Organochlorine exposure and health effects in stranded Steller sea lions (Eumetopias jubatus) and Pacific harbor seals (Phoca vitulina richardii) from Oregon and southern Washington coasts

Organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs) have been detected in a variety of marine mammal species at levels associated with adverse health effects. Little is known about OC levels and impacts on health in pinnipeds with different life histories. We determined the health and levels of 18 OC pesticides and 16 PCB congeners in blubber samples from 20 Steller sea lions and 39 Pacific harbor seals stranded from Oregon and Southern Washington. The most commonly detected OC at the highest concentration was p,p′- dichlorodiphenyldichloroethylene (DDE). PCBs were detected in all samples as well. Hypothesis testing indicated that diseased Steller sea lions (males and females combined) had higher contaminant concentrations than healthy Steller sea lions, and diseased Pacific harbor seals had higher concentrations of total OCs than healthy animals. Differences were also noted between diseased and healthy animals when looking at individual sexes of each species. Diseased Steller sea lions had higher mean contaminant levels than diseased harbor seals and healthy Steller sea lions had higher mean contaminant concentrations than healthy Pacific harbor seals. These results show that species differences exist in both contaminant loads and sensitivity to contaminants, which may be due to differences in life histories and physiology.     

Metabolic indicators in the skeletal muscles of harbor seals (Phoca vitulina)

The goal of this study was to determine the distribution of citrate synthase (CS), beta-hydroxyacyl coenzyme A dehydrogenase (HOAD), and lactate dehydrogenase (LDH) activities and myoglobin (Mb) concentration in the locomotor muscles (epaxial muscles) and heart of harbor seals. The entire epaxial musculature, which produces most of the power for submerged swimming, was removed and weighed, and three transverse sections (cranial, middle, and caudal) were taken along the muscle bundle. Multiple samples were taken along points on a circular grid using a 6-mm biopsy. A single sample was taken from the left ventricle of the heart. Muscle groups of similar function were taken from three dogs as a control. Mean values were calculated for four roughly equal quadrants in each transverse section of the epaxial muscles. There were no significant differences among the quadrants within any of the transverse sections for the three enzymes or Mb. However, there were significant differences in the mean enzyme activities and Mb concentrations along the length of the muscle. The middle and caudal sections had significantly higher mean levels of CS, LDH, and Mb than the cranial section, which may be correlated with power production during swimming. The enzyme ratios CS/HOAD and LDH/CS exhibited no variation within transverse sections or along the length of the epaxial muscles. Relative to the dog, the epaxial muscles and heart of the harbor seal had higher HOAD levels and lower CS/HOAD, which, taken together, indicate an increased capacity for aerobic lipid metabolism during diving.     

A captive feeding study with the Pacific harbor seal (Phoca vitulina richardii): Implications for scat analysis

Seven prey species ( n _total > 2,700) were fed to seven captive male Pacific harbor seals ( Phoca vitulina richardii ) in 177 experimental meals to quantify biases associated with scat analysis and current consumption models. Hard parts from an individual meal were recovered in an average of 3.8 ± 1.8 scats (range 1–10; mean ± SD). Overall, 57.7 ± 33.2% of otoliths and 89.5 ± 15.5% of squid beaks were recovered. Recovery rates varied, and prey with smaller, fragile otoliths were recovered in lesser quantities than prey with larger, robust otoliths. Recovery rates of all prey except pink salmon were improved by a mean of 31.7% when all diagnostic structures were included in estimates. Estimated recovery of pink salmon was 9.5 times that fed seals based on the all-structure technique. Mean length reduction of recovered otoliths was 20.4 ± 10.1%. Correction factors calculated from average length reduction improved length estimates for all fish species. Grade-specific length correction factors (gLCFs) reduced variability in all of the estimates and significantly improved estimates of prey with highly eroded otoliths including Pacific hake and shortbelly rockfish. The Biomass Reconstruction (BR) model accurately predicted biomass consumption within 4% of known consumption, whereas estimates based on frequency of occurrence were inaccurate.     

