Aquatic Conservation-Marine and Freshwater Ecosystems最新文献

The stable isotopes δ¹³C and δ¹⁵N are widely recognized and utilized as biomarkers for analysing trophic links, paleoenvironmental reconstruction, biogeography and nutrient sources. However, it is essential to further develop their applications, as their use in marine environmental monitoring is not as prominent. ¹³C and ¹⁵N have distinct signatures in organic compounds, which can be utilized to identify potential carbon and nitrogen sources. Marine bivalves are often employed in environmental studies as efficient bioindicators because sessile filter feeders tend to bioaccumulate pollutants. The present study analysed δ¹³C and δ¹⁵N in seston and oysters inhabiting two areas with different environmental conditions in a marine extractive reserve. The isotopic values were compared for two trophic levels and three oyster tissues, resulting in a broad view of local dynamics. Seston samples from Forno Beach (FB) exhibited depleted δ¹³C values, possibly reflecting a terrigenous carbon contribution in this area. Considering oyster tissues, δ¹³C and δ¹⁵N values in the hepatopancreas were similar to seston, possibly due to oysters' role as filter feeders, supporting the use of digestive tissues for assessing short-term changes of environmental conditions. Moreover, isotope values for oyster gills and muscles suggest long-term homogeneous conditions for Anjos Beach (AB) and FB, with a predominance of marine carbon and nitrogen sources. Our results underline the relevance of analysing bivalve tissues separately because they display different turnover rates and depict variable time frames of environmental conditions. This article provides valuable information on the variables that must be considered when applying stable isotope analysis in coastal environmental monitoring, highlights knowledge gaps and recommends best practices for future work in this area.

Estimates of apparent survival and abundance are crucial for understanding the population dynamics of sentinel species. To achieve this, it is necessary to establish a baseline of these parameters for effective management planning in areas strongly impacted. This is the case of the dusky dolphin (Lagenorhynchus obscurus), a species inhabiting the Argentine coasts. In Golfo Nuevo, information on the demographic parameters of this species, which coexists with tourism activities, remains insufficient. In this study, the abundance of dusky dolphins in Golfo Nuevo, Patagonia, Argentina, was estimated through long-term monitoring using the mark-recapture model for open populations (POPAN model). Moreover, the apparent survival rate of this species was estimated for the first time through live recaptures using the Cormack–Jolly–Seber (CJS) model. Photo-identification surveys were conducted from 2004 to 2022, and models were built using the MARK program, selecting the best models based on the lowest AIC. Our results suggest that in Golfo Nuevo, the apparent survival rate is high, around 0.95 ± 0.01, whereas the local abundance reached 2862.81 individuals throughout the entire sampling period. The number of individuals showed an increase with an average annual change rate of 4.65%. These findings represent a baseline estimate of abundance, apparent survival and population trend for dusky dolphins. However, future studies should prioritize estimates of site fidelity and emigration to achieve accurate estimations of true survival rates for the species. Our results contribute to the understanding of dusky dolphin population dynamics and can be considered in management and conservation projects at the local level.

Urchin barrens (‘blanquizales’) are habitats dominated by encrusting non-geniculate coralline algae and maintained by urchin grazing. Taxonomic information of coralline communities in Mediterranean blanquizales is limited. Lumpy to fruticose coralline algal specimens, unusual in blanquizales, were found along the southern Spanish coast. Sequences from these specimens resolved with foliose samples morpho-anatomically identified as Lithophyllum dentatum. Initial observations suggested that this protuberant Lithophyllum species increases diversity in the otherwise species-poor exposed blanquizales. When present, higher macroalgal cover was observed with algae and microfauna frequently observed as epibiotic among the coralline's protuberances.

Many species have been threatened over the past century because of anthropogenic disturbances. Parasites are among the most vulnerable groups because they rely on host organisms, many of which are now endangered. While many studies have argued and evaluated the risk of parasite extinction, empirical evidence is still lacking, especially from aquatic ecosystems. Here, we show the highly threatened status of relict populations of the ectoparasitic copepod Salmincola californiensis in Japan. S. californiensis attaches to the branchial cavities of freshwater salmonids of the genus Oncorhynchus spp., and only four local populations have been reported from disparate regions of Japan, isolated probably due to range contractions after glacial periods. Through citizen-led field surveys, we found no copepod infections in half of the S. californiensis populations previously reported, suggesting that local extinction has occurred within the last 50–60 years. The upstream reaches of the Kiso River and the Naka River harboured the only sustained populations, though the Kiso population may also have experienced population decline. Our results indicate that parasites can quickly decline over a large geographic scale, especially at range margins. When focal parasites are visible, citizen science is an effective approach for identifying the distributional range of rare parasites and aiding their conservation.

