International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 2

Number 3

September 2008

311

Total Losses of Fishing Vessels Due to the

Insufficient Stability

P. Krata

Gdynia Maritime University, Gdynia, Poland

ABSTRACT: The paper presents the statistic data analysis of total losses of the fishing vessels. The emphasis

is put on the total losses caused by the insufficient stability of considered ships. The research is focused on the

fishing vessels, which are relatively small ones in marine industry, so they are most affected by the wind and

rough sea. The correlation between type of the vessel, its size, the shape of its hull and the capsizing statistic

is presented. The regularities noticed in course of statistic analysis allows to formulate the suggestions

regarding the influence of some hydrodynamic phenomena on the safety of fishing vessels and the number on

their total losses at the sea.

1 INTRODUCTION

Fishing vessels, especially small fishing vessels, are

the largest class of marine professional vessels. This

group of ships has been built and operated for ages

but it still generates the great danger for the crew,

ships and environment. The huge number of

accidents and serious disasters occur in spite of

the development of naval architecture, weather

forecasting, means of communication, etc. The total

losses of ships and losses of human lives are sad

facts, therefore any investigation of the accidents’

reasons and any attempt to improve present situation

are worthy to be undertaken.

2 STATISTICS OF FISHING VESSELS’ TOTAL

LOSSES AND LOSSES OF HUMAN

The total losses statistics presented in this paper are

based on data collected by last three decades of

twentieth century. Hundreds of marine accidents

where fishing vessels were involved were taken into

consideration. The main source of the accidents

information are The Casualty Returns of Lloyd’s

Casualty Reports. All considered ships were over

500 gross registered tonnage and they were divided

into groups up to different criteria (Achutegui,

Mendiola & Azofra 2000).

0 5 10 15 20 25 30 35 40

percent [%] of total losses

fire and explosion

stranding and grounding

foundering

flooding

collision

struck

capsizing

missing

others

casual reason

Fig. 1. Distribution of the reason of fishing vessel total losses

(source - own study based on data published in (Achutegui,

Mendiola & Azofra 2000))

The distribution of the reason of analyzed fishing

vessels’ total losses is shown graphical in figure 1.

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The loss of stability involving capsizing of the ship

is one of the rarely noticed reason of the total losses.

Its rate is only 4% of all casual causes. Although the

rate of capsized vessels is much higher in the group

of smaller ships, not considered in presented

statistics.

Regardless the danger to the ship, the fishing

vessels operations affect the safety of crew working

on board. Commercial fishing industry is one of

the most dangerous and deadly. Fishers in the United

States in 2000 were ranked as the second in deaths

per thousand workers, right behind timber cutters.

In recent studies performed by Roberts of the

University of Oxford in 2002 fishers had the most

dangerous job in Great Britain (Womack 2002).

The statistic data confirms such judgment.

The insufficient stability of ships is one of the most

important reason of deaths on board of fishing

vessels. The distribution of causes for loss of human

life during fishing vessels’ total losses is shown

in figure 2.

0 10 20 30 40 50

percent [%] of deaths

fire and explosion

stranding and grounding

foundering

flooding

collision

struck

capsizing

casual reason

Fig. 2. Distribution of the causes for deaths during fishing

vessel total losses (source - own study based on data published

in (Achutegui, Mendiola & Azofra 2000))

0 1 2 3 4 5 6 7 8

deaths per one ship's loss

fire and explosion

stranding and grounding

foundering

flooding

collision

struck

capsizing

average

casual reason

Fig. 3. Distribution of the causes for deaths per one fishing

vessel total loss (source - own study based on data published in

(Achutegui, Mendiola & Azofra 2000))

Capsizing is the second often reason of the loss of

human life, although it causes only 4% of all total

losses of fishing vessels. The rate of deaths during

capsizing reaches almost 20%. The rate of death per

one ship’s loss is even worse. It is 7,07 loss of

human being per one fishing vessel lost, when the

average rate is 1,40 only. The distribution of the

causes for deaths per one fishing vessel total loss is

shown in figure 3.

The comparison of the average rate of deaths and

the characteristic high rate noticed for capsizing,

shows the level of threat during the capsizing and

generally the condition of insufficient stability. The

rate of deaths per one capsizing disaster, which is

over five time higher than average one, justify

further consideration of this relative rare

phenomenon.

3 ANALYSIS OF CAPSIZING STATISTIC

As the ship’s capsizing is the type of disaster which

cause lots of deaths, the detailed analysis in

particular groups of fishing vessels were made. All

cases of capsizing reported in official data were

divided into typical sets by three criteria: the type of

fishing vessel, the gross register tonnage and the age.

The distribution of capsizing rate by the type of

the vessels is shown in figure 4. The symbols used in

the graph are following: MST - motor stern trawlers,

MT - motor trawlers, MFV - motor fishing vessels,

MSTFF - motor stern trawlers fish factory, StT -

steam trawlers. The names of vessels types

correspond with the division used for statistic data

collecting (Achutegui, Mendiola & Azofra 2000).

