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The news about mother-of-pearl Tahlequah, who wore her newborn baby for 17 days in the Salish Sea this summer, was heartbreaking and rightly captivated the world's attention. He highlighted the fate of one of the most endangered marine mammals in Canada. The population of southern resident killer whales (orcas) has decreased by 25% in two decades. Only 74 people remain and none has successfully delivered in three years.
The survival of southern residents depends on chinook salmon, their main food. In the Fraser River, one of the largest salmon rivers in British Columbia, 11 of the 15 chinook salmon stocks are heavily depleted and require conservation measures. Habitat destruction, fishing, contaminants, agricultural run-off, global warming and water acidification caused by climate change, as well as the threats of diseases caused by salmon farms with pens in net play a role in the decline of the chinook. Commercial and recreational fisheries compete with whales for salmon, and their presence, as well as all ocean traffic, disrupts the whales that feed.
Sport fishing groups attribute the decline of chinook salmon to seals and sea lions and call for slaughter. But blaming the seals does not explain the low returns of chinook
People almost eliminated seals off the coast of British Columbia in the 20th century. Predator control and over-hunting for the commercial fur trade brought in less than 10,000 people in the 1960s. After seal protection in 1970, their numbers increased to nearly 110,000 by the 1880s, and has remained stable since the late 1990s. Recovery of seal populations can be considered good news.
It is tempting to look for simple linear solutions such as slaughter, but it is very unlikely that the desired result will be achieved. The complexity of marine food webs requires a nonlinear vision that includes millions of ecological possibilities. According to one study, only four percent of the diet of a harbor seal is salmon, and an even smaller proportion is chinook. Seals eat all juvenile salmon species, and rarely the adult salmon targeted by sport fishing. They also eat small fish, such as hake, which are the main predators of smolts, as well as fish that compete with chinook. It is plausible that the presence of a seal increases rather than decreases the number of chinook.
Transient killer whales have been seen more often than their resident cousins in the coastal waters of British Columbia in the last decade. Their population is thought to have increased by about 300 people. These orcas prefer to eat harbor seals, requiring the caloric energy of about one seal a day.
Many people who call for the slaughter of seals and sea lions also consider that increasing hatchery production is the best way to bring down wild salmon stocks. But for over 130 years of hatchery operations on the west coast, fisheries have collapsed and wild salmon populations have declined. The proliferation of hatcheries between 1900 and 2014, among other factors, led to a 97% reduction in wild Puget Sound steelheads.
Pacific salmon is an adaptive species, capable of genetic variation over 17 generations and able to adapt to the varying natural environments in which it was born. Artificial selection of parents in a hatchery removes much of the natural selection needed to ensure effective adaptation. The latest scientific data also show that even short periods of time spent in an artificial environment alter farmed fish, making them less suitable for survival and carrying genes that may harm wild stocks if fish are not suitable for survival. breeding go up to the spawning grounds.
Farming fish can never be really wild. Their presence can do more harm than good. Those who survive compete with wild fish for food and, in some cases, can eat smaller wild fish. With over five billion hatchery salmon released each year, concerns have been voiced regarding the overall carrying capacity of the North Pacific Ocean and the limited food supply. Often, the use of hatcheries is more incentive to fish to justify hatchery costs or to avoid taking necessary measures, such as reducing catches and restoring habitat to rebuild wild fish populations.
Commissioner of the Environment and Sustainable Development Julie Gelfand described the federal government's measures to protect endangered orcas as reactive, limited and late. Humans are the main threat to wildlife. We must badume our responsibilities and change our destructive methods. If we want killer whales and other species to survive, we must look in the mirror and change our own behavior.
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