DETERMINING FISH AGE FROM TEMPORAL SIGNATURES IN GROWTH INCREMENTS

The temporal signature technique can be used to assign age to fish tha t show an incomplete or indistinct growth history at the margins of th eir scales. The temporal signature technique matches part of an indivi dual's ''environmental'' growth history to characteristic patterns fou nd in a master chronology that was developed from reliably aged specim ens of a species in a particular environment. An error sum of squares measures the concordance between an individual's environmental growth history and the master chronology. Ages assigned to walleye (Stizosted ion vitreum) by the temporal signature technique and by examination of scales were compared to assess the performance of the new technique. Scale-age agreed with one of the three most likely signature-ages in 6 7-77% of the comparisons using all observed increments. These results are purposely conservative because of the methods employed and the nat ure of the example. All observed growth increments should be used in a pplying the temporal signature technique, but age may still be accurat ely assigned if as few as three increments are available. The temporal signature technique will perform best for species that exhibit high i nterannual variation in growth.