Safety update

May 1996 Stability of fishing boats

This safety update is for owners and skippers of fishing boats. It is issued to raise awareness of the potential serious risk to safety on board fishing boats which have lost stability. It provides safe practice tips for how best to reduce the risks involved and to alert people to the risk to safety associated with loss of vessel stability.


In the last 12 months, a total of thirteen fishing boats of less than 24 metres in length have capsized or foundered. Maritime New Zealand considers that the majority of these accidents could have been avoided had the Skippers been more aware of the stability characteristics of their boats.

A recent investigation by MNZ into the loss of a 21 metre trawler contained many of the factors which are increasingly of concern to the Authority.

The particular accident resulted in the capsize, in Cook Strait, of a trawler fishing for hoki. The factors which contributed to this accident were found to be:

  • The amount of fish that was loaded on the boat - approximately 54 tonnes.
  • The loss of stability due to:
    • modifications made to the boat following her initial build;
    • weight of fish on the deck and in the landed net at time of capsize;
    • partially full bunker oil tank beneath the freezer hold;
    • fish stowed above the level of the top of the fish hold pound boards; and
    • build up of sea water on the deck of the boat prior to capsize.
  • The Skipper’s failure to recognise the danger posed by factors 1 and 2.
  • The failure of the owners of the boat to provide the Skipper with any information regarding the maximum quantity of fish that could safely be taken by the boat.

Information on stability

Maritime New Zealand concluded that the loss of the boat was caused by a combination of unapproved modifications increasing the top weight of the boat, overloading, carrying fish too high in the boat, and the Skipper’s lack of knowledge of the stability characteristics of the boat. These combined factors resulted in the capsize and loss of the boat in conditions which the boat should normally have been expected to weather.

Safe practice tips

Maritime New Zealand strongly advises owners and skippers of fishing boats of all sizes, and particularly those engaged in trawling, dredging, or purse seining, to make themselves more aware of the actual stability capability of their boats. If stability information has been provided by the designer/builder it should be studied.

If necessary, a qualified naval architect should be employed to present the data in a simplified format including a few basic criteria that can be displayed on the boat. For example:

  • any condition of loading that should be avoided;
  • maximum loadings or minimum acceptable freeboards;
  • any tank(s) which, when slack, has significant effect on the stability.

Check that the stability information is up to date. If modifications have been made since the information was prepared for the newly built boat, the stability information must be amended to take these into account.

For many boats, no stability information has been prepared. In these cases the MNZ recommends that the owner seek a qualified naval architect’s advice as to the current stability characteristics of the boat. The naval architect should be able to advise on any inherent lack of stability and how this might be improved, limitations on loading, and undesirable load conditions.

The attention of Skippers is drawn to safety update “Stability of fishing boats and other small vessels carrying cargo or passengers” which contains very practical and simple advice on avoiding loss of stability when operating small boats.

Owners are reminded, once again, that it is an offence under the Maritime Transport Act 1994 for any alteration which affects a surveyed boat’s stability to be carried out without notifying and obtaining the prior approval of the Director of Maritime New Zealand.

Original source content - Boat Notice 081996, May: Stability of fishing boats.

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