Generalized linear models applied to stranding data of South American sea lions (<i>Otaria flavescens</i>) and South American fur seals (<i>Arctocephalus australis</i>) in southern Brazil


  • P. G. Kinas
  • K. G. Silva
  • S. C. Estima
  • D. S. Monteiro



Monthly strandings of South American sea lions, Otaria flavescens, and South American fur seals, Arctocephalus australis, collected between 1993 and 2002 along the coastline of Rio Grande do Sul, Brazil, are analyzed with generalized linear models (GLM) to describe spatial and temporal stranding patterns and to estimate the annual number of stranded animals by species. Results indicate a strong seasonal pattern for both species with maximum average number of strandings in September and minimum in January. While year effects are not significant, differences between regions (north or south of the Patos Lagoon mouth) are. Estimated numbers of stranded sea lions and seals in a typical year are 115, with 95% confidence interval (76; 160) and 95, with 95% confidence interval (48; 180), respectively. GLMs proved to be a very useful tool to examine the influence of time and space on strandings in a statistically rigorous framework.