title: Long-Term Seasonal and Interannual Patterns of Marine Mammal Strandings in Subtropical Western South Atlantic.
abstract: Understanding temporal patterns of marine mammal occurrence is useful for establishing conservation strategies. We used a 38 yr-long dataset spanning 1976 to 2013 to describe temporal patterns and trends in marine mammal strandings along a subtropical stretch of the east coast of South America. This region is influenced by a transitional zone between tropical and temperate waters and is considered an important fishing ground off Brazil. Generalized Additive Models were used to evaluate the temporal stranding patterns of the most frequently stranded species. Forty species were documented in 12,540 stranding events. Franciscana (n = 4,574), South American fur seal, (n = 3,419), South American sea lion (n = 2,049), bottlenose dolphins (n = 293) and subantarctic fur seal (n = 219) were the most frequently stranded marine mammals. The seasonality of strandings of franciscana and bottlenose dolphin coincided with periods of higher fishing effort and strandings of South American and subantarctic fur seals with post-reproductive dispersal. For South American sea lion the seasonality of strandings is associated with both fishing effort and post-reproductive dispersal. Some clear seasonal patterns were associated with occurrence of cold- (e.g. subantarctic fur seal) and warm-water (e.g. rough-toothed dolphin) species in winter and summer, respectively. Inter-annual increases in stranding rate were observed for franciscana and South American fur seal and these are likely related to increased fishing effort and population growth, respectively. For subantarctic fur seal the stranding rate showed a slight decline while for bottlenose dolphin it remained steady. No significant year to year variation in stranding rate was observed for South American sea lion. The slight decrease in frequency of temperate/polar marine mammals and the increased occurrence of subtropical/tropical species since the late 1990s might be associated with environmental changes linked to climate change. This long-term study indicates that temporal stranding patterns of marine mammals might be explained by either fishing-related or environmental factors.
authors.affiliation: Instituto de Oceanografia, Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, Brazil.
authors.forename: Jonatas H F
authors.initials: JH
authors.lastname: Prado
authors.affiliation: Instituto de Oceanografia, Laboratório de Gerenciamento Costeiro, Universidade Federal do Rio Grande, Rio Grande, Brazil.
authors.forename: Paulo H
authors.initials: PH
authors.lastname: Mattos
authors.affiliation: Núcleo de Educação e Monitoramento Ambiental, Rio Grande, Brazil.
authors.forename: Kleber G
authors.initials: KG
authors.lastname: Silva
authors.affiliation: Instituto de Oceanografia, Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, Brazil.
authors.forename: Eduardo R
authors.initials: ER
authors.lastname: Secchi
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D001938:Brazil; D004289:Dolphins / Q000502:physiology*; D046069:Fur Seals / Q000502:physiology*; D046070:Sea Lions / Q000502:physiology*; D012621:Seasons
references.citation: Nature. 1998 May 7;393(6680):17-8
references.pmid: 9590683
references.citation: Biol Lett. 2005 Jun 22;1(2):147-50
references.pmid: 17148151
references.citation: Braz J Biol. 2013 Nov;73(4):855-62
references.pmid: 24789403
references.citation: Braz J Med Biol Res. 2010 Sep;43(9):816-20
references.pmid: 20838754
references.citation: Philos Trans R Soc Lond B Biol Sci. 2007 Dec 29;362(1488):2351-65
references.pmid: 17553770