abstract

A mother and female calf humpback whale (Megaptera novaeangliae) were observed 72 nautical miles inland in the Port of Sacramento, California on May 16 2007 after first sighting in the Sacramento River May 9 2007. Sequencing of mtDNA from a skin biopsy showed the cow to be an E1 haplotype, which is common in the California feeding population but not from the British Columbia/Southeast Alaska feeding populations. Both animals had lacerations suggesting sharp trauma from boat strike. Daily photographs showed generalized deterioration of skin condition and necrotic wound edges, and histology of a skin biopsy indicated hydropic degeneration of epithelial cells and mild eosinophilic dermatitis. Culture of skin scrapings taken from the cow on May 27 grew mixed bacteria including Acinetobacter sp., Moraxella sp., Klebsiella oxytoca, Comamonas sp., Pseudomonas fluorescens and Aeromonas hydrophila. Based on these observations and the prolonged duration of exposure to freshwater, the whales were treated with antibiotics to reduce risk of septicemia following infection of the necrotic lacerations.

Behavioral responses were recorded during attempts to move the animals to the Pacific; the attempts included playback of alarm tones, humpback and killer whale sounds, banging hollow steel pipes ("Oikami pipes"), spraying of fire hoses on the water surface and use of tug and power boat engine noise and movement. During the 17 days that the whales spent in freshwater, these techniques appeared to influence the movement of the whales, but did not result in significant consistent downstream movement.

Antibiotic was administered by projectile dart using a custom modified Paxarms (paxarms.co.nz) rifle. Antibiotic therapy was administered by dart, representing the first reported antibiotic treatment of free-ranging live whales. Ceftiofur (200mg/ml) was delivered by intramuscular injection using 30 cm long, 0.64 cm diameter needles on 57 ml syringes. Dosage was metabolically scaled so the calf received 57 ml (1 syringe, 2.3 mg/kg), and the mother received 171 ml (3 syringes, 1.3 mg/kg). The day after darting, the animals swam downstream from fresh water at Rio Vista to brackish water, and skin condition noticeably improved 24 hours later. The animals followed the deep-water channel through the Sacramento delta and San Francisco bay, reaching the ocean 20 days after first sighting in the river.

acknowledgements

We thank California Lieutenant Governor John Garamendi for his efforts in saving these whales and his concern for ocean protection, and the U.S Coast Guard, California Office of Emergency Services, California Department of Fish and Game, California Highway Patrol, National Marine Fisheries Service and the staff and volunteers of The Marine Mammal Center for their efforts in this response. We especially thank David Rotstein for histology of the skin biopsy, Gina Ylitalo for blubber lipid analysis, Bob Wilson for photography, Pfizer Animal Health for their generous donation of Excede, Bayer for the donation of Baytril, Grandpa's Compounding Pharmacy for concentrating drugs, and Drs. Jim McBain, Sam Ridgway and Sue Thornton for advice on antibiotic treatment.