Search Results (14)

Invasive species are often central to conservation efforts, particularly when concerns involve potential impacts on rare, endemic native species. The lower New River drainage of the eastern United States is a watershed that warrants conservation assessment, as the system is naturally depauperate of native fish species and it is nearly saturated with non-native fish species: there are 31 natives, including at least nine endemic taxa, and 63 non-natives. For endemic taxa, we examined temporal distribution shifts (range expansions or contractions) based on percent change in the occupied watershed area. We contrasted these findings with time series analyses on distribution trends of non-native minnows (Leuciscidae) and darters (Percidae) based on growth curve models of the cumulative sum of the total area of occupied 12-digit hydrologic unit codes. We documented range reductions for six of nine endemic taxa. We determined that 11 of 18 non-native minnows and 6 of 8 non-native darters were invasive based on range expansions and associated invasion curve models. The endemic taxa are of conservation concern given the limited distribution ranges and documented population declines. Although among-species comparisons of range shifts do not support causal inference, documentation of changes in distribution ranges of endemic and invasive species is critical to inform conservation efforts. Full article

The Chesapeake Logperch (Percina bimaculata) is a medium-sized darter that has had a limited distribution in Pennsylvania and Maryland. It is a threatened species native to the Susquehanna River and historically occurred in the Potomac River. It is currently being reviewed to determine if it should be listed as federally endangered. There are major efforts to reintroduce the Chesapeake Logperch to where it was historically native. Toward this end, we documented the selected habitats and diets, to aid in the selection of new habitats for reintroduction. Because historical data on habitat selection and diet of the Chesapeake Logperch were not available, we compared these habitats selected to those of the closely related Northern Logperch (P. caprodes semifasciata), and diet to the Ohio Logperch (P. caprodes caprodes). The habitat occupied by the Chesapeake Logperch was only a portion of that occupied by the Northern Logperch. Selection of streams for reintroduction can use data presented herein for the Chesapeake Logperch and historical data for the Northern Logperch. The diet of both the Chesapeake Logperch and the Ohio Logperch indicated that their diets differ, thus the prey items reported herein must be present when selecting putative reintroduction sites. These results will help to create more informed choices for streams considered for the reintroduction of the Chesapeake Logperch. Full article

The Chesapeake Logperch, Percina bimaculata, is a small fish endemic to the upper Chesapeake Bay drainage with a range significantly reduced by water quality and habitat degradation. It was described by Haldeman in 1842 and 1844 from the Susquehanna River, Pennsylvania, synonymized with the Logperch (Percina caprodes) by Jordan in 1877, and redescribed by Near in 2008. It is extirpated from the Potomac River drainage and extant in a portion of its historic range within the Susquehanna River drainage of Pennsylvania and Maryland in the United States of America. We reviewed available historic field survey information and defined the likely extent of the historic distribution of P. bimaculata and its change in response to historic environmental perturbations. We performed fisheries surveys during 2004–2023 to fill data gaps and to define the current distribution and abundance in the Susquehanna River drainage within Pennsylvania. Our surveys utilized electrofishing gears, electrified benthic trawls, and seines. Our surveys targeting P. bimaculata on the Susquehanna River and tributaries from York Haven to Holtwood, Pennsylvania, combined with available fisheries surveys conducted by others, confirm it was extirpated from that portion of the drainage. We documented the continued usage of Conowingo Pond, Susquehanna River, and tributaries below Holtwood by populations known to exist in historic field surveys. These populations appear to have been stable since at least the 1960s based on historic data and our current surveys. We documented previously unknown populations in the Octoraro Creek drainage, Octoraro Reservoir, and Muddy Run Pumped Storage Facility. Habitat utilization observations during our surveys indicate that clean sand, gravel, rubble, boulders, and large woody debris are preferred substrates. In the lower Susquehanna River and two tributaries, P. bimaculata has demonstrated a plasticity of habitat usage by continuing to occur in environments converted into impoundments by dams. In these impoundments, shorelines and connections with clean tributaries containing preferred substrates appear to be important given their utilization by P. bimaculata during our surveys. It is our opinion that the Susquehanna River and tributaries above Holtwood once again constitute suitable habitats. Conservation efforts focused on reintroductions, water quality, habitat, and connectivity have the potential to increase the extent of occurrence, abundance, and security of P. bimaculata. Full article

