Wetland Fish Research Articles

Evaluating the Effect of Common Carp Control on Restoration of a Coastal Wetland in the Laurentian Great Lakes

Great Lakes coastal wetlands are under considerable stress from numerous anthropogenic threats, including the introduction of invasive species. Common Carp, an invasive species in North America, has been well documented as an influential wetland stressor. This study documents the impact of Common Carp reintroduction on a restored wetland fish community and abiotic and vegetation variables. Oshawa Second Marsh was restored using an exclusion berm with a fish grate and manual water-level drawdown to re-establish vegetation. Five years into restoration monitoring, Common Carp regained access to the wetland after the fish grate was vandalized. Fish community health was monitored over time using multimetric and multivariate approaches based on abiotic and vegetation variables. Improvements in fish community health were observed during restoration monitoring, but after Common Carp reintroduction, fish community health decreased and the community homogenized. Seven of the ten abiotic and vegetation variables monitored changed significantly after Common Carp reintroduction. This study highlights the impact that Common Carp has on the functional integrity of coastal wetlands and the significance of its management for restoration.

Assessment of Community Dependence and Perceptions of Wetlands in the Upper Chindwin Basin, Myanmar

Understanding the relationship between communities and wetland ecosystems is imperative to facilitate the development of wetland management and conservation strategies that can effectively safeguard wetland health and sustain the flow of ecosystem services. To understand the knowledge, attitude, and perception of communities on wetland ecosystem services, a survey was conducted involving 133 households from 4 villages dependent on 5 wetlands within the Upper Chindwin Basin (UCB), northwestern Myanmar. Most of the respondents extracted wetland resources for subsistence and income. A total of 84% of the households depended on wetland fish for their primary protein consumption, while 70% (n = 94) collected fuelwood from wetlands for subsistence. The survey participants unanimously recognized the benefits of wetland ecosystem services (i.e., provisioning benefits), particularly for fish, food, fiber, fuel, natural medicines, ornamental resources, and minerals. A total of 97% of the participants lacked knowledge of any existing law or regulation that ensures wetland protection in Myanmar. Furthermore, 87% of the respondents concurred that the government has not adequately endeavored to promote awareness of wetland conservation in this remote area due to lack of capacity and resources. This study establishes a baseline for the region and recommends designing and implementing a community-centric wetland action plan. This action plan provides a self-sustaining and cost-effective approach to conserve wetlands and is crucial in enhancing the capacity of dependent communities to participate and eventually lead wetland management of UCB.

Knowledge of Spawning Phenology may Enhance Selective Barrier Passage for Wetland Fishes

Knowledge of Spawning Phenology may Enhance Selective Barrier Passage for Wetland Fishes

Perspective of heavy metal potential risk in wetland soil and fish for amplified waste management around Lake Victoria, Uganda

Ssanyu GA, Kiwanuka M, Lunkuse I, Okumu D, Mbeiza NM. 2023. Perspective of heavy metal potential risk in wetlands soil and fish for amplified waste management around Lake Victoria, Uganda. Lake Reserv Manage. X:XXX–XXX. Increasing unsustainable agricultural and land management activities reduce the effectiveness of wetlands in absorbing heavy metals. This leads to high and detectable heavy metal levels in wetland soil and fish, respectively. This study assessed the content of heavy metals, particularly cadmium (Cd), chromium (Cr), cobalt (Co), lead (Pb), and nickel (Ni), in the water, soils, and commercial wetland fishes (Protopterus aethiopicus and Clarias galiepinus) from Lake Victoria wetlands with different land uses. Heavy metal analysis was done using inductively coupled plasma–optical emission spectrometry. Mean Cd and Pb levels were below the World Health Organization (WHO) permissible limits in all the wetlands’ water samples. Wetlands associated with urban or industrial development presented higher levels of Pb than other wetlands. Wairaka wetland, associated with commercial agriculture, presented a significantly higher mean concentration of Cr (191.2 mg/kg) in the soil than other wetlands. Cr and Ni contents were high in all fish muscle samples, while Cd and Pb contents in fish muscles were below WHO permissible limits, except for Clarias fish from 2 urban/industrial and one commercial agriculture affected wetlands, which had higher Pb than in other fish muscle tissues. The hazard index values of both fish species were greater than one from urban/industrial and commercial agriculture associated wetlands, implying that fish consumers would encounter noncarcinogenic health risks. More efforts are needed to strengthen Lake Victoria industrial and municipal waste management strategies to reduce the potential heavy metal risk in wetland soil and fish.

