Distribution and demographics of mysids (Crustacea: Mysida) as prey for gray whales (Eschrichtius robustus) in northwest Washington state.

Background: The movement and distribution of gray whales (Eschrichtius robustus) during the feeding season is likely dependent on the quality of foraging opportunities and the distribution of prey species. These dynamics are especially important to understand for the Pacific Coast Feeding Group (PCFG) of gray whales which spend the feeding season along the coast from northern California, USA through northern British Columbia, Canada. In Washington state, no previous work has been done to describe available gray whale prey. The main goal of this research was to initiate studies on an important gray whale prey item in northwest Washington, mysid shrimp (Mysida), by establishing a baseline understanding of mysid swarm demographics in the area and investigating patterns in gray whale and mysid presence. Methods: Prey samples were collected during June through November 2019 and June through September 2020 using a vertically-towed plankton net at seven sites in the Strait of Juan de Fuca and seven sites in the Pacific Ocean in areas where gray whales were known to feed. Mysids collected in the samples were counted and the sex, length, species, maturity, and gravidity were documented. Patterns in gray whale and mysid co-occurrence were explored through data visualization. Results: Seven species of mysids were observed in the survey area. In 2019, the number of mysids per tow increased steadily through the season, the most abundant species of mysids were Holmesimysis sculpta and Neomysis rayii, and sampled mysids averaged 4.7 mm in length. In 2020, mysids were abundant in tow samples in June and July but were not abundant in the remaining months of the sampling season. The average length of mysids in 2020 was 13.3 mm, and a large portion were sexually mature males and brooded females identified as H. sculpta. Throughout the survey area, the majority of whale sightings occurred later in the season in 2019 and earlier in the season in 2020, coinciding with the trends of sampled mysids. Discussion: This study provides the first description of mysid swarm composition and temporal variation in northwest Washington. Tows were dominated by a similar assemblage of mysid species as what is observed in other areas of the PCFG range. The differences in sampled mysid assemblages between years, and the presence of whales in the survey area in times and at sites where samples with high mysid counts were collected, suggest evidence for interesting predator-prey dynamics that warrant further investigation.

Coxiella burnetii infection of a Steller sea lion (Eumetopias jubatus) found in Washington State.

A pregnant sea lion stranded in the State of Washington was found to have placentitis caused by a unique strain of Coxiella burnetii. This is the first description of coxiellosis in a sea lion and suggests that exposure to sea lions may be a risk factor for contracting Q fever.

Mortality related to spotted ratfish (Hydrolagus colliei) in Pacific harbor seals (Phoca vitulina) in Washington State.

Tissue perforation and penetration by dorsal fin spines of spotted ratfish (Hydrolagus colliei) were responsible for the death of seven harbor seals (Phoca vitulina) in Washington State (USA) between 2006 and 2011. In six animals, necropsy revealed spines or spine parts that had perforated the esophagus or stomach and migrated into vital tissues, resulting in hemothorax, pneumothorax, pleuritis, and peritonitis. In a seventh case, a ratfish spine was recovered from the mouth of a harbor seal euthanized due to clinical symptoms of encephalitis. Gross examination revealed an abscess within the left cerebrum, which was attributed to direct extension of inflammatory infiltrate associated with the ratfish spine. Between 2009 and 2011, spotted ratfish spines were also recovered from the head or neck region of three Steller sea lions (Eumetopias jubatus) and one California sea lion (Zalophus californianus). Ratfish-related trauma appears to be a novel mortality factor for harbor seals in Washington State and could be related to increased ratfish abundance and a shifting prey base for harbor seals.

Coxiella burnetii infection of marine mammals in the Pacific Northwest, 1997-2010.

Q fever is a zoonotic disease caused by the bacterium Coxiella burnetii. Humans are commonly exposed via inhalation of aerosolized bacteria derived from the waste products of domesticated sheep and goats, and particularly from products generated during parturition. However, many other species can be infected with C. burnetii, and the host range and full zoonotic potential of C. burnetii is unknown. Two cases of C. burnetii infection in marine mammal placenta have been reported, but it is not known if this infection is common in marine mammals. To address this issue, placenta samples were collected from Pacific harbor seals (Phoca vitulina richardsi), harbor porpoises (Phocoena phocoena), and Steller sea lions (Eumetopias jubatus). Coxiella burnetii was detected by polymerase chain reaction (PCR) in the placentas of Pacific harbor seals (17/27), harbor porpoises (2/6), and Steller sea lions (1/2) collected in the Pacific Northwest. A serosurvey of 215 Pacific harbor seals sampled in inland and outer coastal areas of the Pacific Northwest showed that 34.0% (73/215) had antibodies against either Phase 1 or Phase 2 C. burnetii. These results suggest that C. burnetii infection is common among marine mammals in this region.