An outbreak of a herpesvirus infection in harbor seals (Phoca vitulina)

During an outbreak of a herpesvirus infection in juvenile harbor seals, 11 out of 23 seals died. The duration of the disease in these 11 animals varied from 1-6 days. Nasal discharge, inflammation of the oral mucosa, vomiting, diarrhea and fever up to 40 degrees C were observed in the first days of the disease. In later stages coughing, anorexia and lethargy occurred. Severe necrosis of the liver and interstitial pneumonia were the most striking histopathological findings.     

Food habits of harbor seals (Phoca vitulina richardii) as an indicator of invasive species in San Francisco Bay,California

The diet of harbor seals (Phoca vitulina richardii) in San Francisco Bay (SFB), California, was determined from July 2007 to July 2008 using prey hard parts recovered from 442 scats collected at five haul‐out sites. Twenty‐two species of fish and one species of crustacean were identified, but harbor seals primarily ate a nonnative invasive species, yellowfin goby (Acanthogobius flavimanus), which increased in dietary importance since the diet was last studied in 1991/1992. Additionally, another nonnative invasive fish species, chameleon goby (Tridentiger trigonocephalus), was found for the first time in the diet of harbor seals in SFB. Harbor seal diet was statistically different between years (1991/1992 and 2007/2008), between the pupping and nonpupping seasons, and between North SFB and South SFB haul‐out locations. The diet of harbor seals was significantly correlated with fish species caught in trawl surveys conducted by the California Department of Fish and Wildlife (CDFW) during the same time periods as this study (2007/2008). Harbor seals currently are influencing the health of the SFB ecosystem in a positive manner by consuming large quantities of nonnative invasive fish species.     

Haul-out behavior of harbor seals (Phoca vitulina) in Hood Canal, Washington

The goal of this study was to model haul-out behavior of harbor seals (Phoca vitulina) in the Hood Canal region of Washington State with respect to changes in physiological, environmental, and temporal covariates. Previous research has provided a solid understanding of seal haul-out behavior. Here, we expand on that work using a generalized linear mixed model (GLMM) with temporal autocorrelation and a large dataset. Our dataset included behavioral haul-out records from archival and VHF radio tag deployments on 25 individual seals representing 61,430 seal hours. A novel application for increased computational efficiency allowed us to examine this large dataset with a GLMM that appropriately accounts for temporal autocorellation. We found significant relationships with the covariates hour of day, day of year, minutes from high tide and year. Additionally, there was a significant effect of the interaction term hour of day : day of year. This interaction term demonstrated that seals are more likely to haul out during nighttime hours in August and September, but then switch to predominantly daylight haul-out patterns in October and November. We attribute this change in behavior to an effect of human disturbance levels. This study also examined a unique ecological event to determine the role of increased killer whale (Orcinus orca) predation on haul-out behavior. In 2003 and 2005 these harbor seals were exposed to unprecedented levels of killer whale predation and results show an overall increase in haul-out probability after exposure to killer whales. The outcome of this study will be integral to understanding any changes in population abundance as a result of increased killer whale predation.     

Novel and canine genotypes of Giardia duodenalis in harbor seals ( Phoca vitulina richardsi)

