Marine and Freshwater Research最新文献

Sailfin catfishes (Pterygoplichthys spp.) are a group of fishes introduced to several freshwater habitats across the globe. Sailfin catfishes are a hard-armoured fish with no economic importance as a food species. These catfishes have been reported to be affecting the growth of several economically valuable species that are native to different freshwater ecosystems. In this manuscript, we developed a TaqMan-based assay targeting the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene, to specifically detect the presence of catfishes by environmental DNA (eDNA) measurements. The developed assay was screened against 16 species of fish and mussel that co-occur in the habitats along with sailfin catfishes, and the qPCR reaction did not have any non-target amplifications. The assay was further validated under laboratory conditions by measuring eDNA from tanks having different biomass of catfishes (1 and 0.5 g L⁻¹), and the copy number of the amplified product was directly proportional to the biomass maintained in the tanks. Overall, the study provides a robust molecular tool based on eDNA measurements to facilitate detection of invasive sailfin catfishes and, in turn, contributes towards the management of the invaded habitats.

The fugacity of surface-seawater CO₂ (fCO_2sw) and the sea–air CO₂ fluxes in the south-western tropical Atlantic (SWTA) were studied to increase the knowledge about the carbon cycle in this region.

This paper aims to describe the distribution of fCO_2sw in SWTA.

The fCO_2sw was measured from 2008 to 2020 by volunteer merchant ships with an onboard system that measures pCO₂ while the vessels were underway.

Higher values occurred north of 8°S than in the region south of 8°S. The north is a strong source of CO₂ for the atmosphere, with an annual mean value of 3.14 ± 0.52 mmol m⁻² day⁻¹. The south is a weaker source of CO₂, with an annual average of 0.93 ± 0.90 mmol m⁻² day⁻¹. In the months of July and August, a weak sink of CO₂ was observed, with a mean of −0.55 mmol m⁻² day⁻¹.

The differences between these two regions are explained by the origin of the surface-water masses encountered along the ship track. The central branch of the South Equatorial Current (SEC) transports surface water, with a higher CO₂ concentration and lower salinity, north of 8°S, whereas the surface waters between 8 and 14°S come from the southern branch of the SEC. The intertropical convergence zone is another physical process influencing the region north of 8°S.

Handling of wild animals can have adverse effects on individuals that scale up to affect populations and ultimately species. Limited mobility and high harvest pressure expose the threatened Australian freshwater crayfish (Euastacus armatus) to multiple handling events by fishers that cause egg loss.

Our aim was to assess the effects from harvest pressure on the reproductive output of an E. armatus population.

A stochastic model based on empirical data and estimated harvest pressures was used to predict the effect of repetitive handling of individuals on a population of E. armatus subject to harvest and consequent egg loss.

Egg loss resulted in substantial predicted population-level declines, most pronounced in populations subject to high and extreme harvest pressures.

We advocate educating fishers to visually determine the reproductive condition of female crayfish by inspecting gonopore setation, eliminating the need for unfurling the tail.

Maximising species reproductive output through limiting handling loss supports the management and conservation of E. armatus populations.

Overfishing is a major cause of decline for many shark species globally, which can be largely offset by shifting consumer demand to sustainable harvests. The inherent difficulty identifying shark species after processing makes informative labelling fundamental to achieving a sustainable market.

We evaluated the level of mislabelling in Australia from shark flesh samples obtained from seafood suppliers across the country.

We used sequence data from the cytochrome oxidase subunit one gene (COI) and the 12S mitochondrial RNA gene (12S) to identify genera and likely species.

We used genetic sequence data to identify species from tissue samples from 91 fillets labelled as shark. Of these, 64 (70%) were mislabelled, and 9 comprised three species listed as threatened in Australia, the scalloped hammerhead (Sphryna lewini), greeneye spurdog (Squalus chloroculus) and school shark (Galeorhinus galeus). The scalloped hammerhead and greeneye spurdog were being sold under the label ‘flake’. Overall, 70% of samples were mislabelled and the proportion of mislabelling was significantly greater in takeaways compared with fish markets and wholesalers.

High levels of mislabelling of shark product in Australian fish markets and seafood shops was apparent both with respect to the genetically identified shark sample not matching the label and the use of ambiguous labels that do not adhere to the Australian Fish Names Standard. Mislabelling masked the presence of threatened species.

