Habitat association and spatial distribution of Procellariiform seabirds along the continental shelf of the northeast of the United States and the southeastern Canada: Relationships to prey and other top predators

In the first chapter, I compare habitat association among seven species within the order of Procellariiform seabirds that includes shearwaters, storm-petrels and northern fulmars (Fulmarus glacialis) along the northeastern continental shelf of the United States and southeastern Canada (Northwest Atlantic). Environmental factors such as bathymetry, sea-surface temperature (SST), chlorophyll concentration, and frontal features affected seabird densities and influenced their distribution. My model suggested that some species could be influenced by changes to large-scale hydrographic features and that all species will not respond equally to potential climatic fluctuations. In the second chapter, I focus on the northeast Georges Bank and Jeffreys Ledge regions of the Gulf of Maine, recording the presence of marine predators during four hydroacoustic surveys. The primary objective of these surveys was to make annual assessments of the pre-spawning stock of Atlantic herring ( Clupea harengus). I explain the interannual variability of top predators (seabirds, dolphin, whale) using a general additive model that included environmental parameters and fish acoustic index to understand the possible reasons of this variability, including: 1) the effect of environmental predictors on top predators and prey; 2) piscivorous marine predator abundance correlated to fish acoustic biomass index data; and 3) the effect of fishing vessel density effect on marine predators. All predators and Atlantic herring were affected by oceanographic variables; northern gannet (Sula bassana) by fish density, as well. There were also spatial overlap between fishing vessels, humpback whales (Megaptera novaeangliae), great shearwaters (Puffinus gravis) and herring gulls ( Larus argentatus). This study shows the importance of accounting for multiple environmental parameters in order to understand the variability of marine predators abundance in highly productive areas such as Georges Bank, in addition to assess spatiotemporal overlap between aggregated predator and prey for improving fisheries management. Finally, in the third chapter, I examine the foraging associations between Procellariiform seabirds and one species of Pelecaniform (northern gannet), dolphins, whales, and two species of tuna along the continental shelf. The general linear model results suggested seasonality in aggregation types. Great shearwater density increased with humpback and fin whales (Balaenoptera physalus) in the summer, and shifted to common dolphin (Delphinus delphis) in the fall.