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At least 703 records · Page 39Linked to original sources

USGS2026

Composite samples for perfluorooctanesulfonate in fish may change contaminant threshold decisions

The widespread occurrence and persistence of the per- and polyfluoroalkyl substances (PFAS) in the environment may pose significant health risks to humans. Fish consumption is a direct pathway for exposure, prompting extensive monitoring. In the United States and Europe, fish consumption advisories for PFAS generally focus on perfluorooctanesulfonate (PFOS), the most frequent and abundant PFAS compound reported in fish. However, PFAS analysis is costly, leading monitoring programs to frequently use composite samples (i.e., combining different fish of the same species). This financial saving comes at an analytical cost of lost information on individual variation. It is unclear how this may influence threshold-based decisions. To test this, we used a modeling approach (i.e., Monte Carlo) based on aggregated data distributions from freshwater fish species. We simulated the measurement of PFOS for individual fish compared to composite means (three, five, and 10 fish) at different levels of error structure. These values were then compared to a typical do-not-eat threshold of 200 ng•g wet mass −1 and four metrics were estimated: (i) the probability of detecting a PFOS concentration above the threshold, (ii) the maximum simulated PFOS concentration, (iii) the number of false negative samples, and (iv) the rate of false negative samples. These results show that the probability of assigning PFOS levels above or below the threshold is shifted by masking individual value contributions in a composite sample. Because true individual contaminant loads are variable, composite sampling is a more conservative metric for contaminant thresholds. The model suggested that the greater the variability, the lower the detection probability for truly contaminated samples. Our study may help to inform sampling for monitoring programs aimed at managing human exposure to PFAS.

Integrated Environmental Assessment and Management↗

USGS2025

Carbon and nitrogen isotopes of different native fish tissues from the Santa Ana River, California

Objective Stable isotopes are commonly used to understand the role of fishes in aquatic food webs. However, variability in species- and tissue-specific isotopic values can affect the inference that is drawn from a stable isotope study. We evaluated differences in stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) among three tissue types (white muscle, caudal fin rays, and eye lenses) for Santa Ana Sucker Pantosteus santaanae and Arroyo Chub Gila orcuttii to inform the design of a stable isotope study in the Santa Ana River, an urban river that is located in southern California. Methods We used multivariate analyses to test for differences in the stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) among the three tissue types that were collected from Santa Ana Sucker and Arroyo Chub. We also summarized the variability in isotopic values that was recorded over time in fish eye lenses and interpreted this variability in reference to the spatial patterns in isotopic values that have been previously reported throughout the Santa Ana River. Results We found that fin ray tissue and white muscle tissue were not significantly different for either isotope or fish species. Fish eye lenses were significantly higher in δ 13 C than muscle tissue, and eye lenses were significantly higher in δ 15 N than fin ray tissue for both fishes. We also found a greater range in δ 13 C and δ 15 N across eye lens layers for Santa Ana Sucker (δ 13 C = 2.01 ± 0.96‰, δ 15 N = 4.93 ± 4.18‰) than for Arroyo Chub (δ 13 C = 0.96 ± 0.65‰, δ 15 N = 4.63 ± 1.45‰). Conclusion Our results indicate that fin rays may be a viable nonlethal alternative to white muscle tissue for use in a stable isotope study of native fish of the Santa Ana River. Additionally, eye lenses could provide a chemical history of fishes within the river, but species-specific correction factors may be needed if stable isotope values for eye lenses are to be compared with more conventional tissue types (e.g., white muscle).

