Experimental evidence for species‐specific response to turbidity in imperilled fishes

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Biological traits of eastern sand darter (Ammocrypta pellucida) in the lower Thames River,Canada, with comparisons to a more southern population

Eastern sand darter (Ammocrypta pellucida) is listed as Threatened under the Canadian Species at Risk Act. Little relevant biological information is available for most Canadian populations and only limited information is available for populations in the United States. To supplement the paucity of information, this study collected biological information on eastern sand darter during field surveys in 2006–2007 from 10 sites in the lower Thames River, Ontario, Canada. Collected data were used to estimate critical life history traits including: longevity, fecundity, clutch size and number, growth, survival, age‐at‐first‐maturity and cohort age structure. Longevity was 3+ years, with age‐at‐first‐maturity being 1+ for both sexes. Examination of egg sizes from preserved females in 2007 showed a bimodal distribution, suggesting two spawning occurrences of 71 eggs each. Quantitative comparison of lower Thames River biological information with a more southerly eastern sand darter population in the Little Muskingum River, Ohio, demonstrated little variation between the populations. Data comparisons suggest that localised environmental factors are affecting biological traits (growth), in particular water temperature that may be controlled by differences in riparian cover and/or groundwater input.     

Abiotic and biotic associations between the round goby Neogobius melanostomus and tubenose goby Proterorhinus marmoratus with the endangered northern madtom Noturus stigmosus in Canada

1. Quantifying habitat associations and threats to the persistence of imperilled species is a fundamental step for initiating species recovery efforts, but the traits associated with species imperillment (e.g. rarity and vulnerability to stressors) also limit the ability to empirically inform recovery strategies. Novel sampling designs and modelling approaches are therefore needed to quantitatively assess habitat associations and the threats to species persistence.
2. To improve the understanding of habitat associations and threats for one of the rarest endangered freshwater fish species in Canada, northern madtom (Noturus stigmosus), two‐species occupancy models were developed with two invasive gobies: round goby (Neogobius melanostomus) and tubenose goby (Proterorhinus marmoratus). Models were parameterized with data from a multi‐year benthic trawling survey of two large Great Lakes tributaries in southern Ontario, Canada, and subsequently used to evaluate the need for reducing measurement error with future sampling efforts.
3. The probability of detecting northern madtom in the St. Clair (0.163) and Thames (0.194) rivers was low compared with round goby (St. Clair, 0.827; Thames, 0.833) and tubenose goby (St. Clair, 0.297). The best occupancy models indicated a negative association between northern madtom and round goby in the St. Clair River and the importance of gravel substrate for northern madtom.
4. Up to 16 repeated non‐detections using benthic trawls are needed to be 95% confident that northern madtom is absent at a site, indicating that current sampling approaches are likely inadequate.
5. Despite low detection probabilities, intensive trawling surveys combined with the two‐species occupancy modelling framework provided vital information for describing habitat associations for northern madtom and identified a significant negative association with round goby. Nonetheless, alternative sampling methods to improve the detection probability of northern madtom would allow a more robust evaluation of habitat associations and would provide more information on the negative association with round goby.

     

Coping with climate change: Phenotypic plasticity in an imperilled freshwater fish in response to elevated water temperature

1. Climate change has emerged as an increasingly important threat to freshwater systems. To cope with rapidly changing thermal regimes, freshwater fishes must either relocate or adjust through genetic adaptation and/or phenotypic plasticity. Short-term responses to elevated water temperature have been well studied in freshwater fishes; however, far less is understood about change induced by long-term exposure. Furthermore, few studies have investigated the effects of temperature on already imperilled species, which may be more sensitive to environmental change.
2. This study investigated the effects of rearing temperature on critical thermal maximum (CT_max), agitation temperature (T_ag, temperature at which fish show behavioural signs of thermal stress) and gill size in pugnose shiner, Notropis anogenus, a threatened species in Canada. Juvenile pugnose shiner were reared for 4 months across five different ecologically relevant temperatures. CT_max and T_ag were measured under normoxia and acute exposure to hypoxia to test for oxygen sensitivity of the upper thermal limits in this species.
3. CT_max increased with elevated water temperature. T_ag also increased with rearing temperature and occurred, on average, 4.3°C above acclimation temperatures. The CT_max and T_ag were lower when fish were exposed acutely to hypoxia. Interestingly, gill size (e.g. total gill filament length) increased with rearing temperature, which may increase oxygen uptake capacity and support increased metabolic demands of warmer waters.
4. Overall, pugnose shiner show plasticity in several traits in response to long-term exposure to elevated water temperature that may facilitate persistence in warmer waters. However, acute hypoxia exposure reduced thermal tolerance, stressing the importance of evaluating interactive effects of multiple stressors.
5. Identifying source populations of pugnose shiner with greater thermal tolerance or implementing captive breeding under higher temperature regimes may improve the success of re-introduction efforts in the face of climate change, but the consequences to fitness of increased thermal tolerance should be examined.

