Unlike Hawai’i’s terrestrial researchers and resource managers, who meet every summer to catch up on the latest science at the Hawai’i Conservation Alliance’s conference, marine researchers working in Hawai’i rarely gather en masse. But recently, two meetings focusing heavily on local marine issues were held nearly back-to-back.
In late October, the federal Marine Mammal Commission squeezed its annual meeting into a dark conference room in the Royal Kona Resort. For three days, commissioners discussed with local scientists and resource managers everything from legal obstacles blocking the protection of marine mammals to the latest research and programs.
If the MMC meeting was a quiet, intimate affair, the Third Northwestern Hawaiian Islands Scientific Symposium held in Honolulu last month was practically a block party. Scientists studying everything from monk seals to birds to lobsters to climatic processes in the Northwestern Hawaiian Islands met for three days at the Hawai’i Convention Center and were feted with pupus, grilled salmon lunches, live music, and Haeagen-Dazs ice cream. And for good reason.
Scientists working in the NWHI had not shared their work in any kind of forum since the 1980s, when the second scientific symposium was held. At last month’s symposium, some scientists with the National Oceanic and Atmospheric Administration found out for the first time what their peers have been doing.
The following is a sample of some of the findings and discussion at both meetings.
Shark Moves
In the Northwest Hawaiian Islands, understanding the movement of sharks is more than just about assessing shark behavior; it has management implications for the protection of other species, specifically seabirds and endangered monk seals.
Christopher Lowe, a researcher with California State University at Long Beach, Bradley Wetherbee of the University of Rhode Islands, and Carl Meyer and Kim Holland of the Hawai’i Institute of Marine Biology have monitored the movements of tiger and Galapagos shark at French Frigate Shoals, a premiere site for turtles, birds, and monk seals to hatch or give birth to their young.
In 2000, Lowe and his team tagged 13 tiger and 4 Galapagos sharks at French Frigate Shoals with two types of transmitters, acoustic ones sewn into their bellies and satellite transmitters attached to their dorsal fins (The acoustic monitors proved far more useful since, to get a hit from the satellite transmitter, the shark’s dorsal fin had to stay above water for 45 seconds).
The team spent much of their time following the acoustic signals in a boat. Because boating at night is prohibited in the NWHI, the team only tracked the sharks’ daytime movements.
What they found is that while tiger sharks range throughout the atoll, they seemed to spend a lot of time at Easter Island, located in the atoll’s center and surrounded by a lagoon. The sharks would hang out in the placid waters around the island in the morning – between 5 and 6 a.m. and 10 and 11 a.m. – then swim elsewhere by noon.
What’s so special about Easter Island in the morning? The scientists noted that early morning is when fledging albatross take their first flights off the island. As the birds attempt to fly up and over the lagoon to the open ocean, the unsuccessful ones sometimes fall short, where the tiger sharks wait to feast.
The Galapagos sharks, on the other hand, are less interested in the albatross at Easter Island than they are in unweaned monk seal pups at Trig Island, which has become the primary pupping site since a sandy formation known as Whaleskate shrunk to a tiny hump in the water in the late 1990s.
The research team found that the Galapagos sharks stayed mostly at Trig, Shark Island, and Tern Island, which is where the most of the monk seals at French Frigate Shoals are born. Lowe says that unlike the tiger sharks, which have an easily identifiable morning-afternoon behavior, there is no clear pattern of where the Galapagos sharks go during the day, in part because the total number of hits from the acoustic transmitters was so small.
While the sharks don’t seem to prefer any particular time of day to hang around their preferred islands, they do tend to be there during peak monk seal pupping months in the summer and fall.
Shark Culling
When the federal Marine Mammal Commission met last October in Kona, a hot topic of discussion was a proposal to cull some of the Galapagos sharks preying on monk seal pups.
In 1997, the predation was a serious problem at Trig and Whaleskate, but subsided when Whaleskate practically vanished into the ocean in 1998, Bud Antonelis of the National Marine Fisheries Services’ Pacific Island Fisheries Science Center, said at the MMC meeting. But in 1999, predation rose again, leading resource managers to kill 10 sharks. While the action halved the predation rate, Antonelis said the problem has spread to other sites, such as Midway Atoll.
