Collisions between marine vessels and whales are a recognized issue in marine conservation. Public concern often highlights cruise ships, but the reality is that many types of vessels are involved in these incidents. While whales are large marine mammals, their presence near busy shipping lanes can lead to unintended and sometimes fatal encounters. This article explores the frequency of these collisions, the factors that contribute to them, their impact on whale populations, and the efforts underway to reduce their occurrence.
The Reality of Ship-Whale Encounters
Ship strikes, collisions between ships and whales, are a global conservation concern that has been increasing in frequency. While cruise ships are implicated, a wide range of vessels contribute, including cargo ships, ferries, military vessels, whale-watching boats, and recreational private watercraft. Documented cases involve at least 21 large whale species, often in coastal areas where vessels and whales share waters. The actual number of ship strikes is likely higher than reported, as many go unnoticed, especially with large vessels, and studies suggest documented deaths are minimum values. Evidence indicates tens of thousands of whales are injured or killed annually by ship strikes.
Factors Contributing to Collisions
Several factors contribute to ship-whale collisions. Increased global maritime traffic means more vessels traverse whale habitats, raising encounter likelihood, as shipping routes frequently intersect important whale habitats. High vessel speeds make it difficult for operators to detect whales and react, and for whales to avoid ships. Whales’ natural behaviors, such as spending significant time near the surface, also increase risk. Poor visibility due to weather conditions and underwater vessel noise further reduce detection abilities for both.
The Impact on Whale Populations
Collisions can severely injure or kill whales. Injuries typically fall into two categories: propeller wounds, causing external gashes or severed tailstocks, and blunt force trauma from ship impact, leading to fractured skulls, jaws, vertebrae, and internal hemorrhaging. These injuries often result in high mortality, and even non-fatal injuries can impair a whale’s ability to feed, reproduce, or migrate, affecting their long-term health. Certain whale species are vulnerable due to their behavior and habitat use, such as the endangered North Atlantic right whale, highly susceptible due to its slow movement, surface time, and habitat overlap with busy shipping lanes. Other frequently affected species include fin, humpback, blue, and sperm whales, especially when their feeding or migration areas coincide with high vessel traffic, and the cumulative impact can hinder the recovery of already threatened or endangered whale populations.
Global Efforts to Reduce Collisions
Recognizing the severity of ship-whale collisions, various global and national efforts are underway to mitigate this threat.
Speed Restrictions
One primary strategy involves implementing mandatory and voluntary speed restrictions for vessels in areas with high whale concentrations. For example, along the U.S. East Coast, most vessels 65 feet or longer are required to travel at 10 knots or less in Seasonal Management Areas during specific times of the year to protect North Atlantic right whales. Studies suggest that maintaining speeds of 10 knots or less can significantly reduce the risk and lethality of collisions.
Shipping Lane Adjustments
Changes to shipping lanes are another measure employed to separate vessels from whale habitats. Research has led to proposals and adjustments of shipping lanes to route ships around high-density whale areas, such as the shifting of Boston shipping lanes, which reduced strike risk by 81% for all whales and 58% for North Atlantic right whales. Similar adjustments have been made or proposed for areas off the California coast to protect blue, fin, and humpback whales. These routing measures are coordinated through international bodies like the International Maritime Organization (IMO).
Technology and Monitoring
Technological advancements are also contributing to prevention efforts. Whale detection technologies, such as acoustic monitoring systems using hydrophones, are deployed to listen for whale vocalizations and provide real-time alerts to mariners about whale presence. The Whale Safe system, for instance, combines acoustic data, visual observations, and habitat modeling to predict whale locations, allowing ships to adjust their routes or speeds. Reporting protocols for whale sightings and collisions further enhance data collection, informing conservation strategies and enabling dynamic management areas where voluntary speed reductions are encouraged based on real-time detections.