     

Validation of environmental DNA (eDNA) as a detection tool for at‐risk freshwater pearly mussel species (Bivalvia: Unionidae)

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Genetic analyses of European minnow,Phoxinus phoxinus,in a river system outside its native range indicate multiple invasions from different sources

European minnow Phoxinus phoxinus (L.) from four different water bodies (the lakes Eivindbuvatn and Grungevatn, and the hydroelectric reservoirs Ståvatn and Totak) in the upper part of the Tokke drainage system, outside the native range of this species, and from one possible source population (River Hunnselva), were analysed to identify the origin of a newly established population in Ståvatn Reservoir. Amplified fragment length polymorphism analyses identified three genetically different populations in the Tokke drainage system, well separated from the purported source population. Thus, the River Hunnselva population connected to a brown trout, Salmo trutta L., hatchery from which European minnow theoretically could have ‘hitchhiked’ was not the source. As such, the dispersal of European minnow in Norway, even in a restricted area within one drainage system, appears to occur from multiple sources and possibly involves the illegal use of the species as live bait.     

Using occupancy models to assess the effectiveness of underwater cameras to detect rare stream fishes

1. Many conservation efforts for freshwater fishes have been undertaken; however, continuing the monitoring of both the distribution and the abundance of species to determine the effectiveness of these actions can be difficult. As species increase in rarity, they are more difficult to detect in the field, making inferences on occupancy less reliable.
2. Conventional sampling methods, such as electrofishing and seining, require the physical handling of rare fishes, which may cause stress and mortality and, consequently, compromise conservation goals and limit monitoring programmes. Non‐invasive surveillance methods, including underwater video, are playing an increasingly important role.
3. In this study, occupancy models were used to estimate the detection probability of underwater cameras as an alternative to the conventional sampling methods for rare stream fishes. Redside dace (Clinostomus elongatus), a small minnow listed as Endangered, was used as a model organism for rarity. A total of 69 historical redside dace sites were sampled using three sampling methods to determine the effect of gear type on detecting and identifying the habitat preferences of this rare minnow.
4. On average, using multiple underwater cameras is as effective at detecting a rare minnow as conventional sampling methods (backpack electrofisher and seine) and causes no harm.
5. The detection probability of both underwater cameras and backpack electrofishing were adversely affected by turbidity, whereas seining was positively affected by stream velocity. The probability of occupancy of redside dace is driven by open channels and sediment size, and this provides a strong basis for informing stream restoration projects.
6. The use of multiple underwater cameras over conventional sampling methods is recommended when sampling for rare and endangered minnows in systems with low turbidity.

     

How fast is too fast? Water velocity differentially affects growth of four Gila River,native cyprinids

Understanding trade-offs associated with occupying various aquatic habitats provides a mechanistic understanding of habitat needs that can be used to evaluate the consequences of habitat loss or alteration. We used instream enclosures and field observations to identify how velocity affects the growth rates of four native species in the upper Gila River basin: longfin dace (Agosia chrysogaster) and speckled dace (Rhinichthys osculus), two species of no conservation concern, and loach minnow (Tiaroga cobitis) and spikedace (Meda fulgida), two federally endangered species. Elevated velocity was predicted to increase food delivery through drift or stimulation of benthic primary production. Energetic costs of high-velocity habitat were predicted to vary with morphology and behaviour and be lowest for speckled dace and loach minnow because they are adapted to occupy interstitial spaces of the substrate in riffles. Spikedace and longfin dace should perform best in moderate velocities, where the trade-off between exposure to drifting macroinvertebrates outweighs the energetic costs of maintaining position in the water column. Growth rates of loach minnow and speckled dace increased in higher velocities, but contrary to our initial predictions, spikedace growth rates also increased in high-velocity habitats while longfin dace grew fastest in low-velocity habitats; similar to the locations these species occupied based on field observations. These results indicate that for spikedace, the increased abundance of drifting macroinvetebrates in high-velocity habitats outweighs the energy expenditure, but for longfin dace the energetic costs of occupying moderate to high-velocity habitats outweigh the benefit to increased food availability. Our experiment provides a mechanistic understanding of habitat requirements across species and may inform predictions on how modifications or restoration of riverine ecosystems influence native fish diversity.     