California↗

USGS2025

Trophic assessment of potential competition between invasive cichlids and sport fish in Puerto Rico reservoirs

Objective Several species of New World cichlids have recently invaded reservoirs in Puerto Rico, potentially jeopardizing established recreationally important, albeit nonnative, sport fish populations. Interactions between invasive species and important sport fish must be understood so that they can be mitigated when feasible. This study compared monthly prey consumption between three invasive cichlids (Jaguar Guapote Parachromis managuensis and two species of Amphilophus ) and two principal sport fishes (Largemouth Bass Micropterus nigricans and Butterfly Peacock Bass Cichla ocellaris ) to understand potential for competitive interactions. Methods Stomach contents were evaluated quarterly using gastric lavage for sport fish and destructive sampling techniques for invasive species. Prey proportion by mass was calculated for each individual, and mean prey proportion by mass was calculated for each species by reservoir, month, and overall. Multivariate hypothesis testing using permutational multivariate analysis of variance and visualization of potential diet overlap were performed via analysis of variance and nonmetric multidimensional scaling (NMDS), respectively. Results Fish were the most common prey type, and Threadfin Shad Dorosoma petenense was the most prevalent prey species. Although there were significant differences in diets of invasive cichlids and sport fishes ( P < 0.01), there also was considerable overlap based on low percentages of variation in diets explained by species (3–19% < pseudo- R 2 ) and NMDS visualizations. Diets varied little across reservoirs and months (≤4% pseudo- R 2 ; high overlap in NMDS space). Conclusion These data indicate that the diet of Jaguar Guapote and Amphilophus spp. may overlap with that of sport fish populations in Puerto Rico. Jaguar Guapote relied on Threadfin Shad more than other species, with Amphilophus spp. relying more on detritus and noncrayfish invertebrates. Thus, if prey are limited, Jaguar Guapote may have a more direct effect via competition for prey. Finally, we report evidence of Largemouth Bass recruitment failure and local extirpations that support a hypothesis that invasive cichlids are having negative effects on at least Largemouth Bass, although the mechanism is unclear.

Puerto Rico↗

USGS2026

Timing is everything: Drivers of upstream movement of fishes

Objective Understanding whether fishes quickly respond to shifting temperatures and flows, especially as they pass through river reaches that may be thermally unsuitable, may help to prioritize climate-informed management strategies. Methods Here, we use 15 years of daily fish passage data (2005–2020) from the Leaburg Dam on the McKenzie River, Oregon, USA, with water temperatures and river flows from two associated gauges. We examine the relative influence of temperature, flow, and calendar date on fish moving upstream, the range of conditions experienced by each species, and long-term patterns in timing, supported by annual count data from the years 1971–2020. Results Comparisons of timing and conditions while each species passed upstream through the Leaburg Dam fish ladders revealed that some taxa were more consistent seasonally (e.g., Pacific Lamprey Entosphenus tridentatus and Largescale Sucker Catostomus macrocheilus ), experiencing a more restricted range of conditions, while others moved throughout the year under highly variable environmental conditions (e.g., trout). For both groups, calendar date appeared to be a primary driver of movement timing, even when local environmental factors of temperature and flow were considered. We note broad trends toward earlier passage across all species except Chinook Salmon Oncorhynchus tshawytscha . Notable declines in movement of Mountain Whitefish Prosopium williamsoni and Largescale Suckers occurred during years of extreme weather events, indicating that they may be particularly sensitive to the combined impacts of water temperature and flow and could serve as sentinel taxa. Conclusions Although timing is recognized as a driver for the onset of migrations, this suggests that most fish may continue to move upriver during consistent time periods, potentially increasing their risk of exposure to suboptimal environmental conditions. Our results demonstrate the utility of long-term passage data for detecting patterns in local timing, environmental conditions co-occurring with fish movement, and the sensitivity of different fish species in responding to environmental extremes during upstream migrations.

