Kritische Zeiten für Fischlarven - Bestimmng der Trypsinaktivität zur Beobachtung des Ernährungszustands von Fischlarven in Labor- und Felduntersuchungen - ein Überblick

• Main Author: Ueberschär, Bernd
• Format: Article in Journal/Newspaper
• Language: English
• Published: Verl. Natur & Wissenschaft 2006
• Subjects: Gadus morhua; Scophthalmus maximus; Turbot
• Online Access: https://oceanrep.geomar.de/id/eprint/7726/; https://oceanrep.geomar.de/id/eprint/7726/1/Kritische_Zeiten_fur_Fischlarven.pdf

The studies which form the background for this synoptic presentation aimed to contribute to the investigation of the reason for great yearly fluctuations in recruitment in marine fish stocks. In order to evaluate if mass mortality due to starvation in the larval stage contributes to these fluctuations, trypsin activity was suggested as an appropriate indicator to assess individually both the nutritional condition and feeding activity of fish larvae of all age stages. Based on the principle of conventional chromogenic methods a highly sensitive fluorometric measurement was developed, which allows the individual assessment of tryptic activity even in the youngest larval stages. In order to evaluate species-specific features of tryptic activity, larvae of six different marine species were reared under laboratory conditions (herring, Clupea harengus, turbot, Scophthalmus maximus, cod, Gadus morhua, sea bass, Dicentrarchus labrax, gilthead seabream, Sparus aurata, and Brazilian sardine, Sardinella brasiliensis). The exemplary application of the laboratory calibration in field surveys clearly demonstrates that the tryptic activity is appropriate to evaluate the nutritional condition of larvae from field samples. Examples for some species are presented (herring, cod and sprat). The most significant results from laboratory experiments: Larval age and larval size were chosen as the standard for comparison to relate to tryptic activity. Tryptic activity was found even in yolk sac stages of the investigated species. Tryptic activity increases with age in continuously fed larvae following a non-linear pattern which is supposed to be determined in the ontogenetic development of each species. Increase in tryptic activity persists until larvae develop a functional stomach. The amount of maximum tryptic activity at a given size and age is species specific: turbot larvae show the highest whereas herring larvae have the lowest values at a given age. The amount of trypsin which has its origin in the ingested food oganism is of ...