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The skin-associated microbiota of fish competes against pathogens for space and nutrients, preventing colonization by harmful bacteria encountered during environmental transitions such as those faced during stock enhancement. Thus, alterations in bacterial community structure during release of cultured fish have important implications for health of these individuals. This study investigated microbiota structure during acclimation of juvenile hatchery-reared common snook Centropomus undecimalis to the wild by comparing skin-associated microflora among snook in captivity, after 48 h of acclimation at release sites, and from the wild. After two days of acclimation, the microbiota of hatchery-reared snook mirrored that observed on wild snook. Relative abundances of potential pathogens were higher in captive fish, whereas acclimated and wild fish harbored bacterial taxa influenced by geographical factors and water quality at release sites. Predicted microbiota function of acclimated and wild fish showed higher production of protective amino acids and antimicrobials, identifying a mechanism for microbial supplementation of the immune defense of these fish. The two-day transition to wild-type microbiota suggests a temporal scale of hours associated with bacterial succession indicating that the microbiota, whose structure is vital to fish health, aids in acclimation of fish to new environments during stock enhancement efforts.

The need for sustainable bacterial management approaches in aquaculture is crucial for advancement of the industry. Probiotics are a promising strategy as evidenced by benefits demonstrated in intensive larviculture of various marine fish species. In this study we investigate the effects of a mixed Bacillus species (B. licheniformis and B. amyloliquefaciens) probiotic on rearing of larval common snook (Centropomus undecimalis). Experimental treatments included (1) probiotics supplemented to the water and live feed, (2) probiotics supplemented to the water only, and (3) no probiotic controls. Data from two separate trials indicated up to 2.5 times higher survival with probiotic addition, as well as 20% higher survival 7 days following a transport event. These benefits were not explained by faster growth, measured water quality parameters, or innate immune enzyme activities. Microbiota analysis indicated the importance of system stabilization prior to larval stocking to improve rearing success and probiotic performance. ied Potential probiotic benefits include accelerated gastrointestinal tract development, enhanced immunity, inhibition of opportunistic bacteria, and improvements to water quality parameters. Results suggest this probiotic should be tested in other marine fish species in order to reduce larval rearing bottlenecks.

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We describe oocyte development in Common Snook Centropomus undecimalis and, secondarily, present results from a comparison of the wet mount technique with histological preparations of ovarian biopsies. Potential differences in ovarian development between wild and captive broodstock were investigated. Results showed that mean oocyte diameter (µm) was not statistically different between the two groups or within each defined stage and step of reproductive condition. Histological preparations were used to validate the wet mount technique as a rapid, yet accurate, low-cost alternative for assessing reproductive condition in Common Snook. When compared with histology, the wet mount provided a precise method for determining whether female broodstock were candidates for hormone induction in aquaculture applications. However, due to the loss of fine resolution, it was not possible to identify cortical alveoli, oocyte atresia, and postovulatory follicle complexes by using the wet mount technique. Despite these limitations, findings from this study indicate that the wet mount technique may have applications in fishery biology as a noninvasive method for assessing reproductive condition in wild fish stocks.A critical component for many studies of fish reproductive biology is an accurate assessment of the reproductive condition of individual fish. There are numerous macroscopic and microscopic methods for evaluating the gonadal condition of fish, particularly with regard to ovarian development. West (1990) reviewed some of these in detail and discussed the level of accuracy and usefulness for each. The methods in use range from