Data from: Unobserved individual and population level impacts of fishing gear entanglements on North Atlantic right whales

Fishing gear entanglements can compromise health and lower survival and
reproductive output of wildlife, which can slow population growth or cause
population declines. However, entanglements may go unobserved, making it
difficult to quantify their effects on individuals’ vital rates and a
population’s trajectory. Fishing gear entanglements are a leading cause of
death for North Atlantic right whales, Eubalaena glacialis, an endangered
species whose population has declined substantially over the last decade.
Key sources of observation error have not been addressed when quantifying
the effects of entanglement on this species. We formulated a hidden Markov
model that integrated 28 years of photo identification records, visual
health assessments, entanglement assessments, and hormone assays to
estimate body condition dynamics, and entanglement, survival, and
reproductive rates of female North Atlantic right whales. The model also
accounted for observation errors, including entanglements and reproductive
events that were unobserved. Whales entangled in fishing gear were
drastically more likely to experience declines in body condition and had
lower survival rates than whales that were not entangled. Additionally,
only whales in good body condition became pregnant. Between 1994 and 2021
entanglements reduced the expected number of calves born by 12.9% (95%
credible interval: 8.2% – 19.6%) and the expected number of females alive
at the end of 2021 by 18.5% (95% credible interval: 8.6% – 29.4%). Fishing
gear entanglements have reduced the North Atlantic right whale
population’s capacity to recover and have increased the importance of the
health and survival of the remaining living whales. Therefore, reducing
the risk of fishing gear entanglements is likely necessary for the
population to recover.