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GLIN==> July 3 Seminar - Ann Arbor


GLERL, Conference Room 105
2205 Commonwealth Blvd
Ann Arbor, MI

Tuesday, July 3, 10:30 am
GLERL Conference Room 105

Title:"Distribution and activity of pelagic fish – acoustic studies in the Baltic Sea"

Speaker: Tomas Didrikas
Department of Systems Ecology, Stockholm University
Stockholm, Sweden

Animal activity is often strongly influenced by the diel light cycle, which also influences other aspects of behavior. We used a seabed-mounted, upwards-pinging echo sounder to study fish activity and vertical distribution in relation to light and water temperature. Four phases of the fish distribution were distinguished over the diel cycle. By using acoustic tracking, we could estimate individual fish size and swimming speed. Regression models were developed to investigate effects of fish size and environmental factors (water temperature, light intensity at the depth of a fish – i.e. in situ light intensity) on swimming speed. For all phases combined, the model explained 52% of the variation in swimming speed, with fish size, light intensity and temperature being the significant variables. The results have clear implications for fish bioenergetics models. Such models should account for seasonal, light-driven cycles in the activity-induced respiration estimates, in particular when modeling populations at high latitudes.

Fishermen, anglers, and even biologists often utter phrases like “There is no fish in this area in spring” or “when the wind comes from the north…”. We describe and analyze the vertical and horizontal distribution of fish in relation to water temperature, wind direction and fish size in a bay in the northern Baltic Sea using data from biweekly acoustic surveys made through spring to autumn for two consecutive years. The pelagic fish community in this bay is dominated by clupeids, i.e. herring and sprat. The seasonal dynamics in vertical distribution patterns were consistent between years and varied with temperature structure. Fish showed clear horizontal patchiness, but horizontal distributions were not significantly related to wind directions.

For directions, see
David F. Reid, Ph.D.
Director, NOAA National Center for Research on 
Aquatic Invasive Species (NCRAIS)
Senior Research Scientist, Nonindigenous Species Program
U.S. Department of Commerce
National Oceanic and Atmospheric Administration
Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, MI  48105-2945
Voice: 734-741-2019
FAX: 734-741-2055
GLERL home page:
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