Abstract

In 1996 and 1997 the National Marine Fisheries Service (NMFS) conducted surveys which documented large amounts of derelict fishing gear, net, and other debris on reefs in the Northwestern Hawaiian Islands. Because of the high quantity of debris, NMFS is leading a multi-agency group to address the issue, cleaning some reef areas. From October 26 through November 25, 1998 the Center for Marine Conservation (CMC), the National Marine Fisheries Service, U.S. Coast Guard, U.S. Fish and Wildlife Service, other federal, state, and city agencies, and private and conservation organizations joined together in an unprecedented collaborative effort to remove submerged derelict fishing gear, net, and debris from French Frigate Shoals. The objective was to remove this potential threat to the endangered Hawaiian monk seal (Monachus schauinslandi), green sea turtles, seabirds, and other wildlife. The team, comprising two ships (USCGC Kukui and the National Oceanic and Atmospheric Administration (NOAA) research vessel Townsend Cromwell), 14 divers, 5 small boats, 2 inflatables, and 6 scientists, removed 7,500 kg of derelict fishing gear and debris.

Divers removed the derelict debris from the coral reefs around French Frigate Shoals. All items were transported to either of the two ships where gear specialists and scientists processed and collected samples of nets. Scientists took a collective weight from each load and then separated the pile into components: 1) coral rubble 2) nets by type and 3) miscellaneous lines. The various components were weighed. Scientists also collected samples from each net type, measured twine size and diameter, recorded color and material, and attempted to determine if net fragments were intentionally discarded.

The National Marine Fisheries Service (NMFS) will analyze the data collected to attempt to obtain information about the source fishery and type of fishing gear. The preliminary analyses indicate that a substantial amount of the debris was trawl gear, but also included monofilament and multifilament gillnet and seine net. Preliminary analyses also indicate that, from the collected samples, approximately 40 percent were net fragments that had been intentionally discarded. During this research and removal effort, no Hawaiian monk seals were entangled in the gear that was removed.

Future plans include another research and removal cruise in the fall of 1999, perhaps to either Pearl and Hermes Reef or Lisianski Island, and the development of an outreach and education program to nations in the Pacific Rim to heighten awareness and encourage proper disposal of fishing gear and debris. The success of this venture clearly illustrates that these types of collaborative efforts can reduce a known threat to marine wildlife, and assist in the recovery of endangered species like the Hawaiian monk seal.

Introduction

The Hawaiian monk seal (Monachus schauinslandi) is the most endangered marine mammal found exclusively in the United States¹ and is found only in the Hawaiian Islands. It is one of three species of monk seals that once were common in the warm waters of the world. At present, the estimated total population is 1, 300 to 1,400 animals.² The few remaining Mediterranean monk seals live in isolated caves and on beaches scattered through that region, while the other, the Caribbean monk seal, was last sighted in 1952 and is presumed to be extinct.³ Hawaiian monk seals live almost exclusively in the northwestern section of the Hawaiian archipelago.⁴ The low population estimates and their very restricted range have earned the species a listing as "Endangered" under the Endangered Species Act^5,6 and as "Depleted" ⁷under the Marine Mammal Protection Act. The species is also protected internationally, through the Convention on International Trade in Endangered Species of Wild Fauna and Flora and the World Conservation Union.⁸ All monk seals are also listed as endangered on the IUCN (World Conservation Union) Red List.⁹

Accounts from the 19th century reveal that Hawaiian monk seals have been threatened by humans for more than 100 years. These seals, unaccustomed to predators from land, proved easy targets for sealers in the 1800s and shipwreck victims who killed them for food.^10,11 Although directed takes have stopped, the species remains in trouble. Since 1989, the population at one site, French Frigate Shoals, has dropped nearly 55%, primarily due to low size at weaning and low juvenile survival. Surviving pups are underweight, and adults are smaller than average.¹²

Those who remain face an additional threat from human-generated marine debris. The waters frequented by monk seals are cluttered by tens of thousands of derelict, lost fishing nets and other marine debris. From 1982 to 1996, 139 monk seals were found entangled and five were known to have drowned.¹³ Since 1982, marine reef debris has caused 155 observed monk seal entanglements. Given their low population numbers, marine debris poses a serious threat to monk seals.

