Telomeres are evolutionarily conserved sequences capping the ends of linear eukaryotic chromosomes that usually shorten at each cell division, as well as under stressful living conditions. For this reason, telomere length (TL) has been considered as a proxy of age and stress for decades. Globally, most ecological and biology researches have used TL to assess the impact of specific life history traits on organisms life expectancies and persistence of populations. Nevertheless, to our knowledge, ecological studies that consider TL as an approximation of temporal cohorts are rare. In many population monitoring studies, however, knowledge about temporal cohorts are lacking, although they would provide comprehensive information on the natural processes underlying population dynamics. With this in mind, a quantitative PCR approach was used to measure the relative length of telomere sequences of DNA extracted from Paracentrotus lividus sea urchin. The species undergoes intensive harvesting, and some populations are under surveillance in the Mediterranean basin. The results showed that P. lividus experiences a shortening of telomeres with age, suggesting that according to this hypothesis, TL would probably be a relevant biomarker, which could reveal population differences based on their demographic structure, and differential susceptibility to pollution according to size. Future studies are still needed to define the accuracy of TL in detecting specific temporal cohorts in this species and to determine whether the TL should be considered locally in population surveillance studies.