Feces of harbor seals (Phoca vitulina richardsi) and hybrid glaucous-winged/western gulls (Larus glaucescens / occidentalis) from Washington State's inland marine waters were examined for Giardia and Cryptosporidium spp. to determine if genotypes carried by these wildlife species were the same genotypes that commonly infect humans and domestic animals. Using immunomagnetic separation followed by direct fluorescent antibody detection, Giardia spp. cysts were detected in 42% of seal fecal samples (41/97). Giardia-positive samples came from 90% of the sites (9/10) and the prevalence of positive seal fecal samples differed significantly among study sites. Fecal samples collected from seal haulout sites with over 400 animals were 4.7 times more likely to have Giardia spp. cysts than samples collected at smaller haulout sites. In gulls, a single Giardia sp. cyst was detected in 4% of fecal samples (3/78). Cryptosporidium spp. oocysts were not detected in any of the seals or gulls tested. Sequence analysis of a 398 bp segment of G. duodenalis DNA at the glutamate dehydrogenase locus suggested that 11 isolates originating from seals throughout the region were a novel genotype and 3 isolates obtained from a single site in south Puget Sound were the G. duodenalis canine genotype D. Real-time TaqMan PCR amplification and subsequent sequencing of a 52 bp small subunit ribosomal DNA region from novel harbor seal genotype isolates showed sequence homology to canine genotypes C and D. Sequence analysis of the 52 bp small subunit ribosomal DNA products from the 3 canine genotype isolates from seals produced mixed sequences at could not be evaluated.     

Estimating age of harbor seals (Phoca vitulina) with incisor teeth and morphometrics

We compared annuli counts from sets of canine, postcanine, and incisor teeth from 450 subsistence-harvested harbor seals, submitted blind to a laboratory. Postcanine and incisor ages were highly correlated with canine age estimates ( r = 0.985 and r = 0.984, respectively), as were postcanine and incisor teeth ( r = 0.984). Age estimates from teeth of 23 known-aged seals were highly correlated; canine teeth r = 0.987; postcanine r = 0.996; incisor r = 0.992, although age for all tooth-types was underestimated for a 29-yr-old seal. Incisor estimates were variable; comparison of age estimates from two incisors/individual ( n = 42) was r = 0.992 if only high-quality age estimates were used and r = 0.705 if lower-quality estimates were used. Morphometrics and incisor-based ages of 164 live-captured seals were explored to derive a method of estimating ages of harbor seals when age estimates are needed immediately; 39 seals were of known age. Curvilinear length, mass, and axial girth were most predictive of age for females, and curvilinear length and mass for males (equations for morphometrically calculating ages are given). Morphometric-based age estimates were highly correlated with known ages ( r = 0.896) and incisor-based estimates ( r = 0.904) and discrepancies between known and morphometric-based ages were small for younger seals. Morphometric-based age estimates also accurately distinguished between young and mature individuals.     

Play in Harbour seals (Phoca vitulina)

Harbour seals in a breeding colony at Miquelon exhibited 13 distinct types of play behaviour, 80% of which was solitary locomotor play. Most play was displayed by yearlings and juveniles, though a significant amount of adult play occurred as well. Mothers and pups rarely played. Yearlings played socially as often as alone, but seals of other age classes played by themselves most often. Only social play resembled adult activities. It is suggested that the function of mammalian play has been obscured by its similarity to adult behaviour.     

Behavioral effects of environmental enrichment on harbor seals (Phoca vitulina concolor) and gray seals (Halichoerus grypus)

Zoos and aquariums have been incorporating environmental enrichment into their animal care programs for the past 30 years to increase mental stimulation and promote natural behaviors. However, most attempts to document the effects of enrichment on animal behavior have focused on terrestrial mammals. Staff at the National Aquarium in Baltimore conducted an investigation of the behavioral effects of enrichment on the seven harbor seals and two gray seals housed in the aquarium's outdoor seal exhibit. We expected that enrichment would change the amount of time the animals spent engaged in specific behaviors. The behaviors recorded were: resting in water, resting hauled out, maintenance, breeding display, breeding behavior, aggression, pattern swimming, random swimming, exploration, and out of sight. Activity levels (random swimming and exploration) were expected to increase, while stereotypic behaviors (pattern swimming) were expected to decrease. The frequency and duration of behaviors were documented for 90 hr in both the control phase (without enrichment) and the experimental phase (with enrichment). Statistically significant differences (P<0.05) in the time spent in pattern swimming, random swimming, exploration, and out of sight were observed between the two phases. With enrichment, pattern swimming and out of sight decreased, while random swimming and exploration behavior increased. These findings demonstrate that enrichment can promote behaviors (random swimming and exploration) that are likely to be normal for phocids in the wild, and that may contribute to the behavioral complexity of these seals in captivity. Zoo Biol 21:375–387, 2002. © 2002 Wiley‐Liss, Inc.     

