USGS



BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES

Sea Otter


Sea Otter Photo by Don Getty

Sea Otter Photo: www.dongettyphoto.com



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Biological Characteristics

Species

Adult male Enhydra lutris grow up to 1.5 to 2 m in length with a maximum weight of 45 kg; females are considerably smaller. The average length for pups is about 60 cm, with a weight of 2 kg (Orr and Helm, 1989).  The otter’s head is relatively rounded with small ears and a broad snout; the body is long with the tail broad at the base but tapering and equal to about a fourth of the body length (Orr and Helm, 1989). The forepaws are stumpy yet highly mobile with retractile claws while the hind feet are flipper-like and are used for propulsion through the water (Mason and MacDonald, 1986).  The fur of newborn pups is a light brown, wooly coat blending to beige at the neck, which is covered within a few weeks by a coat of longer guard hair with a distinctive yellowish tinge (Kenyon, 1981). The adult fur grows in after a few months and is variable in color from light beige to almost black, with sparse dark or silvery white guard hairs (Kenyon, 1981). Sea otters are divided into three subspecies based on slight cranial variations: Enhydra lutris nereis or the southern sea otter found in California,  Enhydra lutris lutris or the Alaskan sea otter ranging from Prince William Sound  across the Aleutians to Commander Island, and Enhydra lutris gracile or the Asian sea otter from Kurile Islands and the east coast of the Kamchatka Peninsla (Kenyon, 1981; Reidman, 1990).     

Status in Estuarine and Coastal Areas

Sea otters are non-migratory, full time residents in Pacific coastal areas, inshore and out to about 120 foot depth. Breeding occurs at sea throughout the year. Sea otter females gestate for about 8 months and give birth to either a single pup or very rarely two (Mason and MacDonald, 1986). Pups are semiprecocial at birth and are capable of eating solid food after 17 days and diving after a few months (Mason and MacDonald, 1986). The otter pup is dependent on the mother for at least a few months and weaned at one year, but may remain with mother after she has a new pup (Kenyon, 1981). The average life span of a sea otter is believed to be about 12 to 16 years in the wild (VanBlaricom, 1988).

Abundance and Range

There now exist an estimated 150,000 sea otters found along the north Pacific rim from the Kuril Islands into the Kamchatka Peninsula, the Commander Islands east across the Aleutian Islands to Prince William Sound, and spotted populations along the west coast of North America at southeast Alaska, Vancouver Island, Washington from Pt. Grenville to Pillar Pt. and central California from Point Sur to Diablo Canyon (Paine, 1993). The 2001 USGS Washington sea otter census counted 555 otters along the Washington coast. The 2002 USGS California sea otter census counted 2139 sea otters in California. 

Site Fidelity

Sea otters rarely wander more than a few miles from their established feeding grounds (Kenyon, 1981). Otters prefer a protected inshore area with a rocky bottom and an abundance of kelp, especially giant kelp, which are used for rest (they wrap themselves while napping to keep from drifting) and provide the ideal foraging grounds (Riedman, 1990).

Ease of Census

Moderate

Feeding Habits

Sea otters eat a variety of marine life including red sea urchins, abalone, rock crab, and squid. When preferential prey are scarce otters will also eat mussels, kelp crabs, clams, turban snails, octopuses, barnacles, sea stars, scallops, rock oysters, fat innkeeper worms, and chitons (Reidman, 1990). Individual otters will normally specialize in one or two of prey items (Reidman, 1990). The different sea otter subspecies have been shown to include different average proportions of prey type in their diets (Mason and MacDonald, 1986). Otters will typically dive up to 60 feet while foraging and will bring their prey to the surface within folds of skin serving as a bag under their left arms (Mason and MacDonald, 1986). Using rocks as tools they will crack open shellfish using their chest as a table while floating on their backs. Feeding occurs both at day and night (Orr and Helm, 1989).


Sea Otter Contaminant Exposure Data

I.

Organochlorine Contaminants

1.

Selected tissues from sea otters found dead along coastal California between 1968 and 1980 were analyzed for chlorinated hydrocarbon residues (Risebrough, 1989). The following age versus liver DDE concentrations (mg/g, ww) were compared for individual otters and are taken from graphs:  Males : fetus (0), pup (0.5, 3.5, 5.0, 6.0, 6.25, 6.5, 7.0, 31), immature (0, 0.5, 1.0, 5.0, 9.5), sub-adult (0, 1.0,1.5, 2.0, 2.5, 3.0, 3.5, 4.0),  adult (0, 1.0, 1.5, 2.0, 3.0, 3.5, 4.5, 5.5), aged adult (0, 0.5, 1.5, 9.5); Females : fetus (0), pup (1.5, 2.0, 4.0, 5.5, 7.0, 25.5), immature (1.0, 1.25, 1.5, 2.5, 6.5, 12.5), sub-adult (0, 0.5, 1.0, 1.15, 2.5, 4.0, 10.0), adult (0, 1.0, 1.5, 4.0, 5.0, 6.0, 9.0), aged adult (0, 2.0, 2.5, 3.0). DDE did not increase with age for either male or female otters.

Livers of adult sea otters were analyzed for DDE and the following concentrations (mg/g, ww) were found: Males : 1970 (0.75, 3.25), 1971 (1.25, 2.25), 1977 (5.0), 1978 (5.5, 5.75), 1979 (0.5), 1980 (0.25). Females : 1969 (3.5), 1973 (3.75, 8.5), 1977 (1.25, 1.5), 1979 (0, 1.0, 1.25, 6.5), 1980 (0.5).  No significant changes were seen in DDE concentrations in liver samples over the time period 1969 – 1980.

