I'm planning to run some laboratory experiments with similarly sized juvenile northern pike (0+). I know cannibalism is a problem. We plan to keep up to 10 individuals in a 15 L tank. Separating individual fish with nets etc. is not an option. Would some kind of physical refuge help to alleviate the problems of cannibalism? Any experiences on this topic are much appreciated.
I can't speak for pike specifically but, in general, there are some ways.
As you mentioned, periodically grading by size with nets is usually an easy way to reduce this; however, if that is not an option, there are some other ways. 1) you mentioned that they will all be similar sizes, so this should help reduce the cannibalism on its own (although it isn't a 100% fix). 2) if the fish are fed to satiation, the that should reduce their propensity for cannibalism. The should be less likely to try to eat another individual if they are already full. There's still a chance of having some bullies in the group, but those 2 things should help reduce it some.
Thanks Bradley! Feeding prior to incubation is a good idea. However, the fish will need to be kept in the tanks for approx. one week so I guess we will need to feed them during this period. Some papers also suggest that providing food stimulates hunting behavior and increases cannibalism. So..that is also an issue. Tricky... I guess there is no silver bullet here but thanks again for your suggestions.
Hey Martin. Yes, it is true that providing feed can stimulate hunting behavior, but if all of your individuals are of similar size then this should still be fairly minimal. There may be a few runts in the group, or individuals that don't feed as voraciously, that may be cannibalized but I think you should be okay, overall. But, yes, I would suggest feeding them throughout the one week period of being in the tanks (as long as that doesn't mess with your study design).
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