The use of aquatic species is increasing in a range of scientific fields, including biomedical research, evolutionary biology, and environmental research. In December, PRIM&R hosted the webinar Research with Aquatic Species: New Strategies for Health and Welfare to address common concerns and emerging issues for researchers and animal care and use personnel involved in research with fish. Presenter Victoria Braithwaite, DPhil, professor of fisheries and biology and the co-director of the Center for Brain, Behavior and Cognition at Penn State University, addressed considerations related to social housing and environmental enrichment as well as the minimization of pain and distress through innovative methods of administering analgesia, anesthesia, and euthanasia.
After the webinar, Dr. Braithwaite responded to the attendee questions time didn’t permit us to address live. We’re pleased to share those responses with the readers of Ampersand.
Does the fact that fish have fewer C fibers mean that their pain does not last as long as pain responses mammals feel?
Victoria Braithwaite (VB): It is not possible to answer this definitively yet. More research is needed. We do know, however, that trout and several other fish species have some C fibers present in their nerves. These fibers have neurophysiological characteristics that are similar to terrestrial vertebrate C fibers. When they are active, we would expect them to also be involved in longer-lasting pain responses. The mystery remains, however, why fish have less of this fiber type as compared with birds and mammals.
Can creating a more variable environment help fish to become more resilient?
VB: Yes. This is what several experiments have shown to date. Exposing young fish to a degree of change and variation in their environment can help them habituate and adjust more quickly to alterations in their environment or to their daily schedule of events. The variability to which the fish are exposed should not be completely unpredictable or too frequent, as it would probably create a stressful situation rather than a positive one. But adding a low level of change and variation, as well as providing the fish with a degree of self-control (such as allowing them to choose when, or where, to feed) certainly helps fish to be more behaviorally flexible and adjust more quickly to changes in their environment.
Does the variability one could add to the fish tank have to be physical enrichment?
VB: No. The variability can be an alteration of when, how often, or the kind of food that the fish are given each day. The time of day at which they are checked or inspected would also change their environment and experiences. But for some species, having access to physical spaces that they can use to hide in, or to seek shelter from aggressive individuals, will certainly help. This type of variability generally requires physical enrichment items to be placed in the tank.
Does repeated anesthesia (e.g. in studies of growth) have any long term effects on fish?
VB: It depends on the frequency and timing of the exposure to the anesthetic agent. It takes fish anywhere from several hours to several days to recover from being exposed to different anesthetic chemicals. How long the recovery takes depends on the species of fish, the water temperature, the chemicals they are exposed to, and how the fish are handled. If the anesthetic is applied with enough time for the fish to recover in between, there may be few to no side effects, but with increased frequency and insufficient time to recover between anesthesia exposures, adverse effects could arise. Use of a less aversive anesthetic agent such as Etomidate may be helpful in this situation.
Is there any evidence that magnetic resonance imaging (MRI) affects fish (especially when located near a housing location)? I am curious in particular about the effects on larval zebrafish up to 7dpf.
VB: I am not aware of any studies that have directly addressed this, but it is a study that could be done relatively easily by rearing tanks of fish close to an active or an inactive MRI machine (6-10 tanks in each situation), and then comparing the behavior of the fishes. If exposure to active MR has an effect, then fish kept near active MRI equipment will behave in different ways to the control fish.
PRIM&R thanks Dr. Braithwaite for sharing her expertise!
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