Collapsing salmon populations now causing population collapse of killer whales

Saturday, July 22, 2017
By Paul Martin

by: Russel Davis
Saturday, July 22, 2017

A recent study published online in the PLOS ONE website revealed that the depleting Chinook salmon population was be a primary driver for high pregnancy failure rate among southern resident killer whales. According to the study, food scarcity and nutrient deficiency brought by the depleting salmon population was accountable for up to two-thirds of failed killer whale pregnancies between 2007 to 2014.

To carry out the study, a team of researchers at the Center for Conservation Biology at the University of Washington, along with partners at the National Oceanic and Atmospheric Administration‘s Northwest Fisheries Science Center and the Center for Whale Research examined environmental factors — food supply, pollutants, or boat traffic — that have caused a steady decline in killer whale population.

According to the research team, Southern resident killer whales typically feed in the Salish Sea between May and October. The animals were known to spend winters in the open Pacific Ocean along the West Coast. Unlike transient killer whales that prefer marine mammals, Southern resident killer whales were more dependent on salmon for sustenance. In fact, more than 95 percent of the animals’ diet consists of salmon, with Chinook salmon alone accounting for about three-quarters of their diet.

Experts have previously noted that only 78 individual Southern resident killer whales have low fecundity rate in December 2016, compared with their counterparts in the northern British Columbia and southern Alaska region. However, recent data showed that nutritional stress from scarce salmon population has had a greater, direct impact on the reproductive success of the southern resident killer whales compared with increasing boat traffic. This malnutrition-induced pregnancy failure was exacerbated by toxin exposure that accumulate in the fatty tissues.

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