Gender differences in health and aging of Atlantic cod subject to size selective fishery

Abstract

We have analyzed health and physiological aging parameters in male and female Atlantic cod, Gadus morhua, captured in Kattegat, Skagerrak and in Öresund. Gender differences were clearly evident in a number of variables. Males had longer liver telomeres and higher catalase activities than females, while females had higher superoxide dismutase activity, liver somatic index and condition factor. Effects of age were found for males where levels of the antioxidant glutathione and telomere length declined with age, indicating physiological aging. Liver somatic index increased and percentage oxidized glutathione decreased with age. Between-site comparisons of males show that percentage oxidized glutathione and catalase were lowest in Kattegat, whereas protein carbonyls and condition factor were higher in Skagerrak. Females, on the other hand, showed no differences between sites or indications of somatic aging or age-related effects in egg quality, indicating that older and larger female cod are healthy and show no changes in eggs with age. In contrast, males showed indications of physiological aging and lower condition than females. The results emphasize the importance of conserving old mature fish, in particular high egg-productive females, when managing fisheries.

Keywords: Egg quality; Fish; Gender differences; Glutathione; Oxidative stress; Predation effects; Telomeres.

Fig. 1.

(A) CAP analysis on sex (1 = male, 2 = female) for all cod. (B) Correlation analysis for CAP axis 1. Level of significance (df = 61)±0.25 is indicated by red line. Levels of liver somatic index (LSI), condition factor (CF) and superoxide dismutase (SOD) are higher in females, while catalase (CAT) and telomeres are lower, in comparison to males. PERMANOVA, pseudoF_{1, 43} = 5.6, P = 0.001. (C) Results of variables found to differ significantly, illustrating differences between the sexes.

Fig. 2.

(A) CAP analysis on age for male cod (years). (B) Correlation analysis for CAP axis 1. Level of significance (df = 34)±0.349 is indicated by red line. Telomeres, total glutathione (tGSH) and percent oxidized glutathione (%GSSG) decrease with age while liver somatic index (LSI) increases significantly. PERMANOVA pseudoF_{4, 25} = 1.8, P = 0.019. (C) Results of variables found to differ significantly, illustrating differences with age in male cod.

Fig. 3.

(A) CAP analysis on sites (ICES subdivision 20 Skagerrak, 21 Kattegat and 23 Öresund) for male cod. (B) Correlation analysis for CAP axis 1. Level of significance (df = 34) 0.349 is indicated by red line. Levels of percent oxidized glutathione (%GSSG), catalase (CAT) and protein carbonyls (PC) are lower in the Kattegat compared to the other areas. PERMANOVA pseudoF_{2, 25} = 2.8, P = 0.003. (C) Results of variables found to differ significantly, illustrating differences between sites using data from four year old males.