PCBs concentrations (mg/g, ww) in livers taken from graphs are as follows: Males : 1968 (0.25, 0.25), 1970 (0.75, 1.1), 1971 (0.25, 0.25, 0.5, 0.75, 1.5), 1972 (0.25, 0.25, 0.5, 0.5, 0.75, 1.25, 1.6, 3.5, 3.75, 4.0), 1973 (0.75, 1.6), 1977 (1.0, 2.25), 1978 (0.25, 0.5, 0.75, 1.25), 1979 (0.25, 1.25),  1980 (0.25, 0.25, 0.75); Females: 1969 (0.75, 1.75), 1970 (0.25, 0.75, 1.25, 3.0), 1971 (1.0), 1972 (0.75, 0.75, 0.75, 1.0, 1.0), 1973 (0.25, 0.75, 1.0, 1.75, 3.25), 1977 (1.0, 2.0, 3.0), 1978 (0.25, 0.75), 1979 (0.25, 0.75, 1.5), 1980 (0.1, 1.5).

2.

Tissues from sea otters (n=10) found dead or shot along coastal central California during 1969 to 1970 were analyzed for organochlorine pesticide contamination (Shaw, 1971). The following tissues were analyzed (not every tissue was analyzed for each otter): fat (F), liver (L), testis (T), ovary (O), brain (B), kidney (K), heart (H), adrenal (A). The following concentrations (mg/g, ww) were found and are listed in order of (DDE / DDD / DDT) for individual otters *1 through *10:  *1, drowned female from Morro Bay, L = (0.49 / 0.03 / trace), B = (0.17 / 0.008 / trace);  *2, male hit by boat at Monterey Bay, L = (14 / 0.59 / 0.74), T = (13 / 0.55 / 0.46), B = (9.2 / 0.39 / 0.42);  *3, male died of natural cause at Monterey Wharf, F = (7.7 / 0.20 / 0.19), L = (0.87 / 0.044 / 0.029), T = (2.1 / 0.072 / 0.056), B = (0.53 / 0.13 / 0.14); *4, female died of natural cause at Point Lobos, F =  (1.1 / 0.024 / 0.059), L = (0.55 / 0.04 / 0.059);  *5, female died of natural cause at Lover’s Pt.,  L = (7.8 / 0.044 / 0.049), O = (0.84 / trace / trace), A = (7.1 / 0.10 / 1.3);  *6, male shot at Morro Bay, F = (0.39 / 0.0068 / 0.015), L = (3.4 / 0.032 / 0.051), T = (0.093 / 0.036 / 0.019), B = (0.025 / trace / 0.079), K = (0.0069 / trace / trace), H = (0.012 / trace / trace);  *7, male shot at Cambria, F = (34 / 1.5 / 0.64), L = (0.11 / 0.012 / 0.0052), K = (0.64 / 0.032 / 0.020), T = (0.69 / 0.056 / 0.022); *8, male shot at Cambria, F = (7.0 / 0.33 / 0.18), L = 0.03 / 0.0003 / 0.0013), K = (1.5 / 0.067 / 0.023), T = (0.20 / 0.021 / 0.013);  *9, female drowned at Hopkins Marine Station, F = (18 / 1.3 / 0.87), L = 0.059 / 0.0054 / 0.0065), K = (12 / 0.19 / 0.14), O = (1.26 / 0.15 / 0.201);  *10, male hit by boat at Monterey Bay, F = (3.7 / 0.40 / 0.26), L = (0.32 / 0.022 / 0.016), K = (0.47 / 0.031 / 0.021), T = (5.7 / 0.24 / 0.24).

3.

Liver samples from beach-cast sea otter carcasses or recently killed individuals were collected from California (n=9) between 1988 and 1991, southeast Alaska (n=7) during May 1991, and the Aleutian Islands [Adak (n=5) between 1991 and 1992 and Amchitka (n=2) in 1992] and analyzed for organochlorine contamination (Bacon et al., 1999).  The following mean organochlorine concentrations (mg/g, ww) were found: Aleutian (PCB = 310, DDT = 36, Chlordane = 15, NOPCB (non-ortho PCBs) = 0.028, PCDD = 0.001, PCDF = 0.001, DDE = 36, HCB = 2, b-HCH = 5, Dieldrin = 3, TCP methanol = ND);   California (PCB = 190, DDT = 850, Chlordane =  31, NOPCB = 0.036, PCDD = 0.004, PCDF = 0.001, DDE = 840, HCB = 2, b-HCH = 9, Dieldrin = 1, TCP methanol = 4);  Southeast Alaska (PCB = 8, DDT = 1, Chlordane = 1, NOPCB = 0.004, PCDD = 0.001, PCDF = ND, DDE = 1, HCB = 1, b-HCH = 6, Dieldrin = 2, TCP methanol = ND).   Total DDT levels were significantly higher in California than in Aleutians, and significantly higher in the Aleutians than in Southeast Alaska. Total PCB concentrations in sea otters from both the Aleutians and California were significantly higher than those in southeast Alaska. PCDDs, PCDFs, Mono and di-ortho PCBs, and non-ortho PCBs were measured in sea otters from the same three areas. The geometric mean concentrations were found as follows and listed as (California, Aleutian, Southeast Alaska): 2,3,7,8-TCDD (0.58, 0.48, ND);  1,2,3,7,8-PeCDD (1.82, 0.51, ND);  1,2,3,4,7,8-HxCDD (0.96, 0.21, ND);  1,2,3,6,7,8-HxCDD (1.57, 0.71, ND);  2,3,4,6,7,8-HxCDD (0.35, 0.13, ND);  1,2,3,4,6,7,8-HpCDD (1.17, 0.36, ND);  OCDD (ortho-chlorodibenzo-p-dioxin) (1.33, 1.0, 1.02);  2,3,7,8-TCDF (0.13, 0.21, ND);  1,2,3,7,8-PeCDF (0.08, 0.05, ND);  2,3,4,7,8-PeCDF (0.55, 0.52, ND);  1,2,3,4,6,7,8-HpCDF (0.12, 0.11, ND); 2,3,4,6,7,8-HxCDF (ND, 0.11, ND);  OCDF (ortho-dichlorobenzo furan) (0.32, 0.16, ND);  PCB 105 (12400, 5220, 1000);  PCB 118 (17200, 20310, 100);  PCB 156 (6500, 9700, 200);  PCB 167/128 (5900, 22150, 100);  PCB 170/190 (2800, 9840, 100);  PCB 180 (7700, 22150, 400);  PCB 37 (0.82, ND, 0.70);  PCB 77 (1.49, 1.05, 1.41);  PCB 81 (0.53, 0.44, 0.25);  PCB 126 (30, 19, 2.2);  PCB 169 (2.52, 2.33, ND);  PCB 189 (1.40, 2.37, ND).

