Marine

Nephrops on the East Coast

August 9, 2019 by Marine Directorate Communications No Comments | Category Marine Directorate general, Marine Directorate Science, Marine Directorate Surveys, Research Vessel Surveys

MRV Alba na Mara Programme

Survey 1319A

Duration: 8-24 August 2019

Objectives:

• To obtain estimates of the distribution and abundance of Nephrops burrows in the Firth of Forth and the Moray Firth using underwater camera.
• To use the TV footage to record the occurrence of other benthic fauna and evidence of commercial trawling activity.
• To collect trawl caught samples of Nephrops for comparison of reproductive condition and morphometrics in each of the different survey areas.
• If time permits, deployments of the sledge followed by the drop frame will be carried out on the same ground to compare Nephrops burrow density estimates obtained by using the two different methods.

Procedure: 

Where possible, a random stratified approach will be adopted to investigate Nephrops burrow density in different regions of the study areas.  A list of proposed stations for the survey will be made available to the ship prior to sailing.

1. TV Observations: At each station a video camera mounted on the TV sledge will be towed across the seabed, into the tide and for approximately ten minutes at approximately one knot.  Nephrops burrow abundance, other benthic fauna and signs of anthropogenic activity will be recorded on to DVD.  Distance traveled by the sledge, the depth at which the sledge is at and camera height from the seabed will be monitored and recorded automatically.
2. Trawling: Fishing trawls of approximately 60 minutes duration will be made within each sediment type and within each survey area.  A range of biological and morphometric data will be collected on Nephrops caught.
3. Drop Frame: The drop frame will be used where conditions are not suitable for using the TV sledge, recording similar data as to that of the TV sledge.
4. Comparative work: Following on from work carried on previous surveys, on known Nephrops grounds the sledge will be towed along parallel tracks approximately 200 m in length (ten minutes towing time) and 100 m apart.  Video footage and all observed data will be recorded as usual.  Following this, the drop frame will then be drifted across the same area at 90^o to the sledge tracks.  The frequency of this operation will depend on the weather and available time.

General:

TV work will normally take place during daylight hours.

There will be a requirement for trawling to take place in the evening.  On days where trawling will take place, work patterns will be arranged so not to exceed WTR recommendations.

It is proposed that work will initially commence in the Moray Firth and then the Firth of Forth.

The exact date of the half landing will be weather, location and work dependent.

Further Information:

• Alba na Mara Topic Sheet 
• Marine Scotland Science Topic Sheet

Tags: Alba na Mara, benthic fauna, commercial trawling activity, Drop-frame, east coast, Firth of Forth, Moray Firth

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