Osmoregulatory capabilities of the gray snapper, Lutjanus griseus: salinity challenges and field observations

Abstract

We investigated the osmoregulatory responses (plasma osmolality and blood hematocrit) displayed by the gray snapper 6–192 h after abrupt changes in ambient salinity. Fish were challenged with six different salinity treatments including a control (0, 5, 30, 50, 60, and 70 ppt) and blood samples were collected at various time points post-transfer. Gray snapper across all size classes tested (13.5–24.5 cm total length) acclimated successfully to hypo- and hyper-saline environments (0–60 ppt) after an adjustment period of ∼96 h. However, abrupt transfers to 70 ppt resulted in 100% mortality within 48 h. Laboratory results were then compared with field measurements obtained after fish were captured in low salinity (0–4 ppt) or marine (∼30 ppt) habitats, suggesting that osmoregulatory processes occurred similarly in both settings. Overall, findings suggest that gray snapper possess similar or higher osmoregulatory capabilities compared to many euryhaline species examined to date, and thus should be considered a euryhaline species.