Ontogenetic and Long‐Term Diet Shifts of a Generalist Juvenile Predatory Fish in an Urban Estuary Undergoing Dramatic Changes in Habitat Availability

Abstract

AbstractVegetated areas such as seagrass beds provide food and essential habitat for many fish and invertebrate species. In particular, many economically important fishes depend on seagrass beds as nursery grounds. In recent decades, there has been a rapid decline in seagrass coverage due to the development of coastal areas worldwide, altering these ecosystems and their community structure. Within Tampa Bay (Florida's largest estuary), seagrass coverage and water quality underwent a decline followed by a recovery over the past three decades; these changes may have altered the community structure of seagrass‐associated fauna. We examined the diets of juvenile Spotted Seatrout Cynoscion nebulosus, a common estuarine predator, to assess whether documented changes in water quality and habitat were reflected in their trophodynamics. Stomach contents of Spotted Seatrout from Tampa Bay were sampled during three different studies conducted in 1981–1982, 1991–1992, and 2005–2013. We analyzed data from these studies to compare the diet across size‐classes and time periods. Using canonical analysis of principal coordinates, we discerned significant differences in diet composition among size‐classes and among time periods. Ontogenetic shifts in diet during all three time periods were consistent with those previously reported, highlighting the plasticity of a generalist piscivore in a recovering seagrass ecosystem. Subtle shifts in diet were detected among the three time periods, suggesting that changes in seagrass coverage contributed to altered trophodynamics in this estuarine system. Our efforts highlight the utility of using a generalist piscivore's diet as a tool for monitoring and quantifying faunal shifts in an ecosystem.Received July 21, 2015; accepted January 5, 2016 Published online April 18, 2016