An example of minor entanglement scars. Photo: NEAq
Clearly right whales are well-adapted to manage all of the above, but what concerns me most are the things they are not adapted to: the chronic noise pollution from the extensive vessel traffic that transits day and night throughout their range which masks their vocalizations and limits their ability to find each other; the fear that must be palpable when one of those vessels gets louder and louder as it unknowingly steams towards them but can't be seen—which way to turn to escape the deadly hull and propeller?; and the panic that must set in when, while searching for food at depth with a mouth wide open, an unseen rope attaching a buoy at the surface to fishing gear at depth becomes caught in the long baleen plates hanging from the roof of the mouth, causing a frantic struggle to get to the surface to breath and to hopefully escape from the heavy gear and constricting ropes.
Catalog #2301 entangled in 2004. This whale had rope through the mouth which was tightly bound around the flipper, an entanglement that ultimately lead to #2301's death six months later. Photo: NEAq.
This latter scenario of entanglement is the focus of a recently published paper by myself and colleagues here at the New England Aquarium. In this paper we reviewed up to 30 years (1980-2009) of photographs for each individual right whale, looked for evidence of entanglement related scarring on all different areas of the body, and noted which animals were witnessed carrying rope likely to be from fishing gear. We determined that 83% of this small population has evidence of at least one entanglement interaction, with some animals experiencing as many as seven entanglement events.
Due to dedicated survey efforts, many whales are sighted and well-photographed from one year to the next, making it possible to notice when new scars appear in a relatively small time frame. Using this well-documented part of the population, we determined that annually, on average, 26% of these animals had obtained new entanglement scars or were carrying gear.
A total of 1,032 unique interactions were documented, resulting in minor to moderate scarring for many right whales, but serious and often fatal entanglements for 86 individuals. And the rate of serious entanglements has increased over the 30 year period.
An example of significant entanglement scars. Photo: NEAq
The entanglement issue remains the most serious conservation concern facing this small population. Expanded fishing effort along the eastern seaboard over the past several decades and the use of stronger ropes and heavier gear is just one more insult we have imposed in the oceanic realm, where it can be all too easy to ignore the impacts. Right whales are in a very real sense a "canary in the coal mine" for understanding what is happening offshore. And we will continue our efforts to work with government and industry to try to find solutions to this complex issue.
If you are interested in reading the recently published paper for more details, it is available for free at the Marine Ecology Progress Series journal.
– Amy Knowlton