Higher abundance of adult pike in Baltic Sea coastal areas adjacent to restored wetlands compared to reference bays

The abundance of pike, a keystone top-predator, have declined dramatically in the Baltic Sea since the 1990s likely owing to recruitment failure. It has been proposed that wetland restoration can aid the recovery of the pike stock by increasing the number of recruits produced by anadromous populations. Yet, no previous studies have addressed whether wetland restorations are associated with higher abundances of adult pike in the coastal habitat. To address this, we performed standardised rod-and-reel survey fishing in paired bays with and without wetlands across three coastal areas and 3 years. To estimate dispersal and the contribution of wetland pike to the coastal stock, we tagged captured pike with passive integrated responders (PIT) and employed PIT reader stations in wetland inlets. The results showed that pike abundances were on average 90% higher in bays with an adjacent wetland although the effect varied among areas. Moreover, PIT-data uncovered that wetland pike constituted a high proportion of the pike found in adjacent coastal habitats and that some wetland fish dispersed up to 10 km. These results support that wetland restoration is a valuable tool to aid the coastal pike stock and ultimately restore the function and services of the coastal ecosystem.

Community associations of birds with amphibians and fish in wetlands created for biodiversity

Conservation initiatives to support declining water-related biodiversity through wetland creation have increased during the last decades. Multiple studies have evaluated the suitability of created wetlands for birds and amphibians, but only a few have considered the species associations that might also affect the outcome. Using joint species distribution models, we explored species associations of birds, amphibians and fish in 52 created biodiversity wetlands in Sweden. As most of these wetlands were primarily created for increasing bird diversity, we asked whether the occurrence of fish and amphibians relates to bird species richness, pair abundance and chick abundance (as a measure of reproductive success) and whether conservation conflicts or synergies between birds, amphibians and fish can be observed. In general, we found positive bird-amphibian association patterns and negative bird-fish association patterns, although the uncertainties were high for these estimates. In line with previous research, the generally negative bird-fish co-variance indicates potential conservation conflicts between wetland creation for birds and fish, where fish might be introduced for recreational fishing or other ecosystem services. Therefore, our results suggest that it can be hard to benefit bird and fish communities with the same wetland, and separate wetland creation with different goals may be needed. The generally positive bird-amphibian species-species associations and the lack of previous studies revealing conflicts indicate synergies between wetland creation for birds and amphibians. However, research needs to further consolidate such synergies, including amphibian reproductive output from bird-rich wetlands.

Life-history of the Caucasian dwarf goby Knipowitschia caucasica in an Iranian coastal wetland of the southern Caspian Sea

The Caucasian dwarf goby Knipowitschia caucasica is a small fish in the coastal wetlands of the southern Caspian Sea. The objective of this work was to describe its life-history aspects from individuals collected in the Gomishan wetland of Iran, a highly degraded ecosystem. We collected 707 fish along 18 months and calculated a short life span, TL∞=47.25mm for males, and TL∞=43.05mm for females, high mortality rate (1.84 and 5.83 year-1 for males and females, respectively), female dominance (M: F as 1: 1.22), low fecundity (average absolute fecundity: 672 oocytes.female-1 and mean relative fecundity 1209 oocyte.g-1 ), comparatively large oocytes (0.593 mm, ranging from 0.220 to 0.924 mm) and dependence on the wetland for spawning. Given adverse environmental changes in wetlands, we support the hypothesis that life-history traits confer this fish a high probability of extinction.

