by David DeFranza
Every year, sockeye salmon return to the rivers of western Canada to make their arduous upstream journey to calmer spawning grounds. It is a seasonal touchstone that signifies the approaching end of summer, one that has been observed for centuries.
The only problem is that some years, like in 2009, the salmon don't return.
In 2009, watershed managers estimated that 10,488,000 salmon would return from the Pacific. As the month wore on, it became clear that the reality would meet only a fraction of this goal. In the end, 1,370,000 salmon returned, a mere 13 percent of the preseason estimate.
The poor showing sent managers and scientists into a frenzy. After a year of research, no definitive conclusions could be made, but several theories had emerged. Warmer ocean temperatures, diminished food supplies, and an increase in predator populations were among the leading suggestions.
Others thought that offshore salmon farms could be responsible. Sea lice, which are common on the farms, may have spread to wild populations, killing many of the young salmon.
Though the final verdict is still out on the cause of last year's decline, it is clear that this year represents a dramatic rebound. Already, assessments predict 25,000,000 sockeye salmon will return to the Fraser river, the largest since 1913.
Still, even a record return may not be enough to reconcile the shock of last year's turnout.
"Everybody is abuzz about the great return of the Fraser sockeye," Fisheries Minister Gail Shea said, but "we're welcoming this with cautious optimism."
... read more story at TreeHugger.com