4.

Liver samples from 23 sea otters that were obtained in 1991 to 1992 from beached carcasses or freshly killed specimens in central California (n=9), southeast Alaska (n=7), and the Aleutian Islands (n=7) were analyzed for organochlorine contaminants (Estes et al., 1997). The following average concentrations (ng/g, ww) were found: Aleutian Islands PCBs = 309, DDT = 36, Other = 22;  Southeast Alaska PCBs = 8, DDT = 1, Other = 5;  California PCBs = 185, DDT = 846, Other(Total chlordane, PCDDs, PCDFs, HCB, dieldrin, and tris (4-chlorophenyl)-methanol) = 43. There was no apparent relationship between OC concentration and age, sex, or whether the samples were from beached carcasses or freshly killed specimens for any of the three regions. Average PCB and DDT concentrations were significantly higher for the Aleutian Islands and California as compared to southeast Alaska. The PCB concentrations in southeast Alaska were among the lowest reported values for a marine or carnivorous mammal. 

5.

Liver, kidney and brain samples from adult sea otter carcasses collected between 1992 and 1996 along the central California coast from Half Moon Bay to Diablo Canyon were analyzed for organochlorine contamination (Nakata et al., 1998). The otters had died prior to collection by trauma, disease, emaciation, neoplasia, esophageal impaction, intestinal perforation, or unknown causes. The following are the concentrations (ng/g ww) found for individual otters (A – T) and listed in order of (PCB / DDT / HCH / CHL / HCB ): A-liver (140 / 470 / 17 / 14 / 4.6), A-kidney (180 / 1400 / 15 / 30 / 1.9), A-Brain (69 / 300 / 3.3 / 2.6 / 0.64); B-liver (880 / 3800 / 10 / 53 / 1.1), B-kidney (1600 / 7800 / 6.4 / 110 / 0.48), B-brain  (330 / 1400 / 8.1 / 39 / 0.5);  C-liver (120 / 860 / 18 / 8 / 1.6), C-kidney (140 / 2800 / 65 / 40 / 2.6), C-brain (40 / 120 / 6.5 / 2.4 / 0.72);  D-liver (130 / 540 / 4.6 / 5.1 / 4.5), D-kidney (50 / 700 / 6.7 / 8.5 / 0.88), D-brain (35 / 160 / 4.7 / 2.1 / 0.56);  E-liver (280 / 1800 / 68 / 28 / 2.5), E-kidney (560 / 2500 / 7.2 / 23 / 0.5), E-brain (89 / 350 / 5.3 / 4.4 / 0.28);  F-liver (8700 / 2600 / 50 / 500 / 8), F-kidney (4600 / 2300 / 18 / 190 / 1.6), F-brain (ND);  G-liver (510 / 1200 / 65 / 38 / 2),  G-kidney (150 / 500 / 17 / 10 / 0.93), G-brain (ND);  H-liver (300 / 1200 / 5.8 / 21 / 1.3), H-kidney (1400 / 8600 / 19 / 130 / 1.9), H-brain (ND);  I-liver (ND), I-kidney (120 / 290 / 3.8 / 4.4 / 0.28), I-brain (ND);  J-liver (2100 / 2900 / 130 / 91 / 2.4), J-kidney (ND),  J-brain (ND);  K-liver (7300 / 4700 / 35 / 280 / 1.7 ), K-kidney (ND),  K-brain (ND);  L-liver (7000 / 5900 / 15 / 370 / 1.4), L-kidney (ND),  L-brain (ND);  M-liver (360 / 840 / 18 / 24 / 2.2), M-kidney (ND), M-brain (ND);  N-liver (1400 / 1600 / 27 / 53 / 1.9), N-kidney (ND),  N-brain (ND);  O-liver (58 / 280 / 5.3 / 4.1 / 0.94), O-kidney (ND), O-brain (ND);  P-liver (1200 / 2500 / 76 / 260 / 1.4), P-kidney (ND), P-brain (ND);  Q-liver (470 / 290 / 8.7 / 10 / 1.1), Q-kidney (ND), Q-brain (ND);  R-liver (79 / 360 / 24 / 7.3 / 1.7), R-kidney (ND), R-brain (ND);  S-liver (320 / 1200 / 11 / 33 / 2.3 ), S-kidney (ND), S-brain (ND);  T-liver (430 / 1900/ 26 / 28 / 2.1), T-kidney (ND), T-brain (ND);  U-liver (270 / 1100 / 17 / 23 / 0.74), U-kidney (ND),  U-brain (ND).   A comparison of different sampling locations revealed the presence of significantly greater concentrations of DDT, CHL, PCB, and HCH in Monterey Harbor otters (individuals F,J,K,and L). Following are the mean concentrations (ng/g, ww) for the various locations and listed in order of (PCB / DDT / HCH / CHL / HCB): Half Moon Bay (n=1)(140 / 470 / 17 / 14 / 4.6); Moss Landing (n=1)(880 / 3800 / 10 / 53 / 1.1); Monterey Harbor (n=4) (6300 / 4000 / 58 / 310 / 3.4); San Simeon (n=1) (120 / 860 / 18 / 8 / 1.6); Estero Bay females (n=4) (570 / 1100 / 43 / 79 / 1.6);  Estero Bay males (n=4) (490 / 820 / 14 / 22 / 2.4);  Morro Bay (n=3) (300 / 1400 / 28 / 27 / 2.0);  Diablo Canyon (n=2) (350 / 1500 / 22 / 26 / 1.4).  Gender differences in contaminant concentrations were investigated and no significant differences were found at Estero Bay between the four males and the four females. Finally, when health status was compared, DDT concentrations were significantly greater in otters that died from infectious diseases than those that died of trauma and unknown causes.