Ecological value of gravel pit ponds for floodplain wetland fish

Abstract Floodplain wetlands support high biodiversity, but they have been degraded and geographically fragmented due to human activities. Some types of human‐created waterbodies have received growing attention as alternative habitats for conserving wetland biodiversity. Gravel pit ponds (GPPs) are human‐created wetlands formed when a gravel pit is excavated at or below the water table and filled with groundwater. Differences in community structure among GPPs and floodplain wetlands with respect to habitat characteristics are scarcely known, resulting in insufficient evaluations of the ecological value of GPPs for floodplain wetland species. In this study, we evaluated the ecological value of GPPs for wetland fishes in floodplain landscapes. We surveyed fish abundance, community composition, and 10 environmental factors in GPPs and two types of floodplain ponds (remnant ponds and river backwaters) to clarify the biotic and abiotic differences among the pond types. Environmental factors were similar among the pond types, with only water temperature and the distance from the main channel to the pond significantly lower in river backwaters. The richness and abundance of native fish species did not differ among the pond types, but species composition did. Rhynchocypris percnura sachalinensis, Carassius sp., and Lethenteron sp. N (one of the two cryptic species of Lethenteron reissneri) were selected as indicator species in GPPs, remnant ponds, and river backwaters, respectively. These results indicate that GPPs provide valuable habitats for wetland fishes in floodplain landscapes and support regional γ diversity. Since many species inhabited the GPPs in this study, including red list species, appropriate management of GPPs is important to conserve wetland fishes.

Evaluating the Spatial Distribution of Some Toxic Substances Concentration with the Microbial Contamination of Wetland Water, Sediment and Fishes, and Their Potential Health Hazards

This study evaluated the impact of anthropogenic factors on the accumulation of toxic materials in wetland. The wetland was micro-zoned into five sub-regions, namely; NDE, ISN, ISS, UGS and BUR. Sediment, water and fishes (catfish and tilapia) were sampled from each locality. Heavy metals (Cd, Cr, Cu, Ni, Fe, Pb and Zn) and total petroleum hydrocarbon (TPH) of the samples were determined. The pollution indices (Bioaccumulation quotient “BQ”, contamination factor “CF”, geoaccumulation index “Igeo”, enrichment factor “EF” and Pollution load index “PLI”) and potential health risks (Metal Pollution Index “MPL”, Estimated Daily Intake “EDI”, Total Health hazard quotient “THQ” and Hazard index “HI”) of the water, sediment and fish flesh were calculated appropriately. The results revealed that the wetland fishes contained viable bacteria which ranged between 1362.0 cfu/g and 2634.3 cfu/g. Heavy metal level ranking in the sediment and water was Fe > Zn > Cu > Pb > Ni > Cr > Cd. Spatially, the heavy metals concentration in the water, sediment and fish followed the order: BUR > UGS > ISN > ISS > NDE. The TPH concentration in water, sediment and fishes differed significantly across the five sub-regions (p≤ 0.05), and its value ranged from 3.44 mg/kg to 99.38 mg/kg for the catfish, 2.08 mg/kg to 83.73 mg/kg for the tilapia, 25.34 mg/kg to 718.87 mg/kg for the sediment and 0.016 mg/kg to 1.099 mg/kg for the water. Spatial ranking of the TPH levels in the fish flesh was BUR > UGS > ISN > NDE > ISS; sediment TPH level ranked BUR > UGS > NDE > ISN > ISS; and the water TPH level ranked BUR > UGS > ISN > ISS > NDE. Human health risks associated with the consumption of the wetland fish ranked thus BUR > UGS > ISN > NDE > ISS. It was evident from the results that anthropogenic actions from resulting poor regional planning had significant effect on environmental health. The results called for environmental protection for public interest in order to prevent disease epidemics.

Comparison of sampling methods for small oxbow wetland fish communities.

