Food Limited Growth in Larval Atlantic Herring (Clupea harengus L.) in Western Baltic Watersheds

Food limited growth in larval fish seems to be an exception. However, considering a combination of temperature-limited reproduction of key copepod species, as frequently observed in Eurytemora affinis, and high larval abundances in small nursery areas the situation might be different. In Kiel Canal (western Baltic Sea) we observed an annual recurrent pattern of increasing growth rates early in the season followed by decreased growth at the end of the season. This was correlated with a strong decline in abundance of E. affinis and high abundances of large larvae. We found the same pattern in larval growth and comparable larval abundances in the Strelasund, a narrow and relatively deep “natural canal” located in the western Baltic Sea. An opposing trend of increasing growth rates late in the season was observed in the adjacent Greifswald Bay, a relatively large nursery area for larval herring. Potential for food limitation and density-dependent growth will be evaluated by comparing data on larval growth (RNA/DNA ratios), larval abundance and length frequency distribution, copepod RNA/DNA ratio as a measure for copepod condition, and prey availability during 3 consecutive years in both habitats.