Photo-identification has been used to monitor the resident bottlenose dolphin population in the Shannon Estuary SAC (Ireland). Two concurrent photo-identification catalogues (IWDG and NPWS) collected in 2015 were compared to verify if all individuals in the population had been identified, since an extant population estimate of 145 individuals had been derived by IWDG through photo-identification and resultant discovery curve. Revision of the NPWS catalogue resulted in a lower abundance estimate than that derived by the IWDG, suggesting higher survey effort results in better abundance estimates.
Population Viability Analyses, in conjunction with sensitivity analysis, identified that demographic parameters related to female reproductive capacity were the most influential on population trajectories. Modelled management scenarios showed the population would be sensitive to slight increases in adult female mortality due to, for example by-catch, a reduction of life expectancy due to, for instance, the effects of persistent pollutants, or infrequent catastrophic events such as large oil spills. These results provide evidence of the potentially harmful effects of activities that may affect this discrete bottlenose dolphin population, but also of the need to maintain a high research effort in order to gain a better understanding of population dynamics.
