Tuesday, June 19, 2012

Little Fish

The drought has reduced the creek flow to a tiny trickle, but every pool and shallow riffle is full of little fish. 

Pools are small and in some areas the riffles have gone completely dry.  At a glance there is no apparent life in the pools.  A closer examination reveals an abundance of creatures, but all are young and tiny.

The overall color of the fish closely matches that of the creek bottom.  If it weren’t for their shadows, it would be hard to notice the fish.  Once you begin to follow those shadows, it becomes obvious that the pool is full of fish.

The fish cruise constantly and investigate the slightest movement in the water.  When the fish prosper, other organisms suffer.  Even these small fry are effective predators.  No insect larvae can be found anywhere on the creek bottom.  Streamside Salamander larvae, which should be abundant at this time of year, are completely absent.  Small fish begin by eating the gills of the salamander larva and then proceed to pick the body clean.

These fish are too small to identify without actually collecting a sample.  Creek Chubs and Blacknose Daces are the only species that I’ve found spawning in the creek so far.  They move upstream early in the spring when the water is high,  spawn in a gravelly location and then move back downstream as the creek flow begins to subside.  From earlier experience, I’m guessing these to be Blacknose Daces.

Water Strider nymphs compete with the fish for floating food items.  Both are alert for anything that strikes the surface.  The current drought is causing these pools to shrink in size every day.  Unlike many of the other creek dwellers, fish must have a constant supply of open water.  They don’t have the ability to live beneath a wet rock to await the return of their pool.  If we don’t get back into a rainy pattern, most of these fish won’t survive.

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