and blood biochemical examinations determined for the first time for yellow snapper in Macapule Lagoon, showed a wide temporal variation and were related to environmental changes between seasons. This new data can be used as a reference to compare health conditions between wild and captive yellow snapper (L. argentiventris) and other fishes.