          6.

Carcasses of adult sea otters were collected for brain, liver, and kidney tissues along the coast of California (Kannan et al. 2004).  Contaminants in 11 livers were detected at the following levels (ng/g wet weight): 140-8,700 total PCBs, 290-5,900 DDTs, 5.8-500 HCHs, 10-500 chlordanes, 40-9,200 monobutylin + butylin.   Contaminants in 4 kidneys were detected at the following levels (ng/g wet weight): 480-4,600 total PCBs, 1,400-8,600 DDTs, 6.4-19 HCHs, 30-190chlordanes, 4-265 monobutylin + butylin.   Contaminants in 3 brain samples were detected at the following levels (ng/g wet weight): 69-330 total PCBs, 300-1400 DDTs, 3.3-8.1 HCHs, 2.6-39 chlordanes, 3.9-140 monobutylin + butylin.  

II.

Cholinesterase-inhibiting pesticides

 

No direct exposure data available.

III.

Trace Elements, Metals and Metalloids

1.

Kidney and liver samples taken from sea otters found dead along coastal California between 1968 and 1980 were analyzed for metals contamination (Risebrough, 1989). The following mean concentrations (mg/g, dw) were found and listed as (number of samples, liver, kidney): Silver (n=117, 2.45, trace), Mercury (n=124, 4.42, 2.35), Cadmium (n=124, 15.8, 37.0), Iron (n=124, 1078, 497), Manganese (n=123, 12.3, 3.54), Magnesium (n=89, 909, 840), Copper (n=124, 132, 31), Zinc (n=124, 213, 159).   The following observations were made concerning the individual metal results: Silver – The liver concentrations were higher in females than males. Mercury – In both liver and kidneys Hg concentrations increased with body length. Liver concentrations were about twice that of kidneys. Cadmium – Sea otters concentrate high quantities of Cd, particularly in the kidneys. Concentrations increase with age and higher concentrations are found in adult females than in adult males. No increase in kidney Cd was observed over the years of the study period. Magnesium – In kidneys, Mg concentrations increased with body length for males, but this relationship was not seen in females. Copper Cu concentrations were about four times higher in liver than in kidneys. Manganese Mg concentrations were three to four times higher in the liver than in the kidney and the concentrations increased with body length and weight in kidneys of males, but not of females.  Zinc – Concentrations of Zn in kidneys were strongly correlated with Cd concentrations, and with body lengths and weights.

2.

Lead concentrations and stable isotopic compositions of Pb were measured in third post-canine or first molar teeth of pre-industrial (excavated and from about 1900 years before present) and contemporary sea otters (1986 and 1987) from Amchitka Island, Alaska to determine if changes had occurred in the magnitude and source of assimilated Pb (Smith et al., 1990).  The following concentrations (ng/g, dw) were found: Pre-industrial (n=5, including 2 replicate sets, r1 and r2) (19, 14, 72r1, 67r1, 48, 49r2, 61r2). Contemporary (n=5, includes 1 replicate set) (130, 42, 140, 23r, 25r, 26). No significant difference was found in the amount of Pb accumulation in the older and contemporary otter, however isotopic compositions revealed there were different sources of Pb. In the pre-industrial otter Pb was derived from natural deposits in the Aleutian Arc. In the contemporary otter, Pb was primarily from industrial processes originating from Asia and western Canada.

3.

Lead concentrations and stable isotopic compositions of lead were measured in third post-canine or first molar teeth of six pre-industrial (excavated, dating from 500 to 3000 years before present) and seven contemporary sea otters (collected between 1987 and 1989) from the coast around Monterey Bay, California to determine if changes had occurred in the magnitude and source of assimilated Pb (Smith et al., 1992).  The following concentrations (ng/g, dw) were found: Pre-industrial: (61, 170, 170, 45, 130, 72);  Contemporary: (93, 200, 1900, 1800, 960, 140, 300). No relationship was observed between animal age and tooth Pb concentration in the pre-industrial and contemporary otters. Lead isotopic compositions indicate multiple and distinct sources of accumulated Pb. Pre-industrial animals contained Pb derived from natural continental sources in northern California. Essentially all of the Pb in contemporary otters was derived from industrial sources represented by particulate aerosols, likely originated from past and current uses of lead-containing gasoline.  

4.

