In Ecology, what would be a good idea to figure out the population of fish in a pond? 10 POINTs?

Question

Could you do mark and recapture or what?

Answer 1

Obviously tagging the fish is important so that you don't double count. You should probably talk to your state's game commission or a university biologist about what the allowed methods of tagging are. If you use the wrong tagging system you could make the fish an easier catch for predators or make them unattractive to mates and s***w up the ecology of the pond. But tagging is the easy part,

Finding all the fish is the tough bit. I once accompanied an ecologist on a bio-assay of a stream, he had a fish-stunning device that would temporarily paralyze the fish which made them float to the surface for easy and complete collection. You really can't do a decent count without a stunner - for as any fisherman will tell you - some fish don't like to be found.

The stunner is has three main parts, a power supply (battery) a cathode which you trail behind you and an anode on a long stick. You walk (or boat) around the water (in insulating waders!) and zap the fish. It might be helpful to have a second person doing the tagging.

Depending on the size of the pond, you may not be able to collect all the fish and so you will need to use statistical sampling and then apply the proper statistics to extrapolate to the pond's population. For this you should definitely consult a university ecologist/biologist.

Good luck. Doing accurate bio-assays is not easy.

Answer 2

The best way is to electroshock.  The equipment can be expensive, but basically you send an electrical shock into the water (wear rubber boots!).  This shocks the fish, the float to the surface, and you can measure, weigh, and return them unharmed.

You can also do net sampling.  I don't think biologists usually mark the fish -- they just sample of a wide area and release.  This may be a little more difficult in a small pond.  Maybe just take a few swaths with the net at different depths and areas around the pond.