The U.S. Fish and Wildlife Service has wanted the National Marine Fisheries Service to study these sharks for some time, but according to Antonelis, the high research costs, as well as the political and cultural controversy that goes with killing sharks (which are aumakua to some native Hawaiians), has derailed that study. Antonelis said the Fish and Wildlife Service wants to charge $25,000 to conduct the study. And at such great expense, he said, “We need to figure out a better way to do business.”
Still, Marine Mammal Commissioner Paul Dayton of Scripps Institute of Oceanography in La Jolla felt that a few sharks could be culled without a study.
“I’d be dumbfounded that killing 10 sharks would show up on ecosystem models,” he said. “Why the foot-dragging?”
But Don Palawski of the Fish and Wildlife Service disagreed. Before any sharks are killed, he said, “You need to be more site specific. We don’t know the movements of sharks, and we have not asked all the questions in a systematic way to answer your questions.” He added that fishing for sharks near seals also raises questions about impacts to the seals.
Antonelis said that he does not intend to do a “willy-nilly” culling of sharks and that at most, there are 30 individuals causing problems for seals. He proposed taking only a handful at a time, and fewer than 15 a year.
Rehab
No, there’s not a problem with chemical dependency among monk seals. Still, the National Oceanic and Atmospheric Administration is sponsoring a rehabilitation and release program for seals that need a little extra help.
The program has its origins back in the 1980s. Between 1984 and 1995, Bill Gilmartin, then with NOAA, captured and nursed to health 84 female monk seals. As recently as 2003, 13 were known to remain in the population, says Antonelis. Graduates of the program are thought to have given birst to at least 119 pups, he told the Marine Mammal Commissioners.
While a diseased female ultimately halted the project in the mid 1990s, Antonelis has plans to carry on Gilmartin’s work with a new project called Second Chance, slated to begin next year. Under the program, undersized seals will be taken in for a couple of months, fattened up, then released back into the wild.
The program is intended to offset the many threats to the endangered seals. In the 1980s and 1990s, male mobbing of the highly outnumbered females led to the removal of some of those males from Lisianski and French Frigate Shoals. Antonelis says male aggression is not as much of a problem as it used to be. But new concerns have taken its place. Habitat loss resulting from the shrinking, or in the case of Whaleskate, disappearance, of atolls at French Frigate Shoals is a major issue in the Northwest Hawaiian Islands.
In the Main Hawaiian Islands, sportfishing, high-speed boat traffic, and disease are all dangers to seals, he said.
Seal Foraging
While Second Chance may boost monk seal survival in the short term and perhaps speed recovery of the species, knowing what food resources they need in the wild is key to their future existence. Research on seal scat and fatty acids to determine what exactly monk seals eat is ongoing, but little information on what’s been found so far has been released.
At the Marine Mammal Commission meeting, Charles Littnan of the Pacific Islands Fisheries Science Center reported that 2,895 samples of monk seal fatty acid have been collected and about 180 potential prey species have been analyzed. He expects the results to come out some time next fiscal year. Also, Littnan said that the scat to be analyzed has been processed and cleaned. Fish ear bones, called otoliths, have been mined from the scat and now must be identified.
Bud Antonelis said he was not ready to report any specific conclusions about the fatty acid analysis, yet according to findings so far, “It’s very apparent these [monk seal] subpopulations have conspicuously different fatty acid profiles. It’s not one-size-fits-all.”
Knowing where seals go to eat is also important as it may help resource managers establish fishing rules or set aside areas for conservation.
Brent Stewart and Pamela Yochem with Hubbs-SeaWorld Research Institute in San Diego, along with Antonelis and Jason Baker of the Pacific Islands Fisheries Science Center, have used satellite transmitters to track foraging habits of monk seals in six colonies in the Northwestern Hawaiian Islands. Those colonies include Kure, Laysan, French Frigate Shoals, Midway, Pearl and Hermes, and Lisianski.
Between 1996 and 2002, Stewart and his fellow researchers tracked 147 seals. What they found was that monk seals visit other colonies’ reefs and banks to feed, but for the most part, they don’t range much further than about 30 kilometers beyond their colony center.
