The role of predictability in the stress response of a cichlid fish

Abstract

In recent years there has been an increasing interest in the cognitive abilities of fish with implications for animal welfare and management of rearing operations. Although it is known that psychological factors can modulate the stress response in mammals, this aspect has seldom been investigated within stress in fish. In this study we investigate whether the perception (appraisal) that fish make of significant environmental events modifies their behavioural and physiological response. For this purpose we have used a predictable vs. unpredictable paradigm for positive (feeding) and negative (confinement) events using the cichlid fish Oreochromis mossambicus as a model species. Results show that there is a differential effect of predictability for the feeding and confinement events. In the confinement experiment, predictability involved more attention to the visual cue and lower cortisol. The feeding event triggered higher levels of anticipatory behaviour and a tendency for higher cortisol in the predictable group. Therefore, predictable negative events reduce the cortisol response. Predictable positive events may elicit an anticipatory response, and when there is a significant delay between the visual cue and the actual occurrence of the event, it may also contain elements that can be interpreted as a stress response. These findings demonstrate that fish can appraise relevant aspects of the environment, with welfare implications for housing, husbandry and experimental procedures.

Anaesthesia and handling stress effects on pigmentation and monoamines in Arctic charr

“…Further, in this study there were three similar stressful events consecutively and thus stress could be predictable. Predictable stress has been shown to reduce the cortisol response (Galhardo et al 2011), and a comparison to an earlier study (Backström et al 2015b) indicates that there is a lower elevation of cortisol in our study. However, the number of repeated stimuli is low so it might not be a plausible explanation.…”

Variation in the emission rate of sounds in a captive group of false killer whales Pseudorca crassidens during feedings: possible food anticipatory vocal activity?

“…Thus, it could be speculated that the high vocal rates encountered in Qingdao false killer whales during feedings might have been caused by a variation of the routine schedules. If the expectation of these events became inaccurate because of their delay according to the temporal or signaled predictability, anticipation may have caused frustration in the whales with consequent variations of their vocal activity (Amsel, 1958;Johanneson and Ladewig, 2000;Waitt and Buchanan-Smith, 2001;Galhardo et al, 2011). This assumption could be taken into account to explain the higher vocal rate encountered in our recordings during the 12:20 pm pre-and feeding intervals compared to all the other schedules.…”

Behavioural indicators of welfare in farmed fish

“…Increased swimming activity around feeding areas prior to feeding time is often observed in fish farms. This foodanticipatory activity may allow fish to predict the exposure to appetitive stimuli and have some awareness of control, which have been suggested to be Kristiansen and Fernö (2007) Fish Physiol Biochem (2012) 38:17-41 31 important appraisal modulators of the fish responses to their environment (Galhardo et al 2011b). Preference tests that allow animals to display their needs (Dawkins 2004) are used to assess fish welfare.…”

“…Very little is known about the effects of predictability on fish. Galhardo et al (2011b) showed that Mozambique tilapia subjected to predictable confinement exhibit lower cortisol levels than fish that could not predict such stimuli. The relieving effects of predictability have been suggested to rely on a sense of both safety during periods of nonsignalisation and control by allowing selfpreparation for the future events (Orsini et al 2002;Bassett and Buchanan-Smith 2007).…”