Acoustic surveys are generally carried out on spawning and pre-spawning aggregations of fish. Outside of the spawning season many pelagic species are generally very scattered over a large geographical area and difficult to detect using acoustic methods. A cruise track is first formulated with data from previous surveys, commercial catch data and the help of the fishermen and fishing industry.
Purpose of Survey
The aim of an acoustic survey is to determine the relative abundance of the target species. This information is then used to determine catch rates and management advice for the following year.
How Acoustic Surveys Work
These surveys use sound waves emitted from a "transducer" to estimate the density of plankton and fish shoals. The survey vessel tows the transducer under water, which is linked to an echo sounder in the vessel which records the shoals of fish as "marks" on a screen or paper trace.
The species composition of each mark is then identified by taking trawl samples. The density and number of marks are then converted into biomass (weight) of the different species. Acoustic surveys are particularly effective on shoaling species that have a large swim bladder like herring and blue whiting.
Marine Institute Acoustic Survey Programme
Herring Acoustic Survey
Every year FEAS carries out two Herring Acoustic Surveys on the RV Celtic Explorer, the Northwest Herring Acoustic Survey (NWHAS) in early January and the Celtic Sea Herring Acoustic Survey (CSHAS) in the fourth quarter of the year. Ireland also participates in an International Blue Whiting Acoustic Survey (IBWAS), which involves vessels from Norway, Russia and the Netherlands in spring each year.
Survey Tracks for spawning and pre spawning Herring Acoustic surveys
Blue Whiting Acoustic Survey
The 2011 survey was part of an International collaborative survey using the vessels RV Celtic Explorer (Ireland), RV Fridtjof Nansen (Russia), RV Tridens (Netherlands) and the RV Magnus Heinason (Faroes) and the RV G.O. Sars (Norway). The total combined area coverage extended from the Faroe Islands in the north (60.30°N) to south of Ireland (52°N), with east -west extension from 6°-17° W. The survey was the eight coordinated international blue whiting spawning stock survey since 2004.
International Survey Track for Blue whiting Acoustic Survey
Combined CTD stations overlaid onto vessel cruise tracks. WP II: Indicates plankton trawl. CE: Celtic Explorer; MH: Magnus Heinason; TD: Tridens; FN: Fridtjof Nansen: NO: Brennholm. March-April 2010.
Recent Survey Results
Download the most recent and past survey reports from the Northwest Herring Acoustic Survey, Celtic Sea Herring Acoustic Survey and Blue Whiting Acoustic Survey which are available on the Marine Institute Open Access Repository by following this link.