estoration noteR book November 1997 Exxon Valdez Oil Spill Trustee Council

Harbor Seal Phoca vitulina richardsi

Photo by Kathy Frost

tory counted approximately 12,000 harbor seals in this same By Kathryn J. Frost area.2 If this number is adjusted for the seals that weren’t Alaska Department of Fish and Game counted because they were in the water (multiplied by 1.74, based on tagging studies), this would still result in a popula­ arbor seals, Phoca vitulina richardsi, are medium-sized tion estimate of only 21,300 -- a decline of over 80% in the last H “earless” seals belonging to the Family Phocidae. 20 years. Although these numbers are not exact, they indicate They are usually found in nearshore coastal waters, often in a large decline in harbor seal numbers in PWS and the GOA. estuaries or protected coves. They are commonly seen along Counts at individual haulout sites or along survey routes es­ the shores of the northern hemisphere. Harbor seals are found tablished to monitor trends confirm this decline. At Tugidak in both the North Atlantic and the North Pacific. In the eastern Island, south of Kodiak, the average counts declined by 85% North Pacific, their distribution is nearly continuous from Baja, from 1976 to 1988 and have continued to decline since then.2,3 California to Bristol Bay, Alaska. In other parts of the Kodiak Archipelago, counts declined by Harbor seals are one of the most common marine mammals 89% between 1978 and 1992.2,4 In PWS, the number of seals in Prince William Sound (PWS) and the Gulf of Alaska (GOA), at 25 indicator sites declined by 42% between 1984 and 1988.5 where they occur throughout the year. The exact number of In 1995, there were 65% fewer seals at these haulouts than harbor seals in these areas is unknown. In 1973 the Alaska there were in 1984.6 The reasons for the decline are unknown Department of Fish and Game estimated there were about and are the subject of ongoing studies by the Alaska Depart­ 125,000 seals in this area based on harvest data, observed den­ ment of Fish and Game, the National Marine Fisheries Ser­ sities, and the amount of available habitat.1 vice, and the University of Alaska. In the early 1990s, the National Marine Mammal Labora- Harbor seals are found primarily in the coastal zone where

Exxon Valdez Oil Spill Trustee Council 1 n o t eR bestoration o o k they feed, haul out to rest, give birth, care for Reproduction Vital Statistics their young, and molt. Hauling out areas in­ Harbor seal females give birth to single clude intertidal reefs, rocky shores, mud and pups once a year, usually on land or glacial Population sand bars, floating glacial ice, and gravel and ice. In PWS and the GOA, peak pupping oc­ Approx. 34,400 in sand beaches. Pups are born in the same gen­ curs in the first half of June, although some GOA/PWS (1993) eral locations that are used as haulouts at other pups may be born in mid-May and some as Population Trend times of year. late as July. Pregnant females usually move 80% decline during Harbor seals tend to use haulout sites where to isolated sites or to the edge of large groups previous 20 years they have protection from predators approach­ to give birth and remain there while the pups ing over land, direct access to deep water, prox­ are very young. Later, they rejoin the group Lifespan imity to food, and protection from strong winds at the main haulout area. Newborn harbor 30 years, maximum and high surf.7 Based on satellite tagging stud­ seal pups are born with their eyes open, with recorded age - 32 ies in PWS, most adult harbor seals use the same an adult-like coat, and are immediately able Adult Size few sites for most of the year. During spring to swim. Pups are weaned when they are 3-6 5 feet, 175 pounds and summer, each tagged seal used an average weeks old.7 Mating Season of four different haulouts, while in fall and win­ Adult females breed about two weeks after ter they used an average of only two. Over half their pups are weaned. The embryo remains July, two weeks after previous pup weaned the time, they used one “preferred” site for haul­ dormant for about 6-12 weeks after breeding, ing out.6 then implants in the uterus and begins to grow. Gestation Period Female harbor seals first become pregnant 11 months Movements when they are about 3-7 years old and give Number of Pups The distribution and movements of harbor birth about 11 months later. The age of sexual one per year seals at sea are not as well understood. Recently, maturity varies depending on whether popula­ however, some information about at-sea behav­ tions are high and close to the carrying capac­ Size at Birth ior has become available through the use of sat- ity of their habitat (causing seals to mature 30 inches, 26 pounds ellite-linked tags. These tags allow scientists to later), or populations are low and there is plenty Maturity track seals and monitor their diving behavior of food and other resources (causing seals to Pups weaned 3-6 wks when they are in the water. mature earlier). after birth; Sexual Most satellite-tagged seals did not travel far maturity at 3-7 yrs to feed. Generally, they stayed within about 20 Molting miles of their haulouts. A few seals, especially Once each year, harbor seals shed their old Diet juveniles, traveled long distances from the loca­ hair and grow a new coat. During this molt­ Pollock, octopus, cod, tion where they were tagged. ing period, the seals spend more time hauled capelin & herring One subadult seal tagged at Channel Island out than they do at other times. This is prob­ in PWS swam over ably because the new hair grows faster when 200 miles to the seals are out of the water and the skin is Yakutat Bay where warmer.7 it spent the winter While seals are molting, their metabolism making repeated is almost 20% lower than it is at other times.8 trips from there to This lowers their food requirements and al­ the GOA, 60-100 lows them to spend long hours hauled out. miles away.6 An­ The shedding of hair takes about 4-6 weeks other adult male and occurs at slightly different times for seals swam to Middleton of different ages and sex. Yearlings (which Island and made don’t molt during their pup year) usually molt feeding trips in the first, followed by mature females and then GOA all winter, re­ mature males.9 turning to PWS in In PWS and the GOA, shedding seals are Photo by Lloyd Lowry the spring. seen from late June to early October, with Alaska Department of Fish Within PWS, seals used particular areas. peak molting in late July and August.4 Be­ and Game Biologist Kathy Seals in central PWS rarely used haulout areas cause seals spend more time hauled out dur­ Frost glues a satellite tag on a harbor seal at Seal Island. in southern PWS, and vice versa. Similarly, ing the molting period, it is a good time to do seals in eastern PWS did not haul out in either surveys and count seals to estimate popula­ central or southern PWS. tion trends.

