Challenge II UL33 was built at Macduff and launched in 1995. The vessel is designed for both twin-rig and single trawling depending on the fishery. Overall length: 27.70m breadth: 8.70m depth: 5.10m and she is powered by a 1305Hp MAN B&W Alpha engine.


Trial details:

Ice machines

Trial 1

Trial 2

Trial 3

Trial 4

Trial 5

Trial 6

Follow-up project


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FISHING TRIP ONBOARD CHALLENGE II UL33 The use of liquid ice onboard a whitefish vessel and observations and comparisons between fish stored in liquid & flake ice.

Seafood Scotland, Seafish, the vessel Challenge II UL33 and Liquid Ice (Icelandic firm) have been working together to assess the impact liquid ice has on the quality of fish landed. A liquid-ice plant was supplied by the manufacturers on a trial basis and this was installed on the Challenge II UL33 at Christmas 2002.

The main objective of the project was to ascertain whether the quality of fish landed in bins/boxes improved when the fish was stored in liquid ice as opposed to flake ice.

A fishing trip was undertaken onboard Challenge II UL33 to observe practices with regard to the use of liquid-ice. Onboard two ice machines were used: a flake ice-machine, which had been in use since 1995 and a new liquid-ice machine. A number of quality assessments were made during the trip.

  • Pre-cooling of the fish hopper to ascertain fish temperatures.
  • Temperature checks on fish as it moved from the fish hopper through the fish washer and into the fishroom.
  • Regular temperature checks on fish, stored with liquid-ice, in bins and boxes, within the fishroom.
  • Regular temperature checks on fish, stored in flake ice, in bins and boxes, within the fishroom.
  • Temperature checks on fish stored in grading bins alongside conveyor system.
  • Temperature checks of the fishroom and the sea temperature.

Previous work carried out by Seafood Scotland shows that fish temperatures could fall as low as -1.5C before freezing characteristics occur.

Two batches of fish were labelled in the fishroom for follow through work with a processor upon landing. Both samples included a bin of small haddock stored in liquid-ice and a bin of small haddock stored in flake ice. Both sample bins were from the same fishing operation, to eradicate discrepancies. To back up the sample, 10 boxes were also used, 5 boxes of liquid-ice and 5 boxes of flake ice. Both bins were weighed at approx 420kg and each box contained approx 40kg of fish. Batch 1 was completed at 1800hrs on 26th February. Batch 2 was completed at 0300hrs on 1st March. Both batches were to be sent to Lunar Filleting, in Peterhead, on landing.

Summary of conclusions
A number of trials and projects were undertaken both during the fishing trip and onshore, tracing the quality of the catch from the vessel to the processor. Some of the main findings are:


  • Reduction in temperatures, of fish stored in liquid-ice, from 8C to -1C within one hour of packing.
  • Significantly quicker rate of cooling with fish stored in liquid-ice, than flake ice, in both bins and boxes.  Flexibility and easy use of system. 
  • The use of liquid-ice within the reception hopper instantly cools the fish prior to onboard handling.


  • Consistently lower temperatures of the fish stored in liquid ice. This was observed in both the boxes and bins.
  • No ice or crush damage to the fish stored in bins containing liquid-ice.
  • The fish stored in liquid-ice remained firmer than fish stored in flake ice.
  • All fish stored in liquid-ice had a longer shelf life.


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