Fish Habitat Research Articles (Page 1)

The invasive expansion of Phragmites australis in coastal wetlands, including the Long Point wetland complex in Ontario, has led to significant declines in plant and wildlife diversity, impacting ecosystem functions. Despite ongoing management efforts, the long-term ecological outcomes of Phragmites control remain poorly understood. This study developed a framework to evaluate the long-term efficacy of herbicide treatment by tracking changes in target and non-target plant species and fish habitats in Long Point, Ontario, over an eight-year period (2016–2024). High-resolution satellite imagery from WorldView sensors was classified using a random forest algorithm, achieving over 94% mapping accuracy. Results showed a decrease in Phragmites cover (3–21%) and an increase in fish habitat area (7–58%) within treatment areas. However, some sites also experienced increases in Dead Vegetation (up to 23.6%) and declines in Grass/Herbaceous and Typha (up to 20.5% and 32%, respectively). These findings highlight both the success of Phragmites Best Management Practices and the temporary non-target effects on wetland vegetation.

Unlocking flow-habitat relationships in mountain rivers of Epirus, Greece using object detection and hydrodynamic simulation.

Rock weirs are river restoration structures that provide flow diversity and enhance fish habitat, but they may be barriers to fish migrating upstream. The eco-hydraulic characteristics of rock weirs remain poorly understood, limiting the efficiency of rock weir design accounting for fish habitat restoration. Two series of flume experiments to investigate the flow field evolution (using particle track velocimetry) and fish swimming (using juvenile silver carp) around rock weirs on a sediment bed are presented. The experimental results show that: (1) the sudden change of bed elevation at the rock weir forms a vortex system and a high turbulence intensity zone downstream of the weir; (2) the increase in weir permeability reduces flow velocity above the weir and turbulence intensity in the downstream scour hole, facilitating successful weir crossing of fish by reducing their maximum swimming speed, acceleration, rate of work, and energy consumption during fish passage; (3) juvenile silver carp prefer to swim in flows with specific ranges of flow velocity, turbulence intensity, and velocity gradient, with over-weir flow velocity and velocity gradient being key parameters affecting their weir-crossing efficiency. This work improves the understanding of flow characteristics and fish swimming around rock weirs, providing important information for rock weir design in fish habitat restoration.

Tracing PCB contamination in fish using shadow profiles and self-organizing maps.

A comprehensive review on the negative impacts on Sundarbans fisheries: Insights from the hydrological changes modulated by climate change and anthropogenic activities.

Trawling the archives: Long-term trends in fish taxonomic and functional diversity in UK coastal community.

Integration of new methodologies in monitoring native fish habitat and populations in the southwestern U.S.

This research examines the otolith microchemical characteristics of the critically endangered kunming snout trout (Schizothorax grahami) collected from the sources section endemic to the Chishui River, China, a tributary of the upper Yangtze River, and the metal concentrations in the water of fish habitats. Among the analyzed elements, strontium (Sr) exhibited consistent distribution patterns across otolith rings, as observed through face-scan imagery (scanning the polished surface of the otolith cut), with a relatively low coefficient of variation. Statistical analysis using a paired two-tailed t-test revealed significant differences in Sr:Ca ratios among samples from the three river sections. Notably, magnesium (Mg) levels in the otolith core during the early life stages of the fish were notably higher compared to non-core regions. Similarly, Mg concentrations of water were elevated in the spawning grounds relative to non-spawning areas. This suggests that otolith Mg content may be influenced by the specific water conditions of the spawning grounds. Furthermore, Mg:Ca ratios in the otolith core displayed significant variation among samples from U3, L2, and other sites, implying that the fish in these samples originated from distinct spawning locations. These findings demonstrate that strontium and magnesium in otoliths can serve as effective markers for reconstructing the life history of S. grahami in the Chishui River and can contribute to the management of different fish stocks.

