Insect attractants and plant biomass as natural food complements in pond culture of stock chub (Squalius cephalus)

The chub, Squalius cephalus (L.), is an important stocking fish in European rivers. This study investigates sustainable measures for culturing chub in earthen ponds. Two novel treatments were applied to enhance utilisation of natural pond food resources: yellow plates used as insect attractants (YIT) and plant biomass supplementation (PB) as a substrate supporting the development of natural food organisms. While no significant differences were recorded for most environmental variables, average macrozoobenthos biomass was significantly higher ( p < 0.05) in the control (61.51 g.m −2 ) compared with PB (29.3 g.m −2 ) and YIT (36.8 g.m −2 ). However, fish from YIT ponds had significantly higher ( p < 0.05) mean body weight gain (34.7 g) and SGR (1.60 g.day −1 ) compared to the PB (28.65 g and 1.50 g.day −1 ) or control (25.64g and 1.43 g.day −1 ) ponds. Diet analysis indicated a higher amount of animal food (mainly zooplankton, zoobenthos, terrestrial insects and fish) in YIT and PB treatments, while a higher amount of plant (mainly macrophytes) and emergency food (detritus) was observed in the control ponds. Differences in diet were reflected in the fatty acid profile of fish from different treatments, with YIT fish having significantly ( p < 0.05) higher n-3 PUFA, n-3 HUFA and n-3/n-6 ratio, compared to PB fish and controls. Our results confirm that YIT use in pond aquaculture significantly enhances the role of natural food resources in the diet of cultured chub, thereby contributing to its sustainable production.