Oregon↗

USGS2019

Fish culling reduces tapeworm burden in Arctic charr by increasing parasite mortality rather than by reducing density‐dependent transmission

Two common Dibothriocephalus (formerly Diphyllobothrium ) tapeworm species were significantly reduced by experimental culling of their fish host Arctic charr ( Salvelinus alpinus ) in a subarctic lake. Between 1984 and 1991, funnel traps were used to cull ~35 metric tons of Arctic charr, reducing charr density by ~80%. As charr densities decreased, tapeworm prevalence and then intensity also declined over the following three decades, with D. dendriticus (formerly dendriticum ) responding faster than D. ditremus (formerly ditremum ). The two main hypotheses for how culling a host can decrease parasitism are reductions in parasite transmission due to reduced host density and reductions in parasite survival through increases in host mortality rates. We found little evidence that charr density was the main driver for reduced parasite transmission. Instead, decreased survivorship in charr, initially, through fishing‐induced changes in charr age structure, and later through increased predation rates by brown trout, led to increased parasite mortality. Although brown trout, which increased significantly after fish culling, are also hosts, they are often too big for the final host birds to eat, thus becoming parasite sinks. Synthesis and applications . Fish populations with heavy parasite burdens constitute a management problem. Our results show how fish culling can indirectly reduce transmitted parasites through increased parasite mortality. Managing overcrowded fish populations by culling can produce two desirable outcomes: an increase in fish growth rates and reduced parasite burdens.

Journal of Applied Ecology↗

USGS2012

Worldwide trends in fishing interest indicated by Internet search volume

There is a growing body of literature that shows internet search volume on a topic, such as fishing, is a viable measure of salience. Herein, internet search volume for 'fishing' and 'angling' is used as a measure of public interest in fishing, in particular, recreational fishing. An online tool, Google Insights for Search, which allows one to study internet search terms and their volume since 2004, is used to examine trends in interest in fishing for 50 countries. Trends in normalised fishing search volume, during 2004 through 2011, varied from a 72.6% decrease (Russian Federation) to a 133.7% increase (Hungary). Normalised fishing search volume declined in 40 (80%) of the countries studied. The decline has been relatively large in English-speaking countries, but also has been large in Central and South American, and European countries. Analyses of search queries provide a low-cost means of gaining insight into angler interests and, possibly, behaviour in countries around the world.

Fisheries Management and Ecology↗

USGS2019

Effects of ocean climate on the length and condition of forage fish in the Gulf of Alaska

Climatic drivers of the size and body condition of forage fish in the North Pacific are poorly known. We hypothesized that length and condition of forage fish in the Gulf of Alaska (GoA) should vary in relation to ocean temperature on multiple scales. To test this hypothesis, we analyzed morphometric data for capelin (Mallotus catervarius) and Pacific sand lance (PSL; Ammodytes personatus) sampled by a seabird (Cerorhinca monocerata) in two regions of the GoA, 1993–2016. Based on previous studies, we predicted specifically that capelin length and body condition (Fulton’s K) would be negatively related to the Pacific Decadal Oscillation (PDO) and sea surface temperature (SST), whereas PSL length and condition would be positively related. Interannual variation in length and body condition was evaluated relative to seasonal values of ocean climate using regression. Forage fish length and condition varied interannually, between sampling regions, and were dependent on the size/age class of the fish sampled. As predicted, length and body condition of capelin (mostly age 1+) were negatively related to the PDO and SST. Relationships with ocean climate for PSL varied by size/age class: positive for putative age-0 fish and negative for putative age-1+ fish. We conclude that our hypothesis was supported for capelin and partially supported for PSL. This study demonstrates that ocean climate determines key morphometric characteristics of forage fish that may relate to interannual variation in the energetic value of prey, and provides an example of how seabirds can be used to obtain specimens for evaluations of potential prey quality.