Molting phenology of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the Baja California Peninsula,Mexico

We document and compare the annual molt of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the west coast of the Baja California Peninsula that are the northern and southern extremes of its distribution in Mexico. During 2014, observations were made from March to July on Todos Santos Island (northern extreme) and from January to June on San Roque Island (southern extreme). On Todos Santos, the premolt lasted 15 wk (March–June) and the molt 12 wk (April–July). On San Roque, the premolt lasted 22 wk (January–June) and the molt 17 wk (February–June). The proportion of seals undergoing molt peaked on 26 May on Todos Santos and on 7 June on San Roque. Shedding of old hair most commonly initiated on the torso and progressed to the head and flippers (reverse molting pattern). The period when the highest number of harbor seals haul out in Mexico is in late April on the more southerly islands and in early May on the more northerly islands, when a large proportion of seals are in premolt.     

Congenital hemicerebral anomaly in a stranded Pacific harbor seal (Phoca vitulina richardsi)

A stranded 5-month-old female Pacific harbor seal (Phoca vitulina richardsi) was presented displaying tachypnea and diminished lung sounds. No neurological abnormalities were noted. The animal was treated for verminous pneumonia, but died 2 wk later. Gross necropsy examination revealed a severe obstructive verminous pneumonia associated with large numbers of Otostrongylus circumlitus. In addition, the majority of the right cerebral hemisphere was absent, with hypoplasia of the left cerebellar hemisphere, absence of the right pyramid, and malformation of the right occipital bone. Histopathologic findings included multifocal thrombosis and inflammation of pulmonary arteries, verminous pneumonia, and mild vacuolation of the subependymal white matter in the third ventricle representing swelling of myelin sheaths and edema. This is the first report of a hemicerebral anomaly in a marine mammal.     

Antibodies to phocine herpesvirus-1 are common in North American harbor seals (Phoca vitulina)

Phocine herpesvirus-1 (PhHV-1) has been associated with morbidity and high mortality in neonatal harbor seals (Phoca vitulina) along the Pacific coast of California (USA) and in northern Europe. Seals dying with PhHV-1 associated disease in California primarily have histopathologic evidence of adrenal necrosis or adrenalitis with herpesviral inclusion bodies. Little is known about prevalence of exposure to PhHV-1, modes of disease transmission, and viral pathogenesis in free-ranging harbor seal populations. To evaluate the prevalence in North America, 866 serum samples collected between 1994 and 2002 from harbor seals captured or stranded on the Pacific and Atlantic coasts of North America were assayed by enzyme linked immunosorbent assay (ELISA) for evidence of PhHV-1 exposure. Samples from three harbor seal age classes (pre-weaned, weaned, and subadults/adults) were obtained from each of four regions to compare exposure among sex, age class, and region. We found increasing prevalence with age as 37.5% of pre-weaned pups, 87.6% of weaned pups, and 99.0% of subadults and adults were seropositive. When accounting for age, no associations between seropositivity and sex or location of harbor seals were detected. These data indicate that PhHV-1 is endemic in the harbor seal populations of North America.     

