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The Bagrid catfish, Bagrus orientalis, historically sustained communities in the Rufiji River basin (RRB), Tanzania, but has rapidly declined due to high consumer demand and unsustainable fishing. Consequently, a Ramsar site was designated within the RRB, although its potential to revitalize overexploited populations beyond its boundaries is uncertain because of limited information on genetic connectivity. To address this uncertainty, 158 partial cytochrome oxidase subunit I sequences of B. orientalis were analyzed to quantify genetic connectivity in the RRB. We observed significant genetic differentiation, indicating limited connectivity among populations. Populations in the Ramsar site were genetically connected to those in the Kilombero Valley Floodplain (KVFP), but were distinct from those in Ruaha and Rufiji, which clustered separately. Our findings suggested the Ramsar site could revitalize overexploited KVFP populations, and emphasized the need for sustained efforts against its encroachment. However, limited genetic connectivity with Ruaha and Rufiji implied that conservation measures in the site might have restricted effect in these areas. Conservation efforts should extend beyond the Ramsar site, by promoting sustainable fishing and enhancing habitat connectivity in Ruaha and Rufiji. [ABSTRACT FROM AUTHOR]

The round goby (Neogobius melanostomus) is an invasive benthic fish first introduced to the Laurentian Great Lakes in 1990 that has negatively impacted native fishes through increased competition for food and habitat, aggressive interactions, and egg predation. While complete eradication of the round goby is currently not possible, intensive trapping in designated areas during spawning seasons could potentially protect critical native fish spawning habitats. Baited minnow traps were spaced 10 meters apart in shallow water along a 100-meter stretch of shoreline within the Duluth-Superior Harbor during the round goby breeding period (June to October) with captured round gobies removed from interior traps (N = 10) every 48 hours. These traps were bracketed by two pairs of reference traps deployed weekly for 48 hours, from which round gobies were also tagged and released. The number of round gobies captured in the interior traps declined by 67% compared to reference traps over the course of the study, with extended periods of no captures. The tagged round gobies showed high site affinity, with 82.8% of tagged fish recaptured at the previous release site. The results indicate that even at open water sites, which allow natural migration of round gobies into the area, extensive trapping could reduce local population numbers. [ABSTRACT FROM AUTHOR]

We conducted an acoustic telemetry study of native golden perch (Macquaria ambigua) to examine movement behaviour in areas affected by methane seeps and hypoxia in the intermittent Condamine River, Murray‐Darling Basin (MDB), Australia.Fish were collected during periods of no flow and hypoxia (dissolved oxygen [DO] <1 mg/L). Despite these conditions, 38 of 43 fish tagged with acoustic transmitters were detected for >3 months post‐tagging in the study reach and 27 fish were being detected after 14 months. During periods of elevated river flow and relatively high DO, 30 fish moved away from their original tagging locations, with three undertaking movements (>7 km) outside the study reach and not returning.Generalised additive mixed models showed a significant increase in the probability of movement as soon as flow commenced and when water temperatures exceeded 19°C. As flows receded, most fish that had moved exhibited accurate homing behaviour to their original tagging location.The patterns of movement and site fidelity exhibited by golden perch correspond with previous studies of the species in intermittent rivers not affected by methane seeps and severe hypoxia, suggesting that the methane seeps and hypoxia did not inhibit fish movement nor render the affected habitats unsuitable for habitation.Golden perch can survive and remain active in water with much lower DO (<1 mg/L) than previously described for large‐bodied native fishes in the MDB. However, fish condition in the study reach was slightly lower than other regions of the MDB, providing preliminary evidence that fish residing in habitats affected by chronic hypoxia and methane seepage may experience sub‐lethal stress.Our results demonstrate the importance of field‐based data on the behavioural and physiological responses of fish to chronic hypoxia and methane exposure to guide appropriate management responses. [ABSTRACT FROM AUTHOR]

The present study is aimed to document the movement and habitat use of golden mahseers (Tor putitora) inhabiting the Himalayan waters in India. A total of nine adult golden mahseers (two males and seven females) fitted with a VHF radio tag were monitored between pre-monsoon and post-monsoon periods. The individuals were found dispersed with the maximum recorded distance of 4231.23 and 6119.11 m in the Kosi and Kolhu rivers respectively. Home ranges for males (0.0245 sq. km) and larger individuals (0.0697 sq. km) exhibited released side fidelity, whereas females (0.361 sq. km) and smaller individuals (0.459 sq. km) moved long distances. The results of this study identify the movements and spatial ecology knowledge of golden mahseer to conserve fish habitats. [ABSTRACT FROM AUTHOR]

Artificial barriers are one of the most damaging anthropogenic factors, but are also socio-economic constructions, so the decision between removing a barrier and installing a fishway must be justified. The aim was to develop a system to quantify the amount of suitable habitat for migratory fish above barriers, to assess barriers' passability, to prioritise them in current and historical terms and to take into account the impact of the reservoir in the selection of barrier management alternatives. For this purpose, the proportion of suitable area and the potential number of spawners were calculated separately for the flooded and free-flowing river sections above the barrier. The effect of the flooded area and fishway efficiency on the potential number of individuals was assessed and the historical importance of the areas above each barrier was evaluated. The results show that the proportion of suitable area in the total area above the barriers varies between 5 and 31%. Short river stretches of high habitat quality have a higher reproductive potential than much longer stretches of lower habitat quality. Dams with fishways can still be among the most negatively impacting barriers if they are located in the migration route of fish into a large part of the basin. [ABSTRACT FROM AUTHOR]

The development and application of approaches to detect and quantify environmental DNA (eDNA) have potential to improve our understanding of the distribution, abundance, and health of Atlantic Salmon Salmo salar and Pacific salmon Oncorhynchus spp. Here, we review 61 articles focusing on eDNA applications pertaining to salmon occupying natural habitat and aquaculture facilities in the context of advances, opportunities, and challenges. Given recent advances, eDNA now serves as a useful tool for detecting Atlantic Salmon and Pacific salmon and understanding threats to the health of fish and their habitats. Opportunities exist to apply sensitive and minimally invasive eDNA approaches to detect fish and assess fish habitat, assess range expansions of salmon and salmon pathogens, and detect invasive species that may threaten salmon health and abundance. Near real‐time eDNA detection and quantification approaches to inform fisheries management may be on the horizon. Challenges limiting the widespread application of eDNA approaches for informing salmon management include accounting for the many factors affecting detection and quantification of eDNA, limits of data for deriving inference, and expense. Through continued development and refinement, eDNA approaches are anticipated to become increasingly available to, and utilized by, managers of Atlantic Salmon and Pacific salmon fisheries. [ABSTRACT FROM AUTHOR]

Surf zones are crucial habitats for many fish species, where they spend the initial stages of their lives, finding food and shelter. One such species is the pompano (Trachinotus ovatus). The aim of this study was to examine the age and diet of the pompano within the surf zone, along with any potential variations in the environment. The average size of the specimens was 10.61 ± 4.91 cm. The length–weight relationship was total weight (TW) = 0.0136*total length (TL)2.8512 (parameter a: 95% C.I.: 0.0130–0.0142 and parameter b: 95% C.I.: 2.8318–2.8705). The most abundant age classes were 0+ and 1+, making up 97% of the captured specimens, with significant differences in the abundance of age classes depending on the time of the day and season. The pompano primarily fed on clupeiforms, copepods, and mysids, with significant variations in diet based on the time of the day, season, and size of the specimens. This study contributes new information about the use of the surf zone by T. ovatus in its early years of life, underscoring the importance of these areas and their role as an additional ecosystem service. [ABSTRACT FROM AUTHOR]