Alaska↗

USGS2013

Beaver dams maintain fish biodiversity by increasing habitat heterogeneity throughout a low-gradient stream network

Understanding the relationship between heterogeneity and biodiversity is an active focus of ecological research. Although habitat heterogeneity is conceptually linked to biodiversity, the amount and configuration of heterogeneity that maintains biodiversity within ecosystems is not well understood, especially for an entire stream network. Here, we tested alternative outcomes about how habitat alterations caused by beaver dams affected native fish biodiversity. Specifically, we quantified in-stream habitat and fish assemblages above and below all beaver dams ( n = 15) and selected control sites ( n = 9), adjacent to beaver dams, within an entire, low-gradient stream network (Fish Brook, MA, U.S.A.). Beaver dams altered habitat within streams in four ways based on upstream versus downstream differences in stream width, depth, velocity and substratum. In general, habitat heterogeneity, measured using two indices, was greater at beaver dams than control sites. The diversity and abundance of fish around beaver dams were positively related to habitat heterogeneity. Faster water and the coarser substratum below beaver dams increased the amount of fluvial habitat available to native fish. This alteration can be critical for fish with life histories that depend on flowing water and hard substrata. In summary, within a stream network, beaver dams maintained fish biodiversity by altering in-stream habitat and increasing habitat heterogeneity. Understanding the relationship between habitat heterogeneity and biodiversity can advance basic freshwater ecology and provide science-based support for applied aquatic conservation

Massachusetts↗

USGS2013

Comparing two fish sampling standards over time: largely congruent results but with caveats

1. We sampled Lake Bourget (surface area = 44 km 2 ) using CEN standard gillnet and provisional standard acoustic survey methods over 3 years (2005, 2010 and 2011) as the fish community responded to re-oligotrophication. A total of 16 species were caught in benthic gillnets and three species in pelagic gillnets. 2. Lake Bourget results were consistent with a recent study (Emmrich et al., Freshwater Biology , 57, 2012, 2436) showing strong correspondence between average biomass-per-unit-effort (BPUE) in standard benthic gillnets and average acoustic volume backscattering when smaller lakes (0.25–5.45 km 2 ) were treated as sample units. 3. The BPUE of whitefish ( Coregonus lavaretus ), perch ( Perca fluviatilis ) and roach ( Rutilus rutilus ) measured by benthic gillnets all declined significantly with increasing bathymetric depth; 93% of nets set at depths >50 m caught zero fish. 4. Pelagic gillnetting indicated that small (<10 cm) perch and small (<12.5 cm) roach occupied the upper pelagic habitat (0–20 m depths) and that whitefish were predominant in deeper pelagic habitat. The acoustic sampling showed fish biomass in the upper pelagic habitat varied significantly by year. Biomass there was highest in 2010 when a strong perch year-class recruited and lowest in 2011 when recruitment levels of perch and roach were both weak. Whitefish biomass in deep pelagic habitat (>20 m) increased significantly after 2005. 5. Both surveys showed whitefish biomass increased significantly during the study, but whitefish ≥25 cm were poorly represented in benthic gillnet catches. Contrary to the acoustic findings, the BPUE of perch and roach in benthic gillnets did not vary significantly over time. This metric is insensitive to changes in size structure in that a high catch of small fish and a low catch of large fish in different years can provide similar average BPUE estimates. 6. We examined correlations between BPUE in benthic gillnets and acoustic methods at fine spatial scales by averaging acoustic backscattering measurements encompassed by buffers of varying size (250–2000 m) around individual gillnets and by averaging samples collected from lake quadrants. Correlations at fines scales were generally poor, and only in 1 year was the quadrant correlation significant. The lack of correlation can be explained, in part, by the two gears sampling different components of the fish community. Conversely, in pelagic habitat, where the fish community was simpler, we found BPUE in pelagic nets to be strongly correlated with acoustic backscattering. 7. With respect to large lakes like Lake Bourget, we hypothesise that the congruence in average biomass measurements provided by these two survey methods occurs because these different community components are responding similarly to a common driver like lake trophic status (or possibly multiple drivers operating in synergy).

