Inter-Research > MEPS > v193 > p143-156  
Marine Ecology Progress Series

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MEPS 193:143-156 (2000)  -  doi:10.3354/meps193143

Quantifying environmental heterogeneity: habitat size necessary for successful development of cod Gadus morhua eggs in the Baltic Sea

B. R. MacKenzie1,*, H.-H. Hinrichsen2, M. Plikshs3, K. Wieland4, A. S. Zezera5

1Danish Institute for Fisheries Research, Kavalergården 6, 2920 Charlottenlund, Denmark
2Institut für Meereskunde Kiel, Düsternbrooker Weg 20, 24106 Kiel, Germany
3Latvian Fisheries Research Institute, 6 Daugavgrivas str., 1007 Riga, Latvia
4Danish Institute for Fisheries Research, North Sea Centre, PO Box 101, 9850 Hirtshals, Denmark
5Atlantic Scientific Research Institute of Marine Fisheries and Oceanography (AtlantNIRO), 5 Dm. Donskoy St., Kaliningrad 236000, Russia

ABSTRACT: Spatial and temporal variability in environmental factors can exert major influences on survival and growth of living organisms. However, in many key areas of fisheries science (e.g. growth, survival and recruitment determination), environmental heterogeneity is usually ignored because of insufficient environmental or fisheries data or lack of evidence that such heterogeneity impacts response variables. For the eastern Baltic Sea (ICES Subdivisions 25 to 32), we evaluated spatial and temporal differences in conditions affecting the survival of cod Gadus morhua L. eggs at survival on four distinct spawning sites within the assessment area. We intercalibrated ways of quantifying the volume of water ('reproductive volume') at each site where salinity, oxygen and temperature conditions permitted successful egg development. We have developed and compared a time series (1952 to 1996) of reproductive volumes among the areas to identify spatial differences. The results of 2 independent volume-estimation methods are comparable, indicating that highly significant differences exist among the sites, and that the westernmost spawning ground, Bornholm Basin, has on average the highest reproductive volume and the lowest variability among the 4 sites. These findings may be useful in evaluating how spatial and temporal variability in environmental conditions affect egg hatching success and possibly recruitment in the Baltic stock.

KEY WORDS: Baltic Sea · Cod eggs · Environmental heterogeneity · Oxygen · Survival · Spatial distributions

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