Herbivorous fish can mediate spatial competition between algae and corals, which is crucial for coral ecosystems. However, in areas with limited coral coverage like the Mexican tropical Pacific (MTP), this dynamic is not fully understood. This study, using a functional trait approach and ordination analysis, explores whether herbivorous reef fish assemblage influences the benthic habitat components or if physicochemical factors define the habitat variability in the MTP's Cleofas and Marietas insular systems. We analyzed if this relationship persisted across systems and over time, and identified species traits tied to habitat variability. Island comparison analyses between Cleofas and Marietas reveal that both herbivorous reef fish and physicochemical variables shape the habitat. Cleofas had larger mobile herbivorous fish that formed groups related mostly to macroalgae cover. In contrast, temporal analysis of Marietas shows that the habitat is primarily shaped by physicochemical variables with herbivorous fish being mainly small farmer species related to branching corals. Notably, these closely situated insular systems present varied ecosystem mediators, influenced by diverse drivers including fish traits and environmental factors. This study underscores the potential of employing a framework of ecological species traits combined with ordination methods to unravel the distinct site dynamics that contribute to the persistence of coral ecosystems within the MTP. [ABSTRACT FROM AUTHOR]

Queen snapper (Etelis oculatus) is of interest from an ecological and management perspective as it is the second most landed finfish species (by total pounds) as determined by Puerto Rico commercial landings (2010–2019). As fishing activities progressively expand into deeper waters, it is critical to gather data on deep-sea fish populations to identify essential fish habitats (EFH). In the U.S. Caribbean, the critically data-deficient nature of this species has made this challenging. We investigated the use of ensemble species distribution modeling (ESDM) to predict queen snapper distribution along the coast of Puerto Rico. Using occurrence data and terrain attributes derived from bathymetric datasets at different resolutions, we developed species distribution models unique to each sampling region (west, northeast, and southeast Puerto Rico) using seven different algorithms. Then, we developed ESDM models to analyze fish distribution using the highest-performing algorithms for each region. Model performance was evaluated for each ensemble model, with all depicting 'excellent' predictive capability (AUC > 0.8). Additionally, all ensemble models depicted 'substantial agreement' (Kappa > 0.7). We then used the models in combination with existing knowledge of the species' range to produce binary maps of potential queen snapper distributions. Variable importance differed across spatial resolutions of 30 m (west region) and 8 m (northeast and southeast region); however, bathymetry was consistently one of the best predictors of queen snapper suitable habitat. Positive detections showed strong regional patterns localized around large bathymetric features, such as seamounts and ridges. Despite the data-deficient condition of queen snapper population dynamics, these models will help facilitate the analysis of their spatial distribution and habitat preferences at different spatial scales. Our results therefore provide a first step in designing long-term monitoring programs targeting queen snapper, and determining EFH and the general distribution of this species in Puerto Rico. [ABSTRACT FROM AUTHOR]

There have been significant conceptual advances for identifying nursery habitats within coastal systems used by juvenile fishes and crustaceans. The approaches for delineating nursery areas include measures of juvenile abundance, growth, or survival; habitat characteristics; seascape connectivity; population fitness; and contribution to adult biomass (per unit area or total). We used all US coastal states as replicate trials to evaluate the integration of nursery concepts into fisheries management and found an obvious disconnect between expanding academic interest in nursery roles and management application. Among the few states that afford a subset of coastal environments with nursery status, easily obtained metrics (e.g. juvenile density or presence/absence of biogenic structure) are used, and it remains unclear what role nursery designations have played in promoting sustainable fisheries. Gathering the data necessary to use higher-order nursery approaches and metrics (e.g. connectivity and biomass contribution) to designate nurseries will require significant research investment and greater collaboration between ecologists and fisheries scientists. [ABSTRACT FROM AUTHOR]

Lakes and reservoirs provide multiple essential ecosystem services to humans, and several of these require the presence of a cool, oxygen‐rich hypolimnion. These ecosystem services include supporting habitat for recreational fish species and the maintenance of a non‐eutrophic state by limiting internal nutrient loading. However, changes in land use and global warming are modifying the thermal structure of lakes worldwide, creating episodic or prolonged periods of hypoxia, changing a lakes ability to deliver certain ecosystem services. Here, we used National Lake Assessment data and machine learning approaches to identify which lake or watershed features determined the presence of a hypolimnion and which contributed to the development of hypoxia. A random forest of 1000 trees predicted the presence of a hypolimnion with 85% accuracy using commonly measured morphometric and physicochemical variables as well as land use. Mean and maximum depths had a disproportionate influence, entirely obscuring the influence of variables commonly associated with lake mixing, such as light penetration and fetch. In contrast, depth had a more restrained role to predict the presence of hypoxia; the latter was predicted with an overall accuracy of 85%, from epilimnetic nitrogen and carbon concentrations. Although the nutrient‐color groups had a minor influence in the random forests, there was a clear trend of increased hypoxia with higher turbidity. Our approach allows for the broad‐scale assessment of lakes with hypolimnia and suggests that increasing eutrophication and browning will promote profundal hypoxia, altering the delivery of certain ecosystems services. [ABSTRACT FROM AUTHOR]

Oxygen minimum zones in the open ocean are predicted to significantly increase in volume over the coming decades as a result of anthropogenic climatic warming. The resulting reduction in dissolved oxygen (DO) in the pelagic realm is likely to have detrimental impacts on water-breathing organisms, particularly those with higher metabolic rates, such as billfish, tunas, and sharks. However, little is known about how free-living fish respond to low DO environments, and therefore, the effect increasing OMZs will have cannot be predicted reliably. Here, we compare the responses of two active predators (bigeye tuna Thunnus obesus and yellowfin tuna Thunnus albacares) to DO at depth throughout the eastern Pacific Ocean. Using time-series data from 267 tagged tunas (59,910 days) and 3D maps of modelled DO, we find that yellowfin tuna respond to low DO at depth by spending more time in shallower, more oxygenated waters. By contrast, bigeye tuna, which forage at deeper depths well below the thermocline, show fewer changes in their use of the water column. However, we find that bigeye tuna increased the frequency of brief upward vertical excursions they performed by four times when DO at depth was lower, but with no concomitant significant difference in temperature, suggesting that this behaviour is driven in part by the need to re-oxygenate following time spent in hypoxic waters. These findings suggest that increasing OMZs will impact the behaviour of these commercially important species, and it is therefore likely that other water-breathing predators with higher metabolic rates will face similar pressures. A more comprehensive understanding of the effect of shoaling OMZs on pelagic fish vertical habitat use, which may increase their vulnerability to surface fisheries, will be important to obtain if these effects are to be mitigated by future management actions. [ABSTRACT FROM AUTHOR]