Lake Bourget↗

USGS2016

Surface water connectivity drives richness and composition of Arctic lake fish assemblages

Surface water connectivity can influence the richness and composition of fish assemblages, particularly in harsh environments where colonisation factors and access to seasonal refugia are required for species persistence. Studies regarding influence of connectivity on Arctic fish distributions are limited and are rarely applied to whole assemblage patterns. To increase our understanding of how surface water connectivity and related hydrologic variables influence assemblage patterns, we investigated species richness and composition of Arctic lake fishes over a large region, 8500 km 2 , of the central Arctic Coastal Plain, Alaska. We collected fish presence/non-detection data from 102 lakes and used a hierarchical multispecies occupancy framework to derive species richness and inform species composition patterns. Our mean estimate of regional richness was 12.3 (SD 0.5) species. Presence of a permanent channel connection was an overriding factor affecting species richness (mean 3.6, 95% CI 3.1–4.9), presumably driving lake colonisation potential. In lakes without a permanent channel connection, data suggest richness (mean 2.0, 95% CI 1.7–3.3) increased with the availability of in-lake winter refugia and with the potential of ephemeral connections during spring floods. Fish species functional traits and environmental faunal filters contributed to patterns of richness and assemblage composition. Composition corresponded with richness in a coherent manner, where each successive level of richness contained several discrete assemblages that showed similar responses to the environment. Lakes with permanent channel connections contained both widespread and restricted species, while the species-poor lakes that lacked a connection contained mainly widespread species. This work provides useful baseline information on the processes that drive the relations between patch connectivity and fish species richness and assemblage composition. The environmental processes that organise fish assemblages in Arctic lakes are likely to change in a warming climate.

Freshwater Biology↗

USGS2020

Diversity of diatoms, benthic macroinvertebrates, and fish varies in response to different environmental correlates in Arctic rivers across North America

Climate change poses a significant threat to Arctic freshwater biodiversity, but impacts depend upon the strength of organism response to climate‐related drivers. Currently, there is insufficient knowledge about Arctic freshwater biodiversity patterns to guide assessment, prediction, and management of biodiversity change. As part of the Circumpolar Biodiversity Monitoring Program's first freshwater assessment, we evaluated diversity of diatoms, benthic macroinvertebrates, and fish in North American Arctic rivers. Alpha diversity was assessed in relation to temperature, water chemistry, bedrock geology, and glaciation history to identify important environmental correlates. Biotic composition was compared among groups to evaluate response to environmental gradients. Macroinvertebrate α‐diversity declined strongly with increasing latitude from 48°N to 82°N, whereas diatom and fish diversity peaked around 70°N without a clear latitudinal decline. Macroinvertebrate diversity was significantly positively related to air temperature. Diatom diversity was related to bedrock geology and temperature, whereas fish diversity was related to glaciation history. Fish and macroinvertebrate assemblages differed between sites in western Canada, where invertebrate composition was more variable, and Alaska, where fish composition was more variable. In sites with both diatom and macroinvertebrate data, diatom composition was distinct in Alaska, where richness was highest in former glacial refugia. Macroinvertebrate composition was distinct in lowest‐latitude eastern and high‐latitude western Canadian sites where temperature was highest. Temperature, precipitation, geology, calcium, and substrate size were important environmental correlates for diatoms and macroinvertebrates, although the relative importance of each correlate differed. Diatom taxa were most strongly associated with water chemistry, whereas benthic invertebrate composition related most strongly to precipitation and temperature. This large‐scale study provides the most substantial integration and analysis of river diatom, macroinvertebrate, and fish data from the North American Arctic to date. Findings suggest that macroinvertebrates will show the strongest response to climate‐related shifts in temperature, whereas diatoms and fish are more likely to respond to climate‐induced shifts in nutrients and hydraulic connectivity. However, significant gaps in data coverage limited our ability to reliably evaluate spatial patterns and detect change. These gaps could be reduced by improving collaborative efforts between the U.S.A. and Canada to harmonise future monitoring.

