6 - Development of a PIT-tag registration unit for screening of commercial herring and mackerel catches

With use of mark-recapture methodology the abundance of a year class can be estimated by the formula N = M·S/R, where M is the number of survivors among the tagged individuals, S is the number of screened individuals and R is the number of recoveries. The uncertainty in these estimates depends highly on the size of M and S. IMR conducts annual tagging experiments on both herring and mackerel. Individually coded metal tags are injected into the belly or muscular tissues. The tags are detected during scr eening of commercial catches through metal detectors under the surveillance of one person. Tag codes and associated data must be manually read and recorded during both tagging and detection. The present project is based on the assumption that there is a high potential of increasing M and S in a cost-effective way with use of PIT-tag technology, where the individual tag-code and associated data can be automatically recorded in computer-based monitoring systems during both tagging and screening, and where such data could be automatically updated in a database over the internet. The plan is to introduce the PIT-tag technology in two steps. Step 1, which is the principle objective of the present project, is to improve the capabilities of monitoring tag re coveries in the commercial herring and mackerel fishery by developing a PIT-tag registration unit. This unit should be able to screen up to 50 tonnes per on hour, with 100 % detection of tagged fish, on conveyor belt systems during fish processing. If thi s project is successful, then it would be appropriate to continue with Step 2, to develop and fit the PIT-tag technology to effectively tag and automatically record tag code and fish length during mass tagging of herring and mackerel.