Lumpsucker (Cyclopterus lumpus) otoliths: dissection, mounting and age-reading

Summary

A workshop was held at Institute of Marine Research, Flødevigen Marine Research Station, Arendal, Norway, 17-19 February 1999, to investigate methodes for age-determination of lumpsucker (Cyclopterus lumpus) from otoliths. The report summarises the results from the workshop and some subsequent analyses. The otoliths are very small and special training is necessary to locate them. The zonation pattern is relatively distinct and it was usually easy to establish a set of rings assumed to be annuli. The precision of age estimates increased as a result of training and discussions in the group, but was hampered by the lack of verifications available at the time of reading. After the workshop, the resulting age-length relationship was compared to new estimates of length-composition of juvenile lumpsucker prior to and after the migration from the coast. This represents the first documented attempt to verify annuli in otoliths of lumpsucker from Norwegian waters. It is recommended that a new workshop should be arranged to put together more verified age data and to see if a reasonable precision is achievable when the age readings are based on verified patterns.