Arctic↗

USGS2024

Fishes move to transient local refuges, not persistent landscape refuges during river drying experiment

Anthropogenically driven flow intermittency is increasing in freshwater streams, with important implications for the management and conservation of aquatic ecosystems. Because most freshwater fishes are mobile, they are expected to emigrate from intermittent reaches, but this may not be true in streams transitioning from perennial to intermittent. Here, we attempt to determine if riverine fishes vacate drying reaches before intermittency or remain in local refuges. We implemented a controlled, in situ experimental flow reduction resulting in intermittency, reducing flows from ~1.0 to 0 m 3 /s over a 3-week period. We monitored fish and fish-habitat changes over a 5-week period before, during and after flow reductions. During flow reductions, total wetted habitat was ultimately reduced by 91%. Habitat loss over time was not equal among habitat types: pool habitat increased slightly as run habit was lost, and backwater and isolated pool habitats were not strongly related to discharge. Likewise, water depth in run habitats decreased faster than other habitats. Only the river carpsucker Carpiodes carpio appeared to move upstream during flow recession; seven other species remained within drying sites. Habitat loss negatively affected fish populations, but at a lower rate than that at which habitat was lost, until sites dried completely. Overall, two species, red shiner Cyprinella lutrensis and western mosquitofish Gambusia affinis , had increased population growth during the study, whereas the remaining species had population declines. Fishes were able to find transient local refuges during flow reductions but did not vacate sites before intermittent conditions. Accounting for lack of emigration from anthropogenic flow-intermittent reaches will be important for designing conservation actions for fishes threatened by increasing flow intermittency. Creation of refuge habitats may not be effective for widely dispersed species that do not actively seek refuge habitats, unless those habitats support enough individuals to maintain resilience following the intermittent conditions.

New Mexico↗

USGS2024

Fish size structures in lakes of the Lower Mississippi River floodplain

The Lower Mississippi River has a floodplain that includes >1350 perennial lakes carved by shifts in river courses and other hydro-fluvial processes over eons. Notwithstanding their similar provenances, these waterbodies exhibit an immense variety of morphologies and successional stages that illustrate their natural trajectory from aquatic to forested wetlands. A result of this geographical, morphological and temporal diversity is dynamic and varied fish communities. We examined how size structures of fish communities in these floodplain lakes were associated with key in-lake and off-lake environmental drivers. Fish lengths were collected with standardised procedures in a sample of 30 of these lakes to construct a lake-by-length group matrix. Likewise, in-lake and off-lake environmental descriptors were collected to construct a lake-by-covariate matrix. Distance-based linear models were used to assess associations between fish size structure and environmental descriptors. Smaller fish were typically associated with increasing levels of turbidity, chlorophyll- a , phycocyanin and surrounding agriculture. Shallow, hypereutrophic floodplain lakes associated with agricultural landscapes and reduced connectivity experience harsh physicochemical environments. These conditions appeared to hinder the formation of sustained fish communities but may confer a survival advantage to juveniles or small short-lived species. Conversely, larger fish were associated with increasing lake depth, water clarity, connectivity, and extent of surrounding forests-wetlands. Enhanced stability and size structure were observed in communities residing in deeper and clearer lakes, suggesting that these conditions facilitated the development of longer-lived species spanning multiple age groups. The enhanced connectivity that facilitated this increased stability also permitted the presence of larger itinerant species. Size-structure assessments can serve as a valuable ecological and biodiversity indicator in floodplain lakes. Size-structure assessments could supplement and, depending on objectives, even supplant conventional taxonomic analyses, and enhance surveillance of this vast and important natural resource.

Arkansas, Louisiana, Mississippi, Missouri, Tennes↗

USGS2023

Borealization of nearshore fishes on an interior Arctic shelf over multiple decades

