Effect of supplementation of a dry feed with natural food on growth, condition and size distribution of juvenile tench Tinca tinca (L.)

Abstract

Summary In a 120-day experiment, tench Tinca tinca juveniles [initially, 135 days post-hatch, 37.4 mm total length (TL), 0.51 g body weight (BW)] maintained at 28°C received commercial starter alone (control group) or together with a supplement of frozen fly or chironomid larvae, in single or double quantities. Final survival rates were 100% in all treatment groups. Double additives significantly (P ≤ 0.05) improved fish growth in TL (final growth 62.0 or 62.5 mm, respectively) as compared with those fed single quantities (both 60.8 mm) or starter alone (59.1 mm). Significant differences in BW were found only between groups fed double additives and starter alone (final growth 2.96–3.07 and 2.71 g, respectively). Significantly highest Fulton's coefficient values were found in the control group and in the group fed single supplement of fly larvae (both K = 1.22), and lowest in both groups receiving chironomid larvae (K = 1.15–1.17). BW distribution was positively asymmetric in all groups, and the distribution of TL only in the control group and in the group fed with the single supplement of chironomid larvae. From a practical point of view, supplementation of a commercial starter with insect larvae has a minor effect on the results of T. tinca rearing under controlled conditions.