Interannual differences in postrelease movements of rehabilitated harbor seal pups (Phoca vitulina richardii) in the Salish Sea

Despite the large number of harbor seals (Phoca vitulina richardii) rehabilitated worldwide, few studies have been conducted on postrelease movement and behavior of rehabilitated harbor seal pups. We compared interannual differences in movements and survival of 24 rehabilitated seal pups released in the Salish Sea in 2010 (n = 10), 2012 (n = 5), 2013 (n = 5), and 2014 (n = 4). We also compared the postrelease movement of these seals to the movement of 10 wild seal pups tracked in the same ecosystem in 2010. Transmission duration, total cumulative distance, and average daily distance varied annually. Maximum linear distance traveled from the release site was similar for the rehabilitated seal groups. Compared to wild seals (n = 10), and consistent with prior studies, rehabilitated pups (n = 24) traveled significantly farther daily and cumulatively than wild weaned pups. Unlike in a prior study in this ecosystem, we found no significant difference between transmission duration in wild and rehabilitated pups.     

Patterns of extensive genetic differentiation and variation among European harbor seals (Phoca vitulina vitulina) revealed using microsatellite DNA polymorphisms

The harbor seal (Phoca vitulina) has the most extensive distribution of any phocid seal species. An analysis of population structure in this species across its European range was made using 7 phocid derived microsatellites in a sample of 1,029 individuals from 12 separate geographic areas. Despite the species potential for long-distance movement, significant genetic differentiation between areas was observed using an unbiased estimator of RST. Six distinct population units were identified: Ireland-Scotland, English east coast, Waddensea, western Scandinavia (Norway-Kattegat-Skagerrak-west Baltic), east Baltic, and Iceland. Little local substructuring is present along coastlines with a continuous distribution of breeding animals, but differentiation does increase with geographic distance. The degree of differentiation is greater over equivalent distances where the distribution is discontinuous, such as along coasts where breeding colonies are separated by large distances or by stretches of open sea. Patterns of population differentiation derived from microsatellites are very similar to those obtained from previous mitochondrial DNA analysis and suggest that philopatry in harbor seals operates over 300-500 km. In Europe, harbor seals have experienced a complex demographic history and patterns of population structure are likely to have been affected by natural environmental influences such as Pleistocene glaciations and epizootics. Comparison of Nm values from an unbiased estimator of RST, GST, and theta are consistent and, in some cases, may indicate populations where conditions deviate from the expectations of the RST model.      

C‐reactive protein in blood plasma and serum samples of harbor seals (Phoca vitulina)

C‐reactive protein (CRP) belongs to the acute phase proteins. Increased levels are present in inflammatory conditions, trauma, or intoxications. In veterinary medicine CRP is used as powerful diagnostic parameter in health studies, whereas little is known about the role of CRP in Pinnipedia. Therefore, samples were collected from 131 harbor seals from the North Sea between November 2002 and November 2007. CRP blood values were measured and the physiological range was calculated. Furthermore, the influence of age and sex of the animal, geographical location and season was investigated. The CRP concentrations in plasma/serum showed a median of 33 μg/mL, a 5th percentile of 18 μg/mL, and a 95th percentile of 80 μg/mL. No significant influences of sex, season, or geographical location on CRP concentration were detected. Juveniles showed significantly higher CRP levels than adult animals, whereas CRP values in newborns appear to be lower than in juveniles and adults. Our report describes for the first time CRP plasma/serum concentrations in a large group of harbor seals. It suggests that CRP is useful to detect inflammatory conditions and may help to improve health studies of this species.     

Seroprevalence of Toxoplasma gondii in harbor seals (Phoca vitulina) in southern Puget Sound, Washington.

As part of the Puget Sound Ambient Monitoring Program of the Washington Department of Fish and Wildlife, serum samples from 380 harbor seals (Phoca vitulina) were tested for antibodies to Toxoplasma gondii in the modified agglutination test (MAT) incorporating formalin-fixed tachyzoites and mercaptoethanol. Antibodies to T. gondii were found in 29 of 380 (7.6%) seals with titers of 1:25 in 13, 1:50 in 14, and > or = 1:500 in 2 seals. Results indicate natural exposure of these wild marine mammals to T. gondii oocysts.