Banggai Cardinalfish (BCF) habitat is found in protected waters, such as Lalong Bay, Banggai Regency. Banggai cardinalfish are associated with various biota such as sea urchins (especially Diadema setosum) which live close to coral reef, seagrass and mangrove ecosystems. The aim of this research was to analyze marine debris contamination in Banggai cardinalfish habitat in Lalong Bay. This research used a quadrat sampling method (2m x 2m) along 20 m-30 m line transects at 4 research stations. Based on the analysis, organic marine debris types comprised: medium-sized pieces of wood, wood chips, coconuts, coconut husks, leaves and fish carcasses. Inorganic marine debris types comprised glass bottles, tin cans, light bulbs, baby diapers, cooking oil bottles, mineral water bottles, plastic cups, plastic spoons, toothbrushes, buoys, plastic packaging, plastic baskets, lighters, ropes, fishing nets, styrofoam, rubber sandals, tires and other plastic debris. The average amount of debris was 17 items/m2, volume 0.13 m3, weight 1,251 gr/m2 at Station 1; 16.75 items/m2, volume 0.10 m3, weight 1,157 gr/m2; at Station 2; 20.5 items/m2, volume 0.04 m3, weight 2,341 gr/m2 at Station 3 26.3 items/m2, volume 0.07 m3, weight 1,895 gr/m2 at Station 4. Based on observations at these stations in the port, much of the BCF fish habitat was found to be exposed to marine debris due to high levels of human activity and a lack of waste management capacity.

Abstract The potential of coastal regimes for supporting permanent human settlement is tempered by the vulnerability of fixed infrastructure to changes in sea levels. First-millennium AD civic-ceremonial centers on the northern Gulf coast of Florida involved the construction of permanent infrastructure in support of regional gatherings that challenged sustainable settlement in the context of regressive sea. Although rising sea was the more common challenge over millennia of coastal dwelling, marine regression from periods of cooling climate slowly diminished near-shore habitat for fish and shellfish and eventually stranded settlements from tidal water. The challenge was especially acute for a community that built a tidal fish trap for summer solstice feasts, whose utility depended on the reliability of tides to flood the trap. High-resolution lidar data from the Richards Island fish trap enable accurate modeling of the effectiveness of the trap under current and lowered sea levels. The use-life history of the Richards Island fish trap illustrates the limits to intensification of coastal economies inherent to nonportable infrastructure whose utility is tide dependent—in particular, when demands on production are out of sync with optimal tidal conditions.

There is a growing recognition that sediments dredged to maintain navigation and port infrastructure are valuable resources that can be placed in the aquatic environment to achieve ecological benefits if managed appropriately. However, specific interactions and long-term influences of placement on local aquatic ecosystems, particularly fisheries, remain to be fully explored. Therefore, the aim of this review was to identify and synthesize key factors influencing the outcomes of stable underwater features (e.g., berms, reefs, mounds) created from open water placement (OWP) of dredged sediments on fish habitat. Emphasizing ecological, biological, and artificial habitat perspectives, the review explored historic OWP techniques and features, their habitat alterations, and identified reported physical, biological, and chemical factors that influence fish. Results from this review suggest that underwater features can influence fish habitat by changing benthic relief, voids, and rugosity while altering hydrology through upwelling, velocity shelters, and lee waves. Additionally, as short-term disturbances to resident benthic fauna and flora can occur, recolonization rate and successional stages are important biological factors to consider at OWP sites aimed at ecological improvement. Collectively, these data provide insight into integrating intentional design features to improve locally diversified and enhanced aquatic habitats beneficial to fish and other organisms, through attributes such as height, shape, side slope, sediment grain size, micro effects on hydrodynamics and benthic prey resources.

Understanding the population dynamics of fish is vital to maintaining healthy ocean ecosystems and the human communities that depend on them. However, most fish population models lack crucial information about early life stages. Even when fish embryos and larvae (collectively, ichthyoplankton) are sampled, similar morphological features make species-level visual identification difficult, especially for embryos. So, although the Northeast US continental shelf is well-studied, existing ichthyoplankton datasets generally lack species-level information on embryos. Unlike visual methods, DNA barcoding can readily discriminate between morphologically indistinguishable specimens. Thus, our dataset of 2,294 DNA barcoded fish embryos and larvae, collected near New York (USA), contributes valuable insight into local ichthyoplankton assemblages. This dataset contains 50 unique species. Most have previously been documented in our region, but one was novel: we identified an embryo of Bathyanthias mexicanus, a species not known to inhabit or spawn in the sampled area. More broadly, this dataset can be used to address questions about fish habitat across life stages and to help ensure that local fisheries are sustainably managed.

