Spatiotemporal patterns of carrion biomass of marine tetrapods at the ocean-land interface on the southern Brazilian coastline

Abstract

Quantifying how much carrion is produced temporally and spatially in ecosystems is considered one of the most important aspects of carrion ecology. Marine-derived inputs transferred from the ocean to terrestrial ecosystems are the principal source of energy and biomass for many coastal ecosystems. Here, we provide a comprehensive quantification of the carrion biomass of marine tetrapods across space and time at the ocean-land interface on the Brazilian coastline. Based on 3 large datasets, we estimated carrion biomass of 57274 marine tetrapods beached along 1980 km of coastline over a 3 yr period (2016-2019). A total of 1744986 kg of carrion biomass was estimated from 76 species, ranging from a total of 30 g to 14082 kg for each species. The 10 most abundant species accounted for 91.78% of total records but only 21.28% of total estimated biomass. We highlight the importance of both migratory and resident marine tetrapods as a predictable resource for the Brazilian coastline, especially in the winter and spring. Although baleen whales contributed higher values of carrion biomass, their true availability as a food source is affected by management procedures adopted after stranding events. A significant amount of carrion biomass is removed every year from the Brazilian coastal system. It is therefore imperative to assess the impacts of management procedures on the ecology of scavengers and the entire coastal system.

Ups and downs: An insight on the stranding pattern of Guiana dolphins, Sotalia guianensis, in the Amazon Estuary, Northern Brazil

“…The recovery rates of carcasses during systematic beach surveys also could be influenced by various factors, including carcass decomposition, scavenger activity and removal by locals (Peltier et al, 2012; Tavares et al, 2021). For example, adult cetacean carcasses decompose rapidly in warmer conditions than in cold conditions, and the rate of decomposition is also influenced by body size (Gol'din et al, 2013; Moore et al, 2020).…”

“…Strandings rates reflected the seasonality characteristic of the Amazon Estuary and suggested a temporal effect and a human impact in this region. Tavares et al (2021) suggested that strandings of resident marine species such as Guiana dolphins and Franciscana dolphins ( Pontoporia blainvillei ) could be classified as predictable resources in the South and South‐Eastern coasts of Brazil due to their predominance and the constant interaction of these species with fisheries. This predictability could be also assumed for the Northern Brazilian coast, based on the detected temporal variations.…”

Tracking marine tetrapod carcasses using a low‐cost mixed methodology with GPS trackers, passive drifters and citizen science

“…We used fresh carcasses of marine tetrapods (seabirds, sea turtles and cetaceans; Table S1) as biological drifters to simulate their natural trajectories after death at sea. Carcasses were obtained from two sources: (a) beached carcasses (decomposition codes 2 or 3, according to Tavares et al, 2021) found during systematic beach surveys in southern Brazil between 2017 and 2019, or (b) carcasses (decomposition code 2) from a wildlife rehabilitation center. The carcasses were stored frozen at −20°C until the drift experiment and thawed at room temperature for up to 24 h before release.…”

“…In the South Brazil Shelf (SBS) Large Marine Ecosystem (23-34°S), over 55,000 marine tetrapods stranded between 2016 and 2019, many of them coming from bycatch, including threatened species (Tavares et al, 2021). Despite the importance of understanding global patterns of megafauna bycatch for conservation and management efforts, there are still gaps in knowledge that persist (Lewison et al, 2014).…”

“…Negative interactions between marine megafauna and fisheries bycatch (gillnets, longlines, and trawls) have been well‐documented worldwide, including in the southwestern Atlantic Ocean (SWA), where thousands of carcasses strand regularly (Lewison et al, 2014). In the South Brazil Shelf (SBS) Large Marine Ecosystem (23–34°S), over 55,000 marine tetrapods stranded between 2016 and 2019, many of them coming from bycatch, including threatened species (Tavares et al, 2021). Despite the importance of understanding global patterns of megafauna bycatch for conservation and management efforts, there are still gaps in knowledge that persist (Lewison et al, 2014).…”