Foraging values of <em>Mulinia lateralis</em> and <em>Ischadium recurvum</em>: energetics effects of surf scoters wintering in the Chesapeake Bay.

dc.contributor.advisorOttinger, Mary Annen_US
dc.contributor.authorBerlin, Aliciaen_US
dc.contributor.departmentMarine-Estuarine-Environmental Sciencesen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.description.abstractSurf scoter (<em>Melanitta perspicillata</em>) populations wintering in the Chesapeake Bay primarily prey on two food items, the hooked mussel (<em>Ischadium recurvum</em>) and dwarf surfclam (<em>Mulinia lateralis</em>). The decline of oyster reefs (<em>Crassostrea virginica</em>) has decreased availability of mussels inducing surf scoters to switch to a more opportune food item, the dwarf surfclam. The objectives of this study were: 1) to determine the comparative nutrient composition of these prey items; 2) to evaluate the energy assimilated by surf scoters from these prey items; 3) to determine the functional responses of scoters foraging on four different ecologically relevant densities (30, 100, 1000, and 3000 m<sup>-2</sup>) of each prey item; and 4) to model the foraging value (costs - benefits) of both prey items for surf scoters. <em>I. recurvum</em> contained higher ash, protein, lipid, and energy per item than <em>M. lateralis</em>. Metabolizable energy from each prey item by surf scoters was 83% for <em>M. lateralis</em> and 87% for <em>I. recurvum</em>. The shell strength of <em>I. recurvum</em> was significantly stronger than <em>M. lateralis</em>. For scoters foraging in a large diving tank 2 m deep, intake (# s<sup>-1</sup>) for <em>M. lateralis</em> was significantly higher than <em>I. recurvum</em> at high densities, but lower at the low densities. Gross energy intake (kJ s<sup>-1</sup>) and metabolized energy intake (kJ s<sup>-1</sup>) were significantly greater for <em>I. recurvum</em> than <em>M. lateralis</em>. Based on nutrient content, metabolizability, behavior and intake rates, and energy expenditure at naturally occurring densities, the foraging value for <em>M. lateralis</em> was significantly lower than <em>I. recurvum</em>. Despite higher ash content and harder shell, which would partly offset the apparent energetic advantages of <em>I. recurvum</em>, greater foraging value of <em>I. recurvum</em> than <em>M. lateralis</em> provides a more beneficial prey item for wintering surf scoters. Therefore, wintering surf scoters must adapt in order to maintain their daily energy requirement. If surf scoters are forced to feed primarily on <em>M. lateralis</em>, the most advantageous and available prey in the Chesapeake Bay, instead of <em>I. recurvum</em>; there may be insufficient energy for them to build fat reserves needed to make migration.en_US
dc.format.extent1539269 bytes
dc.subject.pqcontrolledBiology, Ecologyen_US
dc.subject.pqcontrolledBiology, Zoologyen_US
dc.subject.pqcontrolledEnvironmental Sciencesen_US
dc.subject.pquncontrolledsurf scoteren_US
dc.subject.pquncontrolledChesapeake Bayen_US
dc.titleForaging values of <em>Mulinia lateralis</em> and <em>Ischadium recurvum</em>: energetics effects of surf scoters wintering in the Chesapeake Bay.en_US


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