The question of how many whales “drown” each year in fishing gear points to a serious, widespread problem of marine mammal mortality caused by human activity. Entanglement in fishing gear is the leading cause of death for many large whale populations globally. Although the final count is difficult to pinpoint, the scale is significant. The process is not technically drowning, but the outcome is the same: the air-breathing mammal is unable to surface for air and suffocates.
Understanding Whale Suffocation
Whales, like all marine mammals, are obligate air-breathers, meaning they must surface to inhale and exhale. Their breathing is a conscious action, unlike the automatic process in humans. If a whale is physically restrained, it cannot execute the necessary swimming movements to reach the water’s surface for air. This physical restraint quickly leads to asphyxiation, or suffocation, as the animal’s oxygen supply is depleted.
Death can result from rapid suffocation if the whale is anchored underwater by heavy gear, or a more prolonged demise from exhaustion or infection. Entangled whales must expend significantly more energy to swim and drag the attached gear, sometimes increasing their expenditure by up to three times the normal rate. This increased effort compromises their ability to forage, migrate, and reproduce, leading to slow death by starvation or systemic infection from deep rope lacerations.
The Overwhelming Factor: Fishing Gear Entanglement
The primary source of this mortality is entanglement in commercial fishing gear, often referred to as “bycatch.” This gear creates a maze of ropes and nets in the water column, especially in productive coastal areas where foraging and fishing activity are concentrated. Fixed-gear fisheries are most often implicated, such as those using gillnets, longlines, and pot or trap lines. These vertical lines extend from the seafloor to the surface, creating a snare for passing whales.
The problem is compounded by “ghost fishing” gear: nets, lines, and traps that have been lost, abandoned, or discarded in the ocean. An estimated 640,000 tons of this derelict gear enters the marine environment annually, continuing to trap and kill marine life for years. Whether active or lost, the gear can wrap around a whale’s body, leading to deep cuts, bone fractures, and the inability to swim or feed normally.
Global Estimates of Mortality
Obtaining a precise, global annual count of whale deaths from fishing gear entanglement is virtually impossible. Many whales die far offshore, sink quickly, or decompose before washing ashore, meaning a large percentage of deaths go unrecorded. Scientific bodies rely on estimates extrapolated from known strandings, necropsies, and observer data.
Global estimates suggest that around 300,000 cetaceans (whales, dolphins, and porpoises) die annually due to entanglement in fishing gear and marine debris. For every documented entanglement, approximately ten more are estimated to go unreported, indicating the true number is far higher. Large whales make up a significant proportion of these deaths, as entanglement is the leading cause of mortality for many large whale populations in certain regions. The cumulative impact is a major factor driving the decline of several endangered populations.
Conservation Measures to Reduce Deaths
Efforts to reduce these preventable deaths focus on technological innovation and regulatory changes. A promising solution is the development of ropeless, or “on-demand,” fishing gear. This system allows traps to be set on the seafloor without a permanent vertical line to the surface. The line and buoy are only released when the fisher signals the gear to rise, removing the entanglement risk from the water column.
Regulatory measures include implementing time and area closures in regions where whales aggregate during migration or feeding seasons. Other conservation efforts require the use of gear with specific features, such as weak inserts or ropes designed to break under less force, allowing an entangled whale a better chance of freeing itself. Mandatory and improved gear marking systems are also being enforced to help scientists identify the origin of the gear, allowing regulators to better target high-risk fisheries.