Wednesday, July 8, 2009

Invasive Species Invade our Inland Waterways

The spiny water flea is an invasive species that has assaulted our inland waterways. It is amazing how such a small creature, one-quarter of an inch (1cm), can be so destructive to native species. It is a predator and a relative of the “fishhook water flea”. In 1982 they were introduced to North America in the ballast waters of European ships entering the Great Lakes. They have spread throughout the Great Lakes and to at least 60 inland lakes in Ontario.
As the name suggests the spiny water flea has a long tail spine with barb-like projections. The head has a large black eye and a pair of swimming antennae. They have a pair of mandibles, or jaws used to pierce and shred their prey. The four pairs of legs are, not for walking, but for catching and holding food while it is being consumed. The two front legs are longer than the others and are used to reach out and catch prey. The other three pairs of legs hold their prey while they eat it.
The spiny water flea preys on small, indigenous organisms called zooplankton, including Daphnia, which are important foods for native fishes. When the populations of this invader reach massive levels, zooplankton consumption can be significant. The invasive species eats about three times as much as our native species and therefore reduces the amount of food available for resident water fleas and juvenile fish.
When water conditions are ideal female spiny water fleas reproduce identical female offspring. Females produce from one to ten eggs that are able to develop into new females every two weeks. When water conditions are poor, low water temperatures or not enough food, females produce only males.
When the females mate they produce “resting eggs” which can remain dormant over long periods of time, ---over winter and even out of water for a period of time. The eggs hatch when conditions improve. The life span of a spiny water flea varies from several days to a few weeks.
The extent of the damage done to fish populations by the spiny water flea has not been clearly determined. Past experience with invasive species indicates that in almost every situation native species have come out second best.
Fish will feed on spiny water fleas but fish smaller than four inches (11cm) long have difficulty swallowing the fleas. The tail spine of the spiny water flea gets caught in the throat of the fish and is literally coughed out. This prevents the fish from getting any nourishment for its efforts.
At the present time the best defence against the spiny water flea is to prevent its transfer to new bodies of water. You should inspect and clean all fishing equipment including lines, nets, lures, boats and trailers before leaving any body of water. Drain the water from your motor, live well, bilge and transom wells. Do not release live bait into any body of water and recheck your fishing gear before every trip on the water.
Your grandchildren will thank you.
Speaking of Nature.
Jim Ferguson, 5313 River Road, R.R.5, Renfrew, Ontario K7V 3Z8 Phone 613-432-2738 email jamesh@nrtco.net

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