Slow, Cruel and Pointless: Cetaceans and Entanglement
A Topic Overview by Cloe Waterfield, Twentyfifty, for Conscious Breath Adventures
February 2010
January, 13th, 2010, Hawaii: “The entanglement remains life threatening. One of the wraps is seated in a deep wound just forward of the dorsal fin. The animal is in poor condition. It is emaciated, has a heavy load of orange-colored cyamid amphipods (whale lice), is blotchy-looking, and has two line scars between the blowhole and the wound in front of the dorsal.”
Of the numerous threats facing cetaceans, injury and death by entrapment in fishing gear must be one of the most heart-wrenching to witness. While reports are thankfully rare on the Silver Bank, a badly entangled young calf was encountered in 2009, and despite a valiant but unsuccessful day long effort to free her, the odds for survival were small and she almost certainly perished as a result. This month we review the issue and efforts to ameliorate a universally tragic consequence of our sharing the seas, and its bounty, with marine animals.
It has been estimated that over 300,000 cetaceans worldwide, die each year as a result of entanglement in lost or active fishing gear (Reid et al 2006), including pot gear (lobster and crab traps), long line and most deadly of all, gill nets (Clapham et al 1999). In Australia, shark nets pose a problem, particularly to humpback whales (Megaptera novaeangliae), a coastal species (Remove Shark Nets, 2010). Along with ship strikes, it is considered a major threat at the population level to the great whales (Clapham et al 1999). Pinnipeds, small whales and dolphins may drown relatively rapidly but for great whales like the humpback, able to drag heavy line, gear and buoys long distances it may be one of the cruelest threats to the species.
Entanglement incidents are widespread although research acknowledges what we see and observe is very likely an underestimation. Tired, emaciated whales, dragging heavy line and buoys long distances, rapidly lose blubber stores and on dying, carcasses will quickly sink and are unrecoverable. Still, entanglement in fishing gear is cited as the most frequent cause of injury and death in the Atlantic humpback population (Wiley et al 1995, Barco et al 2002). In the Pacific, photo identification studies showed that around 30% of individuals in Hawaii and over 50% in southwest Alaska (Neilson et al, 2009) showed scarring consistent with entanglement. For humpbacks this is frequently around the tail (caudal peduncle) and mouth.
Populations in heavily fished regions like the eastern seaboard of the United States are especially at risk (Clapham et al 1999). Numbering only 250-300, studies showed that over 70% of the critically endangered North Atlantic right whale (Eubalaena glacialis), showed scarification consistent with entanglement (Johnson et al 2005).
Interestingly, growth of the whale watching industry in the northeastern U.S. over the last 30-40 years added not only a dimension of empathy and concern for the animals but importantly extra eyes looking out for them. Prior reports to authorities were sporadic and when animals did wash ashore, fishing gear had often been cut away and removed (NOAA, 2010).
Atlantic Large Whale Disentanglement Network
Work to improve the problem focuses on reporting and disentanglement efforts as well as increasing understanding of gear type and subsequent gear modification. More reporting and evidence is needed of gear type first and foremost (Neilson, 2009). Technical modifications include weak links which will rupture, break or experience calculated material failure upon receiving sufficient load. Or ‘pingers’ which provide an acoustic warning in the hopes that whales will avoid the area (Johnson et al 2005). Work on incidental catch of small cetaceans in a north Atlantic long line fishery (Pilot whales and Risso’s dolphins) showed that reducing line length below 20 nautical miles, reduced entanglement events (Garrison, 2007).
Of course, one of the very best things you can do to help whales and the oceans every day is make ethical seafood choices. Do your research: there is a lot of conflicting information. Wild netted, trawled and long line caught species may well entail both by-catch and entanglement risk.
