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Effects of feeding commercial diets on the development of juvenile crucian carp (Carassius carassius): digestive tract abnormalities

Robert Kasprzak*, Teresa Ostaszewska, Maciej Kamaszewski

*Corresponding author:

ABSTRACT: Wild-living populations of the crucian carp (Carassius carassius), a cyprinid fish of European freshwaters, have decreased in recent years, likely due to an increasing competition presented by invasive species. Several initiatives were launched which attempt to reintroduce this fish back into its natural habitat, but such approach requires the use of crucian carp fry reared under controlled conditions. However, the use of popular and inexpensive commercial diets results in developmental abnormalities. The aim of the current study was to analyse the impact of feeding either natural food (Chironomidae sp. larvae) or two commercial diets on juvenile crucian carps, with the focus on the intestinal development of these fish. Histological analysis revealed significant pathologies in the alimentary tracts of fish fed both commercial diets, such as lowered hepatocyte and enterocyte proliferation, as well as shortened intestinal folds, while the digestive enzyme activity patterns suggested a physiological state close to malnutrition. The study confirmed that (at least the two applied) basic commercial diets are not recommendable for the rearing of crucian carp juveniles, even though the initial growth rates of fish might suggest otherwise.