Mowitt, W. P. University of Maryland Center for Environmental Science, mowitt@cbl.umces.edu
Houde, E. D. University of Maryland Center for Environmental Science, ehoude@cbl.umces.edu
Heath, M. R. Marine Laboratory Aberdeen, heathmr@marlab.ac.uk
Sanford, A. University of Maryland Center for Environmental Science, asanford@hpl.umces.edu

 
CONTAINMENT AND SPATIAL SCALE: EFFECTS ON FORAGING ABILITY OF PLANKTIVOROUS FISH
 
Enclosure dimensions influence foraging by planktivorous fishes, affecting their growth and modifying their impact on zooplankton communities. Experiments and models were used to determine how spatial scale might affect foraging by enclosed fish. Two experiments were run with bay anchovy in estuarine mesocosms of two volumes (1 and 10 cubic meters) and two shapes (ratio of diameter:depth). Additionally, an individual-based foraging model simulated fish behavior and, combined with a bioenergetics model, predicted foraging efficiency and impact of containment on anchovy growth. In each experiment, anchovy growth rates were highest in the larger and most pelagic mesocosms-i.e. highest volume:wall area. Anchovy foraging affected zooplankton populations. At termination, zooplankton abundances were lowest and sizes smallest in mesocosms in which anchovy grew most. In the model, foraging efficiency depended upon enclosure dimensions and schooling behavior assigned to the fish. Efficiency declined in small enclosures and in the presence of simulated predators. Small declines in modeled foraging efficiency (10%) resulted in large declines in modeled anchovy growth (50%). Combined experimental and modeling results indicated that containment effects must be considered when 'scaling up' potential effects of foraging fish in natural aquatic ecosystems.
 
Day: Thursday, Feb. 4
Time: 03:30 - 03:45pm
Location: Hilton of Santa Fe
 
Code: SS51TH0330E