Telomere length can be estimated from fish scales

Telomeres, repetitive DNA sequences at the ends of chromosomes, are increasingly studied as biomarkers of physiological stress as well as ageing processes. In ichthyology, fish scales provide valuable information regarding life history and ageing and are thus often preserved in substantial collections. This study aims to adapt a quantitative Polymerase Chain Reaction (qPCR) method to estimate relative telomere length (RTL) from fish scales archived in such collections. Using the brown trout (Salmo trutta) as a model species, we show that archived scales contain enough DNA to perform qPCR-based RTL measurement. RTLs in scales are on average higher than in fins, however we found no significant correlation between RTL values of both tissues at the individual level. Analysing archived scales originating from the subantarctic Kerguelen Islands introduced brown trout populations, we find substantial variation in RTL between rivers, age classes and body size.