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Stability: The Practice of Staying Upright and Watertight


Commercial fishing vessels, registered over 79 feet and built after 1991, if not load lined or substantially altered, are required to be assessed for stability. “Substantially altered” can also mean any weight change of more than 3%, a change of more than 2 inches in a vessel’s vertical center of gravity, or a change of more than 5% in a vessel’s projected lateral area. Alterations that change the vessel’s underwater shape, buoyant volume, or changes to a vessel’s angle of downflooding can also require a stability reassessment (46 CFR 28.501).

Although these guidelines are enshrined in regulations, the regulations are difficult to enforce by regulatory agencies. Many vessel owners do not get their fishing vessel reassessed after an alteration or after many years of service in differing fisheries. This can lead to tragic losses even in vessels that have previously been well sea-tested.

On February 11, 2017, the 98-foot F/V Destination capsized with the loss of six experienced fishermen just north of St. George Island in the Bering Sea. The recently released final casualty report by U.S. Coast Guard Marine Board of Investigation is a reminder of things that can lead to a loss of stability and watertight integrity. Stability and its sometimes related flooding, account for about 50% of casualties in commercial fishing according to the U.S. Coast Guard. Some points to keep in mind include:

  • Severe Icing results in a higher center of gravity which decreases vessel stability. The following chart demonstrates the loss of stability due to ice accretion. The area under the respective curve represents the amount of stability you have. With just 1” of ice you have lost roughly 30% of your ability to stay upright and with 3” of ice you lose roughly 60% of your stability on a similar sized/designed vessel as the Destination.

  • Many weeks at sea results in poor quality and quantity of sleep, as well as physical fatigue. Knocking ice off a vessel is dangerous and requires hard work over a long period of time. Don’t count on the ability of a fatigued, sleep deprived crew to keep up.

  • Sleep deprivation and fatigue increase the risk of making a bad decision in trip planning.

  • Vessels, equipment, fishing gear, and even fishing folks gain weight with time. Vessel “weight creep” over 5 to 10 years can be enough to warrant another stability report. Of the 40 vessels whose crab pots were weighed by Coast Guard in Dutch Harbor late in 2018, every vessel was found to be heavier by 30 to 90 pounds per pot than was assumed in the vessel’s stability reports which were written years ago. On a vessel carrying 200 pots, this could add 6,000 to 18,000 lbs. to a deck load and will raise the vessel’s center of gravity which decreases stability. Storing heavy loads on top of the pots due to lack of space on deck, will decrease your stability, as well.

  • Keep the watertight envelope of your vessel watertight. Close hatches, watertight doors and ports when underway. Give these closures a chance to do what they are designed to do: keep the seas in the ocean and outside of your vessel.

  • On the F/V Destination, freeing ports were less than 50% of the size required for the amount of deck space. Adequate freeing port size is important to quickly drain the deck of standing water on deck. Loose water or fish on deck create “free surface effect,” a great destabilizer.

  • When getting stability assessed, use a qualified, well respected naval architect or engineer. Request a stability report or operational instructions that are understandable for you! architect. You are the person paying for it, so you should expect to be able to understand it in terms of your operational conditions.

  • Voluntary safety checks from Coast Guard are available at no cost from the Coast Guard in many ports in the U.S. In Dutch Harbor, stability checks are also available for crab season. Take advantage of these no-cost/no-fine exams.

Stability problems are not just a cause of casualties in Alaskan fisheries. Every U.S. coast loses fishing vessels due to stability issues caused by flooding, overloading, bottom hang ups, rigging failures, bar crossings, and other causes. The loss of the Mary B II and its crew, as it came into Yaquina Bay in Newport, Oregon on January 8, 2019, is just the latest case.

The first step of the Seven Steps to Survival is Recognition. Recognize that your gear, your vessel and even a successful fishing season is not as important as your life and the lives of your crew. There will always be self-imposed and fishing industry pressure to fish and deliver product. It’s of greater importance however that you live to fish another day. Stay upright and watertight.

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