Conservation Ecology – Amy R. Knowlton, Jooke Robbins, Scott Landry, Henry A. McKenna, Scott D. Kraus and Timothy Werner. doi: 10.1111/cobi.12590

“Entanglement in fixed fishing gear is a conservation concern for whales worldwide, including in the United States where deaths of North Atlantic right and humpback whales have exceeded management limits for decades. We examined fishing gear removed from live and dead entangled whales along the US East Coast and the Canadian Maritimes from 1994–2010 to investigate rope polymer type, breaking strength, and diameter in relation to whale species, age, and injury severity. For the 132 retrieved ropes from 70 cases, average tested breaking strength was 2616 lbs (SD 1863; range 180–8910 lbs), which is 26% lower than strength at manufacture (mean 3530 SD 2224; range 650-12000 lbs). Median rope diameter was 3/8 inch. Right and humpback whales were found in ropes with significantly stronger breaking strengths at manufacture than minke whales (4338 3850 and 2353 mean lbs, respectively). Adult right whales were found in stronger ropes (mean 7664 lbs) than juvenile right whales (mean 3446 lbs) and all humpback whale age classes (mean 3906 lbs). For right whales, injuries have become more severe over the past three decades, possibly due to changes in rope manufacturing in the mid 1990’s that resulted in stronger ropes at the same diameter. Our results suggest that broad adoption of ropes with breaking strengths of 1700 lbs or less could reduce the number of life-threatening entanglements for large whales by at least 72%, and still be strong enough to withstand the routine forces involved in many fishing operations. A reduction of this magnitude would achieve nearly all of the mitigation legally required for US stocks of North Atlantic right and humpback whales. Reduced breaking strength ropes should be developed and tested to determine the feasibility of its use in a variety of fisheries.”