Fisheries Science Services (FSS) carries out the Irish Groundfish Survey (IGFS) as part of an internationally co-ordinated survey effort that takes place in the 4th quarter annually around the Atlantic shelf waters of Ireland.
Purpose of Survey
A broad spectrum of data is collected during the survey, but the overriding objective is to provide information on commercially exploited fish stocks. In particular the survey provides an index of the proportion of juveniles in the stock, which in turn gives an indication of its spawning success. This is an important source of information not available from commercial landings due to the necessary minimum fish length restrictions on commercial catches.
In addition, the survey provides data on species and environmental parameters in areas of both high and low commercial activity. This gives a better context to data for the entire survey area as opposed to focusing entirely on traditional fishing “hot-spots” that can remain stable while significant changes in surrounding background abundance and distribution go un-noticed.
Station Positions Carried out During the Irish Groundfish Survey 2009
In total 170 stations are carried out annually over 6 weeks in the ICES fisheries management areas VIa, VIIb,g&j indicated by red solid lines on the map. Circles indicate completed valid tows and hauls where damage or other problems occurred are indicated by an X.
How the Groundfish Survey works
The International Bottom Trawl Survey Working Group (IBTS) co-ordinates demersal trawl surveys under ICES for the North Sea and Northeast Atlantic. In order to make data as comparable as possible each survey, including the IGFS, operates under a set of agreed standard protocols. Each tow is 30min long and takes place during daylight hours at 3.5-4 knots. Net geometry and ground contact is monitored and logged.
Once the catch is aboard it is sorted into species and samples taken for calculation of number at length for all fish, elasmobranch and commercial squid species. Other species such as the benthos are weighed and/or counted. As management of commercial stocks is largely based on data for each age class of fish, samples are also taken for most commercial fish species to determine their age, sex and maturity.
It is important to recognise that trawls are quite selective in what they catch and their efficiency can change under different conditions. As it is difficult to ascertain what is not sampled by a trawl, a lot of the work of the survey staff involves keeping sample procedures as standard as possible to ensure all catches are as comparable as possible.
Recent Results
Survey summaries are presented in the context of the other co-ordinated IBTS surveys in the annual IBTSWG reports. These include overall numbers, recent trends and species distribution maps. Data from recent Irish groundfish surveys can be viewed and requested online via the Marine Institute 'Web Map Services'.