Comparison of scales, opercular bones, and vertebrae to determine age and population structure in tench, Tinca tinca (L-1758) (Pisces, Teleostei)

Samples of tench, Tinca tinca (L., 1758), were taken from Lake Vegoritis, n orthern Greece (40 degrees 45'N, 21 degrees 47'E). Fish age was determined by comparing different skeletal elements (i.e., scales, opercular bones, an d vertebrae). Determination of age from the scales resulted in an overestim ation of 1 year in 1.9% and an underestimation of 1 year in 3.2% of the cas es when compared to age as determined from opercular bones. In the opercula r bones of older specimens, the first and some of the second annuli were no t easily discernible. A comparison of readings derived from vertebrae and o percular bones revealed that age determined from vertebrae was both overest imated and underestimated by the same percentage (2.5%). Consequently, usin g scales to determine age in tench is not recommended for inexperienced res earchers, unless the annual rings for ages greater than or equal to 3 years , are compared with those of the opercular bones and vertebrae.