NOSB paper

This paper was written as part of the 2002 Alaska Ocean Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.

The Decline of the AT1 Group in Prince William Sound, Alaska


Hannah Cain
Forrest Dunbar
Rory Merrit
Fred Newirth
Elaine Reodica


Team Behemoth
Cordova High School
Post Office Box 140
Cordova, Alaska 99574

Cordova team photo


Killer whales are divided into two classes: the residents and the transients. The central differences between these two types involves their general behavior and diet. Transient groups feed mainly on marine mammals, while resident pods eat mainly fish. Unlike resident killer whales, which travel in large, extended family groups, the transients keep their group sizes small.

The AT1 transient group is a genetically unique sect of the killer whale population that lives in the Prince William Sound/Kenai Fjords area. Formerly, they were a healthy and stable population. Over the past decade, a massive decline in the population of these whales has lead to concern in scientific communities about their fate. The AT1 group numbered 22 whales in the 1980s, but since the Exxon Valdez oil spill, in March of 1989, this number has dropped to 9 whales (Matkin et al, 1999).

Several environmental factors may have contributed to the decline of this group. There has not been a birth to the group since 1986. This low birth rate may be due to the high content of toxins in the groups' systems. The Exxon Valdez Oil Spill also had a large negative impact on this group. Besides oil related toxins, there are other man made chemicals preying upon the whales, DDT (dichlorodiphenyltrichloroethane) and PCB (polychlorinated biphenyls).

The future of the AT1 group looks bleak, but that should not stop us from trying to undo the ecosystem damage that has contributed to this decline. We should not see this decline of a small group of whales as something to be shrugged off, but rather as a warning of a bigger problem.


Genetically distinct, and on the decline, the AT1 group of killer whales is one of the most studied groups of whales on earth. Unlike other Alaskan killer whale groups that seem to roam widely, the unique AT1 transients (also known as the Prince William Sound transients) have only been photographed in the Prince William Sound/Kenai Fjords region. In the 1980s, the AT1 transients were one of the most frequently encountered killer whale groups in Prince William Sound. This group numbered 22 whales in the 1980s, but since the Exxon Valdez oil spill, in March of 1989, this number has dropped to 9 whales (Matkin et al, 1999). They are now proposed for listing as a threatened or endangered population. This paper details possible causes of decline of the AT1 group and discusses recovery possibilities.

What Is the AT1 Group?

Killer whales can be divided into two classes: the residents and the transients. The central differences between these two types lies in the environments in which they live, their general behavior, and their diets. Resident killer whales prey mainly on fish, while transients target mainly marine mammals. After generations of searching for harbor seals, one of their preferred food items, the AT1 transients know the intricate coastlines of their habitat precisely. In contrast to residents, AT1 transients are difficult to find, because they frequently slink quietly along beaches and close to rocky areas where harbor seals hide out. They often follow all the twists and turns of the shoreline as they hunt, entering bays and inlets. AT1 killer whales are often seen foraging in Icy Bay, a glacial fjord in Prince William Sound, also a traditional seal hunting area for Native residents of Chenega Village. Unlike resident killer whales, which travel in large, stable, extended family groups, the stealthy hunting tactics of transients keep their group sizes small. Some of these groups are unusual in composition, including transient groups that consist of only one or two males (Matkin, et al, 1999).

The decline of the AT1 group of killer whales makes research into this enigmatic pod crucial to ensure they continue to exist in the Kenai Fjords/Prince William Sound area.

Population Status

Before the 1989 Exxon Valdez oil spill, the AT1 group had 22 members; there are now only 9 whales left. Two whales disappeared immediately following the spill. Then, in 1990, seven more whales went missing; these whales are considered to be dead. In 1992, two more whales disappeared. Since July of 2000, two more members of the AT1 group have died. These last two were commonly known as Eyak and Eccles.

The total killer whale population for Prince William Sound before the 1989 oil spill was about 251 whales, and was dispersed in to about 15 different pods. In 1992 the total population of PWS was down to only 183. Since the oil spill the AT1 group alone has lost more than half of its 22 members. During the spill several AT1 members were seen swimming through the oil (Eccles, who was at that time seen swimming through the oil, died during the summer of 2001).

Later, they were frequently seen near Resurrection Bay eating seals and other animals covered with oil. This may be one of the reasons that the surviving members of the AT1 group have such a high toxin levels. No one knows why they hunted oiled seals, but it may have been because these seals moved more slowly in the oil and were easier prey.