2 Exxon Valdez Oil Spill Trustee Council Rn estorationo t e b o o k Predator/ Prey capelin, herring) that are also eaten by seabirds, Most information about the foods of harbor fishes, and other marine mammals. In addi­ seals in PWS and the GOA was collected in tion, harbor seals become food for other spe­ the mid-1970s and was based on stomach con- cies. Known predators include killer whales, tents.4 The major prey in both PWS and the Steller sea lions, and sharks. GOA included pollock, octopus, capelin, Pa­ The impact of these predators on harbor seal cific cod, and herring. Pollock was eaten most populations is unknown, but may be significant. often, but even so, over 50% of the samples In PWS alone, killer whales may eat up to 400 contained prey items other than pollock. Young harbor seals per year.10 The incidence of sharks seals ate mostly pollock, capelin, eulachon, and caught on halibut longlines in the GOA has in­ herring. creased greatly in the last decade. The degree Photo by Kathy Frost Harbor seals are one of the top predators in to which these sharks prey on harbor seals is the marine ecosystem of PWS and the GOA. unknown, but seals have been found in their They eat many of the same prey (e.g. pollock, stomachs.10

Pathology and Hydrocarbons centrations of hydrocarbon metabolites all tissues except blubber. Total PAH val­ in the bile clearly indicated that most ues in blubber were greater than 100 ppb In the first few months after the EVOS, seals from oiled areas had been exposed and ranged as high as 800 ppb in 8 of 17 18 harbor seals were found dead or died to and had assimilated hydrocarbons. seals sampled from oiled areas of PWS in in captivity. Fifteen of these were The mean concentra­ April-June 1989, and one of 6 in April externally oiled and 3 were pups. tion of phenanthrene 1990. Milk from a pup had the highest Bleeding in internal organs was equivalents was more PAH value of any tissue in any seal that found in four seals, severe skin ir­ than 70 times greater was analyzed. There is little information ritation in two, inflamed eyes in for oiled seals from available about the effects of hydrocarbons two, and symptoms of malnutri­ PWS than for two on seals. Health implications of these toxi­ tion in three. In three seals, pa­ seals collected near cological findings are unknown. thologists found evidence of nerve Ketchikan, and ap­ Microscopic examination of seal tis­ damage in the brain. Firm con­ proximately 20 times sues (histopathology) revealed severe le­ clusions about the degree and sig­ greater than for sions in the midbrain of a heavily oiled nificance of brain damage in these unoiled PWS seals or seal collected 35 days after the spill.14 recovered carcasses were not pos­ those from the Gulf. Similar but milder lesions were found in sible because of tissue breakdown The highest phenan­ the brains of seals collected three or more between the time of death and threne equivalent con­ months after the spill. Lesions were not Photo by Roy Corral necropsy. present in the Ketchikan seals or in the Dr. Sara Iverson prepares centrations in oiled In 1989, 20 harbor seals were an adult captured on shore PWS seals were more PWS seals collected in 1990. Overall, collected from PWS and the GOA for transport to the vessel. than 1000 times neurological lesions that may have been to obtain complete, high-quality greater than for unex­ associated with oil toxicity were found tissue samples to learn about the effects posed seals. The low concentrations of in the brains of 9 of 12 oiled seals and 2 of the oil spill on seals. Of these, 11 were hydrocarbon metabolites in GOA seals, of 13 unoiled seals. These lesions are heavily oiled, 3 were lightly or moder­ and their similarity to levels recorded for characteristic of hydrocarbon toxicity, ately oiled, and 6 were not externally seals from unoiled areas, suggests that ei­ and may explain