Researchers note slowed coho growth
Juvenile coho salmon on the west coast of Vancouver Island are growing at
the slowest rates yet seen by federal fisheries researchers, raising the
spectre of low returns as survivors return to their spawning grounds
starting later this year.
Juvenile coho sampled off the west coast in October and November were
growing at a rate of 0.8 millimetres per day compared with an average of 1.2
millimetres per day since researchers started keeping such annual statistics
in 1998.
The plight of the coho coincides with record-low breeding success at coastal
seabird nesting colonies off Vancouver Island, and hints at changes in ocean
conditions that are affecting marine life.
The 500,000 pairs of Cassin's auklets breeding at Triangle Island off the
northern tip of Vancouver Island, the largest nesting colony in the world
for that species, achieved only an eight-per-cent breeding success last
summer. A year earlier, they had a record 70-per-cent success rate.
Similar breeding failures were recorded last summer for glaucous-winged
gulls at Cleland Island, a provincial ecological reserve, and Seabird Rocks.
Marc Trudel, a research scientist at the Pacific Biological Station in
Nanaimo, said Tuesday that juvenile coho sampled had spent about one year in
fresh water and six months in salt water. Summer growth rates are a good
indicator of ultimate fish survival, he said, noting "observations would
suggest a reduction in the marine survival of coho in southern B.C."
Other research also suggests that plankton production occurred earlier than
normal last year, reducing the success of the coho. Production of euphausiid
plankton especially was also found to be lower than normal off Barkley
Sound.
Humboldt squid normally found south of San Francisco made their way as far
north as southeast Alaska over the last two years, Trudel said. Whether
these are just normal fluctuations in conditions or indicative of man-made
climate changes causing warmer ocean temperatures are unknown.
Author
Topic: Coho, not looking good for this years return! (Read 1318 times)