Frontiers in Marine Science (Dec 2015)
Cognitive bias test as a tool for accessing fish welfare
Abstract
Introduction With growing focus on fish welfare it is important to develop methods for accessing welfare in farmed fish (Ashley, 2007). One of the biggest issues is to investigate fish affective states (Kittilsen, 2013; Martins et al., 2012). While measuring stress response via corticoid hormones might be a solution in short term stressful events there is a big difficulty in measuring long term welfare. Something that could be stated as “quality of life”. In presented research we investigated whether cognitive bias test (Baciadonna & McElligott, 2015) could be used as a tool for accessing fish welfare in terms of living conditions. Materials and Methods A total number of 96 zebrafish (Danio rerio) wild type was used for this experiment. Fish were preconditioned to recognise and associate green colour with a reward (food) and red colour with punishment (being chased with a fish net). Afterwards fish were divided into two groups. Group I (enriched tank with hiding and gentle light) and Group II (barren tank with strong light). Test consisted of five arm radial maze subjected underwater similar to this used for rats by O. Burman et al. (2009) but with arms of 30cm length. Fish was first presented to red arm and punished, than to green arm and rewarded. Than the actual test began. We tested on how willing the fish is to enter the unknown arms of witch one is more similar and closer to green arm, one neutral in the centre and one more similar and closer to red arm. Results Fish from group I exhibited more exploratory behaviour, they spend in total over 28% of the test time in arms with unknown clues compared to 7,5% in group II. Animals from group II spend most of the time (39% of total observation time) in the safe (green) area as oppose to group I where animals explored more and spend only 12% of the time in the safe zone. Animals from the enriched tanks explored even the punishment zone (red) as they spend 4,8% of the time there. Fish in group II avoided this part of the testing chamber with just an incidental occurrences with just 0,8% of the test time. Conclusions and Discussion Difference in behaviour during the cognitive bias test suggests that fish cognitive bias can be affected by living conditions. Therefore this type of test should be taken to consideration as a tool in further fish welfare studies. It can be especially useful in studies concerning influence of living conditions that cannot be examined in direct way for example by preference test.
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