Determining Fish Age from Temporal Signatures in Growth Increments

Abstract

The temporal signature technique can be used to assign age to fish that show an incomplete or indistinct growth history at the margins of their scales. The temporal signature technique matches part of an individual's "environmental" growth history to characteristic patterns found in a master chronology that was developed from reliably aged specimens 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 (Stizostedion 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 67–77% of the comparisons using ail observed increments. These results are purposely conservative because of the methods employed and the nature of the example. All observed growth increments should be used in applying the temporal signature technique, but age may still be accurately assigned if as few as three increments are available. The temporal signature technique will perform best for species that exhibit high interannual variation in growth.