Abstract

Over a 3-year period, 56 marine mammals of seven different species stranded along the Oregon coast were necropsied. Primary and contributory factors causing the deaths of the animals were determined.

Gunshot wounds were the primary cause of death in 13 animals and contributory in two others. Trauma induced lesions, such as falls or boat propeller wounds were primary causes of death in five animals and contributory in four deaths. Reproductive problems including dystocia, abortion and separation or abandonment were primary or contributory in eight deaths. Predator wounds accounted for the deaths of two animals.

Bacterial diseases were the most important form of infectious disease encountered. Bacterial pneumonia, peritonitis, dermatitis and septicemia were primary conditions accounting for 11 deaths. Secondary bacterial infections were contributory in the deaths of seven others. Parasitic diseases, especially verminous pneumonia, accounted for seven deaths and were a significant contributory factor in seven others. Viral encephalitis in a dolphin and malignant lymphoma in a harbor seal were also observed.

These studies conclude that in spite of federal protection, illegal killing of marine mammals, especially harbor seals, is still a significant cause of death. Infectious diseases, primarily bacterial and parasitic pneumonias are important in young animals. Reproductive failure, especially in harbor porpoises, is important as are traumatic (accidental) causes.

Notes

Dr. Stroud will analyse samples or look for specific diseases on request, if samples are sent to his laboratory.

The harbour seal, northern elephant seal, California sea lion, Steller's sea lion, harbour porpoise, common dolphin, Risso's dolphin, gray whale and sea otter were studied.

List of Pathologic Findings

• Gunshot wounds were the most common finding.

• Trauma - boat propellers, falls - one harbour seal had a ruptured uterine artery after a fall.

• Predation - by sharks on the harbour seal and Steller sea lion.

• Reproduction

• Neoplastic

• Parasitic

  Heartworm in a harbour seal causing vasculitis
  Gastric nematodes - bleed to death
  Crassicauda causing sinusitis in a Risso's dolphin.

• Bacterial and Viral

  Bacterial pyoderma secondary to vesicular disease in an elephant seal
  Encephalitis in the common dolphin

• Miscellaneous

  Peritonitis due to a colonic ulcer 
  Fibrinous arteritis causing embolic infarction of kidneys and heart
  Granulomatous pharyngeal abscess causing choke
  Age - worn teeth and arthritic changes

• Undetermined

• Euthanasia.