Comparative study of aggressive behaviour in transgenic and wildtype zebrafish Danio rerio (Hamilton) and the flying barb Esomus danricus (Hamilton), and their susceptibility to predation by the snakehead Channa striatus (Bloch)

Abstract

To address concerns related with incidental release of transgenic zebrafish (Danio rerio) in water bodies, experiments were carried out to document aggressive behaviour (Experiment 1) of transgenic zebrafish towards wildtype zebrafish and flying barb (Esomus danricus). The study also aimed to evaluate their susceptibility to predation (Experiment 2) by snakehead, Channa striatus. In Experiment 1, 15 replicate trials were performed to document aggressive encounters with the following treatments: (1) transgenic zebrafish, monotypic; (2) wildtype zebrafish, monotypic; (3) flying barb, monotypic; (4) transgenic and wildtype zebrafish, polytypic, stocked at 1:1; (5) flying barb and transgenic zebrafish, polytypic, stocked at 1:1; and (6) flying barb and wildtype zebrafish, polytypic, stocked at 1:1. The wildtype zebrafish and flying barb preferred to shoal with fish of similar phenotype in monotypic treatments (2 and 3, respectively), compared to Treatment 6, when more aggression was noticed (P < 0.05). However, when placed with the transgenic zebrafish, both flying barb (Treatment 5) and wildtype zebrafish (Treatment 4) were significantly less aggressive (P < 0.05). Experiment 2 consisted of 15 replicate trials, wherein 10 randomly selected prey were placed into a test aquarium, already containing a snakehead. The treatments were: (1) transgenic and wildtype zebrafish, stocked at 1:1; (2) flying barb and transgenic zebrafish, stocked at 1:1; and (3) flying barb and wildtype zebrafish, stocked at 1:1. Uneaten prey were counted after 12 h. The snakehead consumed 30.6–34.6%, 52–61.4% and 45.4–58.6% of transgenic zebrafish, wildtype zebrafish and flying barb, respectively. The snakehead appeared to avoid the transgenic zebrafish, compared to wildtype zebrafish and flying barb (P < 0.05). The experiments illustrate behavioural mechanisms by which transgenic zebrafish may negatively impact wildtype zebrafish and flying barb under confined conditions in shrinking water bodies, particularly when there is no escape and there is presence of predators like snakehead.