The fishing industry has been pushing for the cod research project in the Celtic Sea for some time now. (Photo: Marine.ie/ Stock File)

'Interesting' results seen so far in Celtic Sea cod project

REPUBLIC OF IRELAND
Thursday, December 04, 2008, 01:30 (GMT + 9)

A cod-tagging project is beginning to yield interesting data about the migration patterns of cod in the Celtic Sea.

Funded by the Irish Sea Fisheries Board (BIM) National Development Plan, the project is a joint effort of the Irish fishing industry and scientists from the Marine Institute in Galway.

The goal of the project is to study the growth and migration of juvenile and adult cod, reports ScienceDaily.

Over the last two years, Institute scientists have tagged and released 4,063 cod into the Celtic Sea from the commercial fishing boat the Dunmore East.

"To date around 10 per cent of the tagged fish have been returned by a combination of fishermen, anglers and processors from Ireland, UK, Spain and France," said Macdara O Cuaig, a scientist with the Fisheries Science Services team of the Marine Institute. "What makes this project such a success is that every fish that is recaptured and reported adds its own piece of information to the jigsaw and helps us get a better understanding of the stock."

Tags were inserted into the guts of fish over 50 cm in length, he said. The electronic devices record time, temperature, and depth of the ocean surrounding the fish, making measurements every four minutes for up to two years.

Once retrieved, the tags allow scientists to figure out where the fish has been in the time between release and capture, letting the team build up an accurate picture of migration patterns.

"While the recapture of DST tagged cod to date has provided some interesting data, the amount of information can be limited if the fish is recaptured shortly after release," said Macdara.

However, some useful information can be gleaned by early recapture of tagged fish if the fish are released again.

"A fish reported to us last month with a conventional tag not only confirmed the rapid growth associated with Celtic Sea cod, but also has the unique distinction of being caught three times and released twice. This fish was originally released in Waterford Estuary on 6 May 2007 when he was 23 centimetres long with an estimated weight of 120g," said Macdara. 

"He was then caught and released again around St Patrick's Day this year by our tagging vessel up river above Dunmore East. At that time the fish was 47 centimetres long and weighed over a kilo. He was finally caught and reported by a local on 26 August at a length of 56 centimetres, weighing a hefty 1.9 kilos, sixty miles south of Hook Head."

The fact that this fish had grown 33 cm in fifteen months highlights the high growth rates of Celtic Sea cod.

"This fish had a total of a sixteen-fold increase in weight in just fifteen months!" said Macdara. "This demonstrates the potential yield possible from the Celtic Sea cod stock."

Related articles:

- Local fishers prod govt on cod survey
- Govt firmly prioritises fisheries: Minister  

By E. Fiske
editorial@fis.com
www.fis.com

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