Influence of turbidity and fluctuating water levels on the abundance and depth distribution of small, benthic fish in New Zealand alpine lakes

Abstract –  Minnow trapping was used to determine the distribution and abundance of two small, benthic species of fish, common bullies ( Gobiomorphus cotidianus ) and koaro ( Galaxias brevipinnis ), in five oligotrophic lakes varying in both turbidity and the extent of water-level variation. Koaro were 5–20 times more abundant in the large turbid lakes than in the clear ones, indicating that turbidity may reduce the extent of salmonid predation on koaro. However, the scarcity of koaro in the clear lakes was related mainly to the prevalence of brown trout ( Salmo trutta ) compared with rainbow trout ( Oncorhynchus mykiss ) as the former were more piscivorous and had a stronger inverse relationship with koaro. Common bullies were more abundant at sites 20 m or more away from the shoreline, and at depths of 9–12 m irrespective of season, year and turbidity level. However, the overall abundance of bullies was reduced by 70–90% in the turbid lakes. As bullies are relatively insensitive to the direct effects of increased turbidity, indirect effects such as reductions in macrophytes from reduced water clarity or smothering of benthic habitats by settled solids are thought to influence their abundance in the lakes affected by glacial turbidity. There was no relationship between the extent of water-level fluctuation and the abundance of koaro or common bullies in the lakes, but the depth distribution of bullies was shallowest in the lake with the least water-level fluctuation and was deepest in the lake with the greatest water-level fluctuation.     

Defining critical habitat conditions for the conservation of three endemic and endangered cyprinids in a Mediterranean intermittent river before the onset of drought

1. Identifying key factors in species' habitat requirements can be of use in defining critical habitats for their conservation, as well as in assisting the prioritization of habitat restoration actions. So far, most studies on habitat use by freshwater fishes have been focused on widespread and economically important species (e.g. salmonids).
2. This study aimed to identify the early summer habitat use (i.e. before the start of the drought period) of three endemic and endangered Greek cyprinids – the Evrotas chub Squalius keadicus, the Spartian minnowroach Tropidophoxinellus spartiaticus and the Evrotas minnow Pelasgus laconicus, with regard to depth, water velocity, substrate and macrophyte cover. In the case of the chub, habitat use by juvenile and adult fish was assessed separately. Data were collected for each fish group from four habitat types (riffles, runs, glides, pools) by using a modified point‐abundance sampling with an electrofishing device. In total, 120 sampling points were sampled, in two near‐reference perennial reaches of the Evrotas River (southern Greece) in early summer 2014, when there was continuous flow and full connectivity between habitats.
3. All three target species had their highest densities in deeper habitats with low water velocities and depositional substrates such as pools and runs. A high overlap in habitat use was evident for the three species. Habitat use curves based on microhabitat data were created for all species. Μinnowroaches, minnows and large chubs actively selected deep habitats. Minnowroaches and minnows favoured slow‐flowing, vegetated habitats with fine substrate located close to the river bank, while chubs had no clear affinity for particular velocities or substrate types. However, size class comparisons in chub indicated differences in both water depth and velocity.
4. Overall, the results of this study provide the first detailed report of the habitat use of these endangered fish species. These patterns of habitat use highlight the importance of deep habitats that must be preserved as refugia while the drought events progress.

     

Reservoir fish assemblage structure across an aquatic ecotone: Can river-reservoir interfaces provide conservation and management opportunities?

