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Knowlton AR, Clark JS, Hamilton PK, Kraus SD, Pettis HM, Rolland RM, Schick RS. Fishing gear entanglement threatens recovery of critically endangered North Atlantic right whales. CONSERVATION SCIENCE AND PRACTICE 2022. [DOI: 10.1111/csp2.12736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Affiliation(s)
- Amy R. Knowlton
- Anderson Cabot Center for Ocean Life New England Aquarium, Central Wharf Boston Massachusetts USA
| | - James S. Clark
- Nicholas School of the Environment Duke University Durham North Carolina USA
| | - Philip K. Hamilton
- Anderson Cabot Center for Ocean Life New England Aquarium, Central Wharf Boston Massachusetts USA
| | - Scott D. Kraus
- Anderson Cabot Center for Ocean Life New England Aquarium, Central Wharf Boston Massachusetts USA
| | - Heather M. Pettis
- Anderson Cabot Center for Ocean Life New England Aquarium, Central Wharf Boston Massachusetts USA
| | - Rosalind M. Rolland
- Anderson Cabot Center for Ocean Life New England Aquarium, Central Wharf Boston Massachusetts USA
| | - Robert S. Schick
- Nicholas School of the Environment Duke University Durham North Carolina USA
- Centre for Research into Ecological and Environmental Modelling School of Mathematics and Statistics, University of St Andrews St Andrews UK
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Stewart JD, Durban JW, Knowlton AR, Lynn MS, Fearnbach H, Barbaro J, Perryman WL, Miller CA, Moore MJ. Decreasing body lengths in North Atlantic right whales. Curr Biol 2021; 31:3174-3179.e3. [PMID: 34087102 DOI: 10.1016/j.cub.2021.04.067] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 04/12/2021] [Accepted: 04/26/2021] [Indexed: 11/19/2022]
Abstract
Whales are now largely protected from direct harvest, leading to partial recoveries in many previously depleted species.1 However, most populations remain far below their historical abundances and incidental human impacts, especially vessel strikes and entanglement in fishing gear, are increasingly recognized as key threats.2 In addition, climate-driven changes to prey dynamics are impacting the seasonal foraging grounds of many baleen whales.2 In many cases these impacts result directly in mortality. But it is less clear how widespread and increasing sub-lethal impacts are affecting life history, individual fitness, and population viability. We evaluated changes in body lengths of North Atlantic right whales (NARW) using aerial photogrammetry measurements collected from crewed aircraft and remotely operated drones over a 20-year period (Figure 1). NARW have been monitored consistently since the 1980s and have been declining in abundance since 2011 due primarily to deaths associated with entanglements in active fishing gear and vessel strikes.3 High rates of sub-lethal injuries and individual-level information on age, size and observed entanglements make this an ideal population to evaluate the effects that these widespread stressors may have on individual fitness. We find that entanglements in fishing gear are associated with shorter whales, and that body lengths have been decreasing since 1981. Arrested growth may lead to reduced reproductive success4,5 and increased probability of lethal gear entanglements.6 These results show that sub-lethal stressors threaten the recoveries of vulnerable whale populations even in the absence of direct harvest.
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Affiliation(s)
- Joshua D Stewart
- National Research Council Postdoctoral Fellow for Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla Shores Drive, La Jolla, CA, 92037, USA.
| | - John W Durban
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla Shores Drive, La Jolla, CA, 92037, USA; Southall Environmental Associates, Inc., Soquel Dr., Aptos, CA, 95003, USA
| | - Amy R Knowlton
- Anderson Cabot Center for Ocean Life, New England Aquarium, Boston, MA, 02110, USA
| | - Morgan S Lynn
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla Shores Drive, La Jolla, CA, 92037, USA
| | - Holly Fearnbach
- Marine Mammal Research Program, SR3, SeaLife Response, Rehabilitation and Research, S 216th St., Des Moines, WA, 98198, USA
| | - Jacob Barbaro
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla Shores Drive, La Jolla, CA, 92037, USA
| | - Wayne L Perryman
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla Shores Drive, La Jolla, CA, 92037, USA
| | - Carolyn A Miller
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole Rd., Woods Hole, MA, 02543, USA
| | - Michael J Moore
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole Rd., Woods Hole, MA, 02543, USA
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Ramp C, Gaspard D, Gavrilchuk K, Unger M, Schleimer A, Delarue J, Landry S, Sears R. Up in the air: drone images reveal underestimation of entanglement rates in large rorqual whales. ENDANGER SPECIES RES 2021. [DOI: 10.3354/esr01084] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Entanglement in fishing gear is a significant threat to many cetaceans. For the 2 largest species, the blue whale Balaenoptera musculus and the fin whale B. physalus, reports of entangled individuals are rare, leading to the assumption that entanglements are not common. Studies of interaction with fisheries in other species often rely on the presence of scars from previous entanglements. Here, scar detection rates were first examined in humpback Megaptera novaeangliae, fin and blue whales using standard vessel-based photo-identification photographs collected between 2009 and 2016 in the Gulf of St. Lawrence, Canada. We then examined aerial images of fin whales collected with a drone in 2018 and 2019 and compared both methods. Entanglement rates were 6.5% for fin and 13.1% for blue whales using photo-identification images of individuals. Prominent scarring was observed around the tail and caudal peduncle, visible only when animals lifted those body sections above water when diving. For the small subset of pictures which captured the entire caudal peduncle, entanglement rates ranged between 60% for blue and 80% for fin whales. This result was similar to the 85% entanglement rate estimated in humpback whales. The assessment of aerial-based photography yielded an entanglement rate of 44.1 to 54.7% in fin whales. Scars were always around the peduncle, often the tail, rarely the dorsal fin and never around the pectoral fins, while the mouth cannot be examined from above. Thus, in species that do not regularly expose their tail or peduncle, aerial imagery is the preferred method to quantify entanglement rates by assessment of scars.
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Affiliation(s)
- C Ramp
- Mingan Island Cetacean Study, St Lambert, J4P 1T3, QC, Canada
- Sea Mammal Research Unit, University of St Andrews, Fife KY16 8LB, UK
| | - D Gaspard
- Mingan Island Cetacean Study, St Lambert, J4P 1T3, QC, Canada
| | - K Gavrilchuk
- Mingan Island Cetacean Study, St Lambert, J4P 1T3, QC, Canada
| | - M Unger
- Mingan Island Cetacean Study, St Lambert, J4P 1T3, QC, Canada
| | - A Schleimer
- Mingan Island Cetacean Study, St Lambert, J4P 1T3, QC, Canada
- Sea Mammal Research Unit, University of St Andrews, Fife KY16 8LB, UK
- Marine Evolution and Conservation, Groningen Institute for Evolutionary Life Sciences, University of Groningen, 9700 CC, Groningen, The Netherlands
| | - J Delarue
- Mingan Island Cetacean Study, St Lambert, J4P 1T3, QC, Canada
| | - S Landry
- Center for Coastal Studies, Provincetown, 02657, MA, USA
| | - R Sears
- Mingan Island Cetacean Study, St Lambert, J4P 1T3, QC, Canada
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