Frequent encounters with the seafloor increase right whales’ risk of entanglement in fishing groundlines

Pk Hamilton,Sd Kraus

doi:10.3354/esr00963

Abstract

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 39:235-246 (2019) - DOI: https://doi.org/10.3354/esr00963 ESR Special: Marine vertebrate bycatch: problems and solutions Frequent encounters with the seafloor increase right whales’ risk of entanglement in fishing groundlines Philip K. Hamilton*, Scott D. Kraus Anderson Cabot Center for Ocean Life, New England Aquarium, Central Wharf, Boston, MA 02110, USA *Corresponding author: phamiltn@neaq.org ABSTRACT: North Atlantic right whales Eubalaena glacialis utilize the entire water column and are frequently entangled in ropes from fishing gear. Data from telemetry tags have shown that right whales can swim/feed at or near the seafloor. Because those data are limited, some uncertainty remains regarding the frequency of dives to the seafloor and thus the likelihood of right whale encounters with fishing ropes there. The North Atlantic right whale photo-identification catalog was used to determine the number of sightings of right whales with seafloor sediment on their bodies and the relative frequency and geographic location of those seafloor encounters. Between 1980 and 2016, there were 2053 detections of right whales with ‘mud’ on their bodies, which represents 2.9% of all sightings (n = 70593), or 58.2% of all cataloged whales (n = 730). Although muddy right whales were found throughout their range and in all months, 92.7% of all detections occurred in the Bay of Fundy in the summer where there was an average annual detection rate of 7.3%, with a maximum of 26% of sightings in 2010. Mud was found on whales of all age classes including calves of the year, and equally among males and females. These seafloor encounters suggest that any rope resting on, or floating above, the seafloor could pose an entanglement hazard. The use of sinking groundlines likely reduces the risk of entanglements for whales swimming near the seafloor, but may not eliminate the risk for whales making contact with the sediment. KEY WORDS: Right whale · Seafloor sediment · Mud · Bay of Fundy · Entanglement · Eubalaena glacialis Full text in pdf format PreviousNextCite this article as: Hamilton PK, Kraus SD (2019) Frequent encounters with the seafloor increase right whales’ risk of entanglement in fishing groundlines. Endang Species Res 39:235-246. https://doi.org/10.3354/esr00963 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 39. Online publication date: July 25, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

Highlights

Entanglements in fishing gear are a known source of injury and mortality to large whales in the western North Atlantic (Kraus 1990, Knowlton & Kraus 2001, Johnson et al 2005, 2007, Kraus et al 2005, 2016, Glass et al 2010, Pace et al 2014)
Distribution, and characteristics of such seafloor encounters in order to evaluate the risks of entanglement in fishing gear placed near the ocean floor
Right whales were seen with mud in most of the

Summary

Introduction

Entanglements in fishing gear are a known source of injury and mortality to large whales in the western North Atlantic (Kraus 1990, Knowlton & Kraus 2001, Johnson et al 2005, 2007, Kraus et al 2005, 2016, Glass et al 2010, Pace et al 2014). Three types of fixed fishing gear may create a risk of near seafloor entanglements for right whales: groundfish gillnets, bottom-set long lines, and pot/ trap gear. Groundlines traditionally were made with floating rope to avoid chafing with rocks on the seafloor, but starting in April 2008, NMFS required all pot fishermen in the Northeast USA seaward of an exemption line in Maine to use sinking groundlines (NMFS 2007). Canada has no such regulations on groundlines. Floating groundlines have an arc height of 1−5 m above the seafloor depending on the currents and how closely spaced the traps in the trawl are set (McKiernan et al 2002, Brillant & Trippel 2010). Brillant & Trippel (2010) showed average arc heights of 1−2 m for groundlines between Canadian lobster traps in the Bay of Fundy and suggested that these ropes present a low risk to right whales because they are less than the 3 m diameter of a right whale’s body

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