Killer Whales Have Extremely High Levels of PCBs and DDT
Killer whales feed and travel along the deep waters of Monterey Canyon, feeding upon diverse prey in this extremely productive region. Top predators, they are highly intelligent whales with culturally distinct patterns that live in family groups. Because of the close proximity of the canyon to shore in Monterey Bay and our consistent year-round boat surveys, killer whales are seen here more often than anywhere else along the California coast. Sightings are unpredictable but occur year-round, providing us with a unique opportunity to study these animals in an open ocean habitat.
|Killer whales off California appear to be the most contaminated animals on earth. photo 2003 Nancy Black/Monterey Bay Whale Watch
At least three eco-types of killer whale occur in the eastern North Pacific: residents, transients, and offshores. All three types have been seen in Monterey Bay. Each eco-type differs genetically, in physical appearance, distribution patterns, vocalizations, and prey preferences. These types do not intermix even though they have overlapping ranges. Transient type whales are most frequently sighted in Monterey Bay and prey on marine mammals – including gray whale calves, California sea lions, elephant seals, harbor seals, Dall’s porpoise, Pacific white-sided dolphins, and common dolphins. Each whale is identified by its natural markings, and we have identified 136 individuals to date.
Since 1987 we have studied the behavior and ecological patterns of these known transient killer whales. We work with other research- ers along the West Coast to look for re-sightings of previously
identified whales. This transient population ranges from southern California to Southeast Alaska, although whales that occur in Monterey Bay are primarily seen in the coastal waters of California.
Part of our research involves collecting a small amount of skin and blubber through biopsy sampling from a research inflatable, with a permit through the National Marine Mammal Laboratory, National Marine Fisheries Service (NMFS). Skin is used for genetic analysis, and the blubber is used to determine levels of toxic chemicals. This research is being incorporated into a
project to compare persistent organic pollutants (POPs) from killer whales ranging from Russia and the Aleutian Islands, through central and southeast Alaska and down the West Coast to California.
Gina Ylitalo, from the Northwest Fisheries Science Center, NMFS in Seattle, analyzes the blubber
samples for toxins.
POPs include PCBs (polychlorinated biphenyls) and DDT (dichlorodiphenyltrichloroethane), which are highly stable organic compounds that were used (and are still used in some countries) as pesticides or by industrial companies. POPs persist in the environment, bioaccumulate through the food web, are fat-soluble, and are toxic to humans and
animals. The long-range atmospheric transport of these chemicals to regions where they have never been produced represents a threat to the global environment. These chemicals are of particular concern to species at the top of the food chain – most significantly, killer whales.
|Figure 1. Eastern North Pacific killer whales: PCB concentrations
PCBs were first produced in the 1920s and were the most lethal chemicals dumped into the environment. They were used as coolants and lubricants for electrical transformers and capacitors and in various industrial products. Monsanto Company, a large North American manufacturer of PCBs, made 635,000 metric tons before the ban in 1977. DDT is a pesticide that was used in many countries to control mosquitoes and was also heavily used by farmers to protect their crops. DDT was banned in the United States in 1972 but degrades slowly and remains in rivers and ocean sediments. Heavy rains throughout California still flush the chemicals into the oceans, and El Niño storms churn up sediments, releasing these chemicals.
The Montrose Chemical Corporation in southern California was one of the world’s largest manufacturers of DDT and disposed of thousands of tons of DDT waste into the ocean between 1949 and 1970. Several other industries also discharged PCBs. These polluted waters, near the Channel Islands, are the main breeding area
for California sea lions, which are major prey for killer whales. Since DDT was banned, levels in California sea lions have greatly decreased but are still high compared to pinnipeds in other regions.
The adult male killer whales sampled in Monterey Bay carry very high levels of POPs – shockingly, the highest levels known for any marine mammal. Levels of PCBs in male transients ranged from 750 to 1,600 micrograms/gram lipid weight and the highest DDT levels were 8,700 micrograms/gram lipid weight. A female transient recently found dead off Washington (an identified whale from our California catalog) contained about 1,000 parts PCB. Comparatively, levels of PCBs from transient whales in British Columbia and Alaska, although still high, average three to ten times lower. Since resident whales are fish eaters, it is expected that their levels would be less than transients, but levels are still high enough to cause concern (Figure 1). These high values are much greater than those known to affect the growth, reproduction, and immune systems of harbor seals. As apex predators, killer whales typically have smaller population sizes than those of their prey. As such, an outbreak of a virus or disease could be disastrous to their survival if their immune systems are compromised.
