Antioxidant biomarker profile of chironomid larvae from carp ponds: Evaluation of the effects of different fish feeding patterns

A 102-day feeding trial was conducted to evaluate the effects of four different fish feeding patterns on carp pond water quality and antioxidant biomarkers [superoxide dismutase (SOD), Catalase (CAT), Glutathione peroxidase (GPx), Glutathione reductase (GR), Glutathione S-transferase (GST) and Thiol groups (SH)], protein content and biomass of the midge Chironomus plumosus. Farmed fish were fed two commercial diets: Soprofish 25/7 Standard (containing 25% protein and 7 % fat) and Soprofish 32/7 Profi Effect (containing 32 % protein and 7 % fat). These feeds were combined during a feeding trial in four different feeding patterns, designated as A, B, C and D. In feeding pattern A, the fish received Soprofish 25/7 Standard throughout the experiment and in feeding pattern D, Soprofish 32/7 Profi Effect. During feeding patterns B and C, a mixed feeding pattern was used, alternating between lower and higher protein diets. The study revealed no significant effects (P > 0.05) of the feeding regimens on water quality, so their effects on C. plumosus larvae can be evaluated independently. The activities of the chironomid enzymes CAT and GR showed a clear statistically significant dependence on the feeding pattern (P < 0.05), which increased with increasing protein content. On the other hand, the activity of SOD as well as larval biomass were noticeably affected by water quality, the former increasing with its deterioration and the latter with its improvement. The activities of GPx and GST were correlated with each other, but no statistically significant relationship was found with any of the measured abiotic factors (P > 0.05). Overall, our results suggest that long-term supplementation with a highly concentrated protein diet may have preventive effects against oxidative stress and support the use of C. plumosus as a model for assessing the effects of organic pollution on pond zoobenthic fauna.