On the mismatch between salinity tolerance and preference for an invasive fish: A case for incorporating behavioral data into niche modeling
Many estuarine species are euryhaline, tolerating a broad range of salinity conditions, such that data on their salinity tolerances can provide little information about a species’ distribution and abundance. This is particularly true for nonnative species, known to be tolerant of a broad range of conditions. Instead, data on a species’ abiotic or habitat preferences may improve prediction of a nonnative species’ potential range, if introduced or if undergoing range expansion. At minimum, information about abiotic preferences may be telling of areas where the probability of nonnative occurrence or density may be higher, and if present, of areas that confer higher fitness. In this study, the salinity preference of the nonnative African jewelfish (Hemichromis letourneuxi), a recent and rapidly-expanding invader in the Florida Everglades, was quantified in laboratory trials. On each trial day, salinity preferences were compared between two treatments: (1) a salinity gradient and (2) a freshwater control.
Despite the broad salinity tolerance of African jewelfish (up to 50), trials show a strong preference for freshwater conditions. When presented with a salinity gradient, over 50% of observations in timed videotaped trials were collected in the lowest salinity chamber (0.3), suggesting an affinity for low salinity, which was unaffected by the sex or body condition of study fish. Fish clearly avoided mid and full salinity conditions. Findings suggest that their distribution may be considerably more limited, and that the species may have higher invasion success in oligohaline habitats, than predicted based on their salinity tolerance. Results have important implications for nonnative species niche modeling, and argue for better integration of behavior along with physiological responses when examining species distributions in dynamic environments.