Abstract
In this paper we tested the hypothesis that potamotrygonid stingrays are expanding their distribution to novel areas via artificial passages constructed for river navigation in the Upper Parana River basin, Southeastern Brazil. Individuals of Potamotrygon falkneri and Potamotrygon motoro were captured, fitted externally with t-bar anchor tags, and released downstream of the Jupia Dam – a hydro power plant constructed in the 1970s that has no fish pass system, but had a navigation lock installed in 1998 for the movement of ships. A total of 182 stingrays were marked, and recaptures of individuals of both species occurred within a period of two to 12 months after the first capture, with recapture rates around 5% for P. falkneri (n=6) and 3% for P. motoro (n=2). Two individuals of P. falkneri were recaptured upstream of the Jupia Dam, about eight kilometers from the first capture site. This fact attests to the ability of stingrays to overcome artificial barriers such as hydro power plants through navigation locks. The Upper Parana River basin is densely populated, so the spread of potamotrygonids will increase the risk of injury from stingrays’ barbs. Their use of navigation locks is relevant for management actions, including reducing the risk of human-stingray interactions.
Highlights
Invasions of non-indigenous species (NIS) are acknowledged as one of the major threats to natural environments - terrestrial, freshwater and marine - having ecological, economic and social consequences
When dealing with the international agreements and measures to prevent introduction of marine Invasive Alien Species (IAS), the following documents are fundamental to the conservation and management of the marine environment: the International Convention for the Control and Management of Ships' Ballast Water and Sediments (IMO 2004), ICES Code of Practice on the Introductions and Transfers of Marine Organisms (ICES 2005), Alien Species in Aquaculture - IUCN considerations for responsible use (Hewitt et al 2006), EC Regulation on concerning use of alien and locally absent species in aquaculture (European Commission 2007) and EC Marine Strategy Framework Directive (European Commission 2008)
A recent study of diatoms and dinoflagellates reported as NIS in European Seas found dubious identifications, and that synonyms were included as separate species (Gómez 2008)
Summary
Invasions of non-indigenous species (NIS) are acknowledged as one of the major threats to natural environments - terrestrial, freshwater and marine - having ecological, economic and social consequences. A recently published Proposal for a Regulation of the European Parliament and of the Council on the prevention and management of the introduction and spread of invasive alien species (European Commission 2013) states that “...The impact of IAS on biodiversity is significant ... The EU Biodiversity Strategy (European Commission 2011) aims that "...by 2020, Invasive Alien Species (IAS) and their pathways are identified and prioritised, priority species are controlled or eradicated, and pathways are managed to prevent the introduction and establishment of new IAS...". Stemming from a recent freshwater invasives conference, Caffrey et al (2014) identified ’the top 20 issues that relate to IAS management in Europe“. We agree and support all the issues proposed, and would like to contribute to this important initiative by adding six important topics that relate to the marine environment
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