Species distribution models (SDMs) are an important tool for conservation and resource management. However, managers are often interested in derived quantities such as range or area occupied, and how these are calculated can have a large impact.Ecosystem‐based management typically requires spatial information about species distributions, which is increasingly generated from SDMs that are then processed to identify occupied habitat. Many types of SDMs exist, but there is little research regarding how this model‐choice affects outcomes when defining occupied habitat, in part because these models generate different types of output.We fit a suite of five SDMs to data for 208 species/life stage combinations in three marine ecosystems while ensuring that they all estimate a 'common currency' of numerical abundance. We then calculate out‐of‐sample predictive performance to weight these constituents in an ensemble SDM.Results show that this approach can reduce bias arising from a priori specification of individual SDMs resulting in a better fit to survey data (constituent SDMs had a median of 7% higher RMSE). The SDMs had a range of responses relative to the ensemble, with MaxEnt typically predicting a median 1.3% higher area occupied, and negative‐binomial GAMs predicting 21.4% lower area occupied.Two potential methods of identifying the area of occupied habitat from SDM outputs are compared—probability‐based and cumulative density‐based methods. We find that cumulative densities result in smaller estimates of area occupied, and we recommend careful consideration of how model‐choice affects occupied‐habitat estimates in spatial management.Policy implications: Finally, we discuss how the patterns identified during the 5‐year Review of Essential Fish Habitat for Alaska should be carefully considered by managers using SDMs to identify habitat that may be impacted by anthropogenic activities. [ABSTRACT FROM AUTHOR]

Cold-water species in temperate lakes face two simultaneous climate-driven ecosystem changes: warming and browning of their waters. Browning refers to reduced transparency arising from increased dissolved organic carbon (DOC), which absorbs solar energy near the surface. It is unclear whether the net effect is mitigation or amplification of climate warming impacts on suitable oxythermal habitat (<20 °C, >5 mgO/L) for cold-loving species because browning expands the vertical distribution of both cool water and oxygen depletion. We analyzed long-term trends and high-frequency sensor data from browning lakes in New York’s Adirondack region to assess the contemporary status of summertime habitat for lacustrine brook trout. Across two decades, surface temperatures increased twice as fast and bottom dissolved oxygen declined >180% faster than average trends for temperate lakes. We identify four lake categories based on oxythermal habitat metrics: constrained, squeezed, overheated, and buffered. In most of our study lakes, trout face either seasonal loss (7 of 15) or dramatic restriction (12 to 21% of the water column; 5 of 15) of suitable habitat. These sobering statistics reflect rapid upward expansion of oxygen depletion in lakes with moderate or high DOC relative to compression of heat penetration. Only in very clear lakes has browning potentially mitigated climate warming. Applying our findings to extensive survey data suggests that decades of browning have reduced oxythermal refugia in most Adirondack lakes. We conclude that joint warming and browning may preclude self-sustaining cold-water fisheries in many temperate lakes; hence, oxythermal categorization is essential to guide triage strategies and management interventions. [ABSTRACT FROM AUTHOR]

Background An ecologically and economically important species in East Asia, the natural resources of pen shell Atrina pectinate have suffered severe population declines due to habitat destruction, pollution, and overfishing. Assessing genetic diversity and population structure is the basis for establishing conservation programs for A. pectinate. Results Our data indicated that high genetic diversity was found in all six populations, with mean allelic richness (Ar) ranging from 8.255 to 9.734, mean observed heterozygosity (Ho) from 0.574 to 0.680, and mean expected heterozygosity (He) from 0.620 to 0.691. The five A. pectinate populations were divided into two clusters. This clustering result was partly consistent with their geographical origin; the RZ population did not cluster with the northern populations (DL, CD), suggesting that there is no genetic divergence and geographical differentiation between the North China Sea (CD, DL, and RZ) and the Southeast China Sea (HK and ST). Conclusion Our results show no significant genetic differentiation between samples from the North China Sea and the Southeast China Sea. High dispersal potential of larvae by passive drift with ocean currents may explain the lack of genetic differentiation between samples. The results suggest a weak level of genetic structure in A. pectinate with a long planktonic larval stage. [ABSTRACT FROM AUTHOR]

Freshwater fish are on the brink of extinction due to the degradation of habitat. The present research focused on the estimation of the environmental flow requirement of significant fish species in the Nambul River, Northeast India. Nambul is an important river that drains directly into Loktak Lake. Loktak Lake is an internationally important Ramsar-designated wetland. The environmental flow requirements of the significant fish, namely Bangana dero and Wallago attu, were estimated using the physical habitat simulation model (PHABSIM). The habitat suitability curves (HSCs) were employed in PHABSIM along with the instream habitat data of the crosssections for estimating the weighted usable areas (WUAs) of the two fish species. Based on the WUA-discharge curve, an optimum environmental flow requirement of 50 cumecs of discharge is recommended for the fish habitats. The estimation of minimum environmental flow requirements can be considered as an essential step toward conservation and sustainability. [ABSTRACT FROM AUTHOR]

Mahseer fish Tor soro, an endemic species in Indonesia, is currently declining its population due to the overreliance on wild captures to meet consumption demands. Furthermore, the survival rate of fry is alarmingly low, necessitating the implementation of sustainable fry cultivation initiatives to bolster the demand for Mahseer fish. Environmentally friendly aquaculture practices, particularly those employing the zero-water discharge principle, offer a promising solution for establishing Mahseer fish nurseries. In cultivation methods, adding bottom substrates to resemble the natural habitat of Mahseer fish can enhance their physical performance and improve fish welfare. This study aimed to evaluate the effects of different substrates on the nursery of Mahseer fish, specifically utilizing (A) coral rock, (B) limestone, (C) crushed stone, and (D) no substrate (control) as treatments. The results demonstrated that the use of substrate media in the cultivation tanks positively influenced water quality, stress levels, and production performance of Mahseer fish. Among the treatments, the utilization of coral rock (A) as a substrate medium yielded the best results in terms of water quality, stress response, and production performance throughout the study compared to the other treatments. [ABSTRACT FROM AUTHOR]

We compared abundance patterns and developed resource selection models for imperilled native southwestern (USA) fishes in the presence and absence of Black Bass (Micropterus spp.) to evaluate how fishes alter their selection for habitats when sympatric with a nonnative piscivore. We collected data using snorkel surveys and in‐stream habitat sampling in Fossil Creek (AZ), upstream (native fish only) and downstream (native and nonnative fish) of a fish barrier. The abundance of all Roundtail Chub (Gila robusta), small (≤127 mm total length [TL]; vulnerable to predation) Sonora Sucker (Catostomus insignis) and Speckled Dace (Rhinichthys osculus) was significantly reduced, but the abundance of both small and large (>127 mm TL; invulnerable to predation) Desert Sucker (Catostomus clarkii) was similar in sampling reaches with and without Black Bass. When sympatric with Black Bass, small Roundtail Chub increased their selection for riffles by 2.57 times and small Desert Sucker reduce their selection for pools by 6.90 times while also selecting for faster flow velocity and finer substrates in lotic mesohabitats. Large native fishes altered selection least, notwithstanding an increased selection for canopy cover in sampling reaches with Black Bass. Observed shifts in resource selection are consistent with predator avoidance strategies. Our study highlights the behavioural consequences of nonnative piscivores on native fish communities and stresses the importance of maintaining lotic mesohabitats as potential refugia for vulnerable native fishes when nonnative piscivores are present. [ABSTRACT FROM AUTHOR]

SCDP-Nucet has an essential activity in aquaculture - especially in the genetic improvement of cultured carp and the preservation and usage of freshwater fish genotypes using advanced integrated technologies for fish farming. Climate changes have a crucial role in fish farming because they negatively affect the water bodies and the fish metabolism. This study aims to monitor the water quality of ponds associated with weather data during two years (i.e., 2022 and 2023), from May to September. The climate change implications on fish habitats were also discussed. [ABSTRACT FROM AUTHOR]

