The prawn (Nephrops norvegicus) are common around the Irish coast occurring in geographically distinct sandy/muddy areas were 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 €30 m at first sale supporting an important indigenous processing industry.
Purpose of Survey
The Marine Institute has been using underwater television surveys to independently estimate abundance, distribution and stock sizes of Nephrops on the Aran Grounds and Western Irish Sea. Data are also collected on Nephrops behaviour and the impact of fishing activity on the seabed.
How Under Water TV Surveys Work
During these surveys an under water video camera is towed over the sea bed for around 200m and 0.8 knots on a purpose built sledge. The number of Nephrops in the seabed are counted by experienced scientists. These burrow density estimates are then interpolated for the entire area of the Nephrops grounds using geostatistical methods.
Recent Survey Results
In 2007 the Marine Institute carried out three underwater TV surveys on the Aran Grounds west of Ireland, in the Celtic Sea and in the Irish Sea. Maps showing provisional abundance estimates (PDF, 302 KB) for each of the surveys can be downloaded. A report of the 2006 UWTV Survey on the Aran grounds (PDF, 1.3MB) is also available.
Areas Covered During the Marine Institute Nephrops UWTV Surveys in 2007 