Carcasses from sea otters found dead along the California coast during 1992 to 1996 were divided into brain, liver, and kidney samples and analyzed for contamination from tributyltin (TBT) and its degradation products monobutyltin (MBT) and dibutyltin (DBT) (Kannan et al., 1998).  The following concentrations (ng/g, ww) were found for individual otters (A – AI) and are listed in order of (MBT / DBT / TBT ):  A-liver (360 / 5820 / 3020), A-kidney (11 / 54 / 200), A-Brain (12 / 24 / 105);  B-liver (236 / 3090 / 1970),  B-kidney (17 / 200 / 210), B-brain (<7 / 9.3 / 72);  C-liver (<7 / 51 / 56), C-kidney (<7 / 3.7 / 10), C-brain (<7 / <2.4 /  3.9);  D-liver (<7 / 54 / 135), D-kidney (<7 / 7.5 / 7.7), D-brain (<7 / <2.4 / 2.7);  E-liver (<7 / 49 / 75), E-kidney (14 / 6.8 / 9.3), E-brain (<7 / 2.8 / 1.8);  F-liver (<7 / 21 / 19), F-kidney (<7 / <2.4 /  4);  G-liver (81 / 860 / 2130), G-kidney (7 / 24 / 120);  H-liver (26 / 220 / 140), H-kidney (<7 / 15 / 16);  I-liver ( 360 / 2360 / 1600);  J-liver (190 / 2080 / 2900), J-kidney (11 / 110 / 170);  K-liver (25 / 53 / 48);  L-liver (10 / 104 / 100);  M-liver (18 / 85 / 130);  N-liver (14 / 83 / 180);  O-liver (19 / 83 / 200);  P-liver (220 / 410 / 760);  Q-liver (14 / 120 / 120);  R-liver (<7 / 29 / 32);  S-liver (12 / 52 / 28);  T-liver (14 / 94 / 150);  U-liver (17 / 144 / 170);  V-liver (18 / 110 / 53);  W-liver (31 / 110 / 53);  X-liver (140 / 1520 / 950); Y-liver (17 / 220 / 190);  Z-liver (140 / 1840 / 2050);  AA-liver (310 / 1560 / 670);  AB-liver (12 / 310 / 330);  AC-liver (140 / 1290 / 920);  AD-liver (14 / 90 / 55);  AE-liver (18 / 240 / 43);  AF-liver (9.4 / 34 / 66);  AG-liver (8 / 120 / 60);  AH-liver (24 / 95 / 59);  AI-liver (16 / 200 / 260).  Total butyltin concentrations in kidney and brain were about 7 and 18 fold less than those in liver. Based on the mean body weight of 21.1 kg for the otters analyzed, the average burden of BT in the liver was estimated to be 1.3 mg. The hepatic concentrations of BTs were correlated with the length and weight in adult males, however the same correlation did not exist with females. In female livers DBT was the predominant butyltin whereas in the male livers TBT was the predominant butyltin.  Concentrations of butyltins varied greatly according to sampling location. Otters collected from enclosed marinas such as Monterey Harbor or Morro Bay contained at least an order of magnitude greater concentration than otters collected from open locations, like San Simeon. The following are the mean concentrations (ng/g, ww) found in otters from the various locations and listed as (MBT / DBT / TBT ):  Morro Bay (n=4) (84 / 1020 / 1060), Moss Landing (n=2) (193 / 2940 / 1530), Half Moon Bay (n=1) (<7 / 51 / 56), San Simeon (n=1) (<7 / 54 / 135), Estero Bay (n=4 male) (10 / 56 / 71), Estero Bay (n=4 female) (23 / 150 / 104), Pismo Beach (n=2) (17 / 83 / 190), Monterey Harbor (n=8) (160 / 1400 / 1200), Montara Beach (n=1) (18 / 85 / 130), Hazard Canyon (n=1) (14 / 90 / 55), Jalama Beach (n=1) (220 / 410 / 760), Diablo Canyon (n=2) (14 / 137 / 55), Port San Luis (n=1) (8 / 120 / 60), Carmel (n=1 female) (24 / 95 / 59), Carmel (n=1 male) (16 / 200 / 260).

IV.

Petroleum

  1.

On March 24, 1989, Exxon Valdez ran aground in Prince William Sound, Alaska spilling an estimated 42 million liters (11,000,000 gallons) of Prudhoe Bay crude oil (Garshelis, 1997). Sea otter carcasses collected by location following the spill include: Prince William Sound: 421 (391 oiled and 30 un-oiled).  Kenai Peninsula: 165 (53 oiled and 112 un-oiled).  Kodiak-Alaska Peninsula: 190 (151 from Kodiak Island Group and 39 from Alaska Peninsula of which 91 were oiled and 99 were un-oiled.

2.

The best estimate for sea otter mortality as a result of the Exxon Valdez oil spill at Prince William Sound, Alaska ranges from 2,650 to 3,905 individual sea otters (Bonnell et al., 1996).


Sea Otter Contaminant Response Data

I.

Organochlorine

 

No response data available

II.

Cholinesterase inhibiting pesticides

 

No response data available

III.

Metals

 

No response data available

IV.

Petroleum

1.

The demographic consequences of the Exxon Valdez oil spill in Prince William Sound in March 1989 on the sea otter population was investigated by surveys of  otter abundance, pup production, activity, and foraging (Garshelis and Johnson, 2001). Pre-spill data was compared to data collected during a seven year period after the oil spill in the western Prince William Sound. This western survey area was the area most affected by the oil spill and included Green Island, Appelgate Rock, Knight Island, Montague Island, and Naked Island.  Counts (converted to densities) of independent sea otters conducted over the 7 year post-spill time period were consistently equal to or higher than counts made before the spill (1977-1985) for three of four oiled sites and one un-oiled site.  The following are numbers of otters counted listed in order of years as (1984, 1989, 1990, 1991, 1993):  Green Island (8, 25, 23, 27, 36),  Naked Island (21, 35, 16, 17, 12),  Knight Island (70, 69, 55, 110, 101), Port Bainbridge (126, 150, 89, 62, 126), Port Nellie Juan (32, 42, 27, 24, 39), Passage Canal (2, 2, 1, 2, 5).

