Ueberschär, Bernd (1995) The use of tryptic enzyme activity measurement as a nutritional condition index: Laboratory calibration data and field application Mass Rearing of Juvenile Fish: a symposium held in Bergen, 21-23 June 1993. ICES Marine Science Symposia, 201 . ICES, Kopenhagen, pp. 119-129.

Abstract

Tryptic enzyme activity of herring (Clupea harengus), turbot (Scophthalmus maximus), and cod (Gadus morhua) larvae kept under defined laboratory conditions was determined. Tryptic enzyme activity was related to larval age, length, days of food deprivation, and feeding time. From 10 days after hatching onwards, significant differences in tryptic enzyme activity appeared when larvae were deprived of food for between 3 and 9 d. Diurnal feeding patterns were monitored by measuring individual tryptic enzyme activity. In short-term feeding, starving and re-feeding experiments, tryptic enzyme activity reflects the digestion processes in relation to food ingestion and re-establishment of tryptic enzyme level within hours of re-feeding. Individual tryptic enzyme activity levels in herring and sprat larvae (Sprattus sprattus) were determined in field samples and compared with laboratory calibration data in order to evaluate the nutritional condition of the field collected larvae from different sampling sites and different seasons. Continuous sampling of sardine larvae (Sardina pilchardus) on an oceanic drift station was used to show diurnal feeding rhythm by applying tryptic enzyme activity as an indicator.

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