Marine and Freshwater Research最新文献

Long-distance movements associated with environmental and ecological drivers are common in a wide array of mobile marine species. Understanding such movements and associated drivers is particularly important for management and conservation of threatened species, which may be exposed to anthropogenic threats throughout their range. Pacific nurse sharks (Ginglymostoma unami) are endangered because of their interactions with fisheries and a lack of biological knowledge as a recently described species. Little is known about this species’ movements throughout its broad distribution in the tropical Pacific coast of Latin America. Using passive acoustic telemetry, we report the longest ranging movement so far observed for Pacific nurse sharks. A male individual, measuring 176-cm total length at the time of tagging, travelled over 390 km within 46 days along the North Pacific coastline of Costa Rica. These findings highlight the importance of collaboration and data exchange among researchers to enable monitoring of broader geographical ranges and provide critical insight into the movement capabilities of this endangered species. Defining marine corridors and identifying essential habitats for Pacific nurse sharks may be necessary to mitigate fishing-related impacts if these longer distance movements are common across their population.

River regulation is a key threat to amphibian communities that continue to face global declines. Prior work in regulated river catchments has indicated that wetland inundation from connecting river flows supports breeding in some frog species more than others.

Our aim was to identify flow metrics influencing breeding and recruitment success in flow-dependent frogs, to derive flow–ecology relationships.

We conducted repeat surveys of frog communities between 2015 and 2020 across two important wetlands in the northern Murray–Darling Basin, Australia. Using random forest analyses, we investigated the influence of 22 explanatory variables on breeding activity and success.

Inundation extent was the most important driver of calling activity by flow-dependent species (increasing breeding attempts), whereas the volume of river flows in the preceding months was most important for increasing breeding success.

Two key features of the flow pulse are linked to breeding success for amphibians in floodplain wetland systems: (1) the size of the pulse as it relates to area of wetland inundated; and (2) the duration of connecting flows as a measure of wetland duration.

By establishing amphibian flow–ecology relationships, these species can be included in governmental environmental water objectives and management.

Passage efficiency is an important metric for quantifying the success of fish-passage remediation. Mark–recapture methods are typically employed to estimate fish-passage efficiency. Although biotelemetry methods have become a benchmark standard for such studies, they remain unfeasible for many small-bodies species because of the excessive size of electronic tags.

This study compares two commonly deployed marking methods that are potentially suitable for estimating passage efficiency for small-bodied species, namely, visible implant elastomer (VIE) tagging and batch immersion staining with Rhodamine B.

The critical swimming speeds and passage efficiency at a remediated culvert of Galaxias maculatus were compared for VIE-tagged, Rhodamine B-stained and control treatments.

Both critical swimming speeds and passage efficiency at the culvert were significantly lower in VIE-tagged Galaxias maculatus than in both control fish and fish stained with Rhodamine B.

Rhodamine B may be a suitable batch immersion stain for short-term (<4 day), non-destructive mark–recapture studies in small-bodied fishes, but VIE-tagging methods may result in underestimation of passage efficiency.

It is important to evaluate the impact of marking techniques on the outcomes of mark–recapture studies to ensure that estimates of passage efficiency are accurate.

Globally, intermittently closed and open lakes and lagoons (ICOLLs) can constitute highly productive coastal environments that support a range of fisheries. With growing pressures on fish communities, understanding the role of ICOLL management in population dynamics is increasingly important for conservation.

To determine whether the flood-driven management and environmental degradation of New Zealand’s largest coastal lake, Te Waihora–Lake Ellesmere, has created a conflict with the life history of diadromous īnanga, Galaxias maculatus Jenyns, potentially limiting persistence of this species.

The timing of post-larval migration of īnanga was assessed over 2 years (2021 and 2022) and compared with historic patterns of managed lake openings. Immigrating īnanga individuals were tagged to assess subsequent development, before potential reproductive output was quantified using artificial spawning substrates.

Peak migration periods were mismatched with the timing of most lake openings. After quickly transiting into tributaries, īnanga seemingly died within a few months. No spawning was detected.

The mismatch between lake opening management and the annual life history of īnanga prevents the reliable supply of post-larvae needed to sustain a persistent population, with severe environmental degradation being likely to restrict subsequent survival through summer conditions. This study has highlighted the need for management interventions to be tuned to the life histories of at-risk species.

Understanding the impacts of salinity on groundwater microbial communities is imperative, because these communities influence groundwater chemistry, quality, and its suitability for use by humans and the environment.

To assess groundwater salinisation and its influence on groundwater microbial communities within the Murray–Darling Basin (MDB), Australia.

Alluvial aquifers were sampled from 41 bores, within the Lachlan, Murrumbidgee and Murray catchments. Environmental DNA (eDNA), microbial activity and water-quality variables were measured to evaluate microbial communities, which were then correlated with electrical conductivity (EC) and other environmental variables.

Our results indicated widespread groundwater salinisation within the MDB, with EC ranging from 63 to 51 257 μS cm⁻¹. The highest EC values were recorded in the Murray catchment; however, mean EC values did not differ significantly among catchments (P > 0.05). The composition of microbial communities differed significantly between sites with low (<3000 μS cm⁻¹) and high (>3000 μS cm⁻¹) EC. Microbial activity, richness and abundances were all greater at low- than high-EC sites.