Pup production, measured as the ratio of  pups to all otters other than pups, did not differ significantly between pre- and post-spill (1990) at un-oiled Montague Island or at the heavily oiled Green Island, however, the pre-spill pup ratio was significantly higher for Appelgate Rock, the most heavily oiled of sites, for the 1990 survey. Pup ratios at Appelgate Rock for the 1994 and 1996 surveys were near pre-spill levels.  Pup ratios at Knight Island were higher in the post-spill surveys, and at the lightly oiled Naked Island the post-spill ratios were also higher.                                 
Activity data at Green Island were obtained from scan-sampling and divided into the categories: feeding, resting, swimming, grooming or interacting, and other. The activities were measured during August of the survey years. The otters spent less time feeding and more time resting at Green Island in 1990 and 1991 than they did before the spill, with hourly variation in feeding and resting behavior being significant. Other activities (swimming, grooming, and interacting combined) increased from pre-spill to 1990, but did not differ between pre-spill and 1991. 

Foraging success about Gibbon’s Anchorage at Green Island was similar in 1980-81, 1990, and 1991 with clams being the primary prey and either crabs or mussels being the next most common prey. At Knight Island, foraging success was higher at oiled than at un-oiled sites for adult females , but was not different for adult male otters.

2.

Medical condition and degree of oiling was evaluated for 339 sea otters collected between March 30 and August 21, 1989 and rehabilitated at Valdez Otter Rehabilitation Center (VORC), the Seward Otter Rehabilitation Center (SORC), and at a temporary care facilty at Homer following the T/V Exxon Valdez oil spill (Williams et al., 1990).  Degree of oiling was based on % body coverage oiled as follows: heavily oiled = >60%, moderately oiled =30 to 60 %, lightly oiled = < 30% of body coverage or light sheen on fur, and unoiled = no visible evidence of oiling.  Based on these criteria, otters received at rehab centers are as follows: VORC: 78 (50%) heavily or moderately oiled, 51 (33%) lightly oiled, and 11 (7%) unoiled, 16 (10%) not documented; SORC: 19 (10%)heavily or moderately oiled, 72 (39%) lightly oiled, 44 (23%) unoiled, 52 (28%) not documented; Homer: 6 otters unoiled, 12 not documented.

Blood samples were drawn from otters upon arrival at the rehab centers. Samples were analyzed for petroleum hydrocarbon concentrations and initial results indicated a positive correlation between total petroleum hydrocarbon concentration and mortality. Blood variables analyzed include: Hematocrit (HCT, %), Glucose (GLU, mg/dL), Blood urea nitrogen (BUN, mg.dL), Serum glutamic pyruvic transaminase (SGPT, mg/L), Serum glutamic oxalacetic transaminase (SGOT, IU/L), Lactate dehydrogenase (LDH, IU/L), creatinine phosphokinase (CPK, mg/L), and creatinine (CREA, mg/dL). Normal values for unoiled otters from a spill free area are as follows (Low value/High value): HCT  (50.3/62.1), GLU (87.6/150.2), BUN (34.3/63.6), SGPT (96.4/240.0), SGOT (87.0/511.0), LDH (94.7/419.3), CPK (169.8/490.3), CREA (0.5/1.4). The following mean values were observed in rehabilitated otters that survived and were eventually released: Heavy oiled – (HCT 52.5 n=7, GLU 105.7 n=6, BUN 72.2 n=5, SGPT 329.5 n=2, SGOT 574.6 n=5, LDH 746.6 n=5, CPK n/a, CREA 0.6 n=5); Moderately oiled - (HCT 48.2 n=7, GLU 110.7 n=7, BUN 70.6 n=7, SGPT 251.5 n=6, SGOT 484.3 n=7, LDH 629.0 n=7, CPK 1283 n=5, CREA 0.5 n=7); Lightly oiled - (HCT 48 n=8, GLU 155.9 n=8, BUN 48.8 n=8, SGPT 420.4 n=8, SGOT 738 n=8, LDH 538.7 n=7, CPK 746 n=8, CREA 0.8 n=8).  The following are values for otters that died during rehabilitation: Heavily oiled – (HCT 60.3 n=6, GLU 53.2 n=6, BUN 189.6 n=7, SGPT 287.3 n=4, SGOT 960.8 n=6, LDH 1332 n=5, CPK 6654 n=5, CREA 1.2 n=6);  Moderately oiled - (HCT 59.2 n=11, GLU 101.8 n=7, BUN 144.5 n=10, SGPT 1384 n=7, SGOT 3917 n=8, LDH 2194 n=7, CPK 2469 n=6, CREA 1.1 n=9);  Lightly oiled - (HCT 49.3 n=8, GLU 119.4 n=11, BUN 108.2 n=11, SGPT 610.1 n=10, SGOT 1009 n=10, LDH 1798 n=10, CPK 4902 n=9, CREA 0.8 n=9).  The hematocrits taken upon arrival showed no correlation with the degree of oiling or survival, although heavily and moderately oiled otters often developed anemia after several weeks in captivity. Plasma glucose was below normal values in the heavily oiled otters that subsequently died. Blood urea nitrogen was about 2-fold higher than normal for otters that died, and was elevated in heavily oiled otters that survived. The indicators of kidney and liver damage (BUN, SGPT and SGOT) were highly variable. Liver enzymes were elevated in otters that did not survive. Although the serum creatinine concentrations were two-fold higher in otters that died, these concentrations were still within normal value range.

Three disorders were commonly diagnosed in oiled sea otters: hypothermia or hyperthermia, hypoglycemia, and emphysema. More than 36% of otters received at VORC were hypothermic on arrival, 27% were hyperthermic usually with moderate to light oiling. Hypoglycemia, tested in more than 45% of otters received, was a major contributor to thermoregulatory and metabolic problems of heavily oiled otters that subsequently died. Mild to severe pulmonary emphysema was seen in 45 post mortem otter examinations, and 70% of all otters that died showed some form of pulmonary emphysema.