Borealization is a type of community reorganization where Arctic specialists are replaced by species with more boreal distributions in response to climatic warming. The process of borealization is often exemplified by the northward range expansions and subsequent proliferation of boreal species on the Pacific and Atlantic inflow Arctic shelves (i.e., Bering/Chukchi and Barents seas, respectively). But the circumpolar nearshore distribution of Arctic-boreal fishes that predates recent warming suggests borealization is possible beyond inflow shelves. To examine this question, we revisited two nearshore lagoons in the eastern Alaska Beaufort Sea (Kaktovik and Jago lagoons, Arctic National Wildlife Refuge, Alaska, USA), a High Arctic interior shelf. We compared summer fish species assemblage, catch rate, and size distribution among three periods that spanned a 30-year record (baseline conditions, 1988–1991; moderate sea ice decline, 2003–2005; rapid sea ice decline, 2017–2019). Fish assemblages differed among periods in both lagoons, consistent with borealization. Among Arctic specialists, a clear decline in fourhorn sculpin ( Myoxocephalus quadricornis , Kanayuq in Iñupiaq) occurred in both lagoons with 86%–90% lower catch rates compared with the baseline period. Among the Arctic-boreal species, a dramatic 18- to 19-fold increase in saffron cod ( Eleginus gracilis , Uugaq) occurred in both lagoons. Fish size (length) distributions demonstrated increases in the proportion of larger fish for most species examined, consistent with increasing survival and addition of age-classes. These field data illustrate borealization of an Arctic nearshore fish community during a period of rapid warming. Our results agree with predictions that Arctic-boreal fishes (e.g., saffron cod) are well positioned to exploit the changing Arctic ecosystem. Another Arctic-boreal species, Dolly Varden ( Salvelinus malma , Iqalukpik), appear to have already responded to warming by shifting from Arctic nearshore to shelf waters. More broadly, our findings suggest that areas of borealization could be widespread in the circumpolar nearshore.

Alaska↗

USGS2008

Middle to late cenozoic geology, hydrography, and fish evolution in the American Southwest

An evaluation of the poorly understood Cenozoic hydrologic history of the American Southwest using combined geological and biological data yields new insights with implications for tectonic evolution. The Mesozoic Cordilleran orogen next to the continental margin of southwestern North America probably formed the continental divide. Mountain building migrated eastward to cause uplift of the Rocky Mountains during the Late Cretaceous to early Tertiary Laramide orogeny. Closed drainage basins that developed between the two mountain belts trapped lake waters containing fish of Atlantic affinity. Oligocene-Miocene tectonic extension fragmented the western mountain belt and created abundant closed basins that gradually filled with sediments and became conduits for dispersal of fishes of both Pacific and Atlantic affinity. Abrupt arrival of the modern Colorado River to the Mojave-Sonora Desert region at ca. 5 Ma provided a new conduit for fish dispersal. Great dissimilarities in modern fish fauna, including differences in their mitochondrial deoxyribonucleic acid (DNA), indicate that late Miocene runoff from the Colorado Plateau did not flow down the Platte or Rio Grande, or through the Lake Bonneville Basin. Fossil fishes from the upper Miocene part of the Bidahochi Formation on the Colorado Plateau have characteristics that reflect a habitat of large, swift-moving waters, and they are closely related to fossil fishes associated with the Snake and Sacramento Rivers. This evidence suggests that influx of fishes from the ancestral Snake River involved a major drainage, not merely small headwater transfers. ?? 2008 The Geological Society of America.

Conference Paper↗

USGS2013

Estimating reef fish discard mortality using surface and bottom tagging: effects of hook injury and barotrauma

We estimated survival rates of discarded black sea bass ( Centropristis striata ) in various release conditions using tag–recapture data. Fish were captured with traps and hook and line from waters 29–34 m deep off coastal North Carolina, USA, marked with internal anchor tags, and observed for release condition. Fish tagged on the bottom using SCUBA served as a control group. Relative return rates for trap-caught fish released at the surface versus bottom provided an estimated survival rate of 0.87 (95% credible interval 0.67–1.18) for surface-released fish. Adjusted for results from the underwater tagging experiment, fish with evidence of external barotrauma had a median survival rate of 0.91 (0.69–1.26) compared with 0.36 (0.17–0.67) for fish with hook trauma and 0.16 (0.08–0.30) for floating or presumably dead fish. Applying these condition-specific estimates of survival to non-tagging fishery data, we estimated a discard survival rate of 0.81 (0.62–1.11) for 11 hook and line data sets from waters 20–35 m deep and 0.86 (0.67–1.17) for 10 trap data sets from waters 11–29 m deep. The tag-return approach using a control group with no fishery-associated trauma represents a method to accurately estimate absolute discard survival of physoclistous reef species.

