1. To compare the selection characteristics of round fish in a 100mm mesh cod-end, 100 open meshes in circumference, using hooped and non-hooped 35mm covers to retain the escaping fish. Both covers fitted over the cod-ends of two identical trawls, fished in a two-warp, twin rig system. The hoops on the cover to be exchanged between trawls every haul.
2. To compare the same twin trawls having an uncovered 100mm test cod-end on one side and the same cod-end with the hooped cover on the other side to check whether the cover affects the quantities of fish retained by the cod-end.
3. Prior to the fishing trials, diving observations to be made to check that the modification to the previous design of hooped cover is satisfactory. Divers to examine the positioning and correct working of three small flow metres located a) in the cod-end; b) between the cod-end and cover; and c) on the outside of the cover.
John Main (Scottish Office Agriculture and Fisheries Department Aberdeen Marine Laboratory)
Biology and fisheries
Quantity: activity duration in days = 2 Description: Trawls took place to the west of Fraserburgh.
Quantity: activity duration in days = 2 Description: The vessel worked off Fraserburgh until one of the trawls was badly damaged.
Quantity: activity duration in days = 2 Description: Off Macduff a number of hauls were taken providing good catches of haddock.
Quantity: number of hauls = 3 Description: A tow was made of Nairn, but fishing was poor. 2 futher hauls took place but had to stop due to poor weather.
Quantity: number of dives = 1 Description: Diving took place off Nairn, but it was abandoned due to poor visibility and expected gales.
Quantity: number of hauls = 1 Description: Gear geometry was checked using Scanmar equipment.