Details

Autor(en) / Beteiligte

• Stewart, Joshua D.
• Durban, John W.
• Knowlton, Amy R.
• Lynn, Morgan S.
• Fearnbach, Holly
• Barbaro, Jacob
• Perryman, Wayne L.
• Miller, Carolyn A.
• Moore, Michael J.

Titel

Decreasing body lengths in North Atlantic right whales

Ist Teil von

• Current biology, 2021-07, Vol.31 (14), p.3174-3179.e3

Ort / Verlag

England: Elsevier Inc

Erscheinungsjahr

2021

Quelle

MEDLINE

Beschreibungen/Notizen

• 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. •Whales with severe entanglements in fishing gear are stunted•Whales whose mothers were entangled while nursing are stunted•Body lengths have been decreasing since 1981•Cumulative impacts in addition to entanglements may contribute to stunted growth Stewart et al. examine trends in body lengths in endangered North Atlantic right whales using aerial photogrammetry. They show that whales that have experienced severe entanglements in fishing gear are shorter than whales with no documented entanglements, and that body lengths of right whales have been decreasing over the past four decades.