Cruise inventory

FRV Alba Na Mara 0115A

Cruise plan

Cruise Info. 
Ship name (ship code)FRV Alba Na Mara (74NM)
Cruise identifier0115A
Cruise period2015-01-05 — 2015-01-21
StatusCompleted
Port of departureFraserburgh, United Kingdom
Port of returnFraserburgh, United Kingdom
PurposeResearch
ObjectivesObjectives

1. To obtain estimates of the Nephrops habitat distribution in South Minch sea lochs and inshore waters, using sediment grabs and underwater cameras.
2. To obtain estimates of the distribution and abundance of Nephrops within these lochs using underwater video cameras.
3. To compare two different methodologies to establish Nephrops burrow abundance (sledge compared to drop frame).
4. To use the video footage to record occurrence of other benthic fauna and evidence of commercial trawling activity.
5. To collect trawl caught samples of Nephrops for comparison of reproductive condition and morphometrics.
6. To trial towing the TV sledge with the armoured cable in shallow water

Procedure

This survey continues on from the work previously completed in the sea lochs of the South Minch in 2014. The findings from earlier work in the North Minch were presented at WKNEPH 2013, and the outcomes from these South Minch surveys will be presented at WGNEPS 2015. This information will assist in determining the influence of the extent of Nephrops habitat in the South Minch sea lochs on the Nephrops management advice for the overall South Minch area.

For each area in the survey, a position outside the suspected Nephrops habitat boundary will be the start point for a search path across the length/breadth of the area. Along this path the drop frame will be deployed to provide a visual record of the seabed type. The search path will continue until the presence or absence of muddy sediment becomes apparent. All significant observations will be recorded on DVD as well as manually. These will include the muddy sediment boundary, the point where Nephrops burrows begin to appear or disappear and any signs of fishing activity.

The distance between, and the duration of, each of these deployments will vary in each area surveyed depending on the environmental conditions, unforeseen obstructions, the size of the survey area and how quickly the boundary between Nephrops and non-Nephrops habitat is detected. A Day Grab will be deployed at a suitable point along the track and on recovery the sediment sample will be frozen.

Once an area has been satisfactorily surveyed to establish the extent of the muddy habitat, a selection of stations will also be surveyed for Nephrops abundance. The vessel will drift over the grounds while a recording is made of the sea bed. The number of Nephrops burrow complexes will be recorded. A sediment grab will follow each of these operations. The number of stations to be completed will be determined by the extent of the muddy grounds and time available. Due to the high probability of creels in the proposed survey areas the drop frame will be used in preference to the sledge.

Areas to be surveyed will be defined by VMS, observer and SCOTMAP data but will be south of Loch Sunnart, this being the most southerly point of survey 0114A, and to include Loch Linnhe.

In a separate exercise, a comparison study between the Nephrops burrow complexes observed will be carried out. The sledge will be deployed five times on known Nephrops grounds, in parallel tracks 200m long and approximately 50m apart. The drop frame will then be deployed over the same ground a further three times, with video of the sea bed being recorded at all times with both methods.

Trawling will take place when appropriate, with Nephrop length, sex and morphometric data being collected for DCF and MSS purposes.
Chief scientistAdrian Weetman (Marine Scotland Aberdeen Marine Laboratory)
Ocean/sea areas 
GeneralInner Seas off the West Coast of Scotland
SpecificSouth Minch sea lochs