A comparison of body height in Crucian carp (Carassius carassius) in lakes with- and without predators

Abstract

Induced morphometrical defenses have been reported in crucian carp (Carassius carassius), and these defenses are presumed to be induced by predators. Crucian carp was sampled during 2018 and 2019 in 12 lakes in southeast Norway. In three of these lakes there were no piscivorous predators, while in the remaining nine lakes there were top predators such as trout (Salmo trutta), perch (Perca flavescens) and pike (Esox lucius). I observed how crucian carp develop a greater body height in the presence of predators and other abiotic variables. Results confirm what other studies have found, that crucian carp grow a higher body with the presence of predators, but that also the abiotic factor lake size have a major impact on the growth. The size of the lake has been poorly reported in the literature as a factor that can drive changes in body height. A larger lake can compromise of a much more complex biological system than a small lake, which maybe can explain the growth in body height.