Dead whale samples reveal little information
21st August 2003
WOODS HOLE, Mass. - Samples taken from four whale carcasses on Eastern Georges Bank last month have tested negative for saxitoxin, a naturally-occurring marine biotoxin believed to have caused the deaths of humpback whales in the late 1980s. One sample from a humpback whale registered a very weak - essentially negative - indication of the biotoxin. The rest of the results were negative.
"We hope this event has passed, but to make progress in figuring out what happened, a full examination of a fresher carcass is almost certainly required," said Katie Touhey, onsite coordinator for the investigation into the whale deaths. "We’re working to get a plane with observers flying the area in search of carcasses, we will examine the whale samples we have for other biotoxins known to affect marine life, and we are expanding our request to include those samples that can be tested for viruses," she said.
Touhey leads the Cape Cod Stranding Network, a nonprofit organization that responds to marine mammal strandings along 700 miles of coastline from Cape Cod to the Rhode Island border. The response and investigation into the deaths is under the authority of NOAA’s National Marine Fisheries Service (NOAA Fisheries), the federal agency responsible for the protection of the nation’s marine mammals and sea turtles.
The samples will next be tested for the presence of domoic acid, another biotoxin produced by algal blooms. This toxin causes amnesic shellfish poisoning in humans, is sometimes present in the Gulf of Maine, and has been known to affect marine mammals in other parts of the world - particularly on the California coast. The biotoxin sample analysis has been coordinated by Dr. Frances Van Dolah, at NOAA’s National Ocean Service Marine Biotoxins Program.
"This is a very difficult sampling situation," said Dr. Frances Gulland, chair of the Unusual Mortality Working Group that advises NOAA Fisheries during such events. "The scientific and technical expertise, the international and interagency cooperation, the laboratory facilities and capabilities available to us, all are first rate. But the samples we have are degraded by time and natural conditions. Without fresher samples, preferably from a full carcass that can be examined in detail, it is hard to eliminate any particular cause at this point."
Gulland is with the Marine Mammal Center near San Francisco, a nonprofit research, education, and conservation organization that focuses its work on marine mammals. She is a marine veterinarian and has extensive experience with unusual mortality events in large whales.
Researchers also say that samples of other tissues can also be tested for viruses. One virus of interest is morbilli, which can cause a measle-like, highly contagious illness in mammals. Liver samples already obtained can be tested for this virus at the Armed Forces Institute of Pathology.
Twenty-one sightings of three species are so far included in the event: one pilot whale, one fin whale, 16 humpback whales, and one carcass of unknown species. Some of these sightings are likely of the same animal, but at different times. U.S. researchers estimate that 15 of these observations are of unique animals. The difficulty in establishing exact counts for the humpback whales occurs because the animals did not all die at the same time, moved with the time and currents, and were sighted at different times.
Three more carcass sightings were reported to the network on Saturday, Aug. 9, but are not yet included in the unusual mortality event. These animals can be included if further information establishes a link.
One humpback whale was photographed floating off Jonesport, Maine, on Saturday, and was re-sighted on Thursday. It was necropsied, and samples will be tested for biotoxin and morbilli. One minke whale carcass was sighted on Saturday and stranded near Chatham on Sunday. Samples were collected and will be tested for biotoxin. The animal had injuries consistent with recent, significant entanglement, that may have contributed to its death.
One carcass was spotted from a U.S. Coast Guard Falcon jet, west of the bulk of the observations presently included in the event. No species identification was possible.