Marine Debris

Due to their bathymetry and remote location in the middle of the North Pacific Ocean, the Northwestern Hawaiian Islands (NWHI) act as a sieve, catching much of the marine debris circling throughout the Pacific Rim. The risk of entanglement from nets and other marine debris here is a major threat to Hawaiian monk seal survival.

NOAA Field team disentangles a weaned pup at Kure Atoll (video contains no audio).
An entangled weaned pup.
An entangled weaned pup.
Marine debris washing ashore.
Marine debris washing ashore.

Hawaiian monk seals have one of the highest entanglement rates of any pinniped species, and pups are the most often entangled. From 1982-2014 a total of 347 seals have been found entangled in marine debris, of which 237 (68%) were rescued, 93 escaped unaided, 9 died, and the fate of 8 others is unknown. About 96% of all entanglements have been observed in the Northwestern Hawaiian Islands (NWHI), however, due to the remoteness of these islands, it is unknown how many additional seals drown or die from entanglement when researchers are not present.

Marine debris capable of entangling monk seals and other wildlife has been collected and removed from the beaches in the NWHI since 1982. Efforts were expanded to include removal of debris from the reefs, and from 1996-2014, NOAA's marine debris team removed nearly 826 metric tons (MT) of derelict fishing gear from various locations within the NWHI. Areas surveyed and cleaned include Pearl and Hermes Atoll, Midway Atoll, Kure Atoll, Lisianski Island, Laysan Island, Maro Reef, and French Frigate Shoals. Even though intensive efforts are undertaken by NOAA and other agencies to remove debris from beaches and nearshore waters, the accumulation rates in the NWHI appear to remain constant.

Further Reading:

Boland RC, Donohue MJ
2003. Marine debris accumulation in the nearshore marine habitat of the endangered Hawaiian monk seal, Monachus schauinslandi, 1999-2001. Marine Pollution Bulletin, 46, 183-194. DOI: 10.1016/s0025-326x(03)00291-1
Donohue MJ, Boland RC, Sramek CM, Antonelis GA
2001. Derelict Fishing Gear in the Northwestern Hawaiian Islands: Diving Surveys and Debris Removal in 1999 Confirm Threat to Coral Reef Ecosystems. Mar. Poll. Bull. 42(12): 1301-1312. DOI: 10.1016/S0025-326X(01)00139-4
Henderson JR
2001. A pre- and post-MARPOL Annex V summary of Hawaiian monk seal entanglements and marine debris accumulation in the Northwestern Hawaiian Islands, 1982-1998. Mar. Poll. Bull. 42(7): 584-589. DOI: 10.1016/s0025-326x(00)00204-6