Their feeding grounds can be divided into three clusters: A Pearl and Hermes-Kure-Midway cluster, a Laysan-Lisianski cluster, and a French Frigate Shoals cluster. Except at French Frigate Shoals, the seals stayed within 32 kilometers of their colony centers 95 percent of the time, and within 16 km 75 percent of the time. Seals at French Frigate Shoals traveled much farther at nearly 57 km 95 percent of the time and 48 km 75 percent of the time.
These patterns, the team found, change with age and sex. For example, at Pearl and Hermes, males and females feed in different parts of the reef with some overlap.
In Depth
In his study of monk seals, Frank Parrish of the Pacific Islands Fisheries Science Center found that they dive as deep as 550 meters. Thinking they might be foraging on fish aggregating around the precious coral beds that also occupy these dark depths, Parrish took a research submarine down to the pink and gold coral beds at French Frigate Shoals, to see what was so enticing about the area.
What he found was not what he expected. The fish were down there all right. Parrish counted some 13,000 fish in his surveys, encompassing 42 taxa. To his surprise, however, the corals, gold or pink, didn’t seem to affect where the fish hung out. Relief, he found, was a greater influence. Only four percent, or 286 fish, were seen in or with the corals.
Parrish says he still doesn’t know why the seals are diving down there, but speculates that they’ve identified a high flow area and are feeding on the fishes there. The corals may just be a point of reference, he says.
Big Fish
Unlike in the Main Hawaiian Islands, the Northwestern Hawaiian Islands ecosystem is dominated by apex predators such as large tunas and sharks. The bulk of those – roughly two-thirds of the predator standing biomass – are tunas or jacks. And where jacks are particularly abundant, researchers with the Pacific Islands Fishery Science Center have found that they affect the average size, and in one case, the life cycle, of other reef fish species.
Ulua, while found throughout the island chain, are most abundant at Pearl and Hermes Reef and Gardner Pinnacles. Edward DeMartini, a NOAA fisheries scientist, has compared shallow reef fish at Pearl and Hermes to those in the NWHI northern atolls of Kure and Midway.
He found that a variety of fishes are smaller at Pearl and Hermes than they are at Midway or Kure. And not only were the fish generally smaller, large parrotfish – a major prey item for ulua – changed sex (and as a result changed color) at a smaller size than at the other atolls, suggesting a relationship between tuna predation and the parrotfish life cycle at Pearl and Hermes.
Bottomfish
The future of bottomfishing in the NWHI is a major concern for many. And the Executive Order establishing the NWHI Coral Reef Ecosystem Reserve allows bottomfishing to continue at Raita and West St. Rogatien banks (considered Reserve Protected Areas) for five years if it’s found to not impact the banks’ resources. To determine fishing’s impacts, Christopher Kelley of the Hawai’i Undersea Research Laboratory and Robert Moffit of the NMFS Honolulu Laboratory took submersible vehicles down to the various bottomfish habitats – identified by fishermen – at Raita and St. Rogatien. With money from the National Ocean Service, they also did a couple of dives at nearby Brooks Bank and Bank 66.
At Raita, Kelly and Moffit found fewer onaga than are present around Kaho’olawe in the Main Hawaiian Islands. Although it seemed as though he was “really seeing a population decrease at one site,” with only six total dives, he could not draw any conclusions. He did note that the landscape down there was mostly barren – with no benthic cniderians on the coral substrate and a weak coral garden – up until 66 meters, which is far shallower than typical bottomfishing depths.
At West St. Rogatien, the team found more, but smaller, onaga than at Raita. Brooks Bank and Bank 66, on the other hand were full of bottomfish, including a “marvelous [onaga] school of big breeders.”
In the end, no conclusions were drawn about the impacts of bottomfishing at Raita and St. Rogatien. And Kelly said he doesn’t really know why the two banks were singled out in the first place.
“The EO directed the study,” Kelly said, but added, “There are other banks more deserving of survey effort in the Northwest Hawaiian Islands.”
Whales and Dolphins
At the MMC meeting, Jay Barlow of the National Marine Fisheries Service in La Jolla presented some of the latest research and knowledge about the lesser known whale and dolphin species living in Hawaiian waters. A few factoids:
— Teresa Dawson
Volume 15, Number 6 December 2004