The extent of the entanglement problem and the sheer scope of the oceans means that these tragedies will continue but we have come a long way in emergency response. On the eastern seaboard of the U.S. the federal government has established the Atlantic Large Whale Disentanglement Network (with authorization under the Marine Mammal Protection Act and Endangered Species Act). Initially set up in Cape Cod in 1984 at the Provincetown Center for Coastal Studies (PCCS), the center operates a network of response teams including a number of agencies and trained respondents.
In partnership with NOAA, the center developed a technique called “kegging,” a modified trick of 19th century Yankee whalers. After harpooning a whale, whalers would attach kegs (barrels) to the harpoon line to tire and slow the animal. PCCS response teams snap a control line to an existing trailing entanglement line then additional buoys or floats can be safely attached to slow the whale down but allow easy snap on/snap off release in the unfortunate event that a rescue attempt fails. Freeing a forty ton great whale is a task left to trained responders: although the Center notes that one of the most important elements of any rescue operation is that of standing by or staying with an observed entangled whale, until rescue teams can get there.
On Boxing Day 2009 (December 26th), the determination and tenacity of two teenage boys to free an entangled humpback in The Bahamas was tested with success. The story also illustrates why it is so important to let professionals complete rescue efforts. The boys managed to cut most of the culprit fishing net away but it took a diver to remove the last pieces. The PCCS stress that removing some but not all of tangled lines can be worse than none: as the load is lightened and the animal can dive again, it is gone. This story had a happy ending. As we work towards cleaning up the oceans, step by step, we hope there are many more.
For sources for this overview and further reading, please see:
Barco, S. G., Mclellan, W. A., Allen, J. M., Asmutis-Silvia, R. A., Mallon-Day, R., Meagher, E. M., Pabst, D. A., Robbins, J., Seton, R. E., Swingle, W. M., Weinrich M. T., Clapham P. J., 2002, Population identity of humpback whales (Megaptera novaeangliae) in the waters of the US mid-Atlantic states. Journal of Cetacean Research and Management 4:135–141.
Clapham, P.J., Young, S. B., Brownell, Jr., L.B., 1999, Baleen Whales: Conservation Issues And The Status Of The Most Endangered Populations, Mammal Rev. 1999, Volume 29, No. 1, 35–60
Garrison, L.P. 2007, Interactions between marine mammals and pelagic longline fishing gear in the U.S. Atlantic Ocean between 1992 and 2004, Fish. Bull. 105:408–417
Johnson, A., Salvador, G., Kenney, J., Robbins, J., Kraus, S., Landry, S., Clapham, P., 2005, Fishing Gear Involved In Entanglements Of Right And Humpback Whales, Marine Mammal Science, 21(4):635-645
Reid, A. J., Drinker, P., Northridge, S., 2006, Bycatch of marine mammals in U.S. and global fisheries. Conservation Biology. 20:163-169.
Neilson, J.L., Straley, J.M., Gabriele, C. M., Hills, S., 2009, Non-lethal entanglement of humpback whales (Megaptera novaeangliae)in fishing gear in northern Southeast Alaska, Journal of Biogeography 36, 452–464
Wiley, D. N., Pitchford T. D., Gannon, D. P. 1995. Stranding and mortality of humpback whales, Megaptera novaeangliae, in the mid-Atlantic and southeast United States, 1985–1992. Fishery Bulletin 93:196–205
www.thebahamasweekly.com/publish/international/Teens_spearhead_rescue_of_entangled_humpback_whale_in_The_Bahamas9153.shtml
www.edf.org/page.cfm?tagID=1521
www.examiner.com/x-20079-Honolulu-Environmental-Policy-Examiner~y2010m2d3-Entangled-humpback-whale-resighted-off-Kona-coast
www.examiner.com/x-/x-20079-Honolulu-Environmental-Policy-Examiner~y2010m1d12-6th-Entangled-humpback-whale-continues-to-elude
www.hawaiihumpbackwhale.noaa.gov/res/marine_debris.html
www.removesharknets.com/?p=123
www.animalsinourhearts.com/whales/help-the-whales.html
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