Methods

Recent surveys by NMFS have discovered an enormous quantity of debris on the reefs. Numerous currents from all over the Pacific Ocean converge on the monk seal's home range in the Northwest Hawaiian Islands. The archipelago acts as a comb or filter, trapping tons of debris originating hundreds and thousands of miles away. French Frigate Shoals, home to about one-third of the remaining population of Hawaiian monk seals, was found to have an average of 230 nets and net fragments per square mile for a total of approximately 27,000 nets.¹⁴ These nets sometimes form floating islands that pose an extreme entanglement risk to monk seals; curious juveniles are especially susceptible to entanglement and drowning. Without a team effort, NMFS estimated that it would them take five to ten years to clean French Frigate Shoals. The objective of the collaborative effort was to: bring non-NMFS agencies into debris mitigation efforts; develop procedures for expanded cleanup efforts; develop expertise for identification of nets; and establish study sites to assess accumulation rates and impact.

From October 26 through November 25, the Center for Marine Conservation, the National Marine Fisheries Service, U.S. Coast Guard, U.S. Fish and Wildlife Service, and other private and conservation organizations conducted a cooperative expedition to remove submerged derelict fishing gear, net, and debris from French Frigate Shoals in the Northwest Hawaiian Islands. The team consisted of two ships (USCGC Kukui and the NOAA R/V Townsend Cromwell), 14 divers, 5 small boats, 2 inflatables, and 6 scientists. Fifteen three-cubic-yard dumpsters were used to transport the processed fishing gear back to Honolulu, Hawaii were it was disposed of in the city's landfill.

Divers from the U.S. Coast Guard, Navy, and the National Oceanic and Atmospheric Administration surveyed and removed debris either by using SCUBA or by snorkeling. Divers transported the fishing gear and net in inflatable rafts to either the United States Coast Guard Cutter Kukui or the NOAA research vessel, Townsend Cromwell, where gear specialists and scientists processed and collected samples of the fishing gear. Scientists recorded a collective weight from each load and separated the pile into components: 1) coral rubble 2) nets by type and 3) miscellaneous lines. The various components were then weighed. Scientists also sampled each net type, measured mesh size and twine diameter, recorded color and material, and attempted to determine if net fragments were intentionally discarded. A net fragment was considered to have been intentionally discarded if it included edges that were judged to have been obviously cut along a row of meshes or a seam. The amount of marine fouling on the debris was also recorded.

Derelict fishing gear poses a threat not only to Hawaiian monk seals, but also to other forms of marine wildlife. These nets can kill coral and damage reefs, which are essential habitats to monk seals, fish, sea turtles, sharks, and hundreds of other marine species. Therefore, to assess accumulation rates and the impact of derelict fishing gear on coral reefs, NMFS established a number of study sites. Two study sites were cleared and will be monitored to estimate accumulation rates. One adjacent study site was left "untreated" and will be used both as a control for accumulation rates and to study the impact of this debris on the coral reef ecosystem. In addition, some nets were intentionally left in place because scientists determined that removing these nets would have harmed and damaged the reef, and that they did not represent an entanglement threat, as they were heavily encrusted and incorporated into the coral reef community.

Results

Approximately 13.8 sq. km. were surveyed, representing 4.5 % of the area of French Frigate Shoals less than 5 fathoms deep. The team removed approximately 7,500 kg of derelict fishing gear and debris. Six thousand kg. were removed during the six days that the U.S. Coast Guard and the USCGC Kukui participated in the removal efforts. NOAA divers on the Townsend Cromwell remained on the site until November 23 and gathered an additional 1.5 kg. of debris. During this research and removal effort, no Hawaiian monk seals were entangled in the gear that was removed.

NMFS will analyze the data collected to attempt to determine information about the source fishery and type of fishing gear. Preliminary analyses indicate that a substantial amount was trawl gear, although monofilament and multifilament gillnet and seine nets were also present. Approximately 40% of the net fragments were judged to have been intentionally discarded. Many of the nets and lines were heavily fouled with encrusting biota, indicating they had been adrift or present on the reef for a long time. A final report is expected by June of 1999.