River damming has brought great benefits to flood mitigation, energy and food production, and will continue to play a significant role in global energy supply, particularly in Asia, Africa, and South America. However, dams have extensively altered global river dynamics, including riverine connectivity, hydrological, thermal, sediment and solute regimes, and the channel morphology. These alterations have detrimental effects on the quality and quantity of fish habitat and associated impacts on aquatic life. Indeed, dams have been implicated in the decline of numerous fishes, emphasizing the need for effective conservation measures. Here, we present a global synthesis of critical issues concerning the impacts of river damming on physical fish habitats, with a particular focus on key fish species across continents. We also consider current fish conservation measures and their applicability in different contexts. Finally, we identify future research needs. The information presented herein will help support sustainable dam operation under the constraints of future climate change and human needs. Plain Language Summary: River damming yields great social‐economic benefits, but also causes significant eco‐environmental impacts, particularly on fish. Dams block fish migration routes, alter hydrological and water temperature regimes, and modify channel morphology. These changes impact fish physical habitats and associated communities. Here, we synthesize the impacts of river damming on fish physical habitats, and review potential conservation measures that could be used to off‐set or mitigate the impacts of dams on fish habitats, populations and communities. Key Points: Dam construction alters river hydro‐geomorphological conditions and hence influences fish habitat quality and quantityKnowledge of river hydrogeomorphology and reservoir properties can inform which conservation measures may benefit fish conservationLong‐term monitoring is needed to understand causal effects and synergies with climate change [ABSTRACT FROM AUTHOR]

Anthropogenic stressors are causing widespread coral mortality, leading to loss of coral cover and decreased structural complexity that threatens reef biodiversity, functioning, and ecosystem services. Reef fishes are intimately linked to coral reef complexity, but we lack a generic understanding of which species are particularly affected by reef flattening and what traits make them susceptible. We used extensive species‐ and trait‐based analyses to build a framework for western Atlantic fish association with both structural complexity and coral cover to better understand the implications of reef degradation. These analyses also highlighted the relative importance of live coral versus the structure it provides to reef fishes, which currently remains unclear. We modeled how 25 biophysical and anthropogenic factors correlated with the densities of 109 fish species across 3292 Floridian reef sites. The importance of a metric of structural complexity and coral cover to the abundance of each species was then isolated. Species with positive associations were categorized as likely future 'losers' and negative associations as 'winners'. We predicted that 53% of species will be losers on low‐relief reefs, while only 11% were losers with decreased coral cover. We found morphological, behavioral, and ecological traits, not phylogeny, mediate species' responses to reef degradation and that the loss of structure seemed more critical than the loss of coral cover. Eight traits explained 79.7% of the variation in species' associations with relief and six traits explained 27.8% of associations with coral cover. Smaller, streamlined, habitat and trophic generalists are more likely winners on flattened reefs and large‐bodied predators, among other taxa, are likely losers of reef flattening. Identifying these important traits provides insight into mechanisms that may link fish and complex habitats, which allows us to better predict assemblage‐wide responses to future reef flattening. [ABSTRACT FROM AUTHOR]

An ecohydraulic model system was developed to evaluate the effects of the Da‐Wei dam construction and possible fish restoration strategies. The ecohydraulic model system consists of a hydrodynamic model, a hydromorphology model, a habitat model, and the logistic and matrix population models. The effects of dam construction and fish stocking strategy on fish habitat and population status were studied in the Jiao‐Mu River, providing the modeled ecological status of Schizothorax prenanti and Schizothorax plagiostomus heckel populations within the river segment. The two fish species richness, fish age structures, and fish density distributions were predicted. Based on the fish number prediction, the optimal number of fish to stock was evaluated with the population models, and an optimal fish stocking proposition was worked out. The results indicated that the two fish species habitat quality and fish richness would decrease due to the hydropower dam construction, and the fish stocking strategy could make up the fish species ecological status. The findings could facilitate the quantity and quality assessment of a dam development plan and increase the success rate of fish restoration. [ABSTRACT FROM AUTHOR]

The use of underwater video techniques has expanded rapidly in ecological studies and is particularly desirable in protected areas since the method does not impact the habitat or remove fish. The Mediterranean Sea is a biodiversity hotspot under high anthropogenic pressure and consequently, non-destructive and non-extractive techniques for fish monitoring are advantageous. Here, we review 110 publications that used underwater video in fish-related studies in the Mediterranean basin. The most common technique used in the Mediterranean Sea was Remotely Operated Vehicles (ROV) (33%), followed by Remote Underwater Video (RUV) systems (20%), Diver Operated Video (DOV) systems (20%) and Baited Remote Underwater Video (BRUV) systems (19%). Approximately one third of the studies used an additional sampling method, such as fisheries-based or molecular methods with the aim to compare the surveying effectiveness or produce complementary data. The most frequent objectives of the reviewed studies were related to fish community structure, i.e., focusing on community wide metrics such as abundance and biodiversity, or behavioral analyses, while the most commonly studied environments were those of the western Mediterranean and shallow waters, usually involving sandy or rocky reef habitats. Sampling protocols differed widely among studies with transect lengths, soak times and baits all varying. Future research should focus on the least studied parts of the region, such as the eastern and southern Mediterranean Sea and deep-sea habitats. Finally, the development of standardized sampling protocols is recommended to ensure that data are comparable among studies. [ABSTRACT FROM AUTHOR]

In Canada's Northwest Territories (NT), industrial activities conducted during the winter, such as ice road construction and exploratory drilling, require the use of water from ice-covered water bodies. Withdrawal in excess of 10% of available under-ice volume can threaten fish habitat or other users. The Land and Water Boards (LWBs) of the Mackenzie Valley require water licences for water withdrawal beyond regulated thresholds. Applicants must provide information including identification and location of proposed water sources, timing and proposed volume of water and winter water withdrawal must be limited to ,10% of available volume to protect fish habitat under the ice. Many applicants are at early project stages and the necessary information on bathymetry and volumes of water is not readily available or requires expertise and effort that may not be feasible at the early stages of smaller projects. This paper describes the alternative method for determining available winter water volumes from lakes to support small-scale projects. A simple formula of 'allowable volume (m3) - surface area (m2) * 0.1 m' was developed and tested to provide a conservative estimate of under-ice volumes from easily available data which is protective in spite of uncertainties inherent in limited data. [ABSTRACT FROM AUTHOR]

This study focused on major fish species caught from different ecological habitats to analyze the habitat changes in economically important fish in the Beibu Gulf. The maximum entropy model was constructed based on the data from 26 voyages obtained through the otter trawl fishery stock surveys conducted in the Beibu Gulf from 2006 to 2018. A total of 10 taxa of major fish catches, belonging to 4 families, 1 genus, and 5 species, were analyzed for their distribution characteristics in potential habitats during various ecological periods, specifically the withered and high-water periods, as well as their relationships with crucial environmental factors. During both the withered and high-water periods, the average area under the curve was 0.927, and all models had values exceeding 0.9. Salinity was identified as the principal factor during both periods. The salinity niche of Acropoma japonicum and the primary productivity niche of Sciaenidae were identified as the most restricted factors. The total distribution area of potentially suitable regions for major fish catches extended between 106°30′–109°45′ E and 17°30′–20°45′ N, and the area was lesser during the withered period. During the withered period, the distribution areas of Sciaenidae, Leiognathidae, and Saurida increased, while the distribution area of Trachurus japonicus increased during the high-water period. Sciaenidae and Trachurus japonicus exhibited the highest rates of change at 6.22% and 10.92%, respectively. This indicates that the high-water period may expand the range of suitable habitats for large catches that have an ideal habitat status in the Beibu Gulf. Therefore, it is crucial to anticipate the potential fish habitats in the Beibu Gulf and clarify their spatial distribution patterns. [ABSTRACT FROM AUTHOR]

