Marine

GOV Comparison Trials in the North Sea

November 29, 2019 by Marine Directorate Communications No Comments | Category Marine Directorate general, Marine Directorate Science, Marine Directorate Surveys, Research Vessel Surveys

MRV Scotia Programme

Survey: 1819S

Duration: 28 November – 9 December 2019

Fishing Gear: 

• BT137 GOV trawl rigged with ground gear A.
• BT237 (Jackson trawl) rigged with Light hopper rig (300mm and 250mm discs).
• Marine Institute (MI) trawl (similar to BT237) complete with rubber disc ground gear and wire rig.
• 2 sets GOV polyvalent trawl doors.

Objectives:

1. To carry out catch comparison trials to compare the fishing performances of the two new survey trawl designs (BT237 and MI trawl) and the standard survey trawl BT137 GOV rigged with A gear.
2. To assess the fishing performance, in terms of gear geometry, of the BT237 and MI trawls 15 minute hauls will be made using Scanmar and bottom contact sensor on water depths ranging from 20 m to 100 m.

Procedures:

General: The fishing gear will be loaded aboard on 25 November and two trawls rigged prior to the start of the survey. Trawls will be rigged onto both net drums (top and lower) but exact trawl configurations to rig first with will be confirmed nearer at the start of the survey. The polyvalent doors will be used with all three trawls throughout the survey, spare set stored on the upper castles. Scotia will sail on 28 November and after all safety drills have been competed make passage for the Moray Firth where a shakedown haul will be made. Thereafter and weather permitting the intention is to work within the Moray Firth for the duration of the survey. Trawling operations will be conducted from 0700 until 2200.

Fishing: The main objective of this survey is to compare the fishing performance between BT137 v MI trawl and BT137 v BT237 using the alternate haul method (Objective 1). Catch comparison hauls will consist of 15 to 30 minute tows depending on fish species mix on the grounds. The hauls will be paired and both paired hauls in a set must run along parallel fishing tracks. The aim is to keep the pattern, timing and environmental factors (daylight/dark periods) as constant as possible between the first and second tow in each set of paired hauls.

During the survey gear geometry data and underwater observation using a self-recording camera will be made to assess the performance of specific area/sections of the two new test trawl designs (Objective 2).

Additional Information:

• Marine Scotland Website
• MRV Scotia Topic Sheet
• MRV Scotia 2019 Blog Posts 

Tags: comparison trials, fishing performance, GOV trawl, MRV Scotia, Scotia

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