Two fishing trawlers collided after one of the skippers left the wheelhouse unattended, marine investigators have found.

Guiding Star sank on October 6, 2022 during a transfer of the catch with sister vessel Guiding Light, 33 miles off Fair Isle, between Orkney and Shetland, during gale-force winds.

The crash happened just before midday after the catch had been hauled on to the deck of Guiding Star shortly before a return journey to Peterhead, Aberdeenshire, after six days of “intensive” fishing.

A report from the Marine Accident Investigation Branch (MAIB) said “with no-one at the navigational controls, Guiding Light’s stern hit and breached Guiding Star’s stern”.

It said Guiding Star’s stern was breached, and the vessel suffered “catastrophic” damage, flooding and sank around an hour later.

The eight crew evacuated to a life raft, with five recovered to Guiding Light and the remaining three winched to safety by a Coastguard rescue helicopter.

The MAIB report said both skippers left their watchkeeping positions needlessly during the transfer of catch.

Lifesaving equipment was stored in flooded cabins and this further put lives at risk, the report said.

The crews worked in tandem but the report said it was likely that “unsafe practice had become routine over time” and leaving the controls unsupervised was considered unremarkable by other workers who were described as “experienced and skilled” and focused on their own roles.

Guiding Light’s skipper was suffering from illness and fatigue after two weeks at sea and made a decision to check the catch on the deck, the report said, while Guiding Star’s skipper went on the deck unnecessarily to oversee removal of unwanted fish, with the actions branded “perilous”.

Three of the crew from Guiding Star spent up to 25 minutes in “very rough” seas after the life-raft capsized, and were winched to safety by a Coastguard helicopter.

The report said they survived due to immersion suits requested by the senior skipper of Guiding Light, which was described as “commendable” by the MAIB.

It added: “Each skipper became actively engaged in the deck activities and, in doing so, dropped their watchkeeping responsibilities. The skippers likely felt compelled to be on deck rather than in the wheelhouse and delegate another crew member to take charge of the operation.

“Guiding Light’s skipper could not wait until the two vessels were a safe distance apart before going on deck; similarly, Guiding Star’s skipper remained on deck to oversee the removal of unwanted catch despite the activity probably not requiring his authority.

“It is likely this unsafe practice became routine over time and was no longer seen as hazardous.”

It said the wheelhouse of Guiding Star had been left unattended for a “significant time” before the crash, and the skipper was “unaware of the proximity of Guiding Light” when the transfer began.

The report warned it “can have catastrophic consequences as evidenced by this accident”, adding the fish transfer had not been risk-assessed, and that Guiding Star’s crew were “unaware” of procedures for flooding after the stern was breached.

The report said crew on the Guiding Star could not access their immersion suits because they were in flooded cabins, but that immersion suits were transferred over from the Guiding Light using a heaving line.

The report said: “Both vessels carried immersion suits because Guiding Light’s senior skipper had witnessed their impact on survivability – a decision which Guiding Star’s crew believed saved their lives.

“Guiding Star’s crew could not access their immersion suits or lifejackets during the emergency because the survival equipment was stored in the crew cabins below the waterline, inside the flooded aft compartment.

“A deckhand became trapped in their cabin while attempting to retrieve their lifesaving equipment, which could have had potentially fatal consequences had another deckhand not been able to come to their aid.

“It is fortunate that crew were able to abandon ship with survival equipment due to the quick transfer of replacement gear from Guiding Light.”

It said proper consideration must be given to the location of the survival equipment for timely use in an emergency.

The report said the skipper of Guiding Light was suffering from “illness, fatigue, and heightened stress levels” and “did not have the cognitive resources to remain focused”.

This led to the skipper leaving the navigational controls and being unable to intervene to prevent the collision, the report said.

It added: “The Maritime and Coastguard Agency has been recommended to review its flooding prevention guidance. The manager of the vessels has been recommended to evaluate the impact of fishing operations on watchkeeping and make sure that its crews are prepared for flooding emergencies.”

The owner of the boats did not wish to comment.

A Maritime and Coastguard Agency (MCA) spokesperson said: “The safety of fishing crew is among our highest priorities, and MAIB’s report is a timely reminder of the importance of industry-wide efforts to prevent incidents at sea.

“Work has already been completed by the MCA to expand relevant training on the vulnerability of fishing vessels without damage stability, including the dangers of flooding; response to flooding emergencies; and considerations for abandoning ship.”

The MAIB report said the operator of the vessels has updated Guiding Light’s risk assessment matrix to include fish transfers.