Anadromous alewife (Alosa pseudoharengus) have drastically decreased in numbers during recent decades throughout New England. These declines have been attributed to the degradation of spawning and nursery habitats owing to intensified human uses of the watersheds surrounding these habitats, and to by-catch at sea. I studied alewife populations along an urbanization gradient of 12 coastal watersheds throughout Cape Cod, New Hampshire, and Maine. Stable isotopic signatures were modeled within the Wisconsin Bioenergetics model to successfully simulate temporal stable isotopic change of δ 15N and δ13C in a predatory fish after diet shifts. In the study of the effect of urbanization on juvenile alewives throughout coastal New England watersheds, δ15N in muscle tissue significantly increased and mean total length and health condition factor in juvenile alewives decreased as urbanization increased. Juveniles leaving more urbanized watersheds were smaller and had poorer condition, when first emigrating to sea. Fish from urbanized coastal watersheds may have reduced prospects for surviving to reproductive age. In the study of the effects of urbanization and overwinter offshore migrations on spawning adult alewives, spawning adult alewives returning to coastal watersheds presented similar and healthy nutritional condition, decoupled from their condition during their juvenile life stage. Differences in size distributions and stable isotopic data of adult alewives, suggested that adults from New Hampshire and Maine rivers feed at lower trophic position than adults from Cape Cod systems. Furthermore, alewife populations from Maine use more northern offshore areas in the Gulf of Maine during their overwintering life in the ocean, whereas fish from Cape Cod may use more nearshore waters in Southern New England. These findings suggest that both land use planning and effective marine management are needed to improve the conditions for these populations. Conversion of land from natural to developed needs to take into consideration the need to protect headwater ponds and estuaries, which are crucial for the growth of juvenile alewives. Furthermore, spatial management regimes in the Gulf of Maine need to take into consideration that alewife populations may use specific regions and that setting closure areas may benefit alewife runs of some regions in detriment of others.
|Advisor:||Limburg, Karin E.|
|Commitee:||Agardy, Tundi, Gibbs, James P., Schulz, Kimberly|
|School:||State University of New York College of Environmental Science and Forestry|
|School Location:||United States -- New York|
|Source:||DAI-B 73/05, Dissertation Abstracts International|
|Subjects:||Natural Resource Management, Environmental science, Aquatic sciences|
|Keywords:||Anadromous alewife, Coastal watersheds, Gulf of Maine, Nursery habitat, Stable isotopes, Urbanization|
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