Monitoring North Atlantic right whale Eubalaena glacialis entanglement rates: a 30 yr retrospective

Abstract

Entanglement in non-mobile fishing gear has been identified as one of the leading causes of mortality in North Atlantic right whales Eubalaena glacialis. To investigate this issue further, all available photographs of right whales taken from 1980 to 2009 were examined for evidence of entanglement with gear used in fisheries based on presence of rope or netting on the whale or scars inferred to have been caused by an encounter with rope. Photographs of 626 individual whales were assessed and 1032 unique entanglement events were documented. Of the 626 animals, 519 (82.9%) had been entangled at least once and 306 of the 519 (59.0%) had been entangled more than once. Males and females were entangled at similar rates. Juveniles were entangled at a higher rate than adults. On average, 25.9% of adequately photographed animals acquired new wounds or scars from fishing gear annually with no significant trend over time detected. However, the annual percentage of animals observed with rope on the body increased significantly during the study period, suggesting that it is becoming more difficult for whales to free themselves completely from fishing gear. Such high annual rates of entanglement remain a serious conservation concern for right whales because entanglements can have both lethal and sub-lethal effects. Federally required changes to fixed-gear fisheries in US waters have not reduced serious injuries and mortality to legally required levels. Here we show how documenting various annual rates of entanglement can monitor progress and impacts that fishing gear regulations may have on right whale recovery.

Strandings as indicators of marine mammal biodiversity and human interactions off the coast of North Carolina

“…The high rate of HI-FI strandings for humpback whales (10 of 23 or 43%) was higher than that reported during 1985-92 from New Jersey to Florida (5 of 20 or 25%) (Wiley et al, 1995). Humpback whales stranded in NC with fresh FI lesions were not necessarily entangled in gear set in NC because some whales carry entangling gear for an extended period of time before the entanglement potentially leads to the animal's death (Knowlton et al, 2012). Entanglement of whales has occurred, however, in gill nets set off NC.…”

Body condition changes arising from natural factors and fishing gear entanglements in North Atlantic right whales Eubalaena glacialis

“…As the purpose of this study was to investigate characteristics of body condition changes in right whales, only the body condition parameter was analyzed, based on observations from 1980 to 2011. The collection of visual health data follows the methodology developed for evaluating scars on right whales (Knowlton et al 2012, Schick et al 2013, Rolland et al 2016. Photographs from all sightings of an individual whale were grouped sequentially by right whale habitat region (e.g.…”

Rebuttal to published article “A review of ghost gear entanglement amongst marine mammals, reptiles and elasmobranchs” by M. Stelfox, J. Hudgins, and M. Sweet

“…Other whale studies cited from the North Atlantic focused on the frequency and impact of documented entanglements on individuals and populations, not the nature of the gear itself (Cassoff et al, 2011;Cole et al, 2006;Glass et al, 2009;Henry et al, 2012;Henry et al, 2014;Knowlton et al, 2012;Knowlton and Kraus, 2001;Nelson et al, 2007;Robbins, 2009;Robbins andMattila, 2001, 2004;van der Hoop et al, 2013).…”

“…These evaluations clearly and intentionally reported on many of the same entanglement cases, but it does not appear that Stelfox et al (2016) recognized nor accounted for this in their totals. As another example, Johnson et al (2005) summarized the gear involved in North Atlantic right and humpback whale entanglements documented between 1993 and 2002, while other aspects of these events were studied in other listed papers (e.g., Cole et al, 2006;Glass et al, 2008;Knowlton et al, 2012;Knowlton and Kraus, 2001;Nelson et al, 2007;van der Hoop et al, 2013). The cases from each published study were treated as unique events by Stelfox et al (2016), and their results are therefore patently incorrect and often counted multiple times.…”