River-reservoir interfaces have been described as aquatic ecotones and contain strong environmental gradients of depth, turbidity and trophic resource abundance. These transitional habitats have traditionally been excluded by riverine and reservoir management schemes despite their prevalence in modern riverscapes. By systematically sampling shoreline habitats along a river-reservoir interface gradient from riverine to lacustrine zones with trammel nets in 2018–2019, strong patterns were identified in total species captured and individuals captured in the San Juan River-Lake Powell inflow, USA. Changes in assemblage structure were driven mainly by increases in relative abundance of benthic omnivores towards the riverine zone, including imperiled razorback sucker, Xyrauchen texanus (Abbott), but also by increases in predatory species, such as striped bass, Morone saxatilis (Walbaum). Inter-annual variation in species distributions along the river-reservoir interface gradient was likely influenced by variation in reservoir water level that differed by nearly 12 m between years. River-reservoir interfaces provide high-quality feeding and potentially spawning areas for both benthic omnivores and piscivores, and these areas should be considered in management and conservation efforts for species using these habitats.     

Analysis of Canadian and American legislation for controlling exotic species in the Great Lakes

• 1. The legislation of the Great Lakes jurisdictions dealing with control of exotic species introduced through ballast water, canals, and recreational boating was analysed to determine whether the USA and Canada have the capacity to manage nuisance exotic species effectively. Despite the deleterious ecological effects attributed to exotic aquatic species, there is a lack of complementary legislation between Canada and the USA to remedy this problem. Current legislation is fragmented at the bilateral, national, and the state/provincial level.
• 2. American legislative initiatives are far ahead of Canada's, especially for regulating ballast water in oceanic shipping. Canada lacks strong federal and provincial legislation to regulate ballast water in shipping and to prevent the secondary spread of exotic aquatic species through watersheds.
• 3. Legislation to regulate ballast water is developing quickly among the US federal government and the Great Lakes states. However, legislation affecting the spread of exotic nuisance species via canals and recreational boaters is needed to complement ballast water laws and to give agencies a broader mandate for management.
• 4. Amendment of the Boundary Waters Treaty Act, the Fisheries Act, and the Canada Water Act could give the Canadian federal government authority to regulate ballast water in vessels entering the St Lawrence and to begin the rehabilitation of aquatic habitats impaired by nuisance exotic species.
• 5. Preventing further species introduction and spread through the Great Lakes basin requires restricting certain shipping and boating practices. This can be achieved only by the enactment of complementary laws among all the American and Canadian jurisdictions.

Copyright © 2002 John Wiley & Sons, Ltd.     

Using occupancy and species distribution models to assess the conservation status and habitat use of the goldline darter (Percina aurolineata) in Georgia,USA

The goldline darter (Percina aurolineata) is threatened by recent increases in urbanisation in the Coosawattee River watershed, but no studies have addressed their current status. Similarly, limited data on habitat use make it difficult to understand factors that may impact this species. We compared occurrence data before (1996–2000) and after (2009–2011) a period of rapid development and population growth within the watershed. Single‐season occupancy models were built to account for imperfect species detection and to identify habitat covariates. MaxEnt was used to identify important stream reaches for conservation and to understand landscape scale factors correlated with the distribution of goldline darters. Our results indicate a high proportion of sites occupied upstream of Carters Lake during the historic and recent time periods, with no evidence of decline. However, occurrences of goldline darters for sites in Talking Rock Creek and the lower Coosawattee River were sparse in the historic period and absent during the recent period. The probability of detecting goldline darters is low and was positively associated with the occurrence of small substrate. Species distribution models were strongly influenced by watershed area and elevation and indicated a high probability of suitable habitat within the Coosawattee River and large tributaries upstream of Carters Lake. While goldline darter occupancy is currently stable upstream of Carters Lake, continued urbanisation is a threat to long‐term persistence. We recommend additional monitoring and describe a protocol that allows for precise estimates of species occupancy while minimising the risk of sampling‐related mortality.     

