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Seals' meals revealed
A study reveals seals' meals as part of the ongoing effort to save the scarce mammals
New information about what Hawaiian monk seals eat could help wildlife managers in their quest to save the species from extinction, federal scientists said yesterday.
Tiny blubber samples taken from 248 healthy seals over the past eight years have been analyzed to determine that the endangered animals' most frequently eaten prey are:
» Gindai (flower snapper): 20-25 percent of diet.
» Squid: 15 percent of diet.
» Boar fish, a deep-water fish that resembles the better-known butterfly fish: 13 to 15 percent of diet.
» Duckbill fish, another bottom fish: 9 to 11 percent of diet.
» Tang and surgeonfish, shallow-water reef fish: 10 percent.
» Box crab: 4 to 5 percent.
The gindai, boar fish and duckbill fish, and some of the squid, live at depths of 600 feet or more, said study participant Charles Littnan, an ecologist with the Pacific Islands Fisheries Science Center.
That is significant because "I don't think anybody knew before now that deep-water species of fish were as large a component of the monk seals' diet as they appear to be," Bill Robinson, regional administrator for the National Oceanic and Atmospheric Administration Regional Office, said yesterday after hearing a presentation on the research.
A notable fact is that lobster was eaten by the seals at an undetectable rate, said Frank Parrish, a NOAA Fisheries habitat ecologist.
There had been speculation that the "crash" of the lobster fishery in the Northwestern Hawaiian Islands in the late 1990s could have deprived the seals of a key food item.
"The new data seems to show that lobsters don't seem to be a part of the monk seals' diet over the last six to eight years," Robinson said. But whether they ate them frequently when they were more abundant might never be known, he said.
Robinson's office ultimately will decide how scientific research conducted by its affiliated science center will be used to guide its management of fisheries and endangered species.
"It is a substantial point that the current diet of the seals includes some of the same species of bottom fish sought by commercial fishermen," Robinson said. "Whether that is competition for the seals is something we don't know."
The information that seals are eating fish from deep waters fits with other recent research that put underwater video cameras on some seals, said Parrish, who participated in that study.
The video showed that the seals dive as deep as 1,500 feet and eat a wide variety of crustaceans, squid, octopus and fish in both shallow and deep water.
The most recent research is "cutting edge" and detects the "fatty acid signature" for each type of prey a seal has eaten recently in its own body fat, Littnan said. "It's based on the concept 'You are what you eat.'"
The information points scientists to the next thing they should study: deep-water fish that the seals seem to eat a lot of, Littnan said.
With an estimated 1,200 individuals left, "monk seals are in critical danger of going extinct," Littnan said. Further research will continue "until we have answers to save the species," he said.
The blubber analysis was arrived at by testing both mature and young seals living in all parts of the Northwestern and main Hawaiian Islands, Littnan said.
If scientists can figure out what foods are helping seals survive or where those foods are located, they might be able to make management decisions in the future to support the dwindling population, Littnan said.
For instance, young seals could be moved to an area with plenty of a type of food that seems crucial for survival.
Solving the puzzle of the seals' decline is a top priority for the scientists because at the current rate of decline, the number is expected to drop below 1,000 in five years.
