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You are here: HomeWellboats


Whilst the use of wellboats can have welfare advantages, their use can also compromise the welfare of fish if the conditions within the wellboat are not carefully controlled. Wherever possible, wellboats should be operated on an open-valve system. In cases where the boat has to travel with the valves closed, such as when the fish are being chilled or the boat is in close proximity to other fish farms, then the carbon dioxide level should be closely monitored. During this time, carbon dioxide strippers must be used to help maintain satisfactory water quality.

The extra handling required when using wellboats can be stressful. Suitable pumps, capable of delivering fish into the boat safely and quickly, should be used (see Removal From Water). Crowding should not be started until the wellboat’s arrival time is confirmed.

Water quality must be regularly monitored during the transport of live fish. The following table identifies the acceptable limits for fish during transport.


Table 1: Humane parameters for wellboat transport of fish1


Acceptable Level

Carbon dioxide

Must be kept as low as possible2


Not below 6mg/l


Not above 0.0125mg/l

Rate of chilling

Not quicker than 1.5°C/hour

Temperature range of well water

Within 4-16°C


Within pH6.5-pH8.0

1Adapted from Standards for Farmed Atlantic Salmon, RSPCA 2004

2At present the Council of Europe recommends 20mg/l maximum for carbon dioxide levels in cages. However, in wellboats levels can rise to over double this. Currently there is little research or practical evidence to suggest this level has an adverse effect on the fish during transport. Until new information is published the HSA recommends that levels are kept to a minimum at all times.


It is essential that trained and experienced staff monitor fish behaviour, in addition to the water quality parameters, throughout the journey to ensure that a high level of welfare is maintained. Before fish are pumped into the wellboat, there must be sufficient water in the well to prevent injury to the first fish to enter.

Boat operators should be fully trained and know:

  • How to load the boat safely;
  • How to monitor the fish during the journey – by visual monitoring of behaviour and by gas levels;
  • How to crowd the fish off the boat;
  • The capacity of the boat, which is dependent on the size of the fish.

There should always be contingency plans in place in case the boat cannot be unloaded for any reason or becomes stuck within a closed-valve area.


Figure 6: Potential stressors when using a wellboat

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