Diversity metrics like species richness provide some measure of state of a community. It is thought that communities with higher diversity may be associated with greater resiliency to disturbance, as well as being more effective at providing ecosystem services. Investigating how these metrics change across landscapes and through time may provide insight into the stability of a community, and identify areas of management concern. Rarefaction analysis can be used to compare richness samples from different locations or time periods, in order to determine whether two assemblages differ in their composition. By doing these analyses across space and through time, we are able to identify patterns in community structure, and use this information to better inform management decisions. For this project, 30+ years of gillnet survey data from Sabine Lake, Galveston Bay, East Matagorda Bay, Matagorda Bay, San Antonio Bay, Aransas Bay, Corpus Christi Bay, Upper and Lower Laguna Madre, and Cedar Lakes were used to identify differences in the marine fish communities of the bays along Texas across space and through time.
Results/Conclusions
Using the package “rareNMtests” in the R statistical environment, comparisons were conducted to identify differences in fish communities for all pairwise combinations of the major bays along Texas. Additionally, survey data was divided into decade subsets for each bay to assess changes in fish communities through time. All pairwise decade comparisons for each individual bay were tested. The results of the bay-to-bay comparisons showed that most bays were significantly different from each other in terms of their fish assemblages, with the exceptions of no significant differences between Galveston Bay, East Matagorda Bay, and Matagorda Bay, no significant difference between Matagorda Bay and San Antonio Bay, and no significant difference between Aransas Bay and Cedar Lakes. For the decade-to-decade comparison, all bays except Cedar Lakes showed significant differences between one or more time periods, with species richness increasing through time for all bays. The results from this project suggest a regional shift in fish community diversity through time, although the magnitude and timing of that change appears to vary spatially. Further analyses should look to quantify the change in communities and identify potential drivers.