Movements of the tiger shark (Galeocerdo cuvier) by life stage are largely unknown yet are necessary to determine essential fish habitat and sustainable fishery management practices. In an effort to elucidate distribution and movements of the tiger shark, we analyzed fishery-dependent and -independent tag (sample size [n]=10,516) and recapture (n=762) records for sharks caught in the North Atlantic Ocean during 1963-2018. Seasonal distribution of the tiger shark was examined by life stage--young of the year, juveniles (immature), and adults (mature)--and distribution patterns were used to identify potential nursery habitat. Tiger sharks were caught over a wide area from the Grand Banks of Newfoundland, Canada, south to Brazil and from coastal to offshore waters and into the eastern North Atlantic Ocean. Seasonal north-south movements were observed in all life stages, and 14 immature sharks were found to have migrated from the western to the eastern North Atlantic Ocean. A broad nursery area and a potential birthing area were identified on the continental shelf between Florida and Georgia on the basis of the repeated presence of neonates in summer across years and of the recapture of multiple tagged young-of-the-year sharks from the same location over a period of at least 2 years. [ABSTRACT FROM AUTHOR]

Florida spring-fed rivers are known for their submerged aquatic vegetation (SAV). which provides habitat for fish and aquatic crustaceans and food for the Florida manatee. Salinization of coastal spring-fed rivers due to climate change and sea level rise have been documented and can cause changes 10 SAV communities. This study investigated patterns and relationships between the SAV community and salinity of the Chassahowitzka River (Citrus County, FL, USA) to extrapolate the long-term effects of river salinization. A distinct dichotomy was seen in the SAV community structure: communities where salt tolerant Chaetomorpha spp. was present and communities where freshwater filamentous algae species were present. Freshwater filamentous algae demonstrated an inverse relationship with salinity. Chaetomorpha spp. replaced the freshwater filamentous algae in regions too salty for freshwater algae to grow. These patterns in the SAV community resulted in three different ecological zones in the Chassahowitzka River: low salinity/freshwater tidal, transition, and brackish zones. While freshwater filamentous algae and Chaetomorpha spp. were characteristic of the freshwater and brackish zones respectively, both species were identified within the transition zone. Utilizing the presence/absence of these macroalgae types could allow for an in-situ approach of characterizing regions of coastal spring-fed rivers that show increased salinization. [ABSTRACT FROM AUTHOR]

Freshwater aquatic ecosystems can be considered sentinels of change as they integrate signals from catchment, hydrology and biogeochemistry to provide an indication of how the system fluctuates. The Coorong estuary acts as a sentinel for the Murray-Darling Basin (MDB), Australia. Its location at the terminus of the Murray-Darling River systems, which drains more than 1 million square kilometres across 22 major catchments, means that any change to climate, water extraction or land use in the upstream catchments will have repercussions for the Coorong. It therefore acts as an indicator of the health of the MDB and the effectiveness of the Murray-Darling Basin Plan at protecting this ecosystem. Environmental water secured through the Murray-Darling Basin Plan and establishment of the Commonwealth Environmental Water Holder has been critical to preventing significant ecosystem decline in the Coorong. For most water years in the last decade environmental water has contributed to the majority of flow through the barrages. This has exported salt from the basin, reduced influx of salt from the ocean, and expanded available habitat for fish in the Coorong. However, the environmental flows have not been sufficient to arrest sand build up, and dredges still operate at the Murray Mouth during all but the highest flow events. There is a clear case for continued water management and reform, extending beyond the boundaries of the MDB, to further increase security of water flowing along the river system through the barrages and supporting the ecological health of the Coorong, and by association the full MDB. [ABSTRACT FROM AUTHOR]

The Least Chub (Iotichthys phlegethontis) is a small minnow endemic to the Bonneville Basin in Utah, where the current distribution of extant populations is limited to a few small spring complexes. We report on the first documentation of Least Chub in the upper Snake River drainage in Idaho. In June 2021, October 2021, and June 2022, we surveyed for small-bodied fishes in off-channel habitat of lower Henrys Fork in Cartier Slough Wildlife Management Area west of Rexburg, Idaho. Small-bodied fishes were sampled at 17 sites in off-channel habitat; 5 baited minnow traps (galvanized steel) were set for approximately 24 h at each site. We captured Least Chub in side-channel habitats during all sampling occasions; we captured 214 Least Chub in June 2021, 34 Least Chub in October 2021, and 41 Least Chub in June 2022. Least Chub were captured at 13 of the 17 sites: 6 sites in June 2021, 6 sites in October 2021, and 12 sites in June 2022. Least Chub ranged in size from 35 mm to 56 mm total length. In both June sampling occasions, female and male Least Chub were mature; females were expressing eggs and males had red/orange breeding coloration laterally. The habitat at sites where Least Chub were captured consisted of muddy or sandy substrate, slow-moving or stagnant water, submerged and emergent macrophytes, and filamentous algae. Additional surveys should be completed to determine the extent of the distribution of Least Chub in Henrys Fork and Snake River. Genetic analyses should also be completed to determine the relationship of this population of Least Chub to populations of Least Chub in the Bonneville Basin. [ABSTRACT FROM AUTHOR]

Bull trout (Salvelinus confluentus) research has historically focused on highly impacted systems or occurred in a reactionary manner following overharvest. Here, we used telemetry and multi‐state capture–recapture modelling to inform management decision‐making for this highly migratory, conservation‐listed species in British Columbia's upper Fraser River watershed (UFW). Our work reduced critical information gaps surrounding the seasonal migration patterns, distribution, and survival rates of fluvial bull trout within the region. By using results of an existing microsatellite DNA analysis, we were able to assign each tagged individual to one of five spawning populations. This assignment allowed us to investigate potential differences in migratory behaviour and seasonal habitat use among the different spawning populations. We identified that the majority of tagged UFW fluvial bull trout made repeated, long‐distance migrations (>300 km one direction) to appropriate spawning, overwintering and foraging habitats. The five populations did not vary in their seasonal transition probabilities at the spatial scale investigated, suggesting key habitats are important to multiple populations. We also detected post‐spawning migration and distribution patterns that suggest UFW bull trout exploit seasonal resource pulses during salmon smolt outmigration. Our results highlight the importance of protecting, restoring and maintaining a diverse assemblage of complex habitats and the natural connections between them (e.g. between tributary spawning habitats and larger rivers) at a spatial scale that supports migratory bull trout life histories. This work provides valuable information for prioritizing conservation actions and identifying restoration opportunities both in the UFW and across the species' range. [ABSTRACT FROM AUTHOR]

This study compares the hydromorphological quality of two sub-Himalayan Rivers, the Mahananda–Balason system (MBS) and the Chel–Neora system (CNS), to analyse the role of human intervention in channel hydromorphology. An indicator-based assessment, developed by Mitra et al. (Adv Space Res 71:1397–1417, 2022), is adopted here to obtain the hydromorphological quality. A hypothesis test using a two-tailed t-test and principal component analysis (PCA) is performed to identify the reaches with similar hydromorphological conditions along with aspects that needed restoration. Results show that the hydromorphological condition is highly influenced by the intensity of human alterations, and their interrelations are strongly proportionate. While the hydromorphological quality of unconfined MBS is highly degraded, that of unconfined CNS and the confined reaches of both systems have remained almost at their least disturbed condition (LAC). Intensive human interventions on MBS have impacted the groundwater table, riverine sediments, and fish habitat. Now, to maintain sustainability regarding riverine resources of CNS, close and regular monitoring must be initiated, and this methodology can serve that purpose. Being dependent on monitoring the ongoing interventions and the channel's physical forms, assessment protocols like this can serve the purpose of rapid hydromorphological assessment for the river systems of data-scarce regions. [ABSTRACT FROM AUTHOR]

