Experimental estimation of the food intake of larval vendace (Coregonus albula L.) under field conditions

Abstract

We estimated the food intake of larval vendace (Coregonus albula L.) directly in an experimental chamber under field conditions. The larvae were stocked into net enclosures and reared without additional feeding for 6 weeks immediately after the ice melted in Lake Yla-Enonvesi, Eastern Finland. The food intake was estimated on the basis of the decrease in zooplankters due to larval predation in the transparent plastic chambers anchored in the littoral zone. The experiments were carried out twice in 1988 and three times in 1989 (May-June). The numbers of zooplankters inside the chambers were counted from the subsamples using an inverted microscope. The relative daily ingestion rate (mg dry mass of prey animals mg dry mass of fish -' 24 h -') of the larvae of different sizes was: 1.09 and 0.84 for 9-11 mm larvae, 1.27 for 11-13 mm larvae and 0.34 for 17-20 mm larvae. The measured ingestion rate is presumed to be near the maximum consumption of the larvae. This method could provide accurate estimates of food consumption in the field or in-the laboratory.

Varying Resistance of Zooplankton Prey to Digestion: Implications for Quantifying Larval Fish Diets

“…Soft-bodied Asplanchna spp. also degraded rapidly to become unidentifiable in larval vendace guts (Karjalainen and Viljanen 1991). In general, the knowledge available from the literature and from visual evaluation of the thickness of the species-specific integument matched well with our ranking of zooplankton taxa according to their resistance to digestion.…”

Diel feeding periodicity in larvae of the vendace (Coregonus albula L.) and influence of food availability and environmental factors on food intake

“…If some components of the diet are processed more rapidly than others, the amount of prey in the whole gut will not reflect the amount of actually eaten at any given time. Karjalainen, Koho & Viljanen (1991) and Karjalainen & Viljanen (1992) found that the evacuation rate of cyclopoid copepodids in vendace larvae was slower than that of nauplii, and concluded that the reduction in gut contents in vendace larvae is relatively linear. In fasting experiments with vendace larvae from Lake Lentua, Sutela & Huusko (1997) found that soft-bodied Synchaeta rotatorians were digested to an unrecognizable condition within 2 h, while investigations carried out by Fossum (1983) on herring larvae (Clupea harengus L.) showed that copepod nauplii and polychaete larvae were digested in 1.5 h, whereas bivalve larvae passed through the gut undigested.…”

The estimation of food consumption in larval and juvenile fish: experimental evaluation of bioenergetics models

“…To construct the bioenergtics model for vendace and smelt, the maximum food consumption (Cmdx) was measured in cylindrical plastic chambers (volume 5 1, Karjalainen & Viljanen, 1992). Six to eight chambers were filled with water at each experimental temperature (6, 12 or 18" C).…”

“…Some bioenergetics models have been built especially for larval or juvenile fish: e.g. yellow perch Perca flavescens (Mitchill) (Post, 1990;Hewett & Johnson, 1992), rainbow smelt Osrnerus mordax (Mitchill) (Lantry & Stewart, 1993), smelt 0. eperlanus (L.) and vendace Coregonus alhula (L.) (Dabrowski et al, 1988(Dabrowski et al, , 1989Karjalainen, 1992;Karjalainen et al, 1997;Helminen et al, 1997). Email: juha.karjalainen(~joensuu.fi In this study, bioenergtics models of vendace, smelt, roach Rurilus rutilus (L.) and perch PrrcaJiuviatilis (L.) were constructed from our own experimental data and published values (Table I).…”