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A comparison of condition indices of Macoma balthica (L.) from the northern and southern Baltic Sea
Bonsdorff, E.; Wenne, R. (1989). A comparison of condition indices of Macoma balthica (L.) from the northern and southern Baltic Sea. Neth. J. Sea Res. 23(1): 45-55
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
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Keyword
    Marine

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Abstract
    Geographical differentiation and seasonal variations of two morphological condition indices (Cl1 = shell-free dwt/shell dwt in mg·g-1 and Cl2 = shell-free dwt/shell length³ in mg·mm-3), and lipid and glycogen content (% of the shellfree dwt) of adult individuals of the bivalve Macoma balthica (L.) were studied from two different areas of the Baltic Sea. Within each area (the Åland Archipelago in the north and the Gulf of Gdansk in the south) a microgeographic gradient is described to illustrate local variations in the parameters measured. For the regions and stations studied, population structure (numbers and size distributions) was very different. Slight differences in the time of onset of spawning (March-early May in the south, and late April-May in the north) were observed between the two areas studied. Both the morphometric indices used showed a strong age-(size) dependence, changing seasonally and microgeographically within each region (in the Gulf of Gdansk Cl1-values ranged trom 100 to 400, and Cl2 from 6 to 25 during 1981). The lipid content in both areas generally increased with depth (on Åland from 14.7% at 1 m and 19.0% at 3 m to 24.3% at 20 m depth in July 1986). Increased values of both lipid content and Cl2 at the deepest stations sampled (20 m in the north, and 75 m in the south) may suggest differences in trophic conditions, illustrating better average nutritive conditions for the adult bivalves. It is concluded that the condition indices used in this study give a sound illustration of the state of the populations studied, and a valuable contribution to the interpretation of the state of animal communities in different regions of the Baltic Sea.

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