Abstract IntroductionFreshwater fauna are increasingly threatened by habitat degradation and climate change. Rising flood frequency and magnitude underscore the need for river restoration to enhance ecosystem resilience. While restoration is widely promoted, outcomes for freshwater fish remain inconsistent. Success depends heavily on restoration design, water quality, and bio‐indication tools. Yet, many studies lack an approach that considers fish demographics, assemblages, and habitat characteristics simultaneously.ObjectivesThis study assessed the effectiveness of remeandering designs on fish communities at both the river and reach scale. We evaluated ecological outcomes using multiple metrics, including the ecological quality ratio (EQR), species composition, demographics, life‐history traits, and environmental drivers.MethodsFish and environmental data were collected in restored and control reaches over 4 years post‐restoration and compared with historical reference data. We evaluated spatial and temporal trends and assessed how specific restoration designs influenced fish metrics.ResultsFive years post‐restoration, no significant river‐scale improvements in EQR were observed. However, several restored reaches showed clear local improvements. A positive trend over time highlights gradual ecological recovery and reflects the disruptive effect of a flash flood 1 year post‐restoration. The reach with a more complex restoration design exhibited higher juvenile abundance, broader reproductive guild diversity, and more complete age‐class structures.ConclusionsWhile river‐scale improvements were limited, reach‐scale results demonstrated that restoration design is crucial in driving fish recovery. Habitat diversity, conceived through in‐stream adaptations, emerged as a key factor for success.

ABSTRACTFish passes, traditionally designed to facilitate upstream migration, are now increasingly recognized for their multifunctionality, including bidirectional fish movement and habitat provision. This four‐year study at the Ottensheim‐Wilhering hydropower plant on the Austrian Danube tracked the migration patterns of the common nase (Chondrostoma nasus) using five PIT tag antenna arrays installed in a 14 km long, near‐natural bypass system, which integrates two natural tributaries. A total of 190 nase were tagged and released in the Danube upstream of the hydropower plant, and fish movement data were collected from November 2020 to June 2024. A large percentage (52.5%) of the tagged individuals entered the fish pass from upstream. Over the years, many individuals utilized the bypass system, including the integrated tributaries, for extended periods and were observed repeatedly visiting the fish pass, highlighting its role not just as a migration corridor but also as a suitable habitat. These findings underscore the multifunctionality of near‐natural fish passes, which not only restore longitudinal connectivity but also provide critical habitats for various life stages of rheophilic fish. The study challenges the assumption that fish passes are ineffective for downstream migration and suggests that such systems can play a significant role in supporting potamodromous fish populations in highly regulated rivers like the Austrian Danube.

The Canadian Environmental Effects Monitoring (EEM) program assesses whether mines in compliance with effluent regulations are associated with environmental impacts to fish populations, fish habitat, and fisheries resources. The EEM's fish population survey assesses indicators of survival (age), energy use (growth and gonad size), and energy storage (condition and liver size) using at least two sentinel species collected from a minimum of one exposure area and one reference area for statistical comparison. If a standard fish population survey is not feasible, proponents are required to implement a recognized alternative survey methodology that will produce data on the required endpoints. The McClean Lake Operation in Saskatchewan completed an assessment of wild bivalve populations (Sphaeriidae) as an alternative to the conventional fish population survey for its Phase 6 EEM program. The purpose of this paper is to describe the novel methods and results associated with this wild bivalve survey. Two species of fingernail clam (Sphaerium nitidum, Pisidium casertanum) were collected with minimal effort (2 days' effort) from both the reference and exposure areas in sufficient numbers for statistical robustness. Measures of survival, energy use, and energy storage were derived from the collections. Those data were deemed by the regulating agencies to meet the requirements of the EEM program under Canada's Metal and Diamond Mining Effluent Regulation (MDMER). Laboratory analysis required specialized equipment including a microbalance that could weigh to 1µg and a muffle furnace. The effort associated with the viable alternative method was similar to that of a conventional adult fish population survey.

