Comparison of abundance and diets of selected fishes in trawling and non-trawling zones in Core Sound, NC, USA / by Kevin Hart.
| Author/creator | Hart, Kevin author. |
| Other author | Luczkovich, Joseph J., degree supervisor. |
| Other author | East Carolina University. Department of Biology. |
| Format | Theses and dissertations |
| Production | 2008. |
| Description | xi, 144 leaves : illustrations, maps ; 29 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | Commercial shrimp trawling is believed to impact estuarine communities by removing target and by-catch species. Within Core Sound, NC, fishes are in adjacent areas that are open (trawled) and closed (non-trawled) to shrimp trawling. Hypotheses included that trawling will reduce the biomass of the common by-catch species in trawled areas as well as change the proportion of prey items in the diets these fishes during the fall 2006 and spring and fall 2007. Sampling was performed in open and closed areas similar in bottom type and depth. Nekton was collected using a small otter trawl replicated three times at 4 stations in three bays, to compare the community (abundance, species richness, evenness, and diversity) between the open and closed areas. The closed areas had higher diversity and species richness in the fall 2006 and spring 2007, possibly showing a trawling-induced difference between the areas. Several species of shrimp trawling by-catch species [e.g., spot (Leiostomus xanthurus), pinfish (Lagodon rhombo̐des), pigfish (Orthopristis chrysopterd), and blue crab (Callinectes sapidus)] had a higher ranked biomass and number of individuals in the closed areas. Although this pattern was consistent for these species at all stations, the bay, season and depth also influenced the ranked biomass/m² and number of individuals/m². Some species showed significant statistical interactions between the season and trawling area, with more pinfish and blue crabs found in closed areas in the fall but not the spring. The sieve fractionation method was used to analyze the diets of pinfish, smooth dogfish {Mustelus canis), pigfish, spot, Atlantic croaker (Micropogonias undulatus), Atlantic menhaden (Brevortia tyrranus), cownose ray (Rhinoptera bonasus), and bluefish (Pomatomus saltatrix). MANOVA analyses (P[less-than-or-equal-to] 0.05 indicates differences) were performed for each species, with proportion of dry mass of prey types used as variables. The diets of these species (except cownose rays and bluefish) differed between the two areas. These species did not differ in the types of prey they consumed, but in the proportion of prey items. Pinfish (P[less-than] 0.001) and pigfish (P=0.001) consumed more plant matter in the closed areas and more annelids in the open areas. Smooth dogfish (P[less-than] 0.001) consumed more blue crabs in closed areas. Atlantic menhaden (P[less-than] 0.001) had a higher proportion of meiofauna in the open areas and more detritus in the closed areas. Atlantic menhaden fed on more bivalves in the closed areas and more annelids in the open areas. Spot (P[less-than] 0.001) fed on more plant and particulate organic matter in the closed areas and more pelagic copepods in the open areas. Abundances of these by-catch species were lower in the closed areas; however, the catches of pinfish and blue crabs also varied by season, depth and bay, with differences between open and closed areas occurring after the shrimp season is over. This result suggests that these species were directly influenced by trawling, either through increased by-catch mortality or avoiding the closed areas. Possibly as a result of trawling, the proportion of the prey found in the diets of these fishes varied significantly between the open and closed areas. Shrimp trawlers in Core Sound may be viewed as predators on many nektonic species, potentially causing a fishery-induced trophic cascade. |
| General note | Presented to the faculty of the Department of Biology. |
| General note | Advisor: Joseph J. Luczkovich |
| Dissertation note | M.S. East Carolina University 2008 |
| Bibliography note | Includes bibliographical references (leaves 42-50). |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
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