In this newsletter: wildlife veterinarians rescue entangled sea lions, new study on how harbor seals get brucellosis, spotlight on Science Advisor Dr. Christine Kreuder Johnson, Marine Science Lecture Series kicks off with a lecture on underwater mapping, and a lot of upcoming events.
Harbor seal (Phoca vitulina richardii) populations in the inland waters of Washington and British Columbia are at or near carrying capacity. Stranded pups often are collected and admitted to rehabilitation centers, and then released when they reach a weight of 22 kg and meet a variety of preestablished health and release conditions. While rehabilitation is common practice, it is unclear if rehabilitated seal pups behave like wild weaned pups. Using satellite transmitters, we compared movement patterns of 10 rehabilitated pups with 10 wild weaned pups. When released, rehabilitated seals were longer and heavier than wild pups, while wild pups had a larger mean axillary girth. No clinically different blood parameters were detected. On average, rehabilitated harbor seal pups traveled nearly twice as far cumulatively, almost three times as far daily, and dispersed over three times as far from the release site compared to wild weaned seals. Additionally, wild harbor seals transmitted nearly twice as long as did rehabilitated seals. These patterns suggest that learned behavior during the brief 3–4 wk nursing period likely enables wild harbor seal pups to move less daily and remain closer to their weaning site than rehabilitated pups.
Vertically transmitted nematodes can be a significant case of morbidity and mortality in some pinnipeds. Examples include the transmammary transmission the infective L3 of Uncinaria lucasi in Northern fur seals (Callorhinus ursinus) and Uncinaria spp. in California sea lions (Zalophus californianus) and in Juan Fernandez fur seals (Arctocephalus philippi).
To the best of our knowledge, transmammary or transplacental transmission of nematodes has never been documented in harbor seals (Phoca vitulina). Four deceased and six live stranded harbor seal pups collected between June and August 2012 in San Juan County, Washington, were studied for evidence of vertical transmission of internal parasites. Samples evaluated included lungs, liver, and gastrointestinal tracts collected from pre-weaned pups at necropsy and fecal samples from live stranded pups in rehabilitation. Tissue samples were evaluated by rinsing through a sieve and resultant material was examined for evidence of parasites. Fecal samples were examined via centrifugal float using zinc sulfate solution. Samples from the live pups showed no evidence of parasite infestation or shedding. However, a single necropsy sample revealed a developing adult male Phocanema decipiens nematode in the gastrointestinal tract of a three-day-old male harbor seal pup, suggesting vertical transmission of this parasite can occur in harbor seals. Infestation with P. decipiens has been widely reported in adult harbor seals in the Salish Sea but this is the first known documentation of infestation in a pre-weaned pup. The prevalence of P. decipiens in pre-weaned pups should be further studied, as should the potential clinical significance of this infection in harbor seal pups.
Wild harbor seal (Phoca vitulina richardii) pups thermoregulate by hauling out of the water before they lose too much heat and expend too much energy. In rehabilitation, however, young
pups are housed in dry areas, but placed in pools for swims. Decreased caloric value of milk replacer means rehabilitated pups reach weaning and release weight slower than wild ones. Increased metabolic expenditure due to bathing also could prolong the time needed to raise pups to release size. Thermography, which measures surface temperature, is a promising method for studying thermoregulation in rehabilitating harbor seal pups. Previous studies in pinnipeds examined seasonal variation of body surface temperature, recovery after minor trauma, and locations of heat dumping over the body. We used thermography to study heat loss associated with standard seal rehabilitation bathing practices to see if bathing resulted in increased energy expenditure, potentially contributing to increasing time to release.
Recovery of severely declining resource stocks often leads to enforced quotas or reduced human access to those resources. Predators, however, do not recognize such restrictions and may be attracted to areas of increased prey abundances where human extraction is being limited. Such targeting by predators may reduce or retard the potential recovery of depressed stocks. In the San Juan Islands, northern Puget Sound, USA, marine reserves were implemented to recover depressed fish populations. We examine the role of harbor seals Phoca vitulina in the San Juan Islands food web. We describe the temporal and spatial variability in their diet, emphasizing species for which reserves were established (rockfish Sebastes spp.) and other important depressed stocks, including salmon Oncorhynchus spp. and Pacific herring Clupea pallasii. During winter and spring, seals primarily consumed Pacific herring, Pacific sand lance Ammodytes hexapterus, northern anchovy Engraulis mordax, and walleye pollock Theragra chalcogramma. During summer/fall, adult salmonids composed >50% of the diet and were particularly important in odd-numbered calendar years, when pink salmon O. gorbuscha spawn. Rockfish were not a primary prey species at any time of the year, suggesting that the abundance of alternative prey species may reduce predation pressure and provide a critical buffer to rockfish predation. The importance of considering increased visitation by marine predators to areas where potential prey are enhanced through restrictions on human extractions should be considered when modeling the efficacy of quotas and reduced access areas, such as marine reserves.
Bacterial cultures collected over 12 yr from stranded harbor seal (Phoca vitulina) pups and weanlings located in the North Puget Sound and San Juan Islands region of Washington were analyzed retrospectively to determine the most common pathogenic isolates and to describe their antimicrobial resistance patterns. Culture attempts (n = 58) from wounds, umbilici, ears, conjunctiva, nares, oral lesions, and feces yielded 134 pathogenic isolates that represented 17 genera. The majority of isolates were Gram-negative (n = 87; 65%) and of the tested isolates were most susceptible to amikacin (n = 76; 99%) and gentamicin (n = 76; 97%) and least susceptible to ampicillin (n = 76; 26%). Of the Gram-positive isolates tested (n = 29), all were susceptible to amoxicillin/clavulanic acid. The most frequent isolates were Escherichia coli(17%), β-hemolytic Streptococcus spp. (15%), Enterococcus spp. (11%), and Pseudomonas aeruginosa (11%), with all four exhibiting resistance to more than 50% of the antimicrobials tested. The variety of organisms isolated, the variation in either Gram-negative or Gram-positive predominance, and the multiple drug resistance patterns observed suggest that when treating stranded harbor seals, culture and sensitivity testing are warranted and that antibiotic therapy should be based on results.