the disorientation and oiled. Thirteen were from oiled areas of ther the GOA seals that were sampled had lethargy observed in seals immediately PWS and the other seven from the GOA. little exposure to oil, or that most of the following the spill. The thalamus where In April 1990 six additional seals were aromatic fraction of the oil had evaporated the lesions were located is responsible collected in PWS; all were collected in by the time it reached the GOA. for relaying messages from sensory sys­ areas that had been heavily oiled, but All seals collected from the GOA and tems to other parts of the brain. If the none showed external signs of oiling. near Ketchikan had non-detectable or very lesions interfered with transmission of Two seals were collected in the Ketchikan low parts per billion (ppb) levels of poly­ these messages, they may have caused area in August 1990 to serve as reference nuclear aromatic hydrocarbons (PAHs) in abnormal behavior. Severe lesions may specimens. liver, blubber, muscle, and brain tissue. have caused the seals to have difficulty Bile from the gall bladders of 33 seals PAH values in seals from oiled areas of with such normal tasks as breathing, was analyzed for hydrocarbons.13 Con­ PWS were also non-detectable or low for swimming, feeding, and diving.

Exxon Valdez Oil Spill Trustee Council 3 n o t eR bestoration o o k Human Factors June, when some of the sites still had oil on Harbor seals also compete with humans for them, and many pups became oiled shortly af­ food, and in turn are eaten for food. In PWS ter birth. In Bay of Isles and Herring Bay in and the GOA, major fisheries occur for pollock, PWS, 89%-100% of all seal pups seen were herring, and salmon. All of these also are food oiled.12 Some of this contamination was prob- for seals. The interactions between seals and ably from contact with oiled mothers. When fisheries are poorly understood, but it is likely pups were entirely coated with thick, heavy tar that each may affect the availability of certain it probably came from oil on the rocks and sea- fish to the other. In addition to competition for weed. Mothers and their pups often hauled out the same fish, seals may be incidentally killed high on the beach where popweed (Fucus) (e.g., tangled and drowned in nets) during com­ grows. Popweed remained oiled long after mercial fisheries. other seaweed and rocks appeared clean. Harbor seals are an important food and handi- Abnormal behavior by oiled harbor seals in craft resource for Native subsistence hunters in oiled areas was observed on many occasions PWS and the GOA. The average annual harvest in April-June 1989.12 Oiled seals were reported of harbor seals during 1992-1994, was approxi­ to be sick, lethargic or unusually tame. Exces­ mately 450 seals in PWS and 350 for Kodiak, sive tearing, squinting, and disorientation were Cook Inlet-Kenai, and the south Alaska Penin­ also observed in oiled seals. The lethargy and sula combined.11 disorientation may have led directly to the deaths of pups due to abandonment and of older seals due to drowning. Effects of the spill Following the Exxon Valdez oil spill (EVOS) Post-spill aerial surveys in March 1989, harbor seals were exposed to In August-September following the EVOS, oil both in the water and on land. In the early the Alaska Department of Fish and Game con- weeks of the spill they swam through oil and ducted aerial surveys of harbor seals in oiled inhaled aromatic hydrocarbons as they breathed and unoiled areas of PWS.15 Results of these at the air/water in­ surveys were compared to earlier surveys of 3600 terface. On the same haulouts conducted in 1983, 1984, and haulout sites in 1988. Before the EVOS, counts in oiled and CountsCounts of of Harbor Harbor Seals Seals in in PWS PWS 3200 oiled areas, seals unoiled areas of PWS were declining at a simi- crawled through lar rate, about 12% per year. From 1988 to

