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The effect of dietary inclusion of soy protein concentrate (SPC) and simultaneous supplementation with taurine on the growth, hematology, blood biochemistry, and liver histology of totoaba (Totoaba macdonaldi) juveniles was assessed. Four isoproteic and isolipidic diets were formulated containing either 30 or 60% of SPC (diets S30 and S60), supplemented or not with 1% of taurine (diets S30T and S60T). A fishmeal-based diet formulated for totoaba nutritional requirements, without SPC and taurine supplementation, was used as a reference diet. Triplicate groups of 32 totoaba juveniles (average body weight 7.5 ± 0.6 g) were fed these diets for 45 days. Results showed that growth performance in fish fed S30, S30T, and S60T was similar to fish fed the reference diet. Red blood cells and hematocrit in fish fed with supplemented taurine in both levels of SPC (S30T and S60T) were similar to the fish fed the RD; the addition of taurine improved the state of hydration of totoaba. Plasmatic hemoglobin in fish fed the lower SPC level was similar to fish fed the RD. The mean corpuscular hemoglobin concentration in fish fed S30T was similar to fish fed the RD, taurine supplementation prevented the development of hypochromic anemia in this group of fish. Plasmatic albumin in fish fed S30 was similar to fish fed the RD. Plasmatic total protein and globulin concentration increased and AL:GLB (albumin:globulin ratio) decreased in fish fed the SPC-based diets despite taurine supplementation. The protein profile showed that taurine supplementation did not prevent a possible inflammatory process (increased globulins, decreased AL:GLB) in juvenile totoaba fed both levels of SPC. Glucose concentration was similar in fish fed S30, S30T, and S60T. The histological hepatic index was highest in fish fed S60. These results suggest that with an appropriate nutritional level, taurine may play an important modulatory role in the hematology and blood biochemistry status in totoaba fed SPC-based diets, contributing to the enhancement of an overall healthy growth performance.

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The ranges of concentrations of Cd, Cu, Pb and Zn of the soft tissues of C. corteziensis collected in seven coastal lagoons of NW Mexico were 1.55-7.45, 17.50-166.36, 4.13-9.49 and 245.34-2,304.12 microg/g (dry weight), respectively. Their distributions were not consistent and there were no seasonal trends, indicating different point sources of the metals in each lagoon. The mean Cd and Pb concentrations were 5.34 and 6.30 microg/g (dry weight), which are higher than the values indicative of polluted areas. Our data indicate that only the levels of Cd are a possible health risk in six of these lagoons, and only in the case of regular local consumers. In one, Cu and Zn reach levels of concern.

Silicon dioxide has been used in aquaculture to increase the abundance of diatoms; however, its relationship with water quality or productive performance has not been investigated. Our study evaluated the effect of diatomite on water quality, growth performance and proximate composition of Penaeus vannamei reared in seawater (E1) and brackish water (E2) with biofloc. Two independent experiments (E1 and E2), each one with three treatments with biofloc were evaluated: treatments D with a weekly addition of diatomite (10 g m-3); the treatments D plus a continuous inoculum of diatom Chaetoceros muelleri (DD); and only biofloc like control, for E1 was used post-larvae with an initial body weight (IBW) of 0.0075 g; while in E2 was used juvenile with an IBW of 1.42 g. After seven weeks in E1, non-significant differences were registered in survival, weight gain (WG), specific growth rate (SGR) and feeding conversion rate (FCR) between DD treatment and control. However, in E2, the treatment D showed significantly higher WG (9.83 g) and SGR (4.25% d-1) compared to control (7.64 g and 3.86% d-1, respectively). Conversely, the FCR was lower in treatment D (1.16) compared to control (1.49). Non-significant differences were recorded in the proximate composition for shrimp, periphyton, and biofloc, among treatments in both experiments. Levels of nitrogenous wastes were similar among treatments. While in E2, the concentration of settleable solids was significantly higher in treatments with diatomite compared to control. Our results recommend the use of diatomite to improve the growth performance of shrimps cultured in brackish water with biofloc.