The predominating group of capsized fishing

vessels represents motor stern trawlers and the

second one motor trawlers. Those both types of

ships suffered over 71% of all capsizing. It is

characteristic for both of them, that the freeboard is

relatively small. Additionally the stern trawlers have

low and almost open stern, what is necessary for the

type of fishing operations. The coexistence of such

shape of the trawlers hull and the high rate of

capsizing should be underlined.

percent [%] of capsized

fishing vessel

MST MT MFV MSTFF StT others

type of capsized fishing vessel

Fig. 4. Distribution of capsizing rate by the type of lost vessel

(source - own study based on data published in (Achutegui,

Mendiola & Azofra 2000))

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percent [%] of

capsized fishing

vessel

500-750 751-1000 1001-

1250

1251-

1500

1501-

2500

>2500

GRT of capsized fishing vessel

Fig. 5. Distribution of capsizing rate by GRT of lost vessel

(source - own study based on data published in (Achutegui,

Mendiola & Azofra 2000))

The next step was taking into consideration

the size of the capsized fishing vessels. Six sizes

up to the gross register tonnage were established.

The distribution of capsizing rate by the GRT of

fishing vessels is shown in figure 5. There is the

strong relationship between the size of considered

vessels and the rate of its capsizing. Over 57 % of

capsized ships were under 750 GRT. The vessels

of size smaller than 500 GRT were not taken into

consideration.

The last factor taken into consideration was

the age of the capsized fishing vessels. Six age

categories were established: ships from 0 to 5 years

old - “new”, 6 to 10 years old - “relatively new”,

from 11 to 15 years old - “middle age”, 16 to 20

years old - “relatively old”, 21 - 25 years old were

considered as “old” and over 25 years old - “very

old”. The distribution of capsizing rate by the age of

fishing vessel is shown in figure 6.

percent [%] of capsized

fishing vessel

0-5 6-10 11-15 16-20 21-25 >25

age of capsized fishing vessel

Fig. 6. Distribution of capsizing rate by the age of lost vessel

(source - own study based on data published in (Achutegui,

Mendiola & Azofra 2000))

The highest rate of capsizing was noticed for

middle age ships (almost 36% of all capsized fishing

vessels). The second most inflicted to capsizing

group of vessels are relatively old ones. The figure 6.

shows, that there is no rule - the older the worse.

4 CAPSIZING AS THE EFFECT

OF INSUFFICIENT STABILITY

Number The capsizing is the fatal phenomenon

caused by the insufficient stability of the ship in

actual operating conditions. For fishing vessels 24 m

or longer, the main mean for determining the intact

stability is evaluating the characteristics of hull’s

static righting arm curve (Womack 2002). The

principal stability criteria are contained in the IMO

1993 Torremolinos Protocol (IMO 1993). There are

various versions of the protocol, adopted by different

countries, but the major modifications to the IMO

version are the addition of a minimum range of

positive stability, typically 60° or more (Womack

2002).

The criteria adopted by IMO represent the simple

static attitude towards complicated nonlinear

dynamic behavior of the vessel. The weather

criterion, which is the attempt of dynamic stability

calculation, is based on the static righting arm as

well. The vessels shall be able to withstand the effect

of severe wind and rolling in associated sea

conditions in which the vessel will operate (IMO

1993). But no dynamic evaluation of the rolling

and wind guests take place in course of stability

calculation. Additionally, when the stability of

fishing vessel is to be evaluated, some important

circumstances are omitted. First of all the influence

of fishing gear’s towing should be taken into

consideration. The arrangement of additional forces

affecting the trawler is shown in figure 7.

Fig. 7. The towing load affecting ship’s stability (source

(Womack 2002))

The stability of the vessel towing the fishing gear

is reduced by some effects. The first is the rise of the

center of gravity, due to fishing gear load placed

virtually on the top of cable reels. The other reason

for the stability decay is the lower freeboard,

especially in the stern of the trawler. That may be the

reason of the loss of relatively small ships, which

capsize the most often (see statistic in figure 5). The

next factor affecting ships’ stability is the shift of

load as the vessel heel. The negative effects of

towing the fishing gear are shown in figure 8.

314

Fig. 8. Negative effects of towing of fishing gear (source

(Womack 2002))

Another effect resulting the danger to fishing

vessels may be the water trapped on deck and its

dynamic influence (Jankowski & Laskowski 2006).

Such situation is most likely during the towing of

fishing gear by the small trawler. There is an

accumulation of free board lowering (see figure 7)

and the characteristic construction of stern trawlers

having almost open stern for fishing operations. The

water trapped on the deck may also come into the

processing spaces, what considerably effects the

ships stability and results deeper rolling on the seas.

The example of such situation may be the capsizing

of fishing vessel Arctic Rose. The disaster was

described in details (Lieutenant 2002).

