Dr. TJ Boyle gave a presentation to the Big Country Master Naturalists on Thursday Jan. 15th. His presentation was titled ”Rhithropanopeus harrisii in Texas, a tale of local adaptation and invasion success”. R. harrisii is an estuarine crab that is native to the east coast of North America from Canada to Mexico. The species was first documented in Possum Kingdom reservoir in the summer of 1997 but has since spread to a total of 10 lakes here in Texas. Dr. Boyle has spent the last 12 years studying all aspects of the biology of this crab and its impacts on our reservoirs.
Key points in his talk from Thursday were:
The inland crab populations are capable of reproducing at a salinity below 2 ppt (which is the recorded lower limit found in previous studies), thus allowing this species to continue to continue to spread from lake to lake.
The inland crab populations likely had this adaptation in their native population due to increased competition with other native species in the estuaries of the Gulf of Mexico. The ability to continue to reproduce at lower salinity levels predisposed this particular species for introduction into freshwater bodies.
The inland populations appear to be replacing native crayfish species by out-competing them for shelter. Lake fish have seemingly transitioned from feeding on crayfish to feeding on the crab species. The crabs do not appear to be adversely affecting the local bivalve population, but this is an area that Dr. Boyle plans on studying further.
Lastly, he showed that based on his research, this species was most likely spreading in its larval stage through the transport of waters with the larvae in it.
It was a great experience for Dr. Boyle who thoroughly enjoyed giving the talk and the corresponding Q&A with the members of the Big Country Master Naturalists. The Master Naturalist program represents a partnering between the Texas A&M AgriLIFE Extension, Texas Parks and Wildlife Department and 370 local partners that work together to instruct local individuals in the biology of Texas and give them the resources to pass on that knowledge.