Caracterització poblacional de la tortuga de rierol al riu Orlina : perspectives de futur

Abstract

The Mediterranean pond turtle (Mauremys leprosa) is one of the two freshwater turtles of the Iberian Peninsula, also distributed in North Africa and southern France. In the past, its populations suffered a sharp decline due to human impact, including habitat fragmentation and loss, capture, and indiscriminate trade. Currently protected by law in Spain, it is considered a vulnerable species, although expanding in Catalonia. However, threats persist, and with climate change, its future remains uncertain. This study analyses the conservation status of M. leprosa in the Orlina River (Alt Empordà), characterizing the population based on size and sex structure, sex ratio, age classes proportions (juveniles/adults), biometrics, population size, and dynamics. Current data are compared with those from previous years: 2001, 2003, 2006, and 2008. The methodology used was Capture-Mark-Recapture (CMR) with custom-made traps. This allowed for the identification of sex, age class, and biometric measurements. Recapture data were entered into the MARK™ program along with data from previous years, enabling the estimation of population size and superpopulation for the period 2001-2024, as well as population dynamics through survival, capture probability, and recruitment parameters. The population structure was graphically compared across years and for the entire period using population pyramids by size and group (juveniles, males, and females). The sex ratio and juvenile-to-adult proportion were statistically tested using the chi-square test and Fisher’s exact test. Biometric data and population estimates were compared between years using ANOVA. The results show a well-structured but aging population, with larger adult individuals and fewer juveniles compared to other years. The sex ratio in 2024 is more skewed towards males tan the first decade of the 2000s. Population estimates indicate a slight decline over the study period, although not statistically significant. The conservation of aquatic ecosystems and connectivity between populations are key to the future survival of M. leprosa in Alt Empordà