Norway prawns (Nephrops norvegicus), also known as the Dublin Bay prawn, are common around the Irish coast. They are found in distinct sandy/muddy areas where the sediment is suitable for them to construct their burrows. Nephrops spend a great deal of time in their burrows and their emergence from these is related to time of year, light intensity and tidal strength. The Irish Nephrops fishery is extremely valuable with landings in recent years worth around €34m at first sale, supporting an important Irish processing industry.
Purpose of Survey
Nephrops are managed in Functional Units (FUs). We have conducted underwater television surveys to independently estimate abundance, distribution and stock sizes of Nephrops norvegicus for:
- Western Irish Sea Nephrops Grounds (Functional Unit 15)
- Porcupine Bank Nephrops Grounds (FU16)
- Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17)
- South and South west Ireland Nephrops Grounds (FU19)
- Labadie, Jones and Cockburn Nephrops Grounds (FU20-21)
- “Smalls” Nephrops Grounds (FU22)
Data are also collected on Nephrops behaviour, the impact of fishing activity on the seabed and benthic megafauna occurrence.
How Under Water TV Surveys Work
Underwater TV sled on the deck of the RV Celtic Voyager
An under water video camera is towed over the sea bed for 10 minutes travelling approx. 200m at 0.8 knots on a purpose built sledge. The number of Nephrops burrows in the seabed are counted by experienced scientists. These burrow density estimates are then calculated up to the entire area of the Nephrops grounds using statistical methods.
A video clip of UWTV footage can be viewed below.
Recent Survey Results
Each year during the summer months, we carry out underwater television surveys on all the Nephrops grounds of interest to Ireland. Results of these surveys are submitted to annual International Council for the Exploration of the Sea (ICES) working groups (WGCSE – Working Group for the Celtic Seas Ecoregion, and also to WKNEPH –Benchmark Workshop on Nephrops assessment).
Areas Covered during our Nephrops UWTV Surveys
In the map above, the blue/black dots illustrate the stations positions during the Marine Institute Under Water TV Surveys. The functional units (FU) are numbered 15-22, and shaded in different colours.