Plastic‐related contaminants in the environment have attracted increasing attention, with plastic pollution becoming a serious issue globally. The present study investigated the potential bioaccumulation and biotransfer of bisphenol (BP) compounds that are widely added in various products such as plastics and other products in a freshwater ecosystem, China. Among commonly applied 14 BP analogues, bisphenol A (BPA), bisphenol F (BPF), and bisphenol S (BPS) were predominant, representing 64%–100% of the total concentrations of BPs (ΣBPs) in freshwater wildlife. Both the concentrations and analogue profiles in the fish showed seasonal differences and species dependence. Higher BP concentrations were observed in fish collected during the dry season than the wet season. Higher percentages of non‐BPA analogues (e.g., BPS and BPF) were observed in fish collected during the wet season. Pelagic species accumulated notably higher levels of BPs than midwater and bottom species. The liver generally contained the highest ΣBPs, followed successively by the swim bladder, belly fat, and dorsal muscle. The analogue profile also showed some differences among tissues, varying by species and season. Lower ΣBPs but higher percentages of non‐BPA analogues were observed in female than male common carp. Time trends of the BPA concentration in fish varied by species, probably related to habitats and diets of the fish. Habitats, feeding behaviors, and trophic transfer may have significant impacts on exposure of wildlife to BPs in natural ecosystems. The BPs did not demonstrate strong potential for bioaccumulation. More research is warranted about metabolism and transgenerational transfer of BPs in wildlife to fully reveal the bioaccumulation and consequently ecological risks of these chemicals in the environment. Environ Toxicol Chem 2023;42:2130–2142. © 2023 SETAC [ABSTRACT FROM AUTHOR]

The nursery function of littoral habitats for juvenile fish is widely recognized, but data on the specific habitat features that contribute to this function is sparse for many species, in part related to the difficulty of studying juvenile fish in their natural environment. However, this information is required to understand the potential risks of environmental change to the nursery functions of habitats. In this context, the habitat choice behaviour, with respect to differences in structural features, was evaluated for three Mediterranean littoral fish species known to be associated to macrophytes as juveniles. The overarching aim of this experiment was to determine if juveniles actively choose between different macrophyte configurations of varying complexity and height. Juveniles were exposed simultaneously to multiple visual habitat stimuli within an experimental choice arena, and their swimming behaviour was tracked by video recordings to determine the amount of time they spent near each habitat configuration. All three species showed a clear association in their occupancy towards more complex habitat configurations demonstrating that juveniles distinguished and actively selected habitats using visual cues. Subtle differences in species' affinity for complex habitats allowed us to appraise their potential vulnerabilities to habitat loss in the Mediterranean under environmental change scenarios. Furthermore, the results of this study provided evidence that differences in juvenile distribution between habitats found in previous observational studies may indeed be caused by active habitat selection, as well as through differential survivorship rates. [ABSTRACT FROM AUTHOR]

Warmwater fish habitat in the San Juan River of the southwestern United States has been reduced by over 30% as a result of water depletion, reservoir inundation, and cold‐water dam releases combined with drought‐related changes in hydrology. This reduction and a suite of other factors have contributed to declines in native fish populations including the federally endangered Colorado Pikeminnow (Ptychocheilus lucius) and Razorback Sucker (Xyrauchen texanus). Conservation efforts for these species include determining flow needs; protecting, managing, and augmenting habitats; and stocking hatchery fish. But the young of stocked fish have low survival due largely to a paucity of nursery habitat not being reformed and maintained under current conditions. Flow recommendations for Navajo Dam releases designed to mimic the river's natural hydrograph have not been met due to water shortages, and the desired outcomes of increased channel complexity and enhanced fish habitat have not been observed. Forecasted hydrology that includes ongoing drought shows that achieving the flow targets through further dam reoperations is unlikely. Mechanical construction of early life‐stage habitats is a highly recommended complement to flow management for offsetting the effects of flow reduction and habitat loss. Habitats with features that are effective and resilient under a range of flows are important in counterbalancing the effects of climate change. [ABSTRACT FROM AUTHOR]

Using unregulated tributaries to compensate fish habitat loss in dammed mainstreams has recently been suggested as a promising strategy for river ecological restoration. One critical prerequisite is to find potential tributaries as alternative habitat, which depends on precise fish community surveys. In this study, both eDNA metabarcoding and electrofishing were used to characterise fish community compositions in the dammed lower Jinsha river and its tributaries (Heishui, Pudu, and Xiaojiang rivers) in China. The fish community composition detected by eDNA metabarcoding was consistent with that detected by the conventional method. Besides, metabarcoding has the advantage of detecting the presence of rare species with relatively low abundances. The non-metric multidimensional scaling showed that there was no significant difference in fish community composition between the mainstream and the Heishui river, while there was large difference in the fish community composition between the mainstream and other tributaries. The effectiveness of using the Heishui river as alternative fish habitat was verified by comparing the changes in fish communities before and after the impoundment of the mainstream. Taken together, this study indicates that eDNA metabarcoding is a viable method to identify the suitable tributaries which at least partly compensate for fish habitat loss in the dammed mainstream. [ABSTRACT FROM AUTHOR]

Fish habitat temperatures are increasing due to human impacts including climate change. For broadly distributed species, thermal tolerance can vary at the population level, making it challenging to predict which populations are most vulnerable to warming. Populations inhabiting warm range boundaries may be more resilient to these changes due to adaptation or acclimatization to warmer temperatures, or they may be more vulnerable as temperatures may already approach their physiological limits. We tested functional and critical thermal tolerance of two populations of wild Oncorhynchus mykiss near the species' southern range limit and, as predicted, found population-specific responses to temperature. Specifically, the population inhabiting the warmer stream, Piru Creek, had higher critical thermal maxima and higher functional thermal tolerance compared to the population from the cooler stream, Arroyo Seco. Arroyo Seco O. mykiss are more likely to experience a limitation of aerobic scope with warming. Piru Creek O. mykiss, however, had higher resting metabolic rates and prolonged exercise recovery, meaning that they could be more vulnerable to warming if prey or dissolved oxygen become limited. Temperature varies widely between streams near the O. mykiss southern range limit and populations will likely have unique responses to warming based on their thermal tolerances and metabolic requirements. [ABSTRACT FROM AUTHOR]

The Arabian/Persian Gulf ('Gulf' hereafter) is bordered by eight countries that consider fishery as their most important renewable resource. This includes artisanal fisheries, which are a major contributor to seafood production and fishers' livelihoods. Despite the importance of the artisanal sector, in-depth studies examining aspects—like total and country-specific production trends, used fishing gears and main threats—remain limited. Inadequate knowledge about such fundamental aspects could jeopardize the sustainability of fisheries and muddle policymaking. Here, we provide a comprehensive account of artisanal fisheries in the Gulf. Specifically, we examined: (i) magnitude of the artisanal sector, (ii) types of fishing gears used, (iii) exploited functional groups, and (iv) threats to and opportunities for sustainable artisanal fisheries. We show that around 71% of the Gulf total catch is produced by artisanal fisheries, and this trend is growing. The dominating fishing gears are gillnets, traps, and lines—collectively accounting for 72% of the total catch. Among these fishing gears, gillnets alone account for a third of the production. Most of the artisanal catch comprises medium to large fish that are demersal, pelagic, and reef-associated. Fisheries are primarily based on gear restrictions, minimum size of capture, seasonal closures, and spatial restrictions. However, weak enforcement is a core issue for the effectiveness of management regulations. Mismanaged fisheries, coastal development, and climate change are primary threats facing fish abundance and essential fish habitats. Engaging artisanal fishers in management and preserving habitats can contribute toward sustainable artisanal fisheries in the Gulf. [ABSTRACT FROM AUTHOR]

