Design of annual acoustic herring survey and data analysis

Cefas designed and participated in annual acoustic herring surveys for the Department of Agriculture and Rural Development (DARD), Northern Ireland government. These surveys have been conducted annually since 1994. The results of these surveys are used by the ICES Herring Assessment Working Group.

We participated in the first week of the survey, the services we provided included:

• calibration of the acoustic survey instruments pre-cruise
• design of the herring survey grid off the Isle of Man
• training of DARD staff to allow them to complete the remaining survey of sprats and juvenile herring around the periphery of the Irish Sea.

Back at our laboratory, the echograms were scrutinised and acoustic targets were allocated to species or species mixes. Acoustic log data, Echoview log data, trawl data, sea surface temperature and salinity data collected during the survey were analysed. Using the results of the survey we calculated:

• the total numbers of herring by age class
• the total biomass and the spawning biomass.
• the biomass of sprat

Training of DARD staff in the interpretation of echograms and analysis of the data was also provided. The results were compared with data collected during previous surveys and a full report was provided for the customer.