No stone unturned in quest to save fish

Some innovative and controversial approaches to such Okanagan Lake problems as control of the Mysis shrimp and water quality were among the approaches discussed at a high-level scientific think tank held in Kelowna late last week on declining kokanee stocks.

Attention at the three-day conference, held at the north campus of Okanagan University College, was focused on the need for rehabilitated and increased spawning habitat before stocks are boosted back up, and on the reduction in kokanee rearing capacity in Okanagan Lake because of such changes as the introduction of Mysis shrimp.

Environment ministry biologist Bruce Shepherd said there were some controversial approaches to Mysis control, including the idea of feeding the kokanee until they’re beyond the size at which they compete with Mysis for feed, and to the stage where they begin to feed on the tiny shrimp.

Experimental approaches such as the possibility of aeration to bring the Mysis from the bottom part of the lake up the water column closer to the surface, where warmer water and feeding fish could kill them and reduce their populations, are also being seriously considered, said Shepherd.

Although a report on the conference probably won’t be completed until the end of this summer, a priority must be remedial: taking inventory and drawing up a plan for the rehabilitation and preservation of spawning areas, both in streams and along shores.

Ironically, scientists even looked at the possibility that Okanagan Lake water is now too clean — that the water’s phosphorus content must be increased to increase the amount of feed available for fish, noted Shepherd.

Such agencies as the Okanagan Basin Water Board have put considerable emphasis on reducing phosphorus entering the lake in the past few years in order to reduce the weed and algae growth.

Controversial projects such as a reopening of the Skaha Lake fish hatchery brought differing comments from the various experts attending the conference, but there was agreement that such a move doesn’t make sense until other experiments for improving lake habitat, and work on increasing and improving spawning grounds is completed.