Nephrops Norvegicus, more commonly known to us as the Dublin Bay prawn is also known as the Norwegian lobster or langoustine. The strange thing is that this creature is not actually a prawn at all, and is found all around our coast, though not in Dublin Bay.
Nephrops is scientifically classified as a lobster and is found in the Irish Sea, the Celtic Sea and all around our west coast. Nephrops are essentially a small orange lobster which can grow to 80cm but can be legally caught at 20cm in the Irish Sea and 25cm in the other fishing grounds. It has a lifespan of around10 years.
Its habitat spreads from Iceland in the North Atlantic to Portugal and Morocco in the south. It reaches into the Mediterranean as far as Egypt, and is found in the North Adriatic, occurring at depths of 15 to 800 metres.
It is a preference of nephrops to inhabit muddy seabed sediments, with more than 40% being silt and clay. This soft mud means the burrow does not need constant maintenance and re-burrowing.
The burrows are of a semi-permanent nature, and vary in structure and size. The typical burrow is 20 to 30 centimetres deep, with a distance of 50 to 80 centimetres between the front and back entrances.
Nephrops spend most of their time either lying in their burrows or by the entrance. They only leave their shelters to forage, or mate.
Nephrops often share their homes with the small Fry’s Goby– which acts as a sentinel keeping guard, alerting it’s landlord of danger when a predator approaches. They are hunted by many species which include cod, dogfish, and ray. The goby thus has a symbiotic relationship with the ‘prawn’ as the goby feeds on scraps the nephrop leaves behind.
The Dublin Bay prawn is the second most valuable species fished by the Irish Fleet. The 2004 catch was worth €19,507 million.
Nephrops are also a very important species for the processing industry in Ireland, using peeled prawn tails to produce the value added ‘scampi’.
Due to difficulties in ageing coupled with their complex biology and behaviour, stock assessment of nephrops is notoriously difficult.Since 2002 the Marine Institute has been using underwater TV surveys to independently estimate abundance, distribution and stock sizes.
In order to ensure the sustainable harvesting the species, it is essential that stock management is underpinned by sound marine science that is clear, impartial and conclusive.
Nephrops is the only shellfish species in Irish waters subject to externally-imposed quotas, with the EU setting the Total Allowable Catch (TAC), for nephrops each year in an attempt to manage the fishery.