2800 oil and rested on 1989, however, there was a 43% decline in oiled rocks and al- counts of seals at oiled sites compared to 11% 12% annual decline before EVOS gae throughout the at unoiled sites. This difference was statisti­ 2400 13% annual decline before EVOS spring and sum- cally significant. ○

○ mer. Oiling was Aerial surveys were also conducted during ○

○ 2000 most severe in the pupping season following the EVOS. In ○

○

○

○ central PWS, the the spill year, pups made up a smaller percent- ○

○ 1600 region from age of seals in the oiled area than they did in ○

○

○

○ Molting Period Eleanor Island later years. In the unoiled area, the percentage Number of Seals ○

○ 1200 Molting Period through the north of pups did not differ significantly between ○

○ Post oil-spill decline ○

○ part of Knight Is- 1989 and post-spill years. Together with the From 1988-89, ○

○ there was a 43% land, and the west fetuses and dead pups found following the spill, ○ 800 6% annual decline ○ drop in oiled areas 6% annual decline ○ since EVOS side of Knight Is- this suggests that pup mortality was higher than ○

○

and 11% drop in ○ land Passage. normal in oiled areas in 1989. ○ unoiled areas ○ 400 Pupping Period ○ More than 80% of Harbor seal biologists estimated that approxi­ ○

○

Pupping Period ○ the seals seen in mately 300 seals died in PWS due to the

○ EVOS

○ 0 these oiled areas EVOS.15 The number of deaths was estimated 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 in May 1989 were mathematically by comparing counts and pro- Harbor seal numbers have observed with oil on them.12 Some seals also portions of seals at oiled and unoiled sites be­ dropped dramatically since became oiled in the GOA west of PWS, but the fore and after the spill. Information such as the 1984 with the sharpest one- year drop immediately degree of oiling was less well documented. lack of sightings of oiled seals in unoiled ar­ following the oil spill. Pups were born on haulout sites in May and eas, the strong fidelity of harbor seals to par­

4 Exxon Valdez Oil Spill Trustee Council Rn estorationo t e b o o k Movements of Satellite Tagged Harbor Seals in Prince William Sound, Fall 1994

Unakwik Columbia Inlet Glacier

Gravina Island Prince Yakutat Bay William Icy Bay Sound

Channel Island Port Chalmers Gulf of Alaska 0 40 80 120 160 Kilometers

Middleton Island

By gluing ticular haulouts, the abnormal behavior of oiled satellite tags seals, and the brain lesions found in oiled seals to their backs, suggests that these seals died rather than left it is possible the area. to track the movements of seals using Long-term effects NOAA By early September 1989, many visible ef- satellites. fects of the EVOS on harbor seals were gone. Each symbol on the map Less than 20% of the seals observed in the represents a oiled area were oiled. Most seals older than tagged seal, Photo by Kathy Frost pups had molted, shedding their oil-stained showing its hair. They did not become re-oiled, since most were still encountering oil in the environment movement over time. Harbor seals tend to stick close to of the oil was gone from the water and most or that they were metabolizing stored fat reserves home, but occasionally major haulouts had been cleaned. By April that had elevated levels of hydrocarbons. The wander great distances, and June 1990, no sign of external oiling was effects of these elevated levels, if any, are un­ such as the Yakutat seal observed on any seals. During September known. Fish collected in PWS during spring (indicated by the half-moon symbol). 1989 and April 1990, seals were no longer ob­ 1990 also had elevated levels of hydrocarbon served acting lethargic and sick. They were metabolites. The presence of hydrocarbon me­ noticeably more wary and difficult to ap­ tabolites was not surprising, since shoreline sur­ proach than they had been immediately fol­ veys in spring 1990 documented oil remaining lowing the spill. on many beaches. One year after the EVOS, none of the tissues Aerial surveys of harbor seals and their pups from seals collected in the spill area showed sig­ only detected differences in adult-to-pup ratios nificantly elevated concentrations of oil-related between oiled and unoiled locations in the spill hydrocarbons.13 However, average concentra­ year. In 1990-1995, the percentage of seal pups tions of hydrocarbon metabolites in bile were at oiled sites appeared to be normal. From 1990­ still significantly higher than they were in seals 1994, the population trend was similar in oiled from the GOA, Ketchikan, or unoiled PWS ar­ and unoiled areas, as it was before the spill. Dur­ eas. Since elevated levels of hydrocarbons in ing those four years, the harbor seal population bile indicate recent exposure to oil, the higher continued to decline at about 6% per year in both levels found in spring 1990 suggest that seals oiled and unoiled areas.