Conventional structures associated with stream crossings such as bridges and culverts can lead to zones of high-velocity water flow that impede fish passage. Such obstacles are likely to harm native fish populations by impacting migrations critical to their life history strategies, causing habitat fragmentation and extirpation, thereby limiting population growth and distribution. Due to the high rates of human population growth and development occurring in Texas, this is an issue of particular concern for fish designated as species of greatest conservation need (SGCN). This project focused on four SGCN fishes native to the Edwards Plateau Ecoregion, namely the Guadalupe Bass, Guadalupe Roundnose Minnow, Guadalupe Darter, and Plateau Shiner, at both adult (all species) and juvenile (Guadalupe Bass only) life stages. Our primary aim was to aid in the design of future culverts associated with stream crossings (or the modification of existing culverts) so that the water velocities through these structures do not exceed the swimming capacities of our target SGCN fishes. To this end, we assessed their maximum sustained swimming speeds (U_crit) under a typical range of Edwards Plateau stream temperatures (15, 22.5, and 30 °C) to be used in site-specific calculations of the maximum allowable culvert water velocities (Vf). A secondary objective was to collect physiological endpoints of relevance to the overall swimming performance including the maximum burst swimming speeds (U_max), metabolic rate measurements (i.e., standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS)), cost of transport (COT), and optimal swimming speed (U_opt). Temperature-related effects were observed that can be used to inform site-specific culvert designs. In general, the highest U_crit values for the tested species were near, or possibly between, 22.5 and 30 °C, while U_max stayed relatively consistent among treatments. Full article

Candy darter Etheostoma osburni, a federally endangered non-game fish, has been extirpated from most of its historic range in Virginia and now occurs in four isolated populations in the New River drainage. Understanding of population genetic structure will provide insights into the recent natural history of the species and can inform conservation management. Our objectives were to: characterize population genetic structure, estimate and compare effective population sizes (N_e), and use this information to infer recent population history. Variation at mitochondrial cytochrome b sequences among 150 individuals showed 10 haplotypes separated by 1–14 mutational steps, some shared and some unique to particular populations. Variation at 12 microsatellite loci among 171 individuals showed lower variation in Dismal Creek than in other populations. All populations showed evidence of having experienced a genetic bottleneck and were highly differentiated from one another based on both types of DNA markers. Population genetic structure was related to stream position in regard to the New River, suggesting that populations were once connected. N_e estimates for all populations were less than the 500 recommended to maintain evolutionary potential, but most estimates were greater than the 100 needed for use as source populations. Our findings indicate that habitat management to allow expansion of populations, and translocations to exchange genetic material among populations, may be effective tactics to promote conservation of candy darter in Virginia. Full article

The yellow-winged darter (Sympetrum flaveolum Linnaeus, 1758, Odonata), which is associated with high mountain areas, can be considered a flagship species. Due to climate change, its natural range will be negatively affected. In this study, we propose global potential distributions for this species up to the year 2100, considering four time periods (2021–2040, 2041–2060, 2061–2080, and 2081–2100) and three shared socioeconomic pathways (optimistic—SSP245, middle of the road—SSP370, and worst—SSP585), by using an ecological niche model to produce two sets of distribution models (80% to 100% and 60% to 100%). It is foreseen that in the worst of the considered climate scenario (SSP585– 2100 year), the distribution of this species could be reduced by almost half, which could pose a risk for the species and provoke the shift from vulnerable to endangered. An analysis of connectivity has also been carried out for all the studied scenarios by applying the MSPA and PC indices, showing that the core habitat of this species will become more important, which is consistent with the decrease in the distribution range. Over time, the importance of the most valuable connectors will increase, implying a greater risk of some populations becoming isolated. Full article

River water temperatures are increasing globally, particularly in urban systems. In winter, wastewater treatment plant (WWTP) effluent inputs are of particular concern because they increase water temperatures from near freezing to ~7–15 °C. Recent laboratory studies suggest that warm overwinter temperatures impact the reproductive timing of some fishes. To evaluate winter water temperature’s influence in the wild, we sampled Johnny Darter Etheostoma nigrum from three urban South Platte River tributaries in Colorado upstream and downstream of WWTP effluent discharge sites. Fish were collected weekly during the spring spawning season of 2021 and reproductive development was determined from histological analysis of the gonads. Winter water temperatures were approximately 5–10 °C greater ~300 m downstream of the WWTP effluent compared to upstream sites, and approximately 3 °C warmer at sampling sites ~5000 m downstream of the effluent discharge. Females collected downstream of WWTP effluent experienced accelerated reproductive development compared to upstream by 1–2 weeks. Water quality, including total estrogenicity, and spring water temperatures did not appear to explain varying reproductive development. It appears that small increases in winter water temperature influence the reproductive timing in E. nigrum. Further investigations into how shifts in reproductive timing influence other population dynamics are warranted. Full article

