Changing fish assemblages in a Mid-Atlantic estuary: sensitivity analysis of a long-term time series to climate change and guild construction

At the beginning of the 21st century, climate change is among the foremost of ecological concerns in both marine and terrestrial habitats. Generally, mobile species, such as fishes, have shifted their ranges poleward in response to changing climatic conditions in the Northern Hemisphere. On a local scale, however, different fish species have displayed differing shifts in latitude and habitat. It is therefore important to study the change in assemblage shifts on a local scale. I examined the change in fish assemblages, environmental conditions, and the relationship between them, over time in the Mullica River-Great Bay estuary, located in southern New Jersey. I used a long-term time series collected by the Rutgers University Marine Field Station and the Jacques Cousteau National Estuarine Research Reserve's System Wide Monitoring Protocol. I also organized fish species into guilds based on reproductive or origin characteristics, and into abundant and rare species assemblages as a proxy for species, and examined the change in these guilds over time as compared to the full assemblage. Water temperatures in the system rose on average, with Average Summer Temperatures explaining the most variance in the change of fish assemblages. Both the full assemblage and guild analyses also indicated that freshwater-favoring and spawning species increased in importance, while juveniles of estuarine spawners decreased overall. Marine spawners and species did not change significantly, suggesting that change in species local to the system has had a greater effect on the assemblage than change in recruits from the marine environment.M.S.Includes bibliographical referencesby Katherine J. Nickerso