In recent years the birth rate of the AT1 group has been extremely low. There has not been a birth to the group since 1986. The low birth rate may be due to the high content of toxins in the groups' systems. Female killer whales reach maturity when they are about 12 to 17 years old; this is usually when their first surviving calf is born. On average, a surviving calf is born every five years, but the interval between calves is sometimes between 3 to 13 years (Matkin et al, 1999). Killer whales are easily stressed, so perhaps with the added stress of the oil spill and with the increase of tour boats, the females in this group have become infertile.

The Decline

When a group faces extinction, you must take all factors into consideration. Old age, disease, a lack of a good food source, pollution of the habitat, and harassment from humans may all be contributing to the decline of the AT1 transient group. However, the two most apparent factors seem to be food availability, and toxins in that food supply. While a definitive link was never established between the 1989 Exxon oil spill and the decline of the whales, there is certainly circumstantial evidence to suggest that the more than 11 million of gallons of oil spilled into the pristine Alaskan waters caused serious damage to the fish stocks of the sound. The population of Pacific Herring, for one, plummeted following the disaster, and their demise must have caused rippling damage through the Prince William Sound food web, and even beyond, in all of the Gulf of Alaska. The AT1 group, unique in their feeding habits, may have felt this impact even more acutely than other killer whale groups. Also, the AT1s are known to stay close to the shore, quietly slinking along the convolutions of the coastline (Matkin, et al, 1999). This practice, usually beneficial to the whale in helping them avoid detection, may have resulted in their receiving an even greater dose of toxic oil fumes at the time of the spill. The oil gradually moved towards the shore, and that was where it remained the longest.

Besides oil related toxins, there are other man made chemicals preying upon the whales. The whale which died near Cordova in July of 2000, named AT1, or Eyak, had extraordinarily high DDT (dichlorodiphenyltrichloroethane) and PCB (polychlorinated biphenyls) levels, at 470 and 370 parts per million, respectively ( DDT is an extremely effective insecticide, used extensively in the 1940s, but banned in the US after complications arose from the effects of the chemical getting into the water cycle ( PCBs are agents used as coolant and as lubricants in various electrical equipment ( In 1977, the manufacturer of PCBs was halted because of evidence of environmental damage caused by these chemicals. Both DDT and PCBs, although no longer used or produced in America, are still present in the environment due to long half-life and continued use in foreign countries.

DDT was originally designed as an insecticide to kill mosquito-borne malaria. There was widespread use of DDT on crops in America until its ban in 1972. There are many forms of DDT, such as aerosols, dustable powders, emulsifiable concentrates, granules and wettable powders ( DDTs physical appearance as a technical product is that of a waxy solid, though its pure form consists of colorless crystals. Although its toxicity as a level is only Class II, as rated by the EPA (Environmental Protection Agency), categorizing it as "moderately toxic," it is persistent in the environment. The tendency of this chemical to build up in the systems of people and animals can cause significant physiological effects. These effects in humans have been documented as including nausea, diarrhea, increases liver enzyme activity, irritation of the eyes, nose, and throat, disturbed gait, malaise, excitability, tremors, and convulsions. The effects on whales, although not as well documented as those in humans, are also negative, and in the case of Eyak, perhaps even fatal. Reproductive, teratogenic, mutagenic, and carcinogenic side effects are also results of DDT exposure (

PCBs are man-made mixtures of up to 209 individual chlorinated compounds. Some PCBs can be found in the air as a vapor, but most of them are either solids or oily liquids which are light yellow and, on some occasions, colorless. The original development of PCBs was to be used as coolants and lubricants in transformers, capacitors, and other electrical equipment ( Evidence finally arose in the late 1970s that PCBs can build up in the environment and cause many harmful health effects. Despite the fact that it is no longer produced in the US, PCBs can still be found in the environment.

