Fishing Vessel Safety: Record of Modifications - SSB No.: 01/2008

RDIMS No .: 2424361
Date (Y-M-D) : 2008-01-15

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This Bulletin has been replaced by Bulletin No. 03/2019


Modifications to the structure or equipment of a vessel may change its stability and its behaviour at sea.  This Bulletin:

  • explains how to record modifications, additions or removals of any kind as they take place;
  • provides guidelines for owners and masters on when to contact a marine consultant to evaluate the impact on vessel stability; and
  • highlights the potential negative effect on vessel stability of a series of small modifications.


The Fishing Vessel Modifications History form and the guidelines set out in this Bulletin are beneficial for the owner/master of any commercial fishing vessel regardless of length or tonnage. All owners/masters of commercial fishing vessels are urged to follow the steps outlined in this Bulletin.

For vessels of more than 15 gross tonnage, details of modifications recorded on the Modifications History will be reviewed when a vessel is monitored for compliance with safety requirements, including at regular inspections, and entered on the vessel’s inspection record.


Accident investigations, notably Le Bout de Ligne (1990) and Cap Rouge II (2002), found that modifications to these vessels were factors in their sinking or capsize.  The Canada Shipping Act, 2001 requires the master to take all reasonable steps to ensure the safety of the vessel and persons on board (S.85). This includes assessing the impact on vessel stability when modifications are made.

Some modifications have an obvious impact on the vessel’s stability, such as a change to a different method of fishing that involves adding equipment or gear on deck.  With other modifications, the impact may not be significant and may not need an immediate reassessment of stability, but without a way of keeping track of the small changes, you can reach the tipping point where the cumulative effect becomes significant without realizing it.  Changes in loading conditions, such as a change in the amount or type of cargo or gear carried, and where and how cargo or gear is stored can impact stability and must be recorded.

At the suggestion of fishing industry representatives, Transport Canada developed the Fishing Vessel Modification History form attached as an Appendix to this Bulletin to give owners and masters a way to track modifications over time and to help them to know when they should request advice from a marine consultant.

Review of the Fishing Vessel Modification History has been made part of the procedure for inspecting and monitoring fishing vessels.  Inspectors will ask to review the form when vessels are inspected or monitored and may use the opportunity to discuss the extent and potential implications of the modifications listed.  The Fishing Vessel Modification History will be considered when issuing certificates. A note of the review and any modifications will be added to the vessel’s inspection records.

Completing and Using the Fishing Vessel Modification History

As changes are made, complete the form with details, to the best of your knowledge, of:

  • additions or changes (other than routine maintenance) to lifting equipment and fishing gear;
  • changes in the fishing method, the type of fish caught or the way the catch is stowed; and
  • modifications to vessel structure, equipment or gear that add, delete or result in relocation of more than 100 kg (220 pounds) in weight.

Add the date of the modification and initial the line. At time of inspection, if no modifications have taken place, put “no modifications”, the date and your initials on the next available line.

Talk to a marine consultant about the effect on your vessel’s stability:

  • before making alterations that add significant amounts of topside weight, remembering that the higher the weight is placed the greater the effect. Weight added below the deck generally improves the vessel’s ability to right itself, but reduces freeboard and may decrease the vessel’s range of stability;
  • when the total weight of all modifications becomes significant.  A change of 2% of displacement can be used as a guideline for “significant”, however, the location of the weight must also be considered.  Weight added that is higher than the vessel’s centre of gravity has a greater negative effect on stability.  Removing weight below deck can also adversely affect stability.

Important Considerations

If you have a stability booklet and don’t know how to use it, the recommended action is to take a course on fishing vessel stability.  At a minimum, have the booklet explained to you.  (The marine consultant that prepared the booklet would be the best person to do this.)

Establish procedures for the conditions listed below in the section Minimizing Stability Risk, explain them to your crew and ensure that they are followed.  A trained and informed crew will reduce the chance that stability is impaired unintentionally.
For more information, consult the Stability page on the Transport Canada website or the nearest Transport Canada Centre.

Minimizing Stability Risk

Safe and efficient operations happen most often when people know what they are supposed to do and have been properly trained.  This includes understanding what affects stability and what to do or not do so that the risks are minimized.  Use the following information to train your crew.

Stability Risks


Water entering the hull decreases freeboard and increases free surface effect.  Potential downflooding points include doors, hatches, scuttles and portholes.  Make someone responsible for checking doors, windows and hatch closures regularly to see that the seals are still effective.  Stress the importance of keeping openings securely closed when underway except when being used.

Free Surface Effect

Free surface effect is liquid sloshing from side to side and is best explained using a rectangular plastic container with the lid on.  Have crewmembers tilt the container from side to side when it is half full, then turn it and tilt it end to end. Repeat with the container full.

Crewmembers should notice that the effect is greater when the container is end to end, representing a wider tank, and that the movement has little noticeable effect when the container is full while the sloshing is evident when the container is only part full.

Emphasize the importance of keeping the number of slack (partially filled) tanks and holds to a minimum.  Explain that ballast tanks and live fish wells must be either empty or completely full and appoint someone to check tank levels regularly.  Establish who can do transfers between tanks and when this can be done safely.  Keep bilges dry.  Appoint someone to check regularly that transfer valves are closed.  Make sure all crew know that scuppers and freeing ports are to be kept clear and unobstructed so that water does not remain on deck.

Abnormal Operating Conditions

Establish normal limits for trim and instruct all crewmembers to let the master know if the vessel has an abnormal trim or list.  Establish procedures for finding the cause of abnormal trim or list before correcting it, such as verification of tank levels and checking that cargo has not shifted.

Make sure that anyone charged with the wheel is experienced and knows the impact of: following seas, quartering seas, and running at the same speed as the wave or swell.  Explain the risks of decreased stability and loss of steering ability and the actions that can be taken if the situation arises, such as decreasing speed or changing course.

Loading and Storing Catch and Gear

Make sure that everyone understands that stability changes with increases and decreases in weight carried and that where weight is placed also affects stability.  Establish procedures and responsibilities for loading catch so that it is distributed evenly and as low as possible.  Follow instructions in the vessel’s stability document, if there is one.  Use penboards to reduce the free surface effect from shifting catch.  Explain that stability is reduced anytime a load is lifted because once the weight is off the deck or out of the water, it effectively acts as though it were at the top of the boom.  Lift over the centreline where possible, reduce the amount of time the lift is in the air and avoid allowing the lift to swing.  Watch the available freeboard and warn the lift operator before half the available freeboard is submerged.


1. Fishing Vessel
2. Modification
3. Stability

Questions concerning this Bulletin should be addressed to:

Luc Tremblay

Transport Canada
Marine Safety and Security
Tower C, Place de Ville
330 Sparks Street, 11th Floor
Ottawa, Ontario K1A 0N8

Contact us at: Email: or Telephone: 1-855-859-3123 (Toll Free).