Posts Tagged ‘alevins’

Situated on the edge of the San Luis Obispo creek, Bambu Batu has some very interesting neighbors.  We see ducks, hummingbirds, phoebes, butterflies, frogs and finches on a regular basis.  On a good year, we are fortunate enough to witness the return of a celebrity species around these parts, the steelhead trout.

These fish are an Endangered Species, and are protected by the Federal Government.  Through their complex life cycle, the Trout utilize several different types of creek habitat that are currently threatened by development, pollution, and barrier construction.  The fish that live in San Luis Obispo creek are reproductively isolated to their area, which makes them a unique population to their territory.

Steelhead trout are anadromous, meaning that they lay their eggs and begin their lives in freshwater streams and then migrate to the ocean where they live for 1-5 years before heading back to their place of birth to spawn and repeat the cycle.  Females can lay up to 2,000 orange pea-sized eggs that eventually hatch into small “alevins” 6-8 weeks after fertilization by a male.  The alevins feed off of their yolk sack until old enough to swim freely as “fry” and fend on their own for insects and plankton.  Once they reach at least 3 inches long, the small fry graduate and adopt a new name —  either “fingerlings” or “parr” — and display vertical camouflage markings along their sides.  By this point, the fish dine mostly in aquatic and flying insects.

Eventually, something in the trouts’ biology compels them to move out towards the open water.  As “smolts”, they undergo many transformations to make the journey from a freshwater to saltwater ecosystem.  Not much is known about where the fish live after they make their way to the ocean, but studies have noted that smolts tend to gather in shallow waters near the continental shelf during their first year of life.  If they survive predation by larger fish, birds and sea mammals, they migrate towards deeper water where they increase in size.

Once mature, the Steelhead venture back in the spring and summer to their home creeks and rivers, aided in their navigation by what scientists speculate as a combination of magnetic fields, a highly developed sense of smell, and celestial orientation.  On average, a steelhead will live to spawn 2-5 times before dying, unlike salmon who only spawn once.

For a chance to glimpse Steelhead fingerlings in the creek, travel to Mission San Luis Obispo de Tolosa and make your way down to the creek.  About 3/4 of the way north of Broad street where Bambu Batu is located, you can spy on the juvenile fish as they grow and prepare to head out to the Pacific!  Let us know how many you have seen!

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