The Mediterranean Sea is frequented by local populations of loggerhead turtle Caretta caretta and green turtle Chelonia mydas. Greek waters host both nesting sites and foraging grounds for the loggerhead turtle, whereas only foraging grounds for the green turtle. Both species face threats in their marine environment sourcing from anthropogenic activity. Here, stranding data, spanning from 2010 to 2021, were used to shed light on the main drivers underneath these threats and to identify seasons and areas of high number of stranding events. Stranding events showed an increasing trend over the years for both species. The majority of the strandings were categorized as “unknown,” while those showing signs of anthropogenic interaction (i.e., strandings related to marine litter ingestion, oil pollution, fishing gear entanglement, and injuries) held a significant part, representing ~25% and ~35% for the loggerhead and green turtle, respectively. The present work identified seasons and areas of concern with emphasis on areas that indicate fishery interaction, providing information that can support the designation of conservation measures in marine Greek waters.

In brown trout, population structure is the result of a combination of factors such as the geographic distance, the altitude, the hierarchy of the hydrography and the presence of physical barriers totally or partially impassable for trout. Structure can even occur within populations, because of the lack of random mating (panmixia) between individuals, which is often a consequence of stocking with exogenous fish. In this study, we aimed to evaluate fragmentation in brown trout populations of the Pedroso River (Duero basin) to assess the effect of artificial barriers in this system. Our results indicated a significant isolation of populations in the headwaters, which translates into a low genetic diversity, a small effective population size and a high rate of inbreeding. We also found an unexpected substructure in one of the downstream localities (PED-02), where the youngest individuals were genetically different. Genetic analysis confirmed that these rare individuals come from a hatchery native stock used to stocking Pedroso River. Because this stock was originated with individuals from Pedroso itself, we must consider that a strong founder effect took place. Over the years, genetic drift accentuated the genetic differentiation of this stock from the original population. From our results, we made some recommendation for the management and conservation of brown trout in the Pedroso River, based on the removal of the main barriers that isolate the upstream populations, after stopping the restocking carried out with ‘native invaders’ fish from the local hatchery.

Hypselobarbus curmuca is an endemic fish species of Family Cyprinidae found in rivers and reservoirs of the Western Ghats, India. An interdisciplinary study was conducted to assess the population genetic structuring of the species with the help of conventional morphometric, image-based truss network and genomic data of a nonprotein encoding mitochondrial DNA region (partial D-loop −494 bp) (n = 106). Fishes were collected from five rivers of the Western Ghats, namely, Kali, Sharavathi and Chalakudy (west-flowing) and Ghod and Tungabhadra (east-flowing) (n = 294). Multivariate analysis of body measurements and truss distances revealed very weak separation among populations. The D-loop sequence analysis showed that genetically distinct populations of fishes inhabit the studied rivers. Principal component analysis (PCA) and linear discriminant analysis (LDA) could not completely distinguish morphologically distinct populations. D-loop sequence analysis indicated 13 haplotypes with low nucleotide diversity and 15 polymorphic sites, with location-specific haplotypes. An overall haplotype diversity of 0.80 and nucleotide diversity of 0.00849 were found. The haplotype network and maximum likelihood phylogenetic tree showed three clusters with two most probable ancestors. Analysis of molecular variance (AMOVA) showed a high value (0.898) of the fixation index (F_ST) among the populations (p > 0.05). Neutrality test and mismatch distribution results indicated that the populations are currently subjected to selection. Application of an integrated approach to characterise the populations of H. curmuca in the wild supports the hypothesis of geographical barriers as major drivers of population genetic differentiation. Different riverine environments have not selected for morphological differences during the evolutionary process in the recent past and showed weak separation of populations. These findings can be utilised while designing conservation strategies for the species in the rivers of the Western Ghats, as the species faces threats due to exploitation in capture fisheries and trade in aquaculture.