Gerry Kristianson: We need to improve our ability to predict salmon abundance

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      By Gerry Kristianson

      No one should ever be surprised when salmon return numbers seem at odds with pre-season predictions. Like other Pacific salmon species, sockeye spend the greatest portion of their life out of our view. We have very little idea of how they are faring during their migratory ocean-life stage.

      We gain an initial sense of possible future abundance when the parents of the next generation return to spawn. But even this data is limited by the resources available to cover a myriad of spawning locations. Having spent at least a year out of view in fresh water, we try to get a sense of the number that have survived to become out-migrating smolts at the few counting locations Fisheries and Oceans Canada can afford to operate.

      The fish are then out of contact throughout their migration down the Fraser, through Georgia Strait, and into the North Pacific for at least two years. We get an some indication of the proportion that survived this lengthy journey when the salmon equivalent of horny teenagers come back a year early as “jacks” but this has not proven to be a satisfactory predictor.

      What we do know this year is that the fish have not “disappeared” because of unreported harvest. The anti-drift-net campaign run by the North Pacific Anadromous Fish Commission has proven very effective. The five salmon-producing countries challenge and if necessary seize any high seas drift-net vessels. Canada makes a major contribution to this campaign by operating two Aurora surveillance aircraft from a U.S. base in the Aleutian Islands.

      As the sockeye return to Canadian waters, the Pacific Salmon Commission conducts test fisheries in the approach waters of Johnstone and Juan de Fuca straits, and there has been no unaccounted-for difference between these numbers and the enumeration that takes place at a number of locations within the Fraser itself. This year, a few fish have been harvested by First Nations and a comparative handful became mortalities when inadvertently hooked and released by recreational anglers trying to catch more abundant chinook salmon in the Fraser. But these numbers are tiny.

      The hard cold fact is that this generation did not do well during its migratory stage. The bottom line is that ocean survival is the great unknown. We need to a great deal more to understand what happens to salmon during this stage of their life.

      Some interesting attempts are being made. A project called POST (Pacific Ocean Shelf Tracking) is using acoustic transmitters placed in the belly cavity of juvenile salmon and a network of receivers anchored to the ocean floor to track fish during their migration, measure their survival rates, and determine where they spend their salt water life.

      Combining this with oceanographic data might finally let us get ahead of the curve and predict return numbers more accurately. It wouldn’t mean that we would have more fish—but it would avoid surprises like the one that has affected everyone this year and led to tension between harvesters on the Fraser.

      Gerry Kristianson represents Canada on both the Pacific Salmon Commission and the North Pacific Anadromous Fish Commission and is chair of the Sport Fishing Advisory Board.