Food availability, toxins among factors threatening orcas today

Over all the world’s oceans, it is believed there are more than 50,000 orcas. Looking at all ecotypes of orcas, orcas are the most widespread and one of the most populous of all marine mammals. Here in the Salish Sea it is estimated there were once 200 individual orcas between J, K and L pod of the Southern Resident Killer Whales (SRKW). Today there are 84 individuals.

In 2005 the Southern Resident Killer Whales were listed as an endangered species under the Endangered Species Act due to their small and stagnant population size. The SRKWs are considered a “distinct population segment” and able to be distinguished from the population of orcas at large. Through research and observation there are several factors that have contributed to the SRKW population decline – prey availability, toxins and orca capture.

Prey Availability

Over the past several decades, due to habitat loss and unsustainable fishing, most of the Pacific coast salmon runs are down 90% or more from their historical numbers. Southern Resident Killer Whales primarily eat salmon and are especially affected by low numbers of salmon returning to the Salish Sea.

During the summer months, SRKWs primarily feed upon Fraser River salmon passing through the Salish Sea. The waters on the west side of San Juan Island are deep and a perfect area for foraging salmon.

Through observations, it has been seen that when prey availability is low, survival and birth rates are also low, and the SRKWs are seen less frequently in the summer months in years of low salmon return to the Fraser River.

Dam removal, sustainable fishing and proper management of aquaculture are the main focuses of salmon recovery, which in turn will benefit the SRKWs.

 

Orca spy hopping with a San Juan Safaris vessel in the background.
Orca spy hopping with a San Juan Safaris vessel in the background. Mike O'Leary

Toxins

Toxins accumulate in the fat of orcas via the food they eat. Pollutants and toxins accumulate up the food chain, and as orcas eat high on the food chain, large toxin loads are found in their blubber or fat.

Toxins are highest in urban areas, such as Puget Sound and the greater Salish Sea. The most problematic toxins are the pesticide DDT and PCBs, which are historically found in coolants and lubricants. Even though these toxins were banned, they still persist in the food chain and remnants still seep into the sound. Today, flame-retardants, or PBDEs, are currently the main toxin of concern.

Toxins are thought to affect overall health of the orca, as well as other marine organisms, causing immune system failures. Toxins are linked to higher occurrence of disease as well as decreased reproductive success.

When mother orcas give birth, they offload toxins in their fatty milk to their calves. It is thought this may be linked to the mortality rate of SRKW calves. This also causes younger whales to have higher levels of toxins and to be more susceptible to disease.

The United States banned DDT in 1972 and PCBs in 1979. Canada followed soon after banning both compounds in the 1980s. In 2011 PBDEs were banned in Washington state.

Orca Capture

During the 1960s and 1970s orcas were subject to capture for aquariums and marine parks. During this time, approximately 47 whales were removed from the Salish Sea. The United States federal government passed the Marine Mammal Protection Act in 1972, making it illegal to harass, feed or capture marine mammals without a permit. However, capture in Washington state did not end until 1976.

Through the efforts of researcher Ken Balcomb and others, a system for cataloging orcas using photos ids was developed and the annual Orca Survey was born. In 1976 it was confirmed that there were 71 individuals left in the SRKW population. The Orca Survey also revealed that there are no individuals in the current population born between 1960 and 1970.

The orca captures caused a dramatic decrease in the population of the SRKWs. While orca captures ended in the Salish Sea in 1976, the effects can still be seen today.

How you can help

You can help the Southern Resident Killer Whales in a number of ways. Always buy local, sustainably caught salmon and support sustainable practices. You can also donate to organizations such as the Center for Whale Research, Long Live the Kings, and Save our Wild Salmon.

By joining San Juan Safaris, $1 of your ticket will be donated to an organization promoting SRKW recovery.