03-21-2011, 09:50 AM
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I would expect it is more of the biological programming in the fish than the weather, though this plays a part. In their habitat, fish have a basically constant seasonal year, but it is not based as much on temperature. The rainy season, lasting 6 months, then the dry season, the remaining six. Fish always spawn near the start of the rainy season--flooded forest means more food for them and their fry, plus they spawn among plants and many streams are plaqnt-less, so the flooded forest provides this too. Interestingly, the water cools from the rain, and the pH shifts, and this sets them off. If you want success spawning fish, do a major water change with slightly cooler water on an overcast (low pressure) day. Fish certainly do feel pressure changes in the atmosphere, most animals do actually. The influx of cooler water during low pressure is a clear trigger for spawning.