Throughout the world, wetlands have experienced degradation and declines in areal coverage. Fortunately, recognition of the value of wetlands has generated interest in preserving and restoring them. Post-restoration monitoring is necessary to analyze success or failure, thereby informing subsequent management decisions. Restoration of oxbow wetlands has become the focus of targeted restoration efforts to promote recovery of biodiversity and sensitive species, and to enhance ecosystem services. The fish communities of oxbows have been the subject of many monitoring studies. However, a recommended sampling methodology for monitoring the fish communities of oxbows has not been described, thereby limiting our capacity to effectively monitor these ecosystems. We compared four sampling methodologies (backpack electrofishing, fyke netting, minnow trapping, and seining) for fish community data collection with a primary objective of determining an effective method for sampling fish communities in small oxbow wetlands. Seining and fyke netting were determined to be effective methods for sampling oxbow fish communities. Backpack electrofishing and minnow trapping produced low taxonomic richness values and sampled a smaller proportion of species present than seining and fyke netting. Although seining and fyke netting produced similar taxonomic diversity and abundance values, these two gears differ in their ease of implementation and potential habitat disturbance generated by sampling. Therefore, consideration must be given to how species present (especially sensitive species) within the wetland could be impacted by sampling disturbance when choosing between seining and fyke netting.

Seasonal variation and tracking of climate niche of a migratory bird

Migratory birds inhabit different areas during breeding and non-breeding seasons. Depending on the time of the year, they may utilize different resources available in seasonal habitats, but also are subjected to changing climate regimes during their annual life cycle. Migratory birds may adopt ecological niche tracking to cope with different environmental conditions between breeding and non-breeding grounds. The American White Pelican ( Pelecanus erythrorhynchos , hereafter ‘AWPE’) is a short-distance migrant between the Gulf of Mexico coastal regions (non-breeding grounds) and the Northern Great Plains (breeding grounds) of Canada and the US. The American White Pelican is a piscivore, feeding on fish, crayfish, and salamanders in inland freshwater wetlands. Cold, icy winter weather conditions substantially reduce and limit food resource availability at the breeding grounds during winters. Thus, we hypothesize that AWPEs would migrate between the breeding and non-breeding grounds to track climatic conditions that allow easier availability of resources. However, the niche tracking strategies have not been tested in AWPEs mainly due to the lack of reliable tracking data. Our objectives were to test whether the niche tracking or niche switching hypothesis would better explain seasonal variations in ecological niche overlap of AWPEs using the GPS locations of 19 tracked migrating birds, which had GPS locations at both breeding and non-breeding grounds. We estimated overlap of climate niche to test for seasonal niche tracking behaviors at both individual and population levels. Our results indicate that six out of 13 GPS-tracked AWPE individuals tracked climatic niche during the annual migration cycle. The analysis of the combined data of all 19 tracked AWPEs demonstrated that AWPEs tracked seasonal climate niche at the population level. Cold winter temperatures below zero (℃) may freeze the water surface of wetlands and shallow waterbodies, preventing AWPEs from acquiring sufficient food. The coupling of winter food resources with winter climatic conditions may result in climate niche tracking. Variation in climate niche tracking among individuals may offer ecological plasticity for AWPEs to cope with climatic changes. • Migratory birds may either track or switch ecological niche during the annual cycle. • American white pelicans are short-distance migratory birds. • American white pelicans tracked climate niche at individual and population levels. • Climate niche tracking may make American white pelicans vulnerable to warming.

Influences of seasonality and habitat quality on Great Lakes coastal wetland fish community composition and diets

Influences of seasonality and habitat quality on Great Lakes coastal wetland fish community composition and diets

Functional Responses and Additive Multiple Predator Effects of Two Common Wetland Fish

