Diel variability of feeding activity in haddock (Melanogrammus aeglifinus) larvae in the East Shetland area, North Sea |
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Authors: | B R MacKenzie B Ueberschär D Basford M Heath A Gallego |
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Institution: | Danish Institute for Fisheries Research, Department of Marine and Coastal Ecology, Kavalerg?rden 6, DK-2920 Charlottenlund, Denmark, DK Institut für Meereskunde an der Universit?t Kiel, Dusternbrooker Weg 20, D-24105 Kiel, Germany, DE FRS Marine Laboratory, P.O. Box 101, Victoria Road, Aberdeen, AB11 9DB, Scotland, UK, GB
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Abstract: | Investigations of factors affecting feeding success in fish larvae require knowledge of the scales of variability of the
feeding process itself and the indices used to assess this variability. In this study, we measured short-term (diel) variability
in feeding rates of wild haddock (Melanogrammus aeglifinus) larvae four times per day during a 10-d cruise in the northern North Sea. Feeding activity was evaluated using indices of
gut fullness, prey digestive state and biochemical measurements (tryptic enzyme activity). The gut fullness and the enzyme
activity indices indicated moderate to high rates of food consumption throughout the cruise. Time series analysis of the three
indices showed significant diel variability in all indices and enabled identification of significant lags between food uptake
and peak digestive enzyme activity. The typical pattern of food consumption and digestion was characterized by maximal ingestion
of prey early in the evening (19:00 hrs) and peak digestive enzyme activity at 01:00 hrs. The time scale over which enzyme
activities reacted to prey ingestion was ca. 6 h, and is consistent with expectations from controlled laboratory experiments
with other larval fish species. Significant diel variability in tryptic enzyme activity suggests that attempts to relate this
measure of feeding success to other variables (e.g. food concentrations) should take care to accommodate natural cycles in
feeding activity before making statistical comparisons.
Received: 29 October 1998 / Accepted: 18 June 1999 |
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