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3. 80 degree aquatic insect tank?

Since the failure of my cold water tank (cooled by running 40 feet of tubing through a mini fridge; got the temps down to about 55 for 3 weeks until the old mini fridge burned out). I was going to put trout fingerlings into the tank before it burned out and already had some mayfly, stonefly nymphs, and caddis larvae along with a few scuds and a helgramite larvae. They are all doing great even though they had a sudden increase in temps and the introduction of a few fish they have never seen before (black ghost knife and german rams). I figured they might live a few days like this and either die in the heat or be eaten by the fish. They, however, seem to be thriving and the caddis even show signs of maybe hatching soon. This changes my mind about some summer streams. I have the water well oxygenated. I think many streams dont support huge hatches in the summer primarily due to the lack of oxygen. Does this conclusion that I have made make any sense?

Jamie-



That could certainly be one factor, but there are others. Among them would be clean water, appropriate habitat, and adequate food supply.

Many invertebrates found in trout streams have a wide range of temperature tolerances and will thrive at room temperature during the summer. Some will not.

It's very interesting to consider why there are fewer hatches during the heat of summer.

I doubt that dissolved oxygen is a primary reason. There certainly aren't enough insects in most streams to significantly deplete what oxygen there is. The overall level will be lower when it's warm, but there are still plenty of nymphs in the stream that are waiting to emerge during the fall, or even at night.

It's more likely that insects are just trying to avoid the hot, dry midsummer midday conditions, because they dry out the adults and the heat probably increases their metabolism and makes them burn through their limited energy more quickly. This idea fits well with the observation that hatches move toward the very early morning and very late evening when it's hot outside.

Another possible reason there are fewer emergences during midsummer may be that floods and droughts are more common and unpredictable at that time. A poorly timed flood at emergence time could really screw up a population.