COLLISIONS BETWEEN SHIPS AND WHALES

TLDR

Although collisions with motorized ships are a recognized source of whale mortality, little has been done to compile information on the frequency of their occurrence or contributing factors. The study aims to assess contributing factors to ship‑whale collisions by compiling descriptions of 58 incidents. The authors searched historical records and computerized stranding databases for ship‑whale strike evidence and compiled descriptions of 58 collisions. Historical data reveal that fatal ship strikes began in the late 1800s, rose sharply from the 1950s to 1970s, and are most common in fin whales, with one‑third of fin and right whale strandings involving strikes; all vessel sizes can cause lethal injuries, especially ships ≥80 m traveling >14 kn, and reducing speed below 14 kn could mitigate impacts on vulnerable populations.

Abstract

A bstract Although collisions with motorized ships are a recognized source of whale mortality, little has been done to compile information on the frequency of their occurrence or contributing factors. We searched historical records and computerized stranding databases for evidence of ship strikes involving great whales ( i. e. , baleen whales and the sperm whale). Historical records suggest that ship strikes fatal to whales first occurred late in the 1800s as ships began to reach speeds of 13‐15 kn, remained infrequent until about 1950, and then increased during the 1950s‐1970s as the number and speed of ships increased. Of 11 species known to be hit by ships, fin whales ( Balaenoptera physalus ) are struck most frequently; right whales ( Eubalaena glacialis and E. australis ), humpback whales ( Megaptera novaeangliae ), sperm whales ( Physeter catodon ), and gray whales ( Escbricbtius robustus ) are hit commonly. In some areas, one‐third of all fin whale and right whale strandings appear to involve ship strikes. To assess contributing factors, we compiled descriptions of 58 collisions. They indicate that all sizes and types of vessels can hit whales; most lethal or severe injuries are caused by ships 80 m or longer; whales usually are not seen beforehand or are seen too late to be avoided; and most lethal or severe injuries involve ships travelling 14 kn or faster. Ship strikes can significantly affect small populations of whales, such as northern right whales in the western North Atlantic. In areas where special caution is needed to avoid such events, measures to reduce the vessel speed below 14 kn may be beneficial.