Additional work is being done by NMFS to characterize the extent of monk seal entanglement, estimate the amount of debris in the Northwest Hawaiian Islands, evaluate the rate that debris is being added to coral reefs, and then remove beached and submerged debris from other areas. After this debris removal effort, NMFS can now revise its estimate of the number of nets that remain on French Frigate Shoals, its estimate of nets per square kilometer, and the amount of time it will take to clean French Frigate Shoals.

Discussion

Much net still remains in the Northwest Hawaiian Islands--this critical habitat for Hawaiian monk seals. The partners plan to continue these debris removal efforts in 1999. Another cruise involving the USCGC Kukui and the NOAA vessel R/V Townsend Cromwell is planned for the fall of 1999 to either Pearl and Hermes Reef or Lisianski Island, two sites that have been identified where debris may have significant impact. NMFS estimates that there may be as many as 38,000 nets and net fragments on Pearl and Hermes Reef. Lisianski Island may have fewer nets, because it is a smaller site and does not comprise an atoll complex with extensive shallow reef area. Nonetheless, the Hawaiian monk seal population at Lisianski experiences the highest entanglement rate of the six major monk seal breeding populations.

CMC and NMFS plan to develop a net reference collection to assist their efforts to better identify the source, type of gear, and potentially the fisheries that use the types of gear recovered during this effort. This reference will aid in identifying material from future marine debris removal cruises, and volunteer cleanups such as: the CMC's international coastal cleanup and its associated underwater cleanups. Other countries should be invited to participate, and domestic and international gear specialists should be sought to help identify the source of and type of gear.

An important component of the program is outreach and education. The information gathered from this cruise and NMFS's previous cruises provides further evidence that marine debris and derelict fishing gear persist in the marine environment and continue to pose a threat to marine life. Although the high fouling of some debris items suggests that they were lost or discarded before ratification of MARPOL V in 1989, we should work domestically as well as with nations throughout the Pacific Rim to do the following:

Remind and reinforce the provisions of MARPOL Annex V; Encourage nations that have not signed and ratified MARPOL Annex V to do so; Ask nations to recommit to working with their fisheries to eliminate the intentional discard of marine debris and fishing gear into the marine environment; Seek the help of nations to identify the sources of marine debris and derelict fishing gear;

Encourage nations to participate in international beach and underwater cleanup efforts;

Urge nations to assist in developing educational programs and materials targeted at their fishing and other maritime industries, stressing the importance of the proper disposal of gear.

The outreach and education component is important both to increase awareness of the problem and to encourage measures to prevent the further degradation of the marine environment.

Finally, the collaborative effort discussed in this paper provides an example for other recovery efforts involving threatened and endangered species. Future, similar partnerships could be formed to undertake important medical-related research and health assessments of wild pinniped populations. With ever decreasing federal funding, partnerships that involve the federal government, the private sector, and the conservation community show great promise as a way to achieve mutual conservation and recovery measures.

References

1.  Gilmartin William G. 1983. NOAA, Recovery Plan for the Hawaiian Monk Seal, Monachus schauinslandi. P.5.

2.  Ragen TJ, TC Johanos. 1998. Population Dynamics and Status of the Hawaiian Monk Seal. Abstract for the Workshop on the Biology and Conservation of the World's Endangered Monk Seals. World Marine Mammal Science Conference. P.29.

3.  Id. At 1

4.  Gilmartin William G. 1983. NOAA, Recovery Plan for the Hawaiian Monk Seal, Monachus schauinslandi. P. 5.

5.  16 U.S.C.A. 1531

6.  41 Federal Register 51611 1976.

7.  41 Federal Register 30120 1976.

8.  Convention of International trade in Endangered Species of Wild Fauna & Flora, Mar. 3, 1973, 27 U.S.T. 1087, T.I.A.S. No. 8247

9.  IUCN, supra note 11, at 412-415.

10. Id. At 1-2.

11. Id. At 1.

12. SW Fisheries Report, supra note 13, at 21-25.: Ragen and Johanos supra note 2 at 28.

13. Henderson JR. Entanglements of Hawaiian Monk Seals in Marine Debris, 1982-1996, and the Effects of MARPOL Annex V. Abstract for Workshop on the Biology and Conservation of the World's Endangered Monk Seals. World Marine Mammal Conference. 1998.

14. Boland Ray. National Marine Fisheries Service Southwest Fisheries Science Center, Honolulu, Hawaii. Personal communication.