With the characteristic of “decentralized distribution and local power supply”, small hydropower (SHP) in China has become a core means of solving the problem of insufficient power supply in rural and remote mountainous areas, effectively promoting the improvement of local livelihoods. However, for a long time, SHP has had many problems, such as irrational development, old equipment, and poor economic efficiency, resulting in some rivers with connectivity loss and reduced biodiversity, etc. The Chishui River Watershed is an ecologically valuable river in the upper reaches of the Yangtze River. As an important habitat for rare fish in the upper reaches of the Yangtze River and the only large-scale tributary that maintains a natural flow pattern, the SHP plants’ dismantling and ecological restoration practices in the Chishui River Watershed can set a model for regional sustainable development. This paper adopts the methods of literature review, field research, and case study analysis, combined with the comparison of ecological conditions before and after the dismantling, to systematically analyze the effectiveness and challenges of SHP rectification in the Chishui River Watershed. The study found that after dismantling 88.2% of SHP plants in ecologically sensitive areas, the number of fish species upstream and downstream of the original dam site increased by about 6.67% and 70%, respectively; the natural hydrological connectivity has been restored to the downstream of the Tongzi River, the Gulin River and other rivers, but there are short-term problems such as sediment underflow, increased economic pressure, and the gap of alternative energy sources; the retained power stations have achieved the success and challenges of power generation and ecological management ecological flow control and comprehensive utilization, achieving a balance between power generation and ecological protection. Based on the above findings, the author proposes dynamic monitoring and interdisciplinary tracking research to fill the gap of systematic data support and long-term effect research in the SHP exit mechanism, and the results can provide a reference for the green transition of SHP.

ABSTRACTThe 2020 Cameron Peak wildfire burned part of the Poudre River catchment in Colorado, USA. The river flows through a high‐gradient canyon before entering a lower‐gradient transition zone with modified channel morphology and flow regime. Widespread post‐fire erosion introduced fine sediment (< 2 mm) to the river, causing sediment deposition and a major fish kill. Fine sediment deposition in the transition zone partially blocked or filled fish habitat in channel margin backwaters and side channels and filled interstices in fish‐spawning habitat along the cobble‐boulder bed channel. During summer 2023, we quantified fine sediment retention at 18 sites along the river by measuring fine sediment volumes and embeddedness. Our objectives were to (i) evaluate whether reach‐scale geomorphic attributes or river distance downstream from the sediment source correlate more strongly with reach‐scale fine sediment volume and embeddedness and (ii) use 2D hydraulic modeling and incipient motion equations to estimate the discharge necessary to mobilize the channel bed and remove excess fine sediment. Reach location (canyon vs. transition zone) best explained the volume of fine sediment and embeddedness, although the reach‐scale variables of gradient and cross‐sectional area were significant predictors of fine sediment retention. Hydraulic modeling indicated that a 2‐year return interval flow mobilizes a substantial portion of the bed at the canyon site, whereas bed mobilization requires a 5‐ to 10‐year flow at the transition zone sites. Management to mitigate post‐fire sedimentation and stressors to fishes may need to emphasize changes in river corridor geometry where consumptive water use limits flushing flows.

Homogeneous fish communities use intertidal salt marshes at high tide, despite environmental diversity: insights from a large-scale monitoring program on French coasts.

Abstract Stocking of hatchery‐reared salmonids is still a common management strategy to supplement natural resources and improve recreational fishing catch. However, concerns have been raised about the effectiveness of stocking as there is evidence that stocked fish may replace prior resident fish or fail to settle at the intended stocking sites, resulting in downstream emigration and may subsequently die. This study evaluated whether stocked masu salmon (Oncorhynchus masou masou), a species widely stocked in Japanese streams, displace prior resident fish or emigrate from stocked site. Experimental stocking trials were conducted in an artificial channel with multiple pools where factors potentially affecting the interactions between residents and intruders can be controlled. We found that stocked intruder fish were more likely to move out of the artificial channel compared to prior resident fish. Our findings indicate that stocking of masu salmon may be ineffective in streams with prior resident fish and few available habitats as most stocked fish are unable to settle at the site stocked. Practical implication: To optimize stocking efficiency for species, which show prior residence advantage such as masu salmon, stocking should only occur in situations where suitable, unoccupied habitats are available and where site fidelity of stocked fish can be expected.

Impacts of dams on fish habitat connectivity greatly outweigh climate change in the Jinsha river basin, China