Gill Lice Blamed for Kokanee Die-Off at Eleven Mile

[DonInDenver]

GILL LICE BLAMED FOR KOKANEE DIE-OFF AT ELEVENMILE RESERVOIR

[font "Arial"]The Colorado Division of Wildlife has confirmed that a small parasitic crustacean known as gill lice (Salmincola spp.) caused a sizeable all age die-off of kokanee salmon at Elevenmile Reservoir over the past year.

Initial visual observations of affected kokanee in the late summer of 2006 indicated that only larger fish were succumbing to the parasite. However, a sonar survey conducted this fall revealed that all ages of kokanee that were present in the lake in late summer of 2006 were affected, causing the overall population to be reduced.

Kokanee in otherwise good health can tolerate a small number of adult Salmincola spp. parasites without serious debilitation. However, there is a breaking point for a fish in any condition at which the damage caused by gill lice weakens, disables or even kills. Warmer than usual water temperatures in the summer of 2006 combined with the parasite resulted in this event.

Gill lice, like most other aquatic parasites, are not harmful to humans as long as the fish is prepared properly (145°F or until the flesh is opaque and separates easily with a fork).

“Rainbows, browns, and Snake River cutthroat trout have a higher resistance to the parasite-- no loss of these species has been detected at Elevenmile Reservoir and their populations are healthy and populations are strong,” said Jeff Spohn, Aquatic Biologist for the DOW. “Despite this die-off, the DOW will continue to manage Elevenmile as a kokanee brood water. Barring any unforeseen circumstances, we expect our age-1 kokanee to grow to catchable size by the winter of 2008/2009.”

Kokanee salmon fishing enthusiasts can continue to pursue their catch in the interim at the following waters: Blue Mesa Reservoir, Carter Lake, Dillon Reservoir, Lake Granby, Green Mountain Reservoir and Taylor Reservoir.
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[font "Arial"]Source: Colorado DOW[/font]
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[JasonMcMillin]

Wow I have never heard of Gill lice, are they common?
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[DonInDenver]

Never heard of them before this year, Jason.
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[JasonMcMillin]

Here is some information I found about the gill lice.
[left]The gill lice (Ergasalis) are the most abundant and prevalent parasite of inland and coastal marine populations of striped bass. They are a parasitic copepod. Copepods are small, sometimes microscopic, invertebrates that are members of the plankton community. Heavy infestations of Ergasalis have occasionally been reported from the vicinities of Baltimore, Philadelphia and Washington DC. Frequently anglers conclude that striped bass with these parasites on their gills are fish newly arrived from the ocean. In fact, the life span of Ergasalis actually decreases when salinity reaches marine concentrations of 32 parts per thousand (ppt). High salinity also exhibited some detrimental effect on Ergasalis egg survival. Ergasalis reproduction and infestation of striped bass takes place throughout the bay in salinities varying from 0.5 to 30 ppt. Females parasites remain attached to the gills of fish throughout the winter. Ergasalis egg sacs appear during January and newly attached larvae are found in April. Juvenile striped bass can become infected as early as their third month of life while still in their natal rivers. As the fish increases in size so does infection intensity. Highest counts of full sized female Ergasalis were seen in late April and early May and again in June and in October. In any school of striped bass, many copepods may be just on a few fish.[/left] [left]Different species [/left]
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