Behaviour of proactive and reactive tilapia Oreochromis niloticus in a T-maze

Abstract

Knowing that individuals with different coping strategies can exhibit different behaviours in associative learning, we evaluated the learning capacity of proactive and reactive tilapia fish. Trained and untrained, proactive and reactive, tilapia were subjected to a T-maze and their behaviour observed while searching for food using landmarks. Forty-four tilapia were first divided into reactive and proactive groups (173.2s±22.0) based on the time taken to leave shelter in Novel Environment test. In Phase 1, fish were trained individually to search for food in a T-maze. Food (stimulus) was placed randomly at one side of the T-maze and gravel (neutral stimulus) was used to mark the food location. The time taken to leave the starting area (latency) and time spent searching for food, were recorded. In Phase 2, the effect of untrained fish joining trained fish was evaluated. Qualitative observations, such as interactions between subjects, were recorded. Latency and search time decreased significantly with successive learning trials (latency time: Kruskal-Wallis test H=68.26; df=9, p<0.01; search time: H=58.16; df=9, p<0.01 – all fish; latency time: H=54.67; df=9, p<0.01 – proactive; H=21.10; df=9, p<0.01 reactive; search time: H=48.4, df=9, p<0.01 proactive; H=47, df=9, p<0.01 reactive), for all fish analysed together, and proactive and reactive fish analysed separately). Proactive fish had a shorter latency time and shorter time to find food than the reactive fish (Mann-Whitney test U=17535.0, N1=158, N2=90, p<0.05), as well as a shorter time to find food (U=16553.0, N1=158, N2=90, p<0.05). When trained and untrained animals were placed together, the trained individuals, irrespective of coping strategy, behaved aggressively and lost focus on searching for food. Among proactive pairs, trained fish fed first on the majority of trials. In conclusion, proactive fish adapted more quickly to, and fed more efficiently in, the T-maze than reactive fish. This raises the possibility of using efficient learning strategies, as well as differences in the speed of learning, as a tool for developing low stress husbandry systems.