ACCLIMATION OF CAPTIVELY REARED JUVENILE COMMON SNOOK TO THE WILD: EFFECTS ON MICROBIOTA AND INNATE IMMUNITY

Research regarding stock enhancement of common snook Centropomus undecimalis has revealed that juveniles survive better in the wild if they are first provided with a three day acclimation in enclosures at the site of release. Hypotheses as to the mechanism behind the improved survival include recovery from transport stress and behavioral adjustments such as learning to feed and avoid predators in the wild. However, the effects of acclimation on the overall health of the snook is not yet understood. An organism's bacterial communities, termed the microbiota, have profound effects on host health. The microbiota influences growth and development, digestion, nutrient acquisition, feed conversion, and disease susceptibility, and as a result plays a large role in the overall health status of the host. The microbiota shifts as fish are brought from the wild into captivity, but to our knowledge, no study has investigated these shifts during release from captivity into the wild, and no study has investigated these changes while simultaneously investigating alterations in innate immune activity. As captive snook may encounter new and different pathogens in the wild, knowledge of these transitions may shed light on increased survival in acclimated snook, as these parameters directly impact the ability of the fish to resist disease.

This study used next-generation sequencing and previously established innate immunity assays to investigate the changes in external skin microbiota and immune parameters during the transition of juvenile snook from captivity to the wild during stock enhancement efforts. Skin mucus was collected from captive fish prior to transport to the release site and following three days of acclimation in enclosures, and from wild individuals collected from the release location. The study was repeated in three different creek systems near Sarasota, Florida (Philippi, Hudson, and Whittaker) in late summer/early fall of 2016. Microbiota was characterized using paired-end Illumina sequencing, and innate immune parameters analyzed included lysozyme, superoxide dismutase, alkaline phosphatase, and protease.

Data presented will include the first characterization of captive and wild juvenile common snook skin microbiota. The ability of the captive microbiota to adapt to wild conditions will be discussed, focusing on relative abundances of known fish pathogens. Comparisons will be made between captive, transitioning, and wild snook in terms of innate immune enzyme activity. Finally, the implications of immunity and microbiota for snook acclimation and disease resistance will be discussed.