The fishing vessel Arctic Rose had been

disappeared in the Bering Sea on April 2, 2001,

killing all fifteen men onboard. The U. S. Coast

Guard convened a Formal Marine Board of

Investigation to determine what had happened to the

vessel and why it had happened. According to the

analysis, the most likely reason the Arctic Rose sank

had been progressive flooding from the aft weather

deck to the processing space and the flooding then

progressed to the galley, fish hold, and engine room

through non-watertight doors and hatches

(Lieutenant 2002). The effect of loss of buoyancy of

the superstructure on the static righting arm curve is

shown in figure9. With the superstructure

nonbuoyant, the angle of maximum righting arm is

at the angle of deck edge immersion. With the

superstructure buoyant, the angle of maximum

righting arm is increased to the angle at which the

top of the superstructure is immersed. However, if

the superstructure cannot physically be kept

watertight due to openings without closures and

operational considerations, the buoyancy is lost

(Lieutenant 2002).

Fig. 9. Arctic Rose righting arm curve RA: openings closed -

upper curve and openings remaining open - lower curve (source

(Lieutenant 2002))

Additionally, water on deck often leads to

progressive flooding into spaces inside the fishing

vessel in which watertight doors and hatches have

been left open, which is precisely the most likely

scenario of the loss of the Arctic Rose (Lieutenant

2002). The sophisticated analysis of dynamic

behavior of Arctic Rose containing the water inside

its hull was performed. The results of the analysis

are shown in figure 10. The great increase in rolling

amplitude is evident.

Fig. 10. Roll angle time history for Arctic Rose (source

(Lieutenant 2002))

The improper use of passive anti rolling tanks

may have the similar effect to the sloshing of water

trapped on deck. It is described in (Transportation

Safety Board of Canada 2006) when capsizing of

small fishing vessel Ryan’s Commander is analyzed.

Just before the capsizing, the combined effects of

beam seas and increasing gust wind force caused the

vessel to roll slowly to port. The significant weight

of some 1.6 tons of slack water in the anti rolling

tank was not evenly balanced, as it also gravitated to

the port side, and, with the liquids in the other tanks,

contributed to the heeling effect. The accumulation

315

of shipped water on the port side of the main deck

continued until eventually it overcame the vessel’s

ability to right itself (Transportation Safety Board of

Canada 2006).

5 CONCLUSIONS

The capsizing is not often occurring phenomenon at

the sea, although it cause considerable number of

fatalities. The statistic analysis of total losses of

fishing vessels and the crew’s deaths suggest several

main factors related with the capsizing rate.

The first feature influencing the capsizing rate is

the size of the vessel. Generally the smaller is the

vessel, the bigger is the risk of capsizing. This is due

o the scalability in vessel stability. It depends on the

square-cubed rule; i.e. the heeling forces, which

depend on water and wind impact areas, go up with

the square of the dimensions, but the righting

moment which depends on the displacement, goes

up with the cube of the dimensions (Womack 2002).

The vessel twice as large as another one has roughly

eight times the righting energy as the smaller vessel

if both have the same righting arm curve. Yet for the

larger vessel the wind impact forces have only

increased four times over the smaller vessel

(Womack 2002).

The next circumstance exposing fishing vessels to

the risk of capsizing is omitting in stability

calculations the load of fishing gear being towed by

the trawlers. The towing load results in lowering of

freeboard and rising in the height of center of

gravity.

Another factor is the influence of the water

trapped on the deck of the vessel. This event is most

likely on the small fishing vessel with low or open

stern. The dynamic behavior of the shipped water,

affects the ship’s intact stability and it also may be

the cause of flooding of the hull. The free surface

effect appearing inside the fish hold, restricts the

righting ability of the vessel considerably. The

sloshing water may be able to lead to ship’s

capsizing, as presented in examples of Arctic Rose

and Ryan’s Commander.

The improvement of present situation could be

significant modification of formal stability criteria

applied for fishing vessels, especially for small

fishing vessels. The first point should be getting rid

of the same stability standards for the vessel of any

size. There should be worked out the restrictions

regarding the freeboard and obligatory advices for

skippers with regard to dynamic behavior of the

vessel on heavy seas and with water trapped on deck.

The steady rise in the level of skipper’s education is

the point to be taken into consideration as well.

REFERENCES

Correa F.J., Achutegui J.J., Mendiola S., Azofra M., Main

causes of the total losses of fishing vessels, 2

International

Congress on Maritime Technological Innovations and

Research, Cadiz 2000.

Jankowski J. Laskowski A., Capsizing of small vessel due

to waves and water trapped on deck, Proceedings of the

9th International Conference on Stability of Ships and

Ocean Vehicles, Rio de Janeiro 2006.

Lieutenant G.A., Research opportunities identified during

the casualty analysis of the fishing vessel Arctic Rose,

Proceedings of the 6th International Ship Stability

Workshop, Washington 2002.

Marine Investigation Report M04N0086 Capsizing and Lost of

Life, Transportation Safety Board of Canada, Canada 2006.

Torremolinos International Convention for the Safety of

Fishing Vessels, 1977, being the Protocol of 1993 together

with the Regulations Annexed to the Convention as

modified by the Annex to the Protocol, IMO 1993,

www.oceanlaw.net/texts/torremolinos.htm .

Womack J., Small commercial fishing vessel stability analysis,

Where are we now? Where are we going?, Proceedings of

the 6th International Ship Stability Workshop, Washington

2002.