Changes to microbial communities as demonstrated here may have impacts on biogeochemical cycling and ecosystem resilience.

The detrimental ecological impacts of salinity are not limited to groundwater microbes, but present a larger ecological issue affecting all groundwater-dependent ecosystems.

Artificial breaching of intermittently closed estuaries has become more frequent in the face of global-change pressures.

This study aimed to determine whether the ecological health of the Great Brak Estuary has been affected by the prolonged loss of marine connectivity arising from below-average inflow and failed breaching attempts.

We characterised primary eutrophic symptoms (inorganic nutrients, dissolved oxygen, microalgae) typical of the various mouth states, i.e. open, closed and semi-closed.

Initially, low inflow and closed mouth conditions facilitated the widespread occurrence of macroalgal blooms (Cladophora glomerata). Phytoplankton bloom conditions (>20 μg Chl-a L⁻¹) ensued only in response to favourable hydrodynamic conditions (e.g. increased water residency, halocline formation) and increased nutrient availability from fluvial sources and macroalgal dieback. These blooms occurred in brackish conditions and comprised numerous taxa, including Cyclotella atomus var. marina, Cryptomonas sp. and Prorocentrum cordatum. Widespread hypoxia (<2 mg L⁻¹) occurred during the semi-closed mouth phase because of the reduced flushing potential associated with the preceding high flow conditions.

Global-change pressures and ineffective breaching practices will promote eutrophic conditions in intermittently closed estuaries in the future.

Allocating sufficient environmental flows is key to preventing ecosystem degradation.

In Tasmania, Australia, the government’s response to range-extending, barren-forming longspined sea urchin (Centrostephanus rodgersii) includes rebuilding of southern rock lobster (Jasus edwardsii) stocks to increase predation. But lobster preference for native species and continued barren expansion challenges the control efficacy.

To determine the impact of lobster predation on C. rodgersii in different habitats.

Multi-method dietary analysis consisting of stomach contents, faecal DNA and stable isotopes was performed on 64 lobsters from four habitats varying in barren extent and density of urchins and lobsters.

C. rodgersii contributed to lobster diet in all barren habitats and was found in lobsters of every size class. Stable isotope and DNA analyses showed that C. rodgersii was more common in lobster diet than were targeted native species at incipient barren sites. Surprisingly, in extensive barrens C. rodgersii is less prominent in lobster diet.

Combined with site-specific urchin population data, our findings indicated that lobster predation may be less effective at sites where most C. rodgersii individuals have reached a size refuge than at sites dominated by small urchins.

Lobster predation may provide a useful control for smaller C. rodgersii, but top–down predatory control may be constrained at sites dominated by urchins that exceed the size suitable for lobster predation.

The collapse of a tailings dam in Brumadinho (Brazil) is considered one of the largest mining disasters worldwide. The mine tailings polluted the water and sediment of the Paraopeba River downstream of the collapsed dam. The effects of the tailings on biological communities remain unknown.

We evaluated the effects of the tailings dam collapse on aquatic macroinvertebrate assemblages in the Paraopeba River and highlighted a potential bioindicator for the cumulative effects of the mine tailings spill.

We sampled the macroinvertebrates upstream and downstream of the collapsed dam during the first dry and wet seasons following the collapse.

We found that turbidity (likely non-related to the tailings) negatively affected the macroinvertebrates’ abundance, but the richness was negatively affected by the presence of the mine tailings. The riparian land use negatively affected the macroinvertebrate richness and composition. We identified Helicopsyche spp. as a bioindicator.

We provide circumstantial evidence of the effects of mine tailings on aquatic macroinvertebrates, suggesting that it may have affected their richness and caused the loss of Helicopsyche spp. in the most affected sites.

We suggest that the richness and Helicopsyche spp. are potential biomonitoring tools for evaluating the effects of the tailings dam collapse on the macroinvertebrate assemblages.

The sandbar shark (Carcharhinus plumbeus) has a global distribution and is caught by commercial fishers and recreational anglers.

To assess the stress physiology, release condition, and post-release survival of sandbar sharks caught in longline surveys conducted in Western Australia.

Post-release survival of sandbar sharks caught in longlining surveys was assessed using an integrated approach that combined the use of hook-timers, qualitative release conditions, satellite-tagging, and blood physiology.

Of 57 individuals examined, there was 100% post-capture survival after a maximum of 4 h on the hook. Most of these animals (88%) displayed a strong release condition, exhibiting minimal behavioural impairment. All 13 satellite-tagged individuals survived 30 days post-capture. Sharks dived up to 307 m deep and showed cyclical depth movement patterns, with some individuals moving through the water column both day and night, whereas others moved almost exclusively at night. The concentration of blood metabolites did not significantly change with time-on-hook.

Post-capture and post-release survival of 100% after up to 4 h on hooks suggested that the use of longlines for surveying sandbar shark abundance had no deleterious effects on captured sharks.

This will support future stock assessments of sharks by quantifying the survival rates in the methods used for long-term monitoring of sandbar shark populations.