Hercos A.P.,Mamiraua Institute for Sustainable Development MISD |
Hercos A.P.,National Institute of Amazonian Research |
Sobansky M.,Mamiraua Institute for Sustainable Development MISD |
Queiroz H.L.,Mamiraua Institute for Sustainable Development MISD |
Magurran A.E.,Center for Biological Diversity
Proceedings of the Royal Society B: Biological Sciences | Year: 2013
Because most species in an ecological assemblage are rare, much of the species richness we value is due to taxa with few individuals or a restricted distribution. It has been apparent since the time of ecological pioneers such as Bates and Darwin that tropical systems have disproportionately large numbers of rare species, yet the distribution and abundance patterns of these species remain largely unknown. Here, we examine the diversity of freshwater fish in a series of lakes in the Amazonian várzea, and relate relative abundance, both as numbers of individuals and as biomass, to the occurrence of species in space and time. We find a bimodal relationship of occurrence that distinguishes temporally and spatially persistent species from those that are infrequent in both space and time. Logistic regression reveals that information on occurrence helps distinguish those species that are rare in this locality but abundant elsewhere, from those that are rare throughout the region. These results form a link between different approaches used to evaluate commonness and rarity. In doing so, they provide a tool for identifying species of high conservation priority in poorly documented but species rich localities. © 2012 The Authors.
Iriarte V.,Mamiraua Institute for Sustainable Development MISD |
Marmontel M.,Mamiraua Institute for Sustainable Development MISD
Aquatic Mammals | Year: 2013
In the Western Brazilian Amazon, interactions of boto (Inia geoffrensis) and tucuxi (Sotalia fluvia-tilis) dolphins with fishing activities are common, but the prevalence of incidental/intentional catches is not known. This article describes incidental mor-tality events and intentional killing of I. geoffren-sis and S. fluviatilis entangled in artisanal fishing gear and the opportunistic use of carcasses as bait. Between October 2010 and November 2011, sur-veys were conducted in waters of the lower Japurá River, between the Mamirauá and Amanã sus-tainable development reserves. In order to obtain information on interactions and to try to estab-lish a stranding/entanglement response program (SERP), informal conversations were exchanged with local inhabitants (n = 174). Intense carcass-search surveys (n = 171) along the river in the four hydrological seasons (e.g., low, rising, high, and falling waters) were conducted, comprising a total of 1,197 h of sampling effort. Twenty-five dolphin-fishing interaction events were recorded (11 I. geof-frensis and 14 S. fluviatilis), 19 in 2011 and six in 2012 (through SERP). A total of 11 necropsies (three I. geoffrensis and eight S. fluviatilis) were performed. Four individuals (two I. geoffrensis and two S. fluviatilis) exhibited evidence of physical violence before death, and two (one I. geoffrensis and one S. fluviatilis) died in abandoned gillnets. Two intentional killing events of I. geoffrensis inci-dentally entangled for bait use in the piracatinga (Calophysus macropterus) fishery were reported by fishermen, while three carcasses (two I. geoffrensis and one S. fluviatilis) with gillnet marks were also used in that activity. At least six of the S. fluvia-tilis entanglement events occurred in fishing gear used for tambaqui (Colossoma macropomum) and pirapitinga (Piaractus brachypomus) (90/100-mm mesh-size gillnet), two of the most important commercial fish species in the Amazon Basin. As seasonal fishing constitutes the main income forriverine human populations, the negative reactions that cetacean presence causes to people could have a catalyst effect for the transition from "inciden-tal capture" to "intentional capture and competi-tor removal." Law enforcement and precautionary measures through good fishing practices inside dolphin critical foraging areas should be taken together with fisheries' managers and fishermen to start to develop multiple-species management and ensure sustainable fishing practices.