Our results reveal labelling practices that are not providing consumers with reliable information to identify shark products, and we demonstrate the utility of molecular methods in seafood trade monitoring.

Hydrological dynamics are crucial in fish ecology.

To evaluate the effect of the flood pulse on the feeding ecology of Doras higuchii in the reduced-flow section of the Belo Monte dam, Xingu River, Brazil.

Collections were conducted between December 2020 and November 2021. The fish were measured and had their stomachs removed. Muscle tissue was also extracted for stable-isotope analysis. Stomach contents were inspected to assess diet, testing the influence of hydrological periods by using GLM. In addition, we evaluated the effect of the flood pulse on the δ¹³C and isotopic ratios of individuals

In total, 362 specimens of D. higuchii were analysed, highlighting a diet mainly on the basis of sediment (74.9%) and aquatic insects (24.8%), not varying between periods characterising the species as a specialist for having detritivorous habit, as well as the extension of the trophic niche. There was variation in food intensity, with higher average food consumption in the flood period. The isotopic composition (δ¹³C and δ¹⁵N) also did not differ between periods. Finally, δ¹⁵N did not vary by length class.

This information helps understand the interface between environmental and biological factors in an environment affected by a hydroelectric dam.

Our results may help fill gaps in knowledge about the diet of doradid fishes.

Water-regulation services significantly affect local social and economic development in the Qinghai area of Qilian Mountain National Park, China, and also affect the role of a ‘solid reservoir’ in China.

The value and change trend of water regulation was assessed through the evaluation and prediction of the water-regulation value of ecosystems.

InVEST water yield model and SVR model are used to evaluate and predict the water-regulation value of ecosystem in this study.

Grassland plays an important role in water regulation, although the area of forestland is not large, its water-regulation monetary value in 2020 accounted for 13.92% of the total evaluation value. From 2010 to 2020, the physical value of water regulation increased by 2.24% and the monetary value increased ~0.97% annually. In 2030, the amount of physical and monetary value of water regulation will be increased.

Grassland plays an important role in water regulation. It is necessary to strengthen the asset management of water regulation and optimise the ecological resources.

The study findings are utilised to enhance monitoring and establish ecological big-data platform, thereby elevating the quality of national park development management and decision-making services.

High temperature and oil pollution are typical examples of environmental stress to sea cucumber (Apostichopus japonicus) in northern China.

Evaluate the combined effects of high temperature and oil pollution on the immune responses of sea cucumbers.

In this study, we investigated the immune responses in the respiratory tree of sea cucumber subjected to the optimal temperature (16°C), high temperature (26°C), Oman crude oil (OCO) water-accommodated fractions (WAF) at 16°C (WAF + 16°C) and OCO WAF at 26°C (WAF + 26°C) for 48 h.

All three treatments significantly up-regulated total antioxidant capacity and disturbed active oxygen species homeostasis in sea cucumbers. Moreover, all three treatments caused immune-enzyme activity disorders, manifested by a significant increase in acid–alkaline phosphatase and nitric oxide synthase activities and a noticeable decline in lysozyme activity.

Combining the integrated biomarker-response index (WAF + 26°C > 26°C > WAF + 16°C), the combined stress could result in a more adverse effect on the immune responses of sea cucumbers than do high temperature or oil pollution alone, which might further exacerbate the health challenges for sea cucumbers in response to environmental stress.

This study has provided an insight into the immune impacts in benthic organisms caused by high temperature and oil pollution.

Global octopus catch has doubled over the past four decades and is likely to grow in importance as many key fisheries continue to decline. Lack of age data is a critical limitation in assessing the resource status of octopus. Over the past ~30 years, studies have investigated various methods to age octopus, with some methods better suited to certain species than others. However, only a small number of researchers have the hands-on knowledge to execute these methods in the laboratory. Here, we present the first step-by-step guide to ageing octopus, as well as a decision tool, which should enable readers to carry out the ageing process and make an informed decision on the most suitable method for their species. We provide guidance on age validation, increment analysis of both beaks and stylets, materials needed, as well as avenues for further research. We hope this guide will provide a starting point for researchers new to octopus ageing, and for those working with octopus species that have never been aged before. We also encourage researchers to use this guide as a forum for open discussion to support the ongoing development of effective octopus ageing methods.