Thermal tolerance experiments help establish survival probabilities for tilapia, a group of potentially invasive aquatic species

Abstract

1. Estimating the probability of establishment is an important step toward managing ecological risk posed by natural or intentional introductions. Species introductions in certain geographic areas may pose less of a threat when environmental conditions are unlikely to promote long-term establishment. Species commonly referred to as 'tilapia' have become widespread in certain areas of the southeastern United States, yet concerns remain regarding their potential spread to other areas. 2. We created a model to predict the survival of tilapia in Georgia (U.S.A.) based on individual 'thermal experience'. Laboratory experiments were conducted to measure the duration of survival of two strains of tilapia, Oreochromis nilotica and O. nilotica · O. aureus hybrids, exposed to a variety of temperature regimes with three minimum temperatures and two rates of temperature decline. 3. We used Mayfield hierarchical logistic regression (MHLR) to describe the daily probability of survival as a function of the rate of temperature decline, average sustained temperature, tilapia strain and mass-length ratio. 4. Tilapia generally survived constant minimum temperatures over 12°C but survival rate was mediated by the rate of decline, mass-length ratio and strain. For every 1°C increase in minimum temperature, tilapia were 2.76 times more likely to survive. Fish exposed to rapid temperature decline were less likely to survive than those exposed to slowly decreasing temperature. More robust fish (higher mass-length ratio) were more likely to survive, and strain had a minimal effect despite being supported by the best MHLR model. 5. Our model can be used to estimate survival probability for tilapia under known surface water temperature regimes. Using MLHR in conjunction with experimental tolerance data may be useful for estimating the likelihood of establishment of potentially invasive species.

Thermal Tolerance and Survival of Nile Tilapia and Blue Tilapia under Rapid and Natural Temperature Declination Rates

“…Blue Tilapia and Nile Tilapia held at constant temperatures for 60 d have exhibited even warmer thermal minima (Figure ; Zale ; Wilson et al. ), but such conditions are unlikely to be reliably sustained that long during winter in North Carolina and similar areas.…”

“…Uppercase letters indicate the source (A = Zale ; B = Paz ; C = Wilson et al. ; D = Charo‐Karisa et al. ; E = Atwood et al.…”

“…), and up to 0.5°C per day (Wilson et al. ) or 1°C per day (e.g., Bennett et al. ; Charo‐Karisa et al.…”

“…; Wilson et al. ) and 1°C per 2 d (Paz ). Although these methods allow for rapid testing and easy comparison of species’ thermal minima, the resulting findings may not apply to fish in water bodies experiencing slower seasonal temperature declines.…”

“…Rate of decline is important when addressing invasion risk, as previous experiments have found significant differences in minimum lethal temperature depending on the rate of decline (Paz ; Wilson et al. ). Zale () and Paz () determined that the estimated thermal minimum for tilapias was lower when temperatures dropped at a rapid rate (0.5°C per 5 h and 1°C per 4 h) than when they were dropped at a slower rate (1°C per day down to 1°C per 3 d).…”