Lessons from 12 years of marine fauna stranding data in the south of Peru

In Peru, while several mass mortality events have been reported in the last two decades, there has been minimal systematic stranding monitoring. In this study, we report on repeated stranding monitoring that took place between October 2003 and October 2015, at Ite beach, Tacna (17° 54′ 47" S 70° 58′ 21" W). The objectives of the study were to assess the proportion of strandings by taxon and whether there were seasonal effects on abundance of stranded marine fauna. The study location was assessed opportunistically by trained observers who recorded and identified every stranded marine animal to the highest taxonomic degree possible. Stranded specimens of seabirds and marine mammals were grouped into overarching taxa of coastal and oceanic seabirds, and cetaceans and carnivorans. A principal component analysis (PCA) to visualize the association among stranded taxa registered along the study period and sea surface temperature anomalies using the Oceanic El Niño Index (ONI 3.4) and El Niño Coastal Index (ICEN) indexes and a Kruskal–Wallis test were conducted to evaluate abundance differences among taxonomic groups, taxa strandings and seasons. A total of 17,827 carcasses were encountered, 92.4% was seabirds and 7.6% marine mammals. Differences in abundances were significant among coastal and oceanic seabirds and marine mammals. Significant differences among seasons for cormorants and boobies were also identified. Coastal seabirds and pinnipeds dominated the stranding counts. A massive mortality of cormorants and boobies was registered between June and July 2014 possibly due to a moderate El Niño event. These strandings provide valuable information that could help lay the groundwork for implementation of a stranding network and science-based management projects in southern Peru.