1. My collaborators in the present study are Tobias Backström and Svante Winberg from Uppsala University, Tom Pottinger and Kim Pulman from CEH in Windermere and Neil Metcalfe from the University of Glasgow. 2. The title of this talk has been slightly changed, and is now: “Behavioural coping strategies in rainbow trout”.
What kind of coping are we talking about? Well, it’s coping with changes that occur in an animals surroundings. This could be changes in their habitat. In abiotic factors like temperature or biotic ones like food availability. It could also be changes in their social situation like the apperance of for example conspecific rivals or predators. The change will have to be percieved and then some kind of evaluation can take place in order to respond with an appropriate reaction. These last two events is what is called coping.
The best way of explaining what these coping strategies are is by their name. In mammals there are at least two different coping strategies that has been discovered and they are called Reactive and Proactive, Shy and bold or Passive and active. 2. Some of the behaviours that are assoiated with the passive coping strategy is a Low level aggression, and they are more likely to freeze and hide instead of running away. They do not respond with the same kind of behaviour to different stress stimuli, but are more flexible in their response.
Our results are in agreement with Sluyter et al. 1996. Mice of two different selection lines with either short attack latencies or Long attack latencies were exposed to the shock probe\\defensive burying test. Aggressive mice would bury the shock probe in both afamiliar and unfamiliar environment. While the nonaggressive mice would only bury the probe in a familier environment. Our result therefore show behaviour in rainbow trout that resembles two fundamentally different strategies to cope with aversive situations.
Behind these behaviours there is the physiological basis. And two of the striking differences between these two coping strategies are the higher HPA activity in Passive animals, while the active animals show a higher catecholamine response to stress. For a more detailed view on how coping strategies and endocrine responses are linked I would like to recomend Svante Winbergs talk tomorrow.
The existance of these behavioural and physiological coping strategies has been observed in mammals. But do they also exist in fish? Tom Pottinger has created two selection lines of rainbow trout that differ in their cortisol response when they are exposed to confinement stress. And experiments with these selection lines have shown that they differ in behaviour. The LR fish is more agressive than the HR fish in that they become dominant when paired with HR fish. The aim of this study has therefore been to answer the quastion: Are the HR and LR traits in fact a reflection of two different coping strategies? In order to do that we have sought to find out if the difference in behaviour between these selection lines is a consistant trait.
I’m going to start at the end of our experiments where we exposed the 20 fish of each selection line to a 30 minute confinement in order to verify that we had the two groups of high and low responders in our study. And to our relief that was indeed the case.
Before this confinement test the same fish were put through a series of behavioural tests. What we did was that we let 20 fish of each selection line acclimate in isolation for 2 weeks prior to the tests. We then introduced a small intruder about 50% the size of the resident fish and watched their agonistic behaviour. We measured the latency to the first attack by the resident fish and found that there were no apparent difference between the two lines.
Another behavioural test that was carried through in their home aquaria was the introduction of a novel object. The activity of the fish was measured as time spent moving before the introduction of the novel object and at 5 - minute intervals after the introduction. There was no difference in their basic activity. After the introduction of the novel object the activity decreased significantly, but there were no significant difference between the two selection lines. This was also the case in the following time intervals.
In the next behavioural test the fish were transferred to a new aquarium with a larger volume and a brighter lighting. The activity of the fish was measured as distance moved during the 12 minutes following the transfer. The data were then divided into 2-minute intervals. The activity of the HR fish did not change throughout the test period. Immediately following the transfer the LR fish had a significantly higher activity than the HR fish. The activity of the LR fish then sank to the same level as the HR fish except for the last time interval where the LR fish in fact showed lower activity than the HR fish.
In our final test the fish were one by one transferred to a cage which was placed at the end of a stream channel. The cage had a remotely operated door which was opened 10 minutes after the fish was placed in the cage. We then measured the time the fish spent in the cage before it left. And what we found was that the LR fish stayed significantly longer in the cage than the HR fish.