Exxon Valdez Oil Spill Trustee Council 5 n o t eR bestoration o o k Restoration Activities tion is useful for determining how much inter­ Since the oil spill in 1989, the EVOS change there is between seals in PWS and else­ Trustee Council has funded studies of harbor where, and whether seals from PWS should be seals to monitor their status and to learn more managed as part of the same stock as other seals about their habits. The continuing harbor seal in Alaska. It also helps to identify important habi­ decline in PWS and the GOA concerns re­ tat for seals, such as feeding and haulout areas. searchers, resource managers, and the public. One of the goals of harbor seal restoration Biological Samples studies, as well as studies funded by other in­ As part of their field studies, researchers catch stitutions, is to learn about the causes of the seals from PWS, the GOA, and southeast long-term decline. Possible causes include Alaska.6,16 They measure and weigh each seal disease, food limitation, predation, or mortal­ and take samples for studies of blood chemistry, ity caused by people. blubber composition, disease, genetics, and diet. Annual aerial surveys have been conducted since Blood is being analyzed to determine whether 1989 to monitor the status of harbor seals in PWS or not seals are healthy, and so comparisons can and to determine if and when the decline stops. be made between seals from declining and in­ The surveys cover the same 25 haulouts that creasing populations.17 Blood is also being ana­ ADF&G began monitoring in 1984. Because these lyzed to learn whether harbor seals in Alaska surveys have been done for nine years using con­ have been exposed to diseases like influenza, sistent methods, researchers have been able to use herpes, and distemper. So far, there is no indi­ the data to develop new ways to analyze survey cation that diseases are a problem in Alaskan data. These techniques will be useful not only in harbor seals. PWS, but for seal surveys around the world. Genetics studies examine the DNA of seals from different parts of Alaska and around the A harbor seal is released after Tracking world to learn about the population structure of it was examined and tagged. As part of restoration studies funded by the harbor seals and how seals in different areas are Photo by Roy Corral EVOS Trustee Coun­ related. So far they have discovered no major cil, researchers are us­ genetic differences between PWS and other ing satellite tags to Alaska seals.16 learn about the distri­ Measurements from seals in the 1990s are be­ bution, movements, ing compared to seals in the 1970s to look for and diving behavior of any changes in body condition, which might af­ harbor seals in PWS. fect survival. Researchers use ultrasound to For the first time it is measure the seal’s blubber thickness.17 possible to measure how deep and for how Diet long seals dive and Researchers are using exciting new techniques where they go when to study the diets of harbor seals and to compare they leave their the diets of seals from different areas. One of haulout sites. these analyzes the fat in seal blubber. The fats Researchers have can contain about 70 different fatty acid building learned that harbor blocks in different proportions. It is possible to seals normally use only match the fatty acid signature of the blubber with a few adjacent haulout the fatty acids in prey species to estimate the seals’ sites and that they have diets. “You are what you eat” as the saying goes. very small home Early analyses of fatty acids show that harbor seals ranges. Some seals, es­ feed differently at each haulout.6 Seals from pecially young ones, haulout sites only a few miles apart may have may make longer trips very different diets. away from home, but Another new technique for studying diets and most of them eventu­ food webs involves the analysis of stable iso­ ally return to the loca­ tope ratios. Scientists analyze and compare the tion where they were carbon and nitrogen in seal whiskers and differ­ tagged. This informa­ ent food items to learn if seals from different