Understanding trophic interactions is essential for the prediction and measurement of structure and function in aquatic environments. Communities in these ecosystems may be shaped by variables such as predator diversity, prey density and emergent multiple predator effects (MPEs), which are likely to influence trophic dynamics. In this study, we examined the effect of key predatory fish in floodplain wetlands, namely Oreochromis mossambicus and Enteromius paludinosus, towards Chironomidae prey, using a comparative functional response (FR) approach. We used single predator species as well as intra- and interspecific paired species to contrast FRs under multiple predator scenarios. Attack rate and handling time estimates from single predator FRs were used to predict multiple predators’ feeding rates, which were compared to observe multiple predators’ feeding rates to quantify potential MPEs. From single fish trials, each species displayed a significant Type II FR, characterized by high feeding rates at low prey densities. Oreochromis mossambicus had a steeper (initial slope, i.e., higher attack rate) and higher (asymptote of curve, i.e., shorter handling time and higher maximum feeding rate) FR, whereas E. paludinosus exhibited lower-magnitude FRs (i.e., lower attack rate, longer handling time and lower feeding rate). In multiple predator scenarios, feeding rates were well-predicted by those of single predators, both in conspecific and interspecific pairs, and thus we did not find evidence for antagonistic or synergistic MPEs. Predator–prey interactions in wetland systems can have significant consequences on the structure and dynamics of ecological communities. In turn, this could have destabilizing effects on resources in tropical wetlands. These results, although experimental, help us understand how trophic interaction among conspecific or interspecific fish species in Austral tropical wetlands might influence their aquatic prey species. This will help us to understand food web dynamics better.

Wetland fishes avoid a carbon dioxide deterrent deployed in the field.

Biological invasions are poorly controlled and contribute to the loss of ecosystem services and function. Altered watershed connectivity contributes to aquatic invasions, but such hydrologic connections have become important for human transport. Carbon dioxide (CO2) deterrents have been proposed to control the range expansion of invasive fishes, particularly through altered hydrologic connections, without impeding human transport. However, the effectiveness of CO2 deterrents needs to be further evaluated in the field, where fishes are situated in their natural environment and logistical challenges are present. We deployed a proof-of-concept CO2 deterrent within a trap-and-sort fishway in Cootes Paradise, Ontario, Canada, to determine the avoidance responses of fishes attempting to disperse into a wetland. We aimed to describe deterrent efficiency for our target species, common carp, and for native fishes dispersing into the wetland. Our inexpensive inline CO2 deterrent was deployed quickly and rapidly produced a CO2 plume of 60mg/l. Over 2000 fishes, representing 13 species, were captured between 23 May and 8 July 2019. A generalized linear model determined that the catch rates of our target species, common carp (n = 1662), decreased significantly during deterrent activation, with catch rates falling from 2.56 to 0.26 individuals per hour. Aggregated catch rates for low-abundance species (n < 150 individuals per species) also decreased, while catch rates for non-target brown bullhead (n = 294) increased. Species did not express a phylogenetic signal in avoidance responses. These results indicate that CO2 deterrents produce a robust common carp avoidance response in the field. This pilot study deployed an inexpensive and rapidly operating deterrent, but to be a reliable management tool, permanent deterrents would need to produce a more concentrated CO2 plume with greater infrastructural support.

Computational study of Richness and Diversity Indices of fish species in rivers and other wetland areas and fish marketplaces under Kurigram District, Banglades

The present study revealed that a total of 101 indigenous species of large fish (28 species) and Small Indigenous fish (73 species) belonging to 63 genera and 31 families were observed and identified while 17 exotic fish species were found under 5 families. Among the indigenous species, the highest number of species were found in family Cyprinidae and Bagridae with a relative diversity of 28.28% and 11.11%. In case of group species richness, highest number 27 fish species were found in catfish group followed by 12 species of carp, 8 species of each barbs and minnows, 6 species of eel fish, 8 species of loaches, 4 species of each prawn, snake-headed or airbreathing fish and glass perches, 3 species of each climbing perches and clupeid, 2 species of each goby fish, knifefish and puffer fish, and rest of the group true perch, leaf fish, halfbeak fish, Needlefish, mullet fish, anchovies and killifish has one species. Of the total species, 47 species were considered as least concerned, 10 species as vulnerable, 11 species as endangered, 11 species as critically endangered, 14 species as nearly threatened and 8 species as data deficient. Considering the seasonal variation for all selected areas simultaneously, Shannon-Weaver diversity (H) index were found ranged from 3.53 (May) to 4.37 (January) where the highest Shannon -Weaver diversity index value 4.37 were found in winter season while 3.01 in Phulkumar, 3.73 in Dudhkumar, 3.87 in Dharla, 3.67 in Tista and 3.79 in Brahmaputra were recorded separately.

