Diel variability of feeding activity in haddock ( Melanogrammus aeglifinus ) larvae in the East Shetland area, North Sea

Abstract

Investigations of factors aecting feeding success in ®sh 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 aegli®nus) 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 signi®cant diel variability in all indices and enabled identi®cation of signi®cant 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 ®sh species. Signi®cant 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.

Hormonal control of tryptic enzyme activity in Atlantic cod larvae (Gadus morhua): Involvement of cholecystokinin during ontogeny and diurnal rhythm

“…feed uptake; Kotani and Fushimi, 2011;Pedro Cañavate et al, 2006), physiological studies on digestive processes are not widespread in the literature and focused mostly on the response of proteolytic enzyme activity in relation to feeding schedules (Applebaum and Holt, 2003;MacKenzie et al, 1999;Ueberschär, 1995). Nevertheless, knowledge of diurnal cycles of physiological aspects, including digestive processes, has gained some attention in recent studies (Fujii et al, 2007;Harboe et al, 2009;Rojas-García et al, 2011;Yúfera, 2011).…”

Small-scale patterns in distribution and feeding of Atlantic mackerel ( Scomber scombrus L.) larvae in the Celtic Sea with special regard to intra-cohort cannibalism

“…Feeding success in marine fish larvae is largely dependent on light (Paul 1983;Blaxter 1986) and larval feeding activity often follows a diel pattern as to quantity and composition of prey in the gut (Conway et al 1998;MacKenzie et al 1999;Hillgruber and Kloppmann 2000). While sufficient illumination is of primary importance, other factors have been suggested to affect larval feeding success, e.g., small-scale turbulence (Rothschild and Osborn 1988;Dower et al 1997), temporal and spatial overlap between predator and prey (Lasker 1975;Cushing 1990), length-specific changes in predator prey capture success and preference, and prey visibility and escape capability (Buskey et al 1993).…”

Effect of light intensity on first feeding of the chub mackerelScomber japonicuslarvae

“…Most marine fish larvae are primarily visual feeders (Blaxter 1986), and thus the light regime of their environment is critical for optimal feeding. Previous studies have also shown that most marine fish larvae are visual feeders in the daytime (Blaxter and Staines 1970;Hunter 1981;Blaxter 1986;MacKenzie et al 1999;Sawada et al 2000) and first-feeding larval fish require a threshold light intensity (at 0.1 lx) to initiate feeding (Blaxter 1986). In this study, feeding intensity showed no significant difference among light treatments.…”