3.

Clinical records and laboratory data for 21 oiled sea otters collected during the Exxon Valdez oil spill and that died within 10 days of arrival at the rehabilitation center were examined (Lipscomb et al., 1994).  Degree of oiling was based on % body coverage oiled as follows: 7 otters heavily oiled = >60%, 5 otters moderately oiled =30 to 60 %,  and 9 otters lightly oiled = < 30% of body coverage or light sheen on fur. Shock was the most common terminal syndrome, characterized by hypothermia, lethargy, and hemorrhagic diarrhea. A high proportion of otters had seizures at or near the time of death. Anorexia was also relatively common.  The following hematological findings: Leukopenia (decrease in white blood cell count) was the most common blood condition for otters of all degree of oiling and was characterized by decreased mature neutrophils with increased numbers of immature neutrophils and decreased lymphocytes. Azotemia (accumulation of nitrogenous waste products in the blood) was also common in otters all three conditions of oiling. Hyperkalemia (abnormally high blood potassium) and hypoproteinemia/hypoalbuminemia (abnormally low blood protein and albumin) were found less common than azotemia, but were probably also related to diarrhea and shock. Increased hepatocellular leakage-associated serum transaminases were only slightly less common than azotemia.

Histopathological exams were performed on 51 oil contaminated otters collected during the Exxon Valdez oil spill and that subsequently died in rehabilitation centers. The degree of oiling was as follows: 16 otters heavy oiling, 13 otters moderate oiling, 22 otters light oiling. The examinations revealed the following: Interstitial pulmonary emphysema was the most common lesion occurring in 11 of 15 heavily oiled otters, in 5 of 11 moderately oiled otters, and in 3 of 20 lightly oiled otters. Incidence of emphysema was threefold higher in oil-contaminated versus uncontaminated otters. Gastric erosions were found in 2 heavily oiled, 7 moderately oiled and 4 lightly oiled otters. Hepatic lipidosis occurred in 8 heavily oiled, 5 moderately oiled and 1 lightly oiled otter. Renal lipidosis was found only in otters that also had hepatic lipidosis. Centrilobular hepatic necrosis was seen in 4 heavily oiled, 3 moderately oiled and 4 lightly oiled otters. No evidence of aspiration pneumonia, a condition associated with mammal ingestion of petroleum hydrocarbons, was found in oil-contaminated sea otters.

4.

Hydrocarbon analysis was performed on tissues taken from heavily oiled (60% or more body coverage) and moderately oiled (30 to 60% body coverage) sea otter carcasses (n=10) recovered dead from Western Prince William Sound, Alaska several days after the Exxon Valdez oil spill of March 1989 (Mulcahey and Ballachey, 1994). Tissues analyzed included kidney, liver, muscle, intestine, fat, and brain. Aliphatic and aromatic hydrocarbons were found in all tissues of each of the ten oiled otters and the mean concentrations (ng/g) were compared to 12 unoiled otters and listed in order of (kidney, liver, muscle): Total aliphatic hydrocarbons: Unoiled otters (3800, 2800, 3200), Oiled otters (7700, 6200, 6100);  Total aromatic hydrocarbons: Unoiled otters (170, 160, 170), Oiled otters (1500, 1100, 600). The ten oiled otters were separated into three groups based patterns of hydrocarbons in tissues. The first group (n=4) had relatively low mean concentrations of both total aliphatic (6000 ng/g) and total aromatic hydrocarbons (700 ng/g) in tissues, expected of animals that died soon after exposure to crude oil. The second group of otters (n=3) had higher mean concentrations of total aliphatic (10,000 ng/g) and total aromatic hydrocarbons (2000 ng/g), expected of otters that survived long enough after crude oil exposure to concentrate hydrocarbons in tissues and start metabolizing them. The final group of otters (n=3) had even higher concentrations of total aliphatic (11,000 ng/g) and total aromatic hydrocarbons (300 ng/g) in tissues, with especially high concentrations of aliphatic hydrocarbons in intestinal tissues and aromatic hydrocarbons in fat tissues. This pattern is expected of heavily oiled otters that survived long enough after exposure to crude oil for hydrocarbons to move into tissues, but died before the hydrocarbons were sufficiently metabolized to reduce concentrations.  

5.

