Thermal biology of bonefish (Albula vulpes) in Bahamian coastal waters and tidal creeks: An integrated laboratory and field study

Little is known about the thermal tolerances of fish that occupy tropical intertidal habitats or how their distribution, physiological condition, and survival are influenced by water temperature. We used a combination of laboratory and field approaches to study the thermal biology of bonefish, Albula vulpes, a fish species that relies on nearshore intertidal habitats throughout the Caribbean. The critical thermal maximum (CTMax) for bonefish was determined to be 36.470.5 and 37.970.5 1C for fish acclimated to 27.371.3 and 30.271.4 1C, respectively, and these tolerances are belowmaximal temperatures recorded in the tropical tidal habitats where bonefish frequently reside (i.e., up to 40.6 1C). In addition, daily temperatures can fluctuate up to 11.4 1C over a 24-h period emphasizing the dramatic range of temperatures that could be experienced by bonefish on a diel basis. Use of an acoustic telemetry array to monitor bonefish movements coupled with hourly temperature data collected within tidal creeks revealed a significant positive relationship between the amount of time bonefish spent in the upper portions of the creeks with the increasingmaximal water temperature. This behavior is likely in response to feeding requirements necessary to fuel elevated metabolic demands when water temperatures generallywarm, and also to avoid predators. For fish held in the laboratory, reaching CTMax temperatures elicited a secondary stress response that included an increase in blood lactate, glucose, and potassium levels. A field study that involved exposing fish to a standardized handling stressor at temperatures approaching their CTMaxgenerated severe physiological disturbances relative tofish exposed to the same stressor at cooler temperatures. In addition, evaluation of the short-term survival of bonefish after surgical implantation of telemetry tags revealed that there was a positive relationship between water temperature at timeof tagging andmortality. Collectively, the data from these laboratory andfield studies suggest that bonefish occupy habitats that approach their laboratory-determined CTMax and can apparently do so without significant sub-lethal physiological consequences or mortality, except when exposed to additional stressors. & 2010 Elsevier Ltd. All rights reserved.