It's fantastic to see that Fraser River sockeye salmon are returning in greater numbers than last year, when total abundance reached a record low.
But what does this mean? Are fisheries now sustainable? Is the judicial inquiry investigating Fraser sockeye declines no longer required? Are habitat loss, parasites and disease from open-pen fish farms, and hotter water and changing ocean conditions due to climate change no longer problems?
Unfortunately one year of good returns doesn't spell the end of trouble. First off, 2010 should be a good year for total returns. It's a "dominant" cycle year. Fraser sockeye have consistent four-year life spans — fish coming back this year are the offspring of those that returned and spawned in 2006. There isn't a lot of mixing between cycles and some cycles tend to be more abundant than others. The 2010 cycle has traditionally been the biggest, or most dominant, since early in the 20th century. In 2006 about 13 million Fraser sockeye returned.
More importantly, looking at just total returns in one year is missing what matters most. The Fraser watershed, which drains about a third of British Columbia, has numerous big, deep lakes. Most of these lakes have a unique population, or populations, of sockeye salmon. You can even see the differences between some of the populations — Stuart Lake sockeye, which travel the farthest to reach spawning grounds, are shorter, more torpedo-shaped, and firm with lots of fat, while Chilliwack Lake sockeye, which don't have to migrate very far, are longer and flatter.
There are about 40 of these distinct Fraser sockeye populations, and some of them are in trouble. Conserving all of these populations, the biodiversity of Fraser sockeye, is the key to their long-term resilience, particularly given increasing climate change impacts. Maintaining salmon biodiversity is also what gives us the best chance of achieving consistently high levels of total abundance of Fraser sockeye over many years, not just in one. The importance of protecting weak salmon stocks and the value of salmon biodiversity was recently shown in the scientific journal Nature, and discussed in a recent Globe and Mail article.
It's worth getting excited about a strong return of Fraser sockeye. But these numbers should not be seen as a sudden recovery for Fraser sockeye. This year should provide a useful starting point of the recovery of all Fraser sockeye, the strong and endangered populations, by demonstrating that given the chance sockeye salmon can thrive. Several years of improving returns and the protection of Fraser sockeye salmon diversity will be necessary to determine whether Fraser sockeye are truly recovering.