Blood and fur samples were taken from sixteen oiled sea otters following the Exxon Valdez oil spill that were captured from the southern Kenai Peninsula, Alaska between 17 and 23 June 1989 (Hill and Tuomi, 1990). These otters were randomly divided into two groups of eight and one group was “de-oiled” by prescribed washing while the other group remained oiled. After fourteen days a second set of blood and fur samples were taken and comparisons were noted to reveal any affects of oiling. The following data was recorded from 1) a subjective grading system (1 = poor, 2 = improving, 3 = ideal) to measure fur condition, 2) from a visual field dichloromethane (FDCM) test, and 3) from complete blood counts and chemistry: 1) Comparison of subjective scores of coat condition for the washed and unwashed otters demonstrated that on some days washed otters had better average scores, but on other days unwashed, oiled otters had better average scores 2) FDCM testing revealed only one fur sample as containing Prudhoe Bay crude oil, when at least eight otters were known to have contamination. 3) blood chemistry revealed the following, listed as *Individual otter number (PCV = packed cell volume, PT = serum glutamic pyruvic transaminase, LDH = lactic dehydrogenase, CPK = creatine phosphokinase, WBC = white blood cell count, Seg = segmented white blood cells, OT = glutamic oxaloacetic transaminase, note listed in order of day 1 value–day 14 value):  Unwashed, oiled otters:  *1 (PCV 49-48, PT 196-88, LDH 424-261, CPK 524-80), *2 (PCV 48-47, PT 190-117, LDH 542-353, CPK634-221, WBC 10,700-9,300, Seg 92-83), *3 (PCV 44-40, PT 217-251, WBC 11,900-6,800, Seg 88-72), *4 (PCV 53-29, PT 258-179, WBC 10,000-5,700, Seg 90-80), *5 (PCV 50-49, PT 236-107, LDH 427-161, CPK 1133-55), *6 (PCV 44-49, PT 289-98), *7 (PCV 50-43, PT 1130-158, LDH 574-296, CPK 485-147, WBC 8,000-9,600, Seg 84-90), *8 (PCV 49-37, PT 292-122, LDH 359-383, CPK 520-218, WBC 12,100-16,700, Seg 86-97)   Washed otters: *9 (PCV 52-48, PT 155-151, LDH 393-246, CPK 356-109), *10 (PCV 52-40, PT 144-168, WBC 8,700-13,400, Seg 83-78), *11 (PCV 53-48, PT 265-123, LDH 541-175, CPK 399-87), *12 (PCV 43-35, PT 178-309, OT 289-421), *13 (PCV 48-43, PT 287-182, LDH 487-349, CPK 166-343), *14 (PCV 51-47, PT 181-97, WBC 9,600-7,000, Seg 83-73), *15 (PCV 51-50, PT 146-111), *16 (PCV 49-42, PT 336-126, LDH 544-306, OT 615-215, CPK 1486-76, WBC 9,000-12,000, Seg 85-87).

  6.

Blood samples (n=25) were obtained from adult male sea otters collected between September 1 and October 4, 1990 which inhabited both Exxon Valdez oil spill affected areas in western Prince William Sound (n=15) and a reference area in eastern Prince William Sound not affected by the oil spill (Bickham et al., 1998).  Flow cytometry was used to evaluate the sublethal, genetic damage caused by the clastogenic effect of crude oil exposure. This damage is measured as the coefficient of variation (CV) of the G1 peak of the white blood cells. The mean CV for the exposed otters was 4.8% and the mean genome size was 62.2, while the mean CV for the unexposed otters was 5.1% with a mean genome size of 62.2.  The values were not significantly different between the exposed and unexposed otters meaning that the mean genome sizes and dispersion of the DNA about the mean value were not significantly increased in the population potentially exposed to oil. Although the mean CV’s did not differ, the variance of the CV’s was significantly increased in the exposed otters, which is indicative of genotoxic damage based on a separate statistical approach.


 
References for Sea Otter

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Bickham, J.W., J.A. Mazet, J. Blake, M.J. Smolen, Y. Lou and B.E. Ballachey. 1998. Flow cytometric determination of genotoxic effects of exposure to petroleum in mink and sea otters. Ecotoxicology 7:191-199.

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Estes, J.A., C.E. Bacon, W.M. Jarman, R.J. Norstrom, R.G. Anthony and A.K. Miles. 1997. Organochlorines in sea otters and bald eagles from the Aleutian Archipeligo. Marine Pollut. Bull. 34(6):486-490.

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Garshelis, D.L. and C.B. Johnson. 2001. Sea otter population dynamics and the Exxon Valdez oil spill: disentangling the confounding effects. J. Applied Ecol. 38: 19-35.

Hill, K. and P.A. Tuomi. 1990. Field test for detecting crude oil on the fur of sea otters. In: Sea Otter Symposium 17-19 April 1990. USFWS Biological Report 90 (12), Anchorage, AK. 485 pp.  

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Lipscomb, T.P., R.K. Harris, A.H. Rebar, B.E. Ballachey and R.J. Haebler. 1994. Pathology of sea otters. In:  Marine Mammals and the Exxon Valdez. Academic Press, San Diego, CA. 395 pp.

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Nakata, H., K.Kannan, L.Jing, N. Thomas, S. Tanabe and J.P. Giesy.  1998. Accumulation pattern of organochlorine pesticides and polychlorinated biphenyls in southern sea otters (Enhydra lutris nereis) found stranded along coastal California, USA. Environ. Pollut. 103:45-53.

Orr, R.T., R.C. Helm. 1989. Marine Mammals of California. University of California Press, Berkeley, CA. 93 pp.

Paine, S. 1993. The World of the Sea Otter. Sierra Club Books, San Francisco, CA. 132 pp.

Reidman, M. 1990. Sea Otters. Monterey Bay Aquarium Foundation. Monterey Bay, CA. 80 pp. 

Risebrough, R.W. 1989. Accumulation pattern of heavy metals and chlorinated hydrocarbons by sea otters, Enhydra lutris in California. U.S. Department of Commerce, National Technical Information Service. 51 pp.

Shaw, S.B. 1971. Chlorinated hydrocarbon pesticides in California sea otters and harbor seals. California Fish and Game 57(4):290-294.

Smith, D.R., S. Niemeyer, J.A. Estes and A.R. Flegal. 1990. Stable lead isotopes evidence anthropogenic contamination in Alaskan Sea Otters. Environ. Sci. Tech. 24:1517-1521.

Smith, D.R., S. Niemeyer and A.R. Flegal. 1992. Lead sources to California sea otters: industrial inputs circumvent natural lead bio-depletion mechanisms. Environ. Res. 57:163-174.

VanBlaricom, G.R., J.A. Estes. 1988. The Community Ecology of Sea Otters. Springer-Verlag, Berlin.  247 pp.

Williams, T.M., J. McBain, R.K. Wilson and R.W. Davis. 1990. Clinical evaluation and cleaning of sea otters affected by the T/V Exxon Valdez oil spill. In: Sea Otter Symposium 17-19 April 1990. USFWS Biological Report 90 (12), Anchorage, AK. 485 pp.  

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