Physiological and Behavioural Responses to Noxious Stimuli in the Atlantic Cod (Gadus morhua)

Abstract

In the present study, our aim was to compare physiological and behavioural responses to different noxious stimuli to those of a standardized innocuous stimulus, to possibly identify aversive responses indicative of injury detection in a commercially important marine teleost fish, the Atlantic cod. Individual fish were administered with a noxious stimulus to the lip under short-term general anaesthesia (MS-222). The noxious treatments included injection of 0.1% or 2% acetic acid, 0.005% or 0.1% capsaicin, or piercing the lip with a commercial fishing hook. Counts of opercular beat rate (OBR) at 10, 30, 60, 90 and 120 min and observations of behaviour at 30 and 90 min post-treatment were compared with pre-treatment values and with control fish injected with physiological saline, an innocuous stimulus. Circulatory levels of physiological stress indicators were determined in all fish at 120 minutes post-treatment. All treatments evoked temporarily increased OBR that returned to pre-treatment levels at 60 minutes (saline, 0.005% capsaicin, hook), 90 minutes (0.1% acetic acid, 0.1% capsaicin), or 120 minutes (2% acetic acid), but with no significant differences from the control group at any time point. Fish treated with 0.1% and 2% acetic acid and 0.1% capsaicin displayed increased hovering close to the bottom of the aquaria and fish given 2% acetic acid and 0.1% capsaicin also displayed a reduced use of shelter. The only effect seen in hooked fish was brief episodes of lateral head shaking which were not seen pre-treatment or in the other groups, possibly reflecting a resiliency to tissue damage in the mouth area related to the tough nature of the Atlantic cod diet. There were no differences between groups in circulatory stress indicators two hours after treatment. This study provides novel data on behavioural indicators that could be used to assess potentially aversive events in Atlantic cod.

Modulation of Stress in Coho Salmon, Oncorhynchus kisutch, using Feed Supplemented with Capsaicin

“…Due to our findings that capsaicin did not produce a statistically significant response in thermally stressed Coho salmon in the biomarkers; blood glucose, SSI, packed cell volume, macrophage activity or condition factor, it can be concluded there was no significant effect of capsaicin at this level of dietary intake. This finding agrees with the findings of Eckroth et al observed in Atlantic cod [26]. to the largest degree of differences between groups.…”

Potential Pain in Fish and Decapods: Similar Experimental Approaches and Similar Results

“…Thus, there is a similarity with pain responses seen in humans and other mammals and these observations are consistent with the idea of pain. However, one should note that experiments using hydrochloric acid on three species of prawns found no such directed activities (14) and experiments on Atlantic cod, Gadus morhua, with acetic acid injection failed to show activities directed at the site of treatment (15).…”

“…Capsaicin causes a burning sensation in humans and appears to cause pain in most mammals, but not birds (44). When capsaicin or acetic acid were injected into the lips of cod there were similar behavioral changes, indicating that fish too have capsaicin receptors (15). By contrast, neither crayfish, P. clarkii (3) nor shore crabs, C. maenas (12) showed any responses to application of capsaicin.…”

Cross-species Analyses of Intra-species Behavioral Differences in Mammals and Fish

“…For example, the rainbow trout exhibits abnormal pectoral fin side-to-side movements and lip rubbing when given a noxious stimulus [169]. Juvenile Atlantic cods treated with capsaicin, acetic acid, or injured by fishing hook, displayed increased opercular beat rate, abnormal lateral head shaking, and frequent bottom hovering [170]. Zebrafish exposed to acetic acid exhibit characteristic abdominal constriction-like response and reduced locomotor activity [171].…”