Fishes of a temperate estuary: ecology and response to an urbanized watershed
Creators: name: Valenti, Jessica
Publisher: name: No Publisher Supplied
Year: 2020

description: Anthropogenic activities have left no part of the global ecosystem untouched; not even the highest mountain peaks or deepest ocean trenches. Of the many ways anthropogenic activities can alter the ecosystem, urbanization (anthropogenic land development) is perhaps one of the most profound ways by which humans physically transform the environment. The urbanization of coastal watersheds has been occurring for centuries and continues today. Nearly 40% of the United States’ population resides within coastal counties, and this percentage is projected to increase due to continued coastal migration and the exponentially growing human population. Unfortunately, the impact of this watershed urbanization on coastal fauna is still not well understood. The understudied fauna includes estuarine fishes, which use these areas as nurseries and are essential to sustaining healthy fish populations. In this dissertation, natural and anthropogenic influences on fish assemblage structure (species composition, abundance, diversity) were studied to determine how watershed urbanization affected the fishes in Barnegat Bay, a temperate lagoonal estuary located in New Jersey, U.S.A.In the first and second chapters, changes in fish assemblage structure in relation to temporal and subhabitat influences were studied to understand the assemblage response to natural variation prior to evaluating the influence of urbanization on assemblage structure. In Chapter I, the long-term response of fishes to the passage of Hurricane Sandy was assessed. Fish assemblage structure remained relatively stable over the three year study period, which encompassed the large episodic disturbance of Hurricane Sandy. The ability of fish to relocate from areas of temporarily unsuitable habitat and annual new recruitment of fishes to the bay likely contributed to the observed stability in the fish assemblage. In Chapter II, fish usage of the dominant subtidal habitats (marsh creeks, sand, submerged aquatic vegetation) within Barnegat Bay were documented. Fishes used all habitats sampled demonstrating the importance of the habitat mosaic within Barnegat Bay. Further, the assemblages in marsh creeks were often as abundant and diverse as those in submerged aquatic vegetation, highlighting the importance of marsh creeks as important fish habitat in addition to submerged aquatic vegetation habitat.In the third and fourth chapters, the influence of urbanization on fishes in Barnegat Bay was assessed at varying spatial scales. In Chapter III, structural characteristics of the fish assemblages along the large watershed-wide urbanization gradient, which increases from the southern to the northern portion of the bay’s watershed, were evaluated. Structural differences in fish assemblages that could be solely attributed to the large-scale urbanization gradient in the watershed were not readily apparent, likely due to a lack of cumulative impacts at this large scale. In Chapter IV, fish assemblages inhabiting unaltered marsh creeks and lagoon housing complexes with heavily armored shorelines were compared. At this smaller scale, differences in fish assemblage structure between unaltered and armored habitats were evident, with species that relied on the salt marsh and shallow waters being less abundant in the lagoon complexes. These findings suggest urbanization in the Barnegat Bay watershed has caused localized changes in fish assemblages which have not accumulated to assemblage impacts on a large-scale, but could do so if urbanization in the bay’s watershed continues unabated.