[MARMAM] new paper on foraging ecology

PeterStevick at aol.com PeterStevick at aol.com
Wed Jul 23 05:58:37 PDT 2008


The following paper has recently been published:
 
Stevick, P.T., Incze, L.S., Kraus, S.D., Rosen, S., Wolff, N. and Baukus,  A. 
2008. Trophic relationships and oceanography on and around a small offshore  
bank. Marine Ecology Progress Series 363:15-28.
 
ABSTRACT: Small offshore banks may be sites of intense feeding by upper  
trophic level predators. We studied the distribution of cetaceans, seabirds,  
pelagic fish, euphausiids and zooplankton over a 9 × 15 km bank to determine the  
conditions and processes that concentrated prey there and to examine the  
relative importance of bottom-up or top-down controls. Euphausiids were the  
primary prey during most foraging activity. While these were widespread in  
subsurface waters, foraging was concentrated on dense surface swarms that formed  
during daylight hours over 2 small crests. Internal wave passage resulted in  
upward movement and concentration of euphausiids in these areas through a  
coupling of physical processes and euphausiid behavior, resulting in surface  
swarms. Thus, internal waves appear to provide a critical mechanism enhancing  
trophic energy transfer. The formation of dense, localized and accessible prey  
concentrations was more important to foraging than was the overall available  
prey biomass. The estimated maximum daily consumption of euphausiids by  
cetaceans, seabirds and herring combined was <0.4% of the estimated  instantaneous 
euphausiid biomass, and top-down control was unlikely to have  substantially 
influenced euphausiid biomass at this site. Some predator species  that do not 
prey extensively on euphausiids or herring were more prevalent in  off-bank 
waters. The scales of predictability and the temporal dynamics of such  features 
determine the manner in which populations of upper trophic level  organisms 
utilize a variable environment.
 
Pdf files of the paper are available from _peterstevick at aol.com_ 
(mailto:peterstevick at aol.com) 
 
Cheers,
Peter Stevick



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