Purpose of the Survey
The survey is intended to collect information on maturity, sex ratio, growth, etc. for a number of species that are of commercial importance. The survey takes place in early spring, the time when most fish spawn. It is important to sample during the spawning season as immature fish can be easily distinguished from mature fish during this time.
Why is it important?
In order to assess the state of a fish stock, fisheries scientists need to know more than just the size of the stock. It is important to know how many fish are reproducing and how fast they grow and reach maturity in order to know how resilient a stock is to fishing exploitation.
Which species are targeted?
The main species that are targeted by the survey are: cod; haddock; whiting; hake; pollack; anglerfish; plaice; megrim; black sole; blue whiting; mackerel; herring and various rays.
When is a fish considered mature?
During the spawning season, the gonads (ovaries and testes) of mature fish expand to many times their original size; it is assumed that fish with undeveloped gonads will not spawn during that particular spawning season and that all other fish will contribute to spawning. The development of the gonads is classified according to a maturity scale. Download maturity scales (PDF, 1.1 MB) for the main commerical fish species of importance to Ireland.
How the survey works
The survey consists of a number of short fishing tows, scattered throughout the survey area. The fish in each haul are sorted by species and then weighed and measured. A number of fish from each haul are selected for age determination and to establish their sex, maturity stage and weight. After the data have been analysed, the results are presented to ICES working groups that assess the stock size and give advice on the management of fish stocks.
Recent Survey Results
Download the 2009 Biological Sampling Survey Report (PDF, 264 KB) which took place in the area to the south-west and south of Ireland. Also available to download are detailed survey reports from the previous biological sampling surveys:
Fishing positions of the biological surveys 2004 to 2009 inc.