We evaluated a wetland habitat modification strategy to contrast fish assemblage structure and the production of young‐of‐the‐year (YOY) fish between different engineered habitats (i.e., spawning pool complexes and connectivity channels) relative to unmodified lateral channels in a large drowned river mouth tributary of the St Lawrence River. Prior to habitat modifications, the coastal wetland was impaired by water level regulations and dominance of the invasive hybrid cattail, Typha × glauca, which collectively replaced or created barriers to seasonally flooded spawning habitats important to fish. Connectivity enhancements provided fish access along a wetland habitat gradient from sedge‐meadows to the deeper water robust emergent main channel. Across an 8‐year fish emigration dataset (2012, 2013, 2016–2021) more than 90% of all captured fish (Ntotal = 218,086 fish) were YOY and modified habitats outperformed the unmodified channels in total fish catch‐per‐unit‐effort (CPUE) per year (both YOY and non‐YOY). Spawning pool complexes had higher YOY species richness than unmodified channel habitats. Fish assemblage structure differed between the modified habitats, where connectivity channels and unmodified channels shared a more similar fish assemblage than spawning pool complexes. Modified habitats, however, supported warmer water and higher dissolved oxygen than the unmodified channels. Redundancy analysis and linear mixed‐effect modelling with abiotic variables (hydrology, temperature and dissolved oxygen) showed significant effects on fish assemblage structure, species richness and CPUE of fish emigrating from the modified and unmodified habitats. Historic flooding in 2017 and 2019 was a primary driver of YOY fish production and fish assemblage structure, but also appeared to be associated with near anoxic conditions systemwide. YOY fish for several species was inversely affected by floods at spawning pool complexes, but CPUE of YOY fish for these species appeared unaffected at the connectivity channels despite low dissolved oxygen. Diversified habitat structure (i.e., connectivity channels and spawning pool complexes) offers a management option to enhance habitat for fish that allowed compensatory effects on the capture of YOY fish of several species during floods. This multifaceted outcome from the habitat modifications resulted in unique fish assemblages between the channelized and spawning pool habitat. A connectivity‐based habitat enhancement strategy provides adaptability for an uncertain climatic and regulatory future for the Laurentian Great Lakes and St Lawrence River. [ABSTRACT FROM AUTHOR]

Although submerged macrophyte (hereafter, "macrophyte") communities are globally prevalent in low-gradient rivers, the net reach-scale effect of macrophytes on drift-feeding fish microhabitat preference is poorly understood. We used snorkeling and bioenergetics to study fish habitat selection for rainbow trout (Oncorhynchus mykiss) in the Henrys Fork, ID, USA, investigating microhabitat preference across a reach-scale gradient of macrophyte growth. Fish preferred microhabitats with deep water, low velocity, and low macrophyte coverage. Preferences for microhabitats with higher net rate of energy intake (NREI) were modulated by reach-scale macrophyte coverage, higher coverage increasing preferences for higher NREI. Macrophyte coverage was a weak positive predictor for depth and NREI, and a weak negative predictor for water velocity and median substrate. Our results suggest trade-offs between fish predation risk and bioenergetic food intake, with macrophytes modulating these trade-offs across scales by affecting reach-scale geomorphology, bioenergetics, and predation risk. As such, this study highlights the important and dynamic role that macrophytes can play in fish population dynamics in rivers, with important implications for management decisions. [ABSTRACT FROM AUTHOR]

Intertidal systems are constrained by landscape morphology. Where these systems do occur, they often experience a wide range of anthropogenic impacts, further exacerbated by sea‐level rise (SLR). By mapping natural morphological constraints, anthropogenic impacts and modeled SLR, at an estuary‐wide scale the Marine Vegetation Management Strategies (MVMS) identify and prioritize sites and interventions that could address key threats and risks to the system enabling rehabilitation. Development of MVMS is part of an initiative within the broader New South Wales (NSW) state government's Marine Estate Management Strategy to deliver healthy coastal habitats. The MVMS are being developed to take a policy of "no net loss of key fish habitats" toward more active management of intertidal systems that maximize and sustain the ecosystem values and services. Spatial indicators were developed for a pilot estuary (Tweed River) to map and quantify "macrophyte potential" which is defined as the capacity for macrophytes (mangrove and saltmarsh) to deliver ecosystem services now and into the future (under scenarios of SLR). The approach incorporates datasets which indicate the geophysical nature of the landscape, anthropogenic exposure, and vulnerability to SLR. This strategic science‐based approach is being rolled out across coastal NSW, with the mapping products and associated resources identified as key tools to assist in the adopting of a more integrated approach to managing coastal wetlands. [ABSTRACT FROM AUTHOR]

Vegetation changes in saltmarsh habitat can influence fish assemblages and abundance. In Tasmania, Australia, mid‐latitude succulent saltmarsh communities have been invaded by the introduced tall grass, Spartina anglica. Eradication efforts have been ongoing since the 1990s with purported benefits for fish access to intertidal foraging grounds, but a lack of knowledge of the impact of S. anglica on fish limits understanding of the benefits and effectiveness of native habitat restoration. Here, we investigate whether fish assemblages in native saltmarshes and non‐native S. anglica grassland differ in species diversity, fish abundance, and size class distribution. We used buoyant pop nets to sample fishes in Sarcocornia quinqueflora herbland and S. anglica grassland swards at three sampling stations in northwest Tasmania. Very few individuals and low species diversity were recorded in both vegetation types at the sampling station with the most well‐established S. anglica infestation. Elsewhere, richness and diversity were higher in S. quinqueflora herbland. Overall fish abundance was higher in S. quinqueflora than in S. anglica, with a very strong effect at one sampling station. Fewer small individuals of the numerically dominant Atherinosoma microstoma were recorded in S. anglica, potentially indicating impaired nursery function. Our results provide important insights for S. anglica control, as we are the first to demonstrate a relationship between S. anglica presence and fish characteristics in southern Australian saltmarsh. These results indicate that S. anglica control is valuable for fish conservation. An extension of our research to document the effects of S. anglica removal on fishes is desirable. [ABSTRACT FROM AUTHOR]

Successful aquatic ecosystem conversation strategies depend on high-quality data from monitoring studies and improved habitat requirement knowledge. Remote Underwater Video (RUV) is a non-extractive alternative to capture-based techniques for studying and monitoring fish and is increasingly used in smaller channels. This study uses field observations made with waterproof Sony HDR-AS100V action cameras positioned in stream channels to determine species and population during various flow conditions across three sites within the Credit River Watershed, Ontario, Canada. Six fish species were identified, and individual fish lengths were estimated using the inverse square law to proportionally adjust size scales to fish positions relative to the camera. Successful identification and measurements were limited by turbidity, with camera placements in >6 NTU conditions (18% of all placements) resulting in at least one fish observed in the frame. With over 24 h of video recordings with 94 individual video clips, the optimal filming duration was determined to be 20–25 min. RUV surveys provide managers with useful monitoring data regarding fish present in an environment in a cost-effective and efficient manner. Additionally, as the method is largely non-invasive, RUV surveys are especially useful for studying fish behaviour, sensitive or endangered species, and working in difficult-to-access channels (e.g., shallow, faster flow). [ABSTRACT FROM AUTHOR]