6 Exxon Valdez Oil Spill Trustee Council Rn estorationo t e b o o k age groups or areas are eating different kinds of This type of brain dam­ prey. This technique doesn’t tell exactly what age would likely inter­ the seal eats, but gives information about fere with normal func­ whether they feed high or low on the food chain. tions such as breathing, For example, in Steller sea lions, stable isotopes swimming, diving, and have shown that young sea lions feed lower on feeding. In severe cases, the food chain than do the adults. seals probably died. Seals that survived the Subsistence hunting first few weeks probably Alaska Native hunters from PWS and the recovered. GOA are very concerned about harbor seals. The Marine mammals are serious decline in the past 10-20 years has made very efficient at elimi­ it much more difficult for them to successfully nating hydrocarbons hunt harbor seals, which are an important part from their system, and of their diet and cultural traditions. Because of blubber was the only their interest and concern about harbor seals, tissue that showed in­ Alaska Natives formed the Alaska Native Har­ creased levels of hydro­ bor Seal Commission (ANHSC) in May 1995. carbons after the The purpose of the ANHSC is to increase the EVOS. However, the role of Alaska Natives in research and resource bile of oiled seals con­ policy affecting harbor seals and their uses, and tained by-products of to address concerns about the harbor seal de­ hydrocarbon metabo­ cline in PWS and the GOA. lism as much as one Since 1995, the ANHSC has received funds year later, confirming from the EVOS Trustee Council to conduct a that seals were still be­ biosampling program in PWS and the GOA. ing exposed to oil. The Hunters collect samples from subsistence- effects of these hydro­ Photo by Roy Corral caught seals and provide them to researchers carbon by-products, if any, are unknown. Dr. Sara Iverson talks to a pup to be analyzed for disease, genetics, fatty ac­ Seal deaths caused by the oil spill contributed to keep it distracted while marine biologist Kathy Frost ids, and stable isotope ratios. They also con­ to a widespread decline of harbor seals in PWS secures an antenna onto its tribute information about the distribution, and the GOA that began before the spill and has back. Frost tracks the abundance, and health of seals in areas where continued since. Any time a wildlife population movements of seals via satellite. they live and hunt. declines it is a cause for concern. For harbor seals in PWS and the GOA, this concern is magnified because the causes for the decline are unknown. Conclusion Seals are a key part of the marine ecosystem, and Studies of harbor seals conducted following they are an important resource for Alaska Natives, the EVOS were the first detailed investigations for the tourism industry, and for everyone who of the effects of an oil spill on seals in the wild. enjoys watching wildlife. If the decline of harbor The Restoration These studies conclusively demonstrated that seals continues much longer, the fishing industry harbor seals did not avoid oil, but that they swam and others could be impacted by regulations de­ Notebook series is and surfaced to breathe in oil-covered waters signed to protect the seals and stop the decline. published for and hauled out on oil-covered rocks and sea­ For these reasons, the EVOS Trustee Coun­ educational purposes. weed. Both pups and adults in oiled areas be­ cil and NOAA are continuing to fund a variety Persons wishing to came coated with oil. of studies to monitor harbor seals in PWS and Many oiled seals acted sick and lethargic for the GOA and to better understand the causes cite this material in the first few months after the spill. Based on aerial for the ongoing decline. scientific publications surveys, it was estimated that at least 300 seals should refer to the died in PWS following the EVOS. Microscopic Kathy Frost has been a marine mammals biologist with the Alaska Department of Fish and Game for 20 years. technical reports and examination indicated that some oiled seals had She is affiliate faculty at the University of Alaska in literature listed at the brain damage that was probably caused by oil. It Fairbanks and Anchorage. She has conducted re­ is likely this damage occurred in the first few days search on a variety of marine mammals in Alaska, end of each account. or weeks after the spill, and was due to breathing especially seals and beluga whales. Her studies have included the food habits, ecology, natural history and airborne hydrocarbons that evaporate quickly. distribution and abundance of these species.

