Abstract
One of the biggest threats to estuarine systems is the alteration of geomorphology and hydrology to meet human needs. Understanding the effects of altered freshwater inflow on estuarine biota is essential for effectively managing estuarine ecosystems and conserving species that rely on these systems. Southwest Florida’s Caloosahatchee River Estuary (CRE) is one of many estuaries that have been altered to meet human needs over multiple decades. Zooplankton—such as decapod crab larvae—are valuable indicators of estuarine ecosystem integrity due to their rapid responses to changes in water quality and flow. This study was conducted in the CRE from February 2021 to December 2023 to assess the impacts of freshwater inflow on the spatial and temporal distribution and abundance of the larvae of five decapod crabs: blue crab (Callinectes sapidus), Florida stone crab (Menippe mercenaria), Harris mud crab (Rhithropanopeus harrisii), flatback mud crab (Eurypanopeus depressus), and green porcelain crab (Petrolisthes armatus). Each species’ abundance and distribution varied between wet and dry seasons. During high freshwater flow periods, organism center of abundance shifted seaward, and catch per unit effort and total abundance decreased. From these data, appropriate salinity envelopes can be developed for these species to assist water managers in making future decisions involving inflow. Because of the importance of blue crab as a valuable commercial and recreational fisheries species in the region, results of the current study were compared to a similar study conducted in the CRE from May 2008–April 2010. In the previous study, higher abundance of blue crab larvae (zoeae) as well as greater seasonal differences (dry vs. wet) were found compared to the present study. These results add to the collection of other studies that assess the impacts of freshwater inflow on estuarine-dwelling species and should be used to better manage inflow in ways that optimize productivity among these species that serve as prey for juveniles of commercial and recreationally important fishes.
