Evaluation of the role of enzyme activities in the silvering process of European eels (Anguilla anguilla)

Abstract

This study was carried out to determine the relationships between various morphological parameters, body condition data, and digestive and stress enzyme activities due to silvering in European eel (Anguilla anguilla L.) collected from four locations in Turkey. The yellow and silver eels were caught from Asi River, Köyceğiz, Güllük Bay, and Bafa Lake in November–December 2020. Total body length, eye diameter, and pectoral fin length were measured as morphological parameters. In addition, body fat percentage, gonado-somatic index, and Fulton’s condition factor were calculated, and also weight was assayed as body condition data. The variations of α-amylase, lipase, trypsin, and pepsin enzymes, and superoxide dismutase, catalase, and glutathione peroxidase enzyme activities were measured. The results supported the differences of yellow and silver stage samples in terms of both morphological and physiological parameters and also showed that the digestive and stress enzyme activities of the silver and yellow stage samples were significantly different (p ≤ 0.05). We think this study will make a physiological contribution in terms of digestive and stress enzyme levels to better understand and elaborate the silvering stage of eels.