Aquatic Conservation-Marine and Freshwater Ecosystems最新文献

The declining population of otter species in Malaysia, including the Asian small-clawed otter (Aonyx cinereus), smooth-coated otter (Lutrogale perspicillata) and hairy-nosed otter (Lutra sumatrana), is primarily attributed to habitat changes. Understanding the ecological aspects of otters, including their diets, is crucial for formulating effective conservation management strategies. To address this knowledge gap, we employed Next Generation Sequencing (NGS) as an alternative approach to enhance our understanding of the species' food chain. Specifically, this study investigated the diets of Asian small-clawed otters and smooth-coated otters by analysing an ~130 bp segment of the Cytochrome b (Cytb) gene using Illumina Miniseq platform. The analysis successfully generated 572,311 reads, identifying four families, nine genera and 11 food species consumed by both otter species. Smooth-coated otters primarily consumed fish (96%) and frogs (4%), whereas Asian small-clawed otters exclusively fed on fish (100%), with the genus Esomus being the predominant fish genus found in the spraints. The diversity analysis of their diets revealed significant differences between two species (p < 0.05). As a result, DNA metabarcoding provides a reliable method for verifying otter dietary information and can serve as a valuable tool in assessing fish diversity, thus contributing significantly to the management and conservation of otter populations, particularly in Malaysia.

Fish hybridization is common in aquaculture worldwide, including in Brazil, with cross-breeding between species of the genera Piaractus and Colossoma taking the lead. However, little is known about the genetic damage caused by hybrids that escape into natural environments. In the upper Paraná River region, hybrid fishes are overproduced; therefore, the use of molecular techniques for their monitoring and identification is necessary. This study aimed to detect the presence of possible hybridization between Piaractus and Colossoma in the upper Paraná River using the molecular markers cytochrome c oxidase subunit 1 (COI) and α-tropomyosin (TROP). Fragments from 53 fish samples were analysed, and 41 samples were considered hybrids, with 12 confirmed pure, six as Piaractus mesopotamicus (pacu) and six as Piaractus brachypomus (pirapitinga). This is the first record of P. brachypomus, which is an invasive species in this basin, while Colossoma macropomum has not been observed. Molecular markers efficiently detected hybrids in the Ivinhema and Paraná rivers. The results showed a predominance of hybrid specimens from P. mesopotamicus × P. brachypomus. Our study suggests that more restrictions on hybridization and better supervision of fish farms are needed to prevent the escape of hybrids and the consequent ecological and genetic damage to native populations. We warn of the risk of a decline in the population of P. mesopotamicus, as this species is of great importance for fishing and maintaining the ecosystem.

North American river otters (Lontra canadensis) are semiaquatic mammals distributed throughout the North American continent. They are generalist carnivores with a high potential to affect community structure and dynamics. However, habitat degradation and ecosystem changes have the potential to impact their trophic interactions. Therefore, investigating their diet is critical to understand how anthropogenic disturbances can affect their ecological roles, particularly in the urbanised ecosystems in Florida, where such diet information is currently unavailable. Due to their elusive nature, direct observation of feeding events is a major challenge. Here, we have applied DNA metabarcoding of faecal matter (fDNA), opportunistically collected from river otters killed by road traffic in eastern Florida. Two mitochondrial markers were used to identify prey species' DNA—one for fish and one for vertebrates. A total of 23 unique exact sequence variants (ESVs) were identified, the majority belonging not only to teleosts but also to amphibians, reptiles, birds and mammals. The prey species identified are known dietary resources for river otters and the recovered dietary profiles provided independently by the fish and vertebrate assays were similar. Among the identified teleost prey, three fish species are considered invasive. Here, we show that when sufficient reference sequences are available, fDNA metabarcoding provides high prey species resolution. The collection and metabarcoding of faecal samples is particularly advantageous for scaling diet studies, both geographically and longitudinally, highlighting the potential of fDNA metabarcoding for the investigation of the diet of predators. This can provide foundational information on the organisation of ecological networks, which is vital for implementing successful ecosystem-based conservation management.

Greater Caribbean manatees Trichechus manatus manatus face complex conservation challenges throughout their distribution range, many of which are associated with human factors; and in consequence, the subspecies is considered Endangered (EN) by the International Union for Conservation of Nature (IUCN). Human-related threats as hunting for meat consumption, collisions with boats, entanglement in fishing nets, pollution and loss of habitat put the Greater Caribbean manatee at risk in Colombia. Studies aiming to describe traditional knowledge and local perceptions provide information that can be useful to design local manatee conservation programmes. We analyse the fishers' perceptions regarding manatees in Ayapel, Córdoba. One hundred semi-structured interviews were conducted, focusing on personal data, fishing practices, perceptions and knowledge about the manatees. According to the interviews, bycatch is the greatest threat to manatees (56%), followed by pollution (16%), whereas boat collisions (12%), hunting (11%) and drought (5%) are lower ranking threats. Our results demonstrated that participants have a good understanding of manatee biology and ecology. However, a human–manatee conflict was evidenced, as 39% of fishers consider that manatees negatively impact fishing by competition for the fishing resources and/or by damaging fishing gear. We recommend strengthening awareness about the importance of manatee to guarantee an optimal management of this subspecies and its habitat. Fishers should be directly involved in the formulation of management and conservation plans for the subspecies, as their knowledge becomes critical to understanding and mitigating the risks to manatee populations. This work has a clear application to understand the human factor in manatee recovery not only in our study area but also in other locations where manatees share habitat with people, particularly in marginalized human communities.