The Eastern English Channel survey (August - September)

Area.

ICES Division VIId and IVc, the Southern North Sea and Eastern English Channel.

Objectives.

To provide independent (of commercial) indices of abundance of all age groups of sole and plaice on the east channel grounds, and an index of recruitment of young (1-3 year old) sole prior to full recruitment to the fishery.

History.

A July / August beam trawl survey has been carried out annually by MAFF/Defra since 1989 using a commercial 4m beam trawl. The standard survey had a total of 107 tows of 30 minutes duration (Primary stations), of these 79 were in 107d and 29 were in 104c. All tows in the eastern Channel (107d) have equal priority those in 104c are worked time permitting. Since 1999 the number of tows worked has been reduced to 75 in 107d and 16 in 104c this is because of the time allocated to the survey being cut.

Vessel and Gear.

The sampling gear consists of commercially rigged (1989 style) 4m beam trawl (measured between inside edges of shoes) fitted with a chain mat, flip-up ropes, and a 40mm cod-end liner. The liner needs to be sufficiently long, that when attached to the forward end of the cod-end it extends to about 1 metre below the cod-line. The gear is towed at 4 knots (ground speed) for 30 minutes on a warp length appropriate to the depth of water (on Corystes a ratio of between 3.5 and 4.0). Fishing is only carried out in daylight on this survey, as catch rates can be very different in the dark under certain conditions. To date there have been no rigid guidelines to determining dark, but we have usually aimed to have the catch on deck within 30 minutes of sundown approximately. All stations are identified by unique numbers (Prime station no.) that never change irrespective of the survey station number. All tows (positions) should be stored on a disc held onboard Corystes with a backup held at the laboratory. There is no particular order in which the stations should be worked, although attention to the historical calendar period would be sensible. If static gear or other restrictions prevent the execution of a primary station there are often alternative tows in the same area.

Results

Current survey results can be mapped by ICES rectangle from iSEA - interactive Spatial Explorer and Administrator