Modelling habitat use by the Guiana dolphin, Sotalia guianensis, in south‐eastern Brazil: Effects of environmental and anthropogenic variables, and the adequacy of current management measures

Abstract

1. Species distribution modelling has been used to identify critical habitats for the delimitation of Marine Protected Areas. Although Marine Protected Areas may often overlap with the distribution of key marine species, illegal human activities often continue within these areas, causing negative impacts on the local biodiversity. 2. A generalized linear model with spatial eigenvector mapping was used to investigate, for the first time, the influence of environmental variables and anthropic activities on the number of Guiana dolphin, Sotalia guianensis sightings/grid, and to determine whether a Marine Reserve, in south-eastern Brazil, is adequate for the protection of the local population. Data were collected between May 2007 and October 2013 onboard a 7.5-m vessel with an inboard engine.3. The models for the different periods (annual, dry, and rainy seasons) all indicated that depth, the distance to seafood farms and fishing grounds, and mean sea surface temperatures influenced the distribution of the dolphins within the study area. The annual and seasonal models predicted that the dolphins prefer a continuous area between Cedro and Pico Islands, a large area that lies outside the limits of the Marine Reserve. 4. Although the habitat of Ilha Grande bay is still much less degraded than that inhabited by other nearby Guiana dolphin populations, the results of the present study indicate that anthropic activities in this area influence habitat use by the dolphins. Less than 30% of the area used by the dolphins is protected by the Tamoios Ecological Station (ESEC Tamoios). 5. Sotalia guianensis is classified as 'Vulnerable' in Brazil, although the marine reserve (ESEC Tamoios) does not protect the core area used by the local dolphin population. The results of the present study provide specific locations for the creation of a new multiple-use MPA, as suggested by the Brazilian National Action Plan for the Conservation of Small Cetaceans, or the inclusion of a special management programme for the area between Cedro and Pico islands to better protect the dolphins in the ESEC Tamoios buffer zone. The continuation of surveys to better

Identifying priority habitat for conservation and management of Australian humpback dolphins within a marine protected area

“…The lack of spatially explicit information on species distributions and habitat preferences can compromise their effective protection, even when they occur within designated MPAs [17][18][19][20][21] . Although the implementation of MPAs has grown exponentially since the 1960s 22 ; only a small proportion contain no-take zones, and, overall, the global tendency is for MPAs to be located in remote areas or those unpromising for extractive activities, leading to the questioning of their effectiveness for conservation 23,24 .…”

Study and conservation of the Guiana Dolphin (Sotalia guianensis) (Van Bénéden, 1864) in French Guiana

“…and observation data would allow the realization of Ecological Niche Modeling (ENMs) in order to identify the favorable sites, or not, to the species along the coastline. Several studies have used this method, in particular to identify areas of interaction between animals and human activities, but also future marine protected areas (Tardin et al, 2020;Lobo et al, 2021).…”

“…The lower encounter rates could also be explained by the higher level of turbidity generated by the suspended sediments, which decreases the detection rate of individuals. Moreover, water temperature, salinity, prey distribution, and prey abundance can also influence the distribution of marine mammals (Vidal et al, 1997;Garcia and Trujillo, 2004;de Godoy et al, 2015;Tardin et al, 2020). In Nicaragua, the distribution and behavior of Guiana dolphins appear to be influenced by similar environmental…”

Critically endangered franciscana dolphins in an estuarine area: fine-scale habitat use and distribution from acoustic monitoring in Babitonga Bay, southern Brazil

“…In recent years, many marine protected areas (MPA) have been designated with the aim of managing human activities for the protection of marine mammals (Hoyt 2012). Dynamic approaches with flexible spatial and temporal limits of protection areas have been recommended for mobile species such as dolphins (Castro et al 2014, Santos et al 2017, Hazen et al 2018, Tardin et al 2020). However, there are many difficulties for the creation or effective implementation and maintenance of MPA’s in Brazil, such as lack of staff and funding, deficient or absent interinstitutional governance, excessive bureaucracy, and lack of political incentives for any significant change (Gerhardinger et al 2011).…”