Assessment and evaluation of temperament traits in carp (Cyprinus carpio L.), with contrasts between mirror and scaled morphological phenotypes

Individual variation in behavioral traits of animals has, if at all, been recognized only reluctantly as temperament, defined as consistency in individual behavioral variation over time and / or across situations. Temperament traits like boldness, exploration, activity, aggression and sociability have been identified in a wide variety of taxa, including various fish species. It was only recently discovered that behavioral traits can correlate with one another to form behavioral syndromes and that these correlations across contexts can be stable over time. So far, little is known about temperament traits, behavioral syndromes and repeatability of temperament traits in the carp (Cyprinus carpio L.). Furthermore, little is known about the effects of domestication on temperament and the repeatability of individual behavior as a consequence of artificial selection in captive environments. To address these issues, a laboratory study was conducted to assess several behavioral variables in carp with the goal of extracting temperament traits and behavioral syndromes respectively, focusing on boldness, exploration and sociability. To maximize behavioral variability and to examine possible effects of domestication on behavioral performance, two genotypes of carp, exhibiting a different degree of domestication (scaled and mirror carp), were used. The experimental setup involved four behavioral contexts. These contexts included exploration behavior in a novel environment, investigation of a novel object, feeding under simulated predation and tendency to associate with a group of conspecifics. All behavioral measurements were repeated after six weeks to test for repeatability and consistency of behavior over time. This study revealed that individual carp differ in their behavioral responses, despite habituation effects over the study period and potential individual differences in habituation degree. Several behaviors are consistent over time and / or situations, i.e. temperament traits respectively behavioral syndromes exist in carp. Two distinct temperament dimensions were identified as the temperament traits boldness and exploration. In the case of exploration, a context-independent temperament trait was found. Regarding domestication effects, only minor behavioral differences between mirror carp and scaled carp of the “wild type” phenotype were found under standardized laboratory conditions, possibly indicating context-dependency of behaviors. This study provides evidence for the existence of the temperament traits boldness and exploration in carp.