When we summarize the data we see that the challenges that occurred in the aquarium where the fish had acclimated – their home aquaria – showed that there were no difference in behaviour between the two selection lines.
While in the tests where the challenges were made in an un familiar environment gave rise to differences in behaviour between the two selection lines.
Our result show behaviour in rainbow trout that resembles two fundamentally different strategies to cope with aversive situations.
When we then counted the total number of attacks made by the resident fish in the 30 minutes following the first attack the HR fish made twice as many attacks as the LR fish did. At a first glance this tells us that the
The HR fish
Stress coping in hig and low stress responsive rainbow trout
UPPSALA UNIVERSITY Context dependent differences in behaviour between two strains of rainbow trout (Oncorhyncus mykiss) - effects of stress responsiveness. 1 Schjolden, J., 1 Backström, T., 2 Pottinger, T.G., 3 Metcalfe, N., 2 Pulman, K. & 1 Winberg, S. 1 Evolutionary Biology Centre, Uppsala University, Sweden 2 Centre for Ecology and Hydrology, Windermere, UK 3 Institute of Biomedical & Life Sciences, University of Glasgow, Scotland
Perception Evaluation Reaction Coping Coping with challenge UPPSALA UNIVERSITY Non-social challenges Social challenges
Coping strategies BEHAVIOUR UPPSALA UNIVERSITY Reactive Proactive Aggression Low High Active avoidance Low High Novel investigation Low High Flexible behaviour High Low
Sluyter et al. 1996 Mice Nonaggressive Aggressive Flexible behaviour UPPSALA UNIVERSITY Familiar Unfamiliar Familiar Unfamiliar Proactive Proactive Proactive Reactive
Coping strategies PHYSIOLOGY Cortisol Adrenaline UPPSALA UNIVERSITY HPA activity High Low Reactive Proactive High Low Catecholamines
What about fish ? Two selection lines of rainbow trout High and Low cortisol response to stress LR has a higher catecholamine response than HR Are the HR and LR traits in fact a reflection of two different coping strategies? LR more aggressive than HR UPPSALA UNIVERSITY
UPPSALA UNIVERSITY 10 20 30 40 50 60 70 80 90 Cortisol (ng/ml) Confinement HR LR
1 UPPSALA UNIVERSITY HR LR 100 200 300 400 500 600 700 800 Aggression Attack latency (sec)
HR LR 5 10 15 20 25 Novel Object Movement (% of total time) Basic activity 0 -5 min 5-10 min 10-15 min UPPSALA UNIVERSITY
UPPSALA UNIVERSITY * * 100 200 300 400 500 600 700 5 HR LR Open Field Movement (cm) 0 -2 min 2-4 min 4-6 min 6-8 min 8-10 min 10-12 min Time intervals after transfer
UPPSALA UNIVERSITY HR LR Exploration 200 400 600 800 1000 1200 1400 1600 1800 Latency to leaving cage (sec)
Challenge in home aquaria No difference between selection lines UPPSALA UNIVERSITY HR LR 100 200 300 400 500 600 700 800 Aggression Attack latency (sec) HR LR 5 10 15 20 25 Novel Object Movement (% of total time) Basic movement 0 -5 min 5-10 min 10-15 min
Challenge away from home Difference between selection lines UPPSALA UNIVERSITY HR LR Exploration 200 400 600 800 1000 1200 1400 1600 1800 Latency to leaving cage (sec) * * HR LR 100 200 300 400 500 600 700 Open Field Movement (cm) 0 -2 min 2-4 min 4-6 min 6-8 min 8-10 min 10-12 min Time intervals after transfer
Conclusion Our results show that the behaviour of the HR and LR fish in this study resembles the the coping strategies found in mammals. UPPSALA UNIVERSITY
UPPSALA UNIVERSITY HR LR 20 40 60 80 100 120 Aggression Total number of attacks
2 4 6 8 10 HR LR Number of fish paired UPPSALA UNIVERSITY Number of dominant fish