The Okaloosa darter (Etheostoma okaloosae) is a diminutive, perch-like, benthic fish that inhabits only six small, clear, and shallow creek systems that flow almost entirely within Eglin Air Force Base in the panhandle of northwest Florida. Listed as Endangered by the U.S. Fish and Wildlife Service (USFWS) in 1973, improvements in erosion control and habitat restoration led to the Okaloosa darter being downlisted from Endangered to Threatened in 2011. However, the long-term management of the species is hampered by the lack of knowledge of the spatial extent of the recharge areas that ultimately support creek flow through groundwater discharge. To address this lack of data, we collected groundwater samples from the sand and gravel aquifer beneath 11 headwater and 11 downgradient sites across six creek basins during February and December 2020. The groundwater samples were collected from 1 to 1.2 m beneath the creek bottom. Concentrations of sulfur hexafluoride (SF₆) were analyzed and used to calculate groundwater age (residence time), and indicated that at the 11 headwater sites, recharge occurred between 11 and 28 years ago. Groundwater ages in downgradient parts of the same creeks indicated that recharge occurred between 5 and 25 years ago. When combined with representative values of hydraulic conductivity for the sand and gravel aquifer, the ages reveal that the extent of the maximum recharge distance from the sampling sites ranged from about 222 to 2011 m from the creeks. This new information can be used by natural resource managers as additional evidence to support the USFWS Recovery Plan and proposed delisting of the Okaloosa darter from the Endangered Species List. Moreover, these results may also be useful to fisheries biologists to incorporate groundwater inputs to facilitate fisheries management. Full article

The longnose darter Percina nasuta is a rare and cryptic fish that recently disappeared from much of its historic range. We developed and used an environmental DNA (eDNA) assay for longnose darter paired with visual surveys to better determine the species’ range and compare detection probability between sampling approaches in an occupancy modeling framework. We detected longnose darter eDNA further upstream in the mainstem St. Francis River than previously reported and in a tributary for the first time. Our multi-scale occupancy approach compared models where detection was constant against a model that allowed detection to vary by survey method. The constant model received the most support indicating survey method was not a strong predictor and detection was estimated at 0.70 (0.45–0.86; 95% CI) across both methods. Our study produced effective longnose darter eDNA primers and demonstrated the application of eDNA for sampling small-bodied, cryptic fish. We detected longnose darter eDNA 27 km upstream of their known range and determined that snorkel surveys are the most efficient sampling method if water clarity allows. We recommend target sample sizes to achieve various detection goals for both sample methods and our results inform future design of distributional and monitoring efforts. Full article

Direct and indirect measures of individual movement provide valuable knowledge regarding a species’ resiliency to environmental change. Information on patterns of movement can inform species management and conservation but is lacking for many imperiled fishes. The Candy Darter, Etheostoma osburni, is an endangered stream fish with a dramatically reduced distribution in Virginia in the eastern United States, now known from only four isolated populations. We used visual implant elastomer tags and microsatellite DNA markers to directly describe movement patterns in two populations. Parentage analysis based on parent-offspring pairs was used to infer movement patterns of young-of-year and age-1 individuals, as well as the reproductive contribution of certain adults. Direct measurements of movement distances were generally similar between methods, but microsatellite markers revealed greater distances moved, commensurate with greater spatial frames sampled. Parent-offspring pairs were found throughout the species’ 18.8-km distribution in Stony Creek, while most parent-offspring pairs were in 2 km of the 4.25-km distribution in Laurel Creek. Sibship reconstruction allowed us to characterize the mating system and number of spawning years for adults. Our results provide the first measures of movement patterns of Candy Darter as well as the spatial distribution of parent-offspring pairs, which may be useful for selecting collection sites in source populations to be used for translocation or reintroductions. Our results highlight the importance of documenting species movement patterns and spatial distributions of related individuals as steps toward understanding population dynamics and informing translocation strategies. We also demonstrate that the reproductive longevity of this species is greater than previously described, which may be the case for other small stream fishes. Full article

