Woods Hole Analysis of Line Entanglement Decision Support Tool

Reducing risks to endangered North Atlantic right whales while maintaining sustainable fisheries is a complex conservation challenge that requires thoughtful and creative solutions. Right whales migrate across vast distances through some of the most productive fishing grounds in the North Atlantic. They are vulnerable to entanglement in fixed-gear commercial fisheries. Fixed-gear fisheries use stationary gear—including traps, pots, and gillnets—that are anchored to the ocean floor with an endline leading to a surface buoy. To effectively understand entanglement risk to right whales, we need to know where the whales and fishing gear overlap.

An Analytical Tool to Determine Entanglement Risk

The Woods Hole Analysis of Line Entanglement Decision Support Tool provides a useful way for managers, scientists, Take Reduction Team members, and other stakeholders to compare relative changes in entanglement risk to North Atlantic right whales—and other large whales—under various management scenarios.

Access the Woods Hole Analysis of Line Entanglement Decision Support Tool 

NOAA scientists developed this spatiotemporal tool in 2019 in response to members of the Atlantic Large Whale Take Reduction Team. They requested a way to quantify reduction of entanglement risk to large whales achieved by potential management measures. This tool uses a gridded map and overlays three layers of information to determine the amount of entanglement risk a whale is exposed to from fixed-gear fishing in U.S. Atlantic waters during a given month.

Fixed-Gear Fishery Layer

Quantifies the amount and configuration of commercial fixed-gear fishing from gillnets and trap/pots. Scientists developed fishery input layers for all fixed-gear fisheries on the U.S. East Coast, grouped by fishing method and target species. These layers quantify the amount of gear in the water and how it is configured, based on historical data.

Species Habitat Model

Provided by Duke University’s Marine Geospatial Ecology Lab, estimates the density and distribution of North Atlantic right whales using historical aerial and shipboard survey data of observed whales.

Gear Threat Model

Quantifies the threat of mortality or serious injury based on gear configuration (e.g. number of traps per trawl) and rope strength.

The tool calculates the total entanglement risk estimate by multiplying the three layers. This provides baseline risk estimates which represent the current landscape of whale and gear density and distribution. It then compares these to scenario co-occurrence and risk estimates that result from testing potential management scenarios, which include measures such as:

• Seasonal restricted areas where fishing with vertical buoy lines is prohibited in an area during a specific time of the year
• Gear modifications designed to set a maximum rope strength and reduce the number of buoy lines

Each management measure can be simulated in specific areas for a given amount of time, and multiple measures can be combined into an individual scenario.

Decision support tools are platforms to test the potential effectiveness of alternative strategies designed to reach a stated goal. They can provide insight on whether or not a potential strategy is likely to reach the goal, and inform modeled behavior in response to those evaluated actions.

The Woods Hole Analysis of Line Entanglement Decision Support Tool is a model that informs where and when entanglement risk occurs throughout the U.S. Northwest Atlantic using estimates of:

• Distribution of North Atlantic right whales
• Distribution of commercial fixed-fishing gear
• Lethality of fixed-fishing gear to inform where and when entanglement risk occurs throughout the U.S. Northwest Atlantic

The model then simulates alternative management strategies to estimate how entanglement risk changes under those scenarios. It also estimates potential effects to the fisheries through simulated management scenarios, including changes in gear configuration, gear density, and displacement around modeled restricted areas.

Right Whale Entanglement

Entanglement in commercial fishing gear is one of the primary causes of mortality for large whales in the U.S. Northwest Atlantic, including the endangered North Atlantic right whale. In 2017, NOAA Fisheries declared an Unusual Mortality Event for right whales. Long-term monitoring efforts show that about 80 percent of right whales have been entangled in fishing gear at least once in their lives. Documenting and quantifying the distribution of fixed-gear fisheries that pose risk for large whale entanglement is important for the success of this tool.

Entanglement Risk Reduction Through Collaboration

Members of the Atlantic Large Whale Take Reduction Team include fishermen and industry representatives, scientists, state and federal managers, academics, and non-governmental organizations. The Team was formed in 1996 to provide recommendations to NOAA Fisheries to reduce mortality and serious injury from entanglements in commercial fixed-fishing gear through an established take reduction plan. The Woods Hole Analysis of Line Entanglement Decision Support Tool has played a critical role in assisting members of the Team in exploring and evaluating potential management scenarios that may reduce the risk of entanglement in commercial fixed-fishing gear. This collaborative team works toward feasible measures that are effective for reducing risk to whales and informed by input from the commercial fishing industry and other key stakeholders.