North Carolina↗

USGS2019

Evidence for a role of arginine vasotocin (AVT) receptors in the gill during salinity acclimation by a euryhaline teleost fish

The neurohypophysial nonapeptide arginine vasotocin (AVT) plays a role in regulation of osmotic balance in teleost fishes, but its mechanisms of action are not fully understood. Recently, is was discovered that nonapeptide receptors differentiated into V1a-type, several V2-type, and two isotocin (IT) receptor paralogs in teleost fishes, and it remains unclear which of these nonapeptide receptors mediate AVT’s action on gill osmoregulation. Here, we examine the role of nonapeptide receptors in gill osmoregulation by examining the transcriptional responses of gill nonapeptide receptors in euryhaline Amargosa pupfish (Cyprinodon nevadensis) acclimated to 7.5 ppt salinity, and then transferred to fresh water (0.3 ppt), seawater (35 ppt), or hypersaline (55 ppt) conditions. Transcript abundance of the teleost V1a-type receptor v1a2 was up-regulated over 4-fold in gill 24 h after transfer of fish from 7.5 ppt to 35 ppt or 55 ppt, and down-regulated upon transfer to 0.3 ppt, but returned to baseline levels by 14 d after transfer when fish had re-established osmolality. Transcripts for the nonapeptide degradation enzyme leucyl-cystinyl aminopeptidase (LNPEP) also increased in the gill of fish acclimating to 35 ppt, but returned to baseline levels by 14 d. To test whether AVT’s effects on the gill might be mediated by a V1a-type receptor, we also administered exogenous AVT or a V1-type receptor antagonist (Manning compound) to pupfish acclimated to 7.5 ppt prior to transfer of fish to 0.4 ppt or 35 ppt. AVT inhibited the increase in gill Na+/Cl- cotransporter 2 (ncc2) mRNA abundance that occurs when fish are transferred to hypo-osmotic environments, and V1-type receptor antagonism increased mRNA levels for ncc2 even without a change in salinity. Pupfish transferred to 35 ppt also exhibited elevated gill mRNA abundance for cystic fibrosis transmembrane conductance regulator (cftr), which diminished under V1-receptor inhibition. Taken together, these findings provide evidence for AVT acting via a V1-type receptor to regulate gill Cl- transport by inhibiting Cl- uptake and facilitating Cl- secretion during seawater acclimation.

American Journal of Physiology - Regulatory, Integ↗

USGS2024

Length-weight relationships of native and non-native fishes in the lower Red River catchment, USA

Length-weight relationships are useful for stock assessments and modeling alternative conservation and management strategies for both native and non-native fishes. We developed length-weight relationships for 18 native and non-native riverine fishes in the lower Red River catchment. Fishes were sampled in the summer and autumn seasons between May 2021 and March 2024 via electrofishing and gill nets. Measurements for each specimen consisted of total length (mm) and weight (g). We provide L-W relationships for 14 native fishes consisting of 5 families (Lepisosteidae, Catostomidae, Ictaluridae, Sciaenidae, and Polyodontidae) and 4 non-native species belonging to the family Cyprinidae. We collected 6,845 individuals ranging from 67 alligator gar to 1,848 smallmouth buffalo. All the L-W relationships were significant ( p < 0.05), and the majority (72% of species) of relationships between length and weight had r 2 values > 0.70. Our findings provide insight into the L-W relationships of riverine fishes and can be useful for modeling alternatives targeted at native fishes of recreational value and the removal efforts of non-native fishes.

Arkansas, Oklahoma, Texas↗