Both of these chemicals are detrimental to the health of aquatic life. Algae and other very small life forms are exposed first. These, in turn, are eaten by small fish, which are then eaten by bigger fish. These fish are eaten by many of the animals which transient killer whales prey upon, such as harbor seals. On every step in this course of nutrients, the chemical exposure for the animals gets higher and higher. This process of buildup through the food chain is called bioaccumulation, and while it is never quite this simple, the basic premise is the same. Because the whales are the apex of their particular food chain, they receive a massive dose of these hazardous materials (

Were the AT1 group to disappear completely, the environment effects, although damaging in their own way, would probably go unnoticed by a majority of the sound. However, the AT1 group may be an indicator of a wider environmental problem. Pat Lavin, of the Prince William Sound Alliance for the National Wildlife Federation, once likened this pod to a marine "canary in the mine." He was quoted as saying, "We see the AT1 whales and their difficulties as indicative that the ecosystem is suffering (" Certainly, the extinction of this pod would reverberate back through the food web. With fewer whales to prey on harbor seals and the like, an imbalance will have been created in the food chain. The effects will be negative to all concerned.

The economic impact at the loss of these whales may be negligible. There will be fewer whales for tourists to see, but with nearly 200 other Orcas in the sound, the expiration of a handful of whales can be absorbed economically. The fisheries too, will not be overtly affected by the loss of a mere nine whales. However, the AT1 group is known as a transient group, feeding on other marine mammals ( The death of a harbor seal at the hands of a killer whale is something truly spectacular, and definitely appealing to tourists. More important than this however, is that these whales are genetically distinct; they are a unique subset of the orca population, and their loss would mean the death of a small fraction of the Earth's life.

The Recovery of the AT1 Group

With the harmful effects of the 1989 Oil Spill, the bioaccumulation of chemicals such as PCB's and DDT's, and the reduction of the group's food supply, the plight of this particular genetic subset of Prince William Sound's killer whale population is dire indeed. The AT1 group is at the top of the aquatic food chain, but they are now falling victim to civilization's negligence, and the subtle effects of its chemicals. Now the question arises: is there hope? Can they be saved? It is the opinion of this group of researchers that, despite the majestic and powerful nature of these whales, and the dedication of Prince William Sound's scientific and environmental community, the future of the AT1 group has little hope.

It is the nature of the factors that contribute to this group's decline that makes it such a difficult problem. While PCB's and DDT's have been banned in the US, many other nations continue to use them. Ocean currents and winds carry these chemicals to regions that may be a considerable distance from the source. Because of their diet and position on the food chain, the AT1 group is affected more by these chemicals than other species; this is reflected in their recent decline. Both DDT and PCBs are fat-soluble chemicals which, having entered a body, are nearly impossible to remove. Nothing, short of a sweeping, global policy could prevent the release of these chemicals. Many nations may weigh the potential economic impact with the loss of one, albeit unique group of whales, and not go along with potential treaties. What we must realize is that the plight of these whales may be an indication of a wider environmental problem. These chemicals are omnipresent in today's ocean, and it may be only a matter of time before other populations and species experience similar negative trends.

As has been mentioned several times during the course of this paper, the 1989 Oil Spill also had a large negative impact on this group. Now, more than a decade later, even as the rest of the environment struggles to recover, it may be too late to undo the damage dealt to this group. From 22 to 9 animals, is more than just a drop, it may be a sign of coming extinction. The last birth in this group was in 1986. Thus, a lack of breeding stock also contributes to this group's bleak outlook.

However, just because damage has been done to the AT1 group, this should not be an excuse to do nothing to try and save them. Although we do not believe that we could cure and treat all the damage that has been done to these transients, we are hopeful that prevention of further damage to the AT1 whales will be taken into action. The decimation of the AT1 whale population also involves damaging the aquatic life's balance. Deterioration of the entire ecosystem is at hand, but we could diminish the chances of this, if we start caring about these distressed whales by helping prevent damages that could be done in the future. If the governments of foreign nations still using PCBs and DDT can be informed about the danger those chemicals pose, perhaps there will be a drop off in use. If the US provides funds to these companies, or alternative technologies, maybe the use can be halted entirely. Even if the AT1 group never recovers, any effort to help them that is aimed at the sources of the decline will also benefit the environment as a whole. If the AT1 group dies out, a chapter of the planet, however minute, will be closed forever

References Cited

National Marine Mammal Laboratory. 1991. A Catalogue of Prince William Sound Killer Whales. Homer, Alaska: North Gulf Oceanic Society. 50 pages

Marine Mammal Commission. 1994. Killer Whale (Orcinus orca): Biology and Management in Alaska. Homer.Alaska: North Gulf Oceanic Society. 46 pages

Matkin, Craig, Ellis, G., Saulitis, E., Barrett-Lennard, L., Matkin, D., C. 1999, Killer Whales of Southern Alaska, North Gulf Oceanic Society, Homer, Alaska

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