In aquatic habitats, many invasive species are generalist crustaceans (e.g. crayfish, crabs) which have caused lasting and significant impacts on aquatic ecosystems. Thus, any time an exotic generalist crustacean arrives in a new region, there is a significant concern the species will pose a new invasive threat. Since 2011, Asian tiger shrimp (Penaeus monodon) have steadily appeared in commercial shrimp catches from North Carolina to Texas. Their consistent presence is concerning because the tiger shrimp’s large body size, broad carnivorous diet, and estuarine distribution suggest they may impact economically and ecologically important native shrimp species through predation and/or competition. Furthermore, their large adult size also suggests there may be limited biotic resistance from gape-limited fish predators. To assess these concerns, we used mesocosm experiments to examine predatory and habitat displacement interactions between tiger shrimp and native shrimp. We also used large mesocosms to differentially compare red drum (Sciaenops ocellatus) predation rates on tiger shrimp and native shrimp and each shrimp’s anti-predator responses.
Results/Conclusions
In contrast to initial fears, tiger shrimp predation rates on native shrimp were low and a majority of both brown and white shrimp survived encounters with tiger shrimp. However, interactions between native shrimp and tiger shrimp often displaced native shrimp from preferred habitats. This displacement response was dependent on habitat type (marsh grass or seagrass) and appeared to be driven by anti-predator responses, as tiger shrimp often chased and attempted to consume native shrimp. The displacement of native shrimp from estuarine habitats suggested that native shrimp may suffer higher predator mortality in the presence of tiger shrimp. However, interactions between tiger shrimp and native shrimp did not increase predator-driven mortality in the presence of red drum. Both tiger shrimp and native shrimp displayed anti-predator responses to red drum predators, but red drum consumed fewer tiger shrimp than native shrimp. Together these results suggest that tiger shrimp may have few negative impacts on native shrimp, even though there appears to be limited biotic (predator) resistance to tiger shrimp invasion.