The role of intraspecies variation in fish neurobehavioral and neuropharmacological phenotypes in aquatic models

•Zebrafish and other fish models are widely accepted in CNS research and drug screening.•Intraspecies behavioral variation plays a key role in fish drug-evoked responses.•Sex, strain and individual differences contribute markedly to intraspecies variance in fish.•Epigenetics, gut microbiota and gene-environment interactions influence intraspecies variance in fishes.•Here, we outline recent findings and discuss the existing challenges in this field. Intraspecies variation is common in both clinical and animal research of various brain disorders. Relatively well-studied in mammals, intraspecies variation in aquatic fish models and its role in their behavioral and pharmacological responses remain poorly understood. Like humans and mammals, fishes show high variance of behavioral and drug-evoked responses, modulated both genetically and environmentally. The zebrafish (Danio rerio) has emerged as a particularly useful model organism tool to access neurobehavioral and drug-evoked responses. Here, we discuss recent findings and the role of the intraspecies variance in neurobehavioral, pharmacological and toxicological studies utilizing zebrafish and other fish models. We also critically evaluate common sources of intraspecies variation and outline potential strategies to improve data reproducibility and translatability.