California’s pinnipeds and cetaceans, prey of the transients, are all known to have relatively high levels of POPs. Since transient killer whales are at the top of the food chain, they bioaccumulate these toxins from their prey. Female whales offload some of the toxins to their calves through milk, transferring up to 90 percent of their contaminants to their first born. Females first reproduce at around fifteen years, but after the age of forty to fifty they are post-reproductive and can then continue to accumulate these toxins. The males have no way of offloading these chemicals and continue to accumulate them throughout their lives. Killer whales are long-lived animals, with males living forty to fifty years and females, eighty to ninety years. The shorter male lifespan could be due to higher toxins in their bodies.
Killer whales off California appear to be the most contaminated animals on earth and are indicators of the health of the marine environment. Our long-term research will continue to sample toxin levels from more individuals and to monitor this population and their survival rates. Efforts to decrease these toxins worldwide and attempts to prevent continued contamination of the oceans, including looking for source points and researching clean-up methods, should increase.
Nancy Black1, Richard Ternullo(1), and Marilyn Dahlheim(2)
(1)Monterey Bay Cetacean Project
(2)National Marine Mammal Laboratory, NMFS
The “Invasion” of Sea Lions in Monterey Bay
The California sea lion (Zalophus californianus), one of the most obvious marine mammals off California, also occurs from Mexico north to British Columbia. California sea lions breed from June through July in southern California and Mexico, and adult males and juveniles often migrate north after the breeding season, whereas most females remain south. The population has increased dramatically since passage of The Marine Mammal Protection Act in 1972. There are an estimated 204,000 to 214,000 sea lions in U.S. waters and possibly an additional 80,000 to 100,000 animals along Baja California (Figure 1).
|Sailboat in Monterey Harbor with thirty-five to forty unwanted crew members. photo Jim Harvey
Increasingly, some people are concerned because sea lions are using marinas, docks, and other structures and affecting fisheries. California sea lions in Monterey Harbor and elsewhere have destroyed docks, sunk boats, damaged facilities, fouled spaces, and intimidated people. Certain sea lions have entered boats to steal fish, and one animal snatched a salmon from a boy and his father as they got their picture taken with their catch. California sea lions compete with many commercial and recreational fisheries along the California coast – directly, by causing entanglement and damage to fishing gear and loss of catch, and indirectly, by competing for resources.
In Monterey Harbor, most sea lions are juveniles. These tend to stay in Monterey year round, whereas during most of the year adults are elsewhere. Typically, there is a peak in abundance off central California in August through October as the animals are moving northward and another peak in March through May as they head southward for breeding. Formerly, sea lions used the jetty and underneath the commercial wharf in the harbor; however, in recent years juveniles have become more bold and have invaded the beaches,
finger piers, and moored boats within the harbor.
The increased use of Monterey Harbor and other marinas is probably due to an increasing population size, increased access to areas used by humans (e.g., breakwaters, docks, vessels, floats), and changes in food supply, all of which attract animals into this area. They are also attracted to some harbors where fish carcasses are thrown into the water. (This happens to a limited extent in Monterey Harbor but probably has not caused the population increase here.) During the 1983, 1992, and 1997-98 El Niño events, the number of sea lions increased along central California because prey was less available in the Southern California Bight. Whatever the cause, increasing numbers of sea lions are using
harbors and associated structures and causing havoc.
|Figure 1. Population increase of California sea lions in U.S. and Mexican waters throughout the twentieth century
We hypothesize that California sea lions respond to climate-induced shifts in productivity with shifts in their distribution and foraging behavior. The prey are variable in the numbers and locations where they occur because of seasonal differences; therefore, we suspect that there will be pronounced differences in the seasonal foraging behavior and seasonal food habits as sea lions follow ephemeral and locally abundant prey. After they leave the area, the animals can move great distances in search of prey resources.
Some of the resources sea lions seek are also popular with humans. California sea lions in the Monterey Bay area primarily
eat market squid, anchovy, hake, sardine, and rockfishes. Some individuals, however, supplement their diet with salmon caught by fishermen. From 1997 to 1999 we examined the interaction of sea lions with the commercial and recreational salmon fishery in Monterey Bay and found that generally, 10 to 15 percent of the fish hooked are removed and eaten by sea lions, but it can be as great as 30 percent in an El Niño year (1998). The increasing sea lion population and the increasing number of individuals that have learned this behavior would predict that the problem will only worsen.
California sea lions stretching out along docks and breakwaters is a wonderful sight for some, bringing joy to many local residents and tourists. However, for others (e.g., marine operators, boat owners, fishermen) the increasing number of sea lions in the area only means trouble.
Jim Harvey(1) and Mike Weise(2)
(1)Moss Landing Marine Laboratories
(2)University of California Santa Cruz