Population Viability Analysis of Critically Endangered Marine Mammals Under Multiple Stressor Scenarios

Abstract

This paper examines the effect of different environmental stress factors on the population viability and success of migration in endangered marine mammals. The study can simulate the population paths in the presence of various stressor conditions (high pollution, habitat degradation, and combined stressors) via Population Viability Analysis (PVA) and least-cost path analysis. Findings indicate that with the current state of affairs, the marine mammal population is at a stable survival level of 75 (SD = 5), and high pollution and loss of habitat are severe determinants of population. The worst drops were recorded when there were combined conditions of stressors, and the population size fell to half the normal level. Statistically, the negative impact of pollution and habitat fragmentation on population survival is statistically significant (p < 0.01 for each). The regression analysis shows that the population survival is strongly and negatively correlated with the habitat quality (= -0.45, p = 0.01). Environmental stressors also had a strong influence on the migration distances, and in favorable conditions, species moved on an average distance of 150 km (SD = 20 km). Nevertheless, both migration distances and the cost of migration were amplified in the presence of stressing factors, especially when natural boundaries and artificial impediments were met. Critical migration corridors, including California coast, were identified in the least-cost path analysis, which had the minimum migration cost. The results highlight the need to safeguard migration routes and to positively affect the quality of the habitat to increase the survival and migration rates of the species. The findings point to the necessity to apply detailed conservation approaches that would mitigate several stressors at the same time and the necessity to focus on the connectivity of essential habitats.