Remote sensing technology offers the ability to derive information on freshwater fish habitats across broad geographic areas and has the potential to transform approaches to monitoring. However, the numerous platforms, sensors and analytical software that are available may overwhelm those interested in utilizing this important technology and thus limit its broad application and uptake. Our review is intended to shed light on the capacity of this technology to transform freshwater fish habitat monitoring by examining the fundamental characteristics of the major remote sensing technologies that have been used for characterizing freshwater habitats, conducting a systematic literature review of studies that have used remote sensing technologies to characterize freshwater fish habitats and, highlighting some of the key habitat features, fish species and regions, that have been examined. Lastly, we identify the relative strengths and weaknesses of the various remote sensing technologies that can be used, recommend future research that could help improve the use of these technologies, and, provide a series of important considerations for those who are interested in utilizing these technologies for freshwater fish habitat characterization. [ABSTRACT FROM AUTHOR]

Near‐future climate change projections predict an increase in sea surface temperature that is expected to have significant and rapid effects on marine ectotherms, potentially affecting a number of critical life processes. Some habitats also undergo more thermal variability than others, and the inhabitants therefore must be more tolerant to acute periods of extreme temperatures. Mitigation of these outcomes may occur through acclimation, plasticity or adaptation, although the rate and extent of a species' ability to adjust to warmer temperatures is largely unknown, specifically as it pertains to effects on various performance metrics in fishes that inhabit multiple habitats throughout ontogenetic stages. Here, the thermal tolerance and aerobic performance of schoolmaster snapper (Lutjanus apodus Walbaum, 1792) collected from two different habitats were experimentally assessed under different warming scenarios (temperature treatments = 30, 33, 35, 36°C) to assess vulnerability to an imminently changing thermal habitat. Larger subadult and adult fish collected from a 12 m deep coral reef exhibited a lower critical thermal maximum (CTmax) compared to smaller juvenile fish collected from a 1 m deep mangrove creek. However, the CTmax of the creek‐sampled fish was only 2°C above the maximum water temperature measured in the habitat from which they were collected, compared to a CTmax that was 8°C higher in the reef‐sampled fish, resulting in a wider thermal safety margin at the reef site. A generalized linear model showed a marginally significant effect of temperature treatment on resting metabolic rate (RMR), but there were no effects of any of the tested factors on maximum metabolic rate or absolute aerobic scope. Post hoc tests revealed that RMR was significantly higher for creek‐collected fish at the 36°C treatment and significantly higher for reef‐collected fish at 35°C. Swimming performance [measured by critical swimming speed] was significantly lower at the highest temperature treatment for creek‐collected fish and trended down with each successive increase in temperature treatment for reef‐collected fish. These results show that metabolic rate and swimming performance responses to thermal challenges are somewhat consistent across collection habitats, and this species may be susceptible to unique types of thermal risk depending on its habitat. We show the importance of intraspecific studies that couple habitat profiles and performance metrics to better understand possible outcomes under thermal stress. [ABSTRACT FROM AUTHOR]

Iceland's fisheries system is well-governed, data-rich, and has adapted to past ecological change. It thus provides an opportunity to identify social-ecological attributes of climate resilience and interactions among them. We elicited barriers and enabling conditions for adaptation in Iceland's fisheries from semi-structured expert interviews, using projections of fish habitat shifts by mid-century to guide discussion. Interviewees highlighted flexible management, highly connected institutions that facilitate learning, ample assets to expand adaptive options, and cultural comfort with change. However, examining how these attributes interact in reinforcing feedback loops revealed potential rigidity traps, where optimization for resilience to stock shifts may render the system more vulnerable to extreme environmental change and social backlash. This study articulates resilience attributes that Iceland and other fisheries systems might prioritize as the climate changes. It further explores circumstances in which these same attributes risk forming traps, and potential pathways to escape them. [ABSTRACT FROM AUTHOR]

The accelerating pace of climate-induced stress to global ecosystems threatens the sustainable management and conservation of biodiversity. To effectively respond, researchers and managers require rapid vulnerability assessment tools that can be readily implemented using diverse and existing knowledge sources. Here we demonstrate the application of multi-criteria analysis (MCA) for this purpose using a group of coastal-pelagic fishes from south-eastern Australia as a case-study. We show that MCA has the capacity to formally structure diverse knowledge sources, ranging from peer-reviewed information (which informed 29.2% of criteria among models) to expert knowledge (which informed 22.6% of criteria among models), to quantify the sensitivity of species to biophysical conditions. By integrating MCA models with spatial climate data over historical and future periods, we demonstrate the application of MCA for rapidly assessing the vulnerability of marine species to climate change. Spatial analyses revealed an apparent trend among case-study species towards increasing or stable vulnerability to projected climate change throughout the northern (i.e. equatorward) extent of the study domain and the emergence of climate refugia throughout southern (i.e. poleward) regions. Results from projections using the MCA method were consistent with past analyses of the redistribution of suitable habitat for coastal-pelagic fishes off eastern Australia under climate change. By demonstrating the value of MCA for rapidly assessing the vulnerability of marine species to climate change, we highlight the opportunity to develop user-friendly software infrastructures integrated with marine climate projection data to support the interdisciplinary application of this method. [ABSTRACT FROM AUTHOR]

Vegetated habitats play a key role in the structure and function of ecosystems by modifying local environmental conditions and providing food and habitat to a great range of organisms. The aim of this study is to assess the relative importance of two widely distributed macroalgae species in providing ecosystem functions in coastal areas where they are prevalent (Patagonia, Argentina, Lat 43.73°, Lon 64.92°) in comparison to low-vegetated areas without these two species. In October 2018 and May 2019, we tested whether Ulva spp. and Undaria pinnatifida perform a series of ecosystem functions commonly associated with vegetated coastal environments. Our study suggests that Ulva spp. decreases water current and provides habitat for epifauna, as the adjacent low-vegetated areas without Ulva spp. present higher gypsum block dissolution rates, lower biomass and richness of total epifauna, and lower grazer biomass than areas dominated by Ulva spp. U. pinnatifida, on the other hand, only showed a positive effect on epifauna biomass relative to low-vegetated areas, and no effect on the rest of the variables measured, despite providing similar levels of coverage to Ulva spp., and having a larger and more complex structure. None of the two macroalgae influence the habitat use by fishes. Despite smaller size and a labile structure, Ulva spp. presence had an effect on more variables than U. pinnatifida, and the function provided by U. pinnatifida was also provided by Ulva spp., namely U. pinnatifida did not provide new functions to the system. [ABSTRACT FROM AUTHOR]

Lake water clarity is an indicator of water quality, trophic status, and habitat condition. Changes in clarity impact lake ecosystems and may reflect land use changes or presence of invasive species. Quantifying temporal changes in water clarity can be challenging because clarity varies seasonally, annually, and spatially within and among lakes. We developed a hierarchical generalized additive model to quantify trends in water clarity (Secchi depth) from 1979 to 2018 for 909 Minnesota lakes, accounting for seasonal and spatial variability. Water clarity increased by 0.41 m across lakes from 1984 to 1988 and 2014 to 2018. Lake‐specific clarity trends varied: clarity did not change significantly in 59.0% of lakes, increased in 34.5% of lakes, and decreased in 6.5% of lakes. Water clarity dynamics caused considerable variability in littoral area between seasons and years. Our results have wide applications in aquatic ecology, including understanding changes to food webs, assessing fish habitat, and evaluating impacts of invasive species. [ABSTRACT FROM AUTHOR]