Correction to: Fish composition, but not richness or abundance, differ among Phragmites, Typha, and Schoenoplectus zones during a high-water year

Phragmites australis (ssp australis) is an aggressive colony-forming species that displaces emergent vegetation in North America, including native bulrushes (Schoenoplectus sp.) and both native and invasive cattails (Typha sp.). Phragmites expansion can alter habitat and negatively affect reptiles, amphibians, and birds; less is known about Phragmites’ utility as fish habitat and its impact on fish communities in freshwater coastal wetlands. To assess fish use of Phragmites in summer, we compared habitat characteristics, water quality, and fish community composition, diversity, and abundance among stands of flooded Phragmites, Typha, and Schoenoplectus at 16 sites across four regions of the Laurentian Great Lakes. Despite marked differences in water quality (higher pH and morning dissolved oxygen in Schoenoplectus) and habitat characteristics (higher stem density in Phragmites), there were no significant differences in fish species richness or catch per unit effort among vegetation types; there was a distinct fish assemblage in Schoenoplectus (more Cyprinids) compared to both Phragmites and Typha (more Centrarchids). This suggests that expansion of Phragmites or Typha at the expense of Schoenoplectus may alter wetland fish assemblages; however, with no clear differences in other fish community metrics, flooded Phragmites may provide habitat for some fishes during the summer, in the study wetlands.

Spatiotemporal characteristics of hydraulic performance and contaminant transport in treatment wetlands

Wetlands have been proven to be efficient and cost-effective ecological treatment systems for municipal and domestic wastewater. It is essential to understand the hydrodynamic characteristics and the related contaminant transport process to optimize the treatment efficiency in free water surface wetlands. Thirty-six tracer experiments were conducted under different water depths and wetland configurations, such as installing static obstacles and dynamic disturbances. The particle image velocimetry and a novel color-concentration transform method were developed to reveal spatiotemporal flow velocity and residence time distribution. The flow fields are categorized into short-circuiting, circulation flow, dead zones, and the corresponding contaminant transport phenomena are flow advection, shear dispersion, and eddy diffusion. The flow circulation dominates the formation of the dead zone and decreases contaminant dissipation. The flow path could have effectively meandered, and the dead zone and short-circuiting could be reduced by increasing the length of the obstacles. The improved flow field is close to the plug flow, indicating enhanced hydraulic performance and treatment efficiency. The dynamic disturbance reflects the movement of fish in wetlands and provides momentum flux to promote the dissipation of pollutants in the circulation field and dead zone, alleviating the deterioration of water quality caused by pollutant accumulation. The findings of this study may provide a critical reference for the optimal design of wetlands.

A multi-model analysis of growth and maturity biometrics in common Snakeheads, Channa striata, and Channa punctatus collected from Hakaluki Haor, Northeast Bangladesh

The Snakeheads are the most common fishes in freshwater wetlands of Bangladesh, but in recent years they are subjected to decline by overfishing pressure, anthropogenic factors, and climate changes. A one-year-long biometric investigation was undertaken which involve monthly random sampling of Channa striata and Channa punctatus from local wetland waters and measured total length, body weight data, and gonad’s weight in the laboratory. Then data were treated and analyzed by following the different multi-model tools i.e., Fulton’s condition factor, relative condition factor, allometric condition factor, and Pearson’s correlation coefficient. The results exhibit a strong correlation between the total length and body weight of Channa striata and Channa punctatus with an r2 value of 0.826, 0.819, respectively. Pearson’s correlation showed a trend of both positive and negative correlation coefficients between different conditions factors and morphometry for both species. The peak value for gonad’s weight, gonadosomatic index, and Dobriyal index was reported in the monsoon while the bottom value was in winter for both sexes of both species. The temperature, dissolved O2, and turbidity were found as fluctuating throughout the season while dissolved NH3 and pH remained constant. This data will help in the betterment of conservation, management, and fishing policy by the government, scientists, and fisheries industry.