Exxon Valdez Oil Spill Trustee Council 7 n o t eR bestoration o o k References

1 Pitcher, K. W. 1984. The Harbor seal (Phoca vitulina richardsi). Pages 65­ 9 Thompson, P., and P. Rothery. 1987. Age and sex differences in the timing 70 in J. J. Burns, K. J. Frost, and L. F. Lowry, eds. Marine mammals species of moult in the common seal, Phoca vitulina. J. Zool. Lond. 212:597-603. accounts. Alaska Dep. Fish and Game, Game Tech. Bull. 7. 10 Matkin, C., North Gulf Oceanic Society, P.O. Box 15244, Homer, AK 99603­ 2 Hill, P.S., D.P. DeMaster, and R.J. Small. 1996. Draft Alaska Marine Mam­ 6244. mal Stock Assessments. NMML/NMFS/NOAA, 7600 Sand Point Way, N.E., Seattle, WA 98115. 121 pp. 11 Wolfe, R. J. and C. Mishler. 1995. The subsistence harvest of harbor seal and sea lion by Alaska Natives in 1994. Tech. Pap. No. 236. Alaska Dep. Fish 3 Pitcher, K. W. 1990. Major decline in number of harbor seals, Phoca vitulina and Game, Juneau, AK. 69 p. richardsi, on Tugidak Island, Gulf of Alaska. Mar. Mamm. Sci. 6: 121-134. 12 Lowry, L. F., K. J. Frost, and K. W. Pitcher. 1994. Observations of oiling of 4 Pitcher, K. W., and D. G. Calkins. 1979. Biology of the harbor seal, Phoca harbor seals in Prince William Sound. Pages 209-226 in T. R. Loughlin, ed. vitulina richardsi, in the Gulf of Alaska. U.S. Dep. Commerce/NOAA/OCSEAP, Marine Mammals and the Exxon Valdez. Academic Press, Inc., San Diego, CA. Environmental Assessment Alaskan Continental Shelf Final Rep. Principal In­ vest. 19(1983):231-310. 13 Frost, K. J., C-A Manen, and T. L. Wade. 1994. Petroleum hydrocarbons in tisuues of harbor seals from Prince William Sound and the Gulf of Alaska. 5 Pitcher, K. W. 1989. Harbor seal trend count surveys in southern Alaska, Pages 331-358 in T. R. Loughlin, ed. Marine Mammals and the Exxon Valdez. 1988. Final Rep. Contract MM4465852-1 submitted to U.S. Marine Mammal Academic Press, Inc., San Diego, CA. Commission, Washington, D.C. 15pp. 14 Spraker, T. R., L. F. Lowry, and K. J. Frost. 1994. Gross necropsy and histo­ 6 Frost, K. J., L. F. Lowry, R. J. Small, and S. J. Iverson. 1996. Monitoring, pathological lesions found in harbor seals. Pages 281-311 in T. R. Loughlin, ed. habitat use, and trophic interactions of harbor seals in Prince William Sound, Marine Mammals and the Exxon Valdez. Academic Press, Inc., San Diego, CA. Alaska. Exxon Valdez Oil Spill Restoration Project Annual Report (Restoration Projects 95064), Alaska Department of Fish and Game, Division Wildlife Con­ 15 Frost, K. F., L. F. Lowry, E. Sinclair, J. Ver Hoef, and D. C. McAllister. 1994. servation, Fairbanks, AK. 87 pp + appendices. Impacts on distribution, abundance, and productivity of harbor seals. Pages 97-118 in T. R. Loughlin, ed. Marine Mammals and the Exxon Valdez. Aca­ 7 Hoover-Miller, A. A. 1994. Harbor seal (Phoca vitulina) biology and manage­ demic Press, Inc., San Diego, CA. ment in Alaska. Contract No. T75134749. Marine Mammal Commiassion, Washington, D. C. 45 pp. 16 Lewis, J. P. 1996. Harbor seal investigations in Alaska. Annual report, NOAA grant NA57FX0367. Alaska Dep. Fish and Game, Juneau, AK. 203pp. 8 Ashwell-Erickson, S. M., and R. Elsner. 1982. The energy cost of free existence for Bering Sea harbor and spotted seals. Pages 869-899 in D. W. 17 Fadely, B. S., and M. A. Castellini. 1996. Recovery of harbor seals from Hood and J. A. Calder, eds. The eastern Bering Sea shelf: oceanography and EVOS: condition and health status. Exxon Valdez Oil Spill Restoration Project resources. Vol. 2. U. S. Dep. Commer., NOAA, Off. Mar. Pollut. Assess., Ju­ Annual report (Restoration Project 95001), University of Alaska, Fairbanks, neau, Alaska. Alaska. 39pp.

8 Exxon Valdez Oil Spill Trustee Council Rn estorationo t e b o o k