Nile Tilapia -- Free Ranging “Aquatic Chickens”: Modeling the Spread of a Non-Native Species in the Northern Gulf of Mexico Under Different Climate Change Scenarios

The invasion process is defined by a progression of stages (e.g., introduction, establishment, spread, and impact) that are both biologically and environmentally filtered at each step. In this paper, we summarize previous work by our group documenting the introduction and establishment of Nile tilapia (Oreochromis niloticus) in coastal Mississippi.  We then integrate long-term, spatial environmental data with a predictive model derived from experimental physiological tolerances in order to model the spread of Nile tilapia throughout the region under various climate change scenarios (i.e., normal, extremely wet, and extremely dry years).  Model predictions suggest that, during normal summers, Nile tilapia is capable of surviving throughout Mississippi’s coastal waters but growth and reproduction are limited to river mouths or upriver.  Overwinter survival is also limited to river mouths.  During extremely wet and dry years, the areas where Nile tilapia could survive, grow, and reproduce increased (2-368%) and decreased (86-92%), respectively, in the summer with a similar pattern holding for overwinter survival.  These results indicate that Nile tilapia are capable of 1) using saline waters to gain access to other watersheds throughout the region and 2) establishing populations in nearshore, low-salinity waters, particularly in the western portion of coastal Mississippi.