The effluent from municipal wastewater treatment plants is a major point source of contamination in Canadian waterways. The improvement of effluent quality to reduce contaminants, such as pharmaceuticals and personal care products, before being released into the environment is necessary to reduce the impacts on organisms that live in the river downstream. Here, we aimed to characterize the metabolic and gill physiological responses of rainbow (Etheostoma caeruleum), fantail (Etheostoma flabellare), and greenside (Etheostoma blennioides) darters to the effluent in the Grand River from the recently upgraded Waterloo municipal wastewater treatment plant. The routine metabolism of darters was not affected by effluent exposure, but some species had increased maximum metabolic rates, leading to an increased aerobic scope. The rainbow darter aerobic scope increased by 2.2 times and the fantail darter aerobic scope increased by 2.7 times compared to the reference site. Gill samples from effluent-exposed rainbow darters and greenside darters showed evidence of more pathologies and variations in morphology. These results suggest that darters can metabolically adjust to effluent-contaminated water and may also be adapting to the urban and agricultural inputs. The modification and damage to the gills provide a useful water quality indicator but does not necessarily reflect how well acclimated the species is to the environment due to a lack of evidence of poor fish health. Full article

Larval fish ecology is poorly characterized because sampling is difficult and tools for phenotypically identifying larvae are poorly developed. While DNA barcoding can help address the latter problem, ‘universal’ primers do not work for all fish species. The Roanoke River in the southeastern United States includes seven darters (Family Percide: Tribe Etheostomatini). We made 393 collections of larval fishes in 2015 and 2018, examined darter larvae for morphometric and pigmentation traits, developed PCR primers amplifying darter DNA, and evaluated three gear types for collecting larval darters. Amplified DNA sequences for 1351 larvae matched archived mitochondrial cytochrome oxidase I sequences for darters occurring in the ecosystem. Larval darters were classified to genus with 100% accuracy using the ratio of pectoral fin length to body length; however, identification to species using morphometrics alone was subject to a misclassification rate of 11.8%, which can be resolved by considering pigmentation patterns. Gear-types varied considerably in their capture efficacy for larval darters; most Percina larvae were collected in drift nets. Larval Percina species appeared in the drift before Etheostoma species in both study years. Application of molecular genetic and phenotypic tools to larval fish identification can advance understanding of larval darter ecology. Full article

The River Darter (Percina shumardi) is a native, rarely sampled fish that has been detected in relatively small numbers since the 1930s. It has a wide North American distribution, but little is known about the species biology and distribution across the Canadian portion of its range. We revisited many historic sampling locations and sampled additional areas to (i) confirm and update the distribution of River Darters in Canadian waters; (ii) assess relative abundance; (iii) update life history characteristics; (iv) collect diet information; and (v) identify characteristics of River Darter habitat. Since 1990, a total of 1032 River Darters were recorded from 29 waterbodies across three ecoregions. River Darters were observed in relatively high abundances in both the Saskatchewan-Nelson River and Southern Hudson Bay-James Bay ecoregions. While still extant in the Great Lakes-Upper St. Lawrence ecoregion, River Darters persist at low abundance. Life history analyses indicate similar maximum age (age 4) and growth (10 mm/year) to conspecific populations in the United States, while sex ratios are generally skewed towards female dominance. River Darter populations had high flexibility in habitat use and diet, using a range of flows and depths and a variety of seasonally available prey types. Full article

Both centromeric alpha-satellite sequences as well as centromeric protein A (CENP-A) are highly variable in eukaryotes. CENP-A, a histone H3 variant, is thought to act as the epigenetic “mark” for assembly of centromeric proteins. While most of the histone fold domain (HFD) of the CENP-A is fairly well conserved, a portion of this HFD as well as the N-terminal tail show adaptive variation in both plants and animals. Such variation may establish reproductive barriers that may lead to speciation. The family Percidae contains over 200 species most of which are within the subfamily Etheostomatinae. This subfamily represents a species rich radiation of freshwater fishes in North America and these species exhibit both allopatric and sympatric distributions. In order to study the evolution of CENP-A in percid fish species, we have isolated and characterized the CENP-A gene from Etheostoma tallapoosae by PCR based gene walking. As a result of this study we have demonstrated that the Tallapoosa darter CENP-A gene HFD sequences can be isolated from genomic DNA by nested PCR in a manner that does not lead to the amplification of the highly sequence related histone H3 gene. We also demonstrated that PCR based walking can be subsequently used to isolate the rest of the CENP-A gene and adjacent gene sequences. These adjacent gene sequences provide us with a primer binding sites for PCR isolation of the CENP-A gene from other percid species of fishes. An initial comparison of three percid species shows that the N-terminal tail of the percid CENP-A gene shows adaptive evolution. Full article