Phylogenetic signal found in fish–community response to an acoustic common carp deterrent

Abstract Non‐structural deterrents may limit invasive fish dispersal and range expansion without altering waterflow or navigation. Despite extensive research in laboratory and artificial environments, few studies have been conducted in situ and, of those, few have evaluated the full community response of fishes interacting with the deterrent. We deployed acoustic deterrents within a physical trap‐and‐sort fishway at Cootes Paradise, Ontario, Canada, to determine the avoidance responses of a community of fishes attempting to disperse into the wetland. To test the effectiveness of an acoustic deterrent, the catch rates of fishes entering Cootes Paradise were compared when the deterrent was off (control) and on (treatment). Community diversity was fit to candidate generalised linear models, and common carp catch abundance was fit to candidate generalised additive models, both of which were compared with backwards selection. The presence of a phylogenetic signal in fish responses was assessed with Pagel's λ and Blomberg's K indices of trait evolution. Over 11,500 fishes, representing 16 species and 12 families, were captured. The acoustic deterrent did not alter the Shannon diversity of fishes challenging the fishway, but a significant phylogenetic signal in species‐specific avoidance responses was observed. There was a modest decrease in the catch rates of common carp (ambient trials = 1.03 fish/hr, deterrent trials = 0.84 fish/hr), a species of major management concern. Fish avoidance responses to acoustic deterrents were widely variable, and species specific. The avoidance response of common carp, the target species, was weak, probably due to a complex acoustic environment surrounding the fishway. Group size did not alter deterrent efficacy, but precipitation, water temperature, and turbidity did. Our study successfully quantified acoustic deterrent responses across an entire community of wetland fishes, including both native and invasive species. We are the first to demonstrate that there is a phylogenetic component to deterrent responses across species. We also identify environmental parameters that alter deterrent efficacy in the field, and describe important considerations for the deployment of non‐structural deterrents in the field.

Pushed to the edge: Environmental factors drive ecological responses of Aphanius fasciatus when in sympatry with invasive Gambusia holbrooki

Abstract Interspecific competition may be particularly exacerbated when occurring between native and invasive alien species, with environmental conditions affecting drivers of natural selection and shaping spatio‐temporal dynamics of animal communities. The effects of invaders are particularly evident in aquatic ecosystems with delicate and complex balances, such as Mediterranean coastal wetlands, characterized by unpredictable water flows and variable reserves. Understanding how native species respond to human‐induced biological invasions is of paramount importance for planning management measures aiming at conservation purposes. This study investigated whether the occurrence of a competing invader species resulted in changes in the ecological adaptations of a native species by comparing two coastal wetland fish species: the invasive eastern mosquitofish Gambusia holbrooki and the native Mediterranean killifish Aphanius fasciatus of conservation concern. The hypothesis was tested by sampling fishes at a coastal Ramsar site in central Italy, over 2 years. Generalized linear mixed models were used to examine the occurrence of killifish in relation to water parameters and the presence of its putative competitor. The aim was to determine whether salinity, temperature, and water depth influenced the presence and abundance of killifish when in sympatry with mosquitofish. Both the probability of presence and abundance of killifish increased with water salinity, but this increase was stronger when mosquitofish was present. Increasing water temperature and water depth were associated with a higher probability of presence and abundance of killifish respectively, although the effect of water depth was small. Both salinity and the presence of the invader acted synergistically in characterizing and shaping the population structure of the native species. Living in the most extreme and stressed environments, the killifish is potentially at higher risk of extinction. These results highlight the importance of considering the interplay between multiple abiotic stressors combined with comparative data between invasive and native species as increasingly critical to aid in conservation efforts.