Multiple survey methods reveal greater abundance of endangered pupfish in restored habitats

1. Freshwater organisms inhabiting arid ecosystems are imperilled by human alterations to water-limited landscapes. This is especially true among desert-dwelling cyprinodontid fishes, 90% of which are imperilled by habitat destruction within limited or shrinking ranges. Constructing habitats that mimic natural habitat form and function may provide a tool for species conservation, especially within freshwater protected areas. However, pupfish population assessments within degraded compared with restored habitats are infrequent, and few comparisons among survey methods exist.
2. Density estimates were developed for Endangered Comanche Springs pupfish Cyprinodon elegans throughout altered and restored habitats in a freshwater protected area by using mark–recapture and N-mixture models fitted to data collected using minnow trap and visual count survey methods. This allowed comparison of habitats, survey methods, and statistical methods commonly used to generate population size estimates for imperilled pupfish.
3. Population estimates varied across major habitat types and were largest among habitats constructed to mimic naturally occurring ciénegas. Estimates using visual counts were higher than estimates from minnow traps where water was deeper and where macroalgae cover was highest. N-mixture models generally estimated higher abundances than mark–recapture and were not limited by recapture ability.
4. The results provide strong evidence that restored habitats house greater abundances of pupfish, but survey and statistical methods commonly used to detect these differences have trade-offs in performance according to the habitats surveyed. This work benefits the field of conservation biology by providing guidance for existing and emerging monitoring programmes assessing abundance-based fish responses to habitat improvements.

     

Occurrence,abundance and associations of Topeka shiners (Notropis topeka) in restored and unrestored oxbows in Iowa and Minnesota,USA

1. In the USA, the Topeka shiner (Notropis topeka) is a federally listed endangered species that has been in decline for decades. A key reason for the decline is the alteration of naturally flowing streams and associated oxbow habitats resulting from land‐use changes. The focus of recent conservation efforts for Topeka shiners has been the restoration of oxbow habitats by removing sediment from natural oxbows until a groundwater connection is re‐established. This restoration practice has become common in portions of Iowa and south‐west Minnesota.
2. The goals of this study were to compare the occurrence and abundance of Topeka shiners in restored and unrestored oxbows and to determine the characteristics that influenced their presence in these systems.
3. In 2016–2017, 34 unrestored and 64 restored oxbows in the Boone, Beaver Creek, North Raccoon and Rock River basins in Iowa and Minnesota were sampled for their fish assemblages and abiotic features. Topeka shiners were present more often and with higher average relative abundances in restored oxbows.
4. Nonmetric multidimensional scaling ordinations indicated that fish assemblages found in oxbows where Topeka shiners were present were less variable than assemblages found at oxbows where they were absent, but that abiotic characteristics were similar between oxbow types.
5. Logistic regression models suggested that the presence of Topeka shiners in oxbows was positively associated with species richness, brassy minnow (Hybognathus hankinsoni) catch per unit effort (no. fish/100 m²; CPUE), orangespotted sunfish (Lepomis humilis) CPUE, dissolved oxygen and turbidity, and negatively associated with oxbow wetted length. These results highlight the use of restored oxbows by Topeka shiners while also providing new information to help guide restoration and conservation efforts.

     

Objective classification of Navarro River salmon habitat: a watershed‐based critical habitat case study

• 1. Prevailing freshwater conservation approaches in the USA stem from policy‐based ecosystem management directives, science‐based gap analyses, and legal interpretations of critical habitats. In California, there has been no systematic prioritization of freshwater habitats critical to the persistence of anadromous salmonid populations.
• 2. Anadromous salmonids provide an optimal focal species for conservation prioritization of freshwater habitats in California owing to their flagship, umbrella and keystone status.
• 3. The Navarro River is a key watershed for both Endangered Species Act and Clean Water Act recovery efforts in the state of California. This watershed serves as a case study in the use of iterative discriminant analysis to objectively classify freshwater habitats critical to the persistence of two species of threatened anadromous salmonids, steelhead (Oncorhynchus mykiss) and coho (Oncorhynchus kisutch).
• 4. Riverscape parameters were used initially to define suitable habitat for focal species; subsequent refinement accounted for human disturbance within the watershed. Results from this study identify 22.1 km of riverine habitat critical to the persistence of coho salmon in the Navarro River watershed, which need active conservation or restoration; it also identified an additional 269.4 km of riverine habitat in need of protection for its aquatic habitat values.

Copyright © 2007 John Wiley & Sons, Ltd.     

Lack of genetic population structure of slimy sculpin in a large,fragmented lake

Most of what is known about sculpin population structure comes from research in streams; however, slimy sculpins are also a common benthic species in deep lakes. In streams, sculpins are considered to be a relatively inactive species, moving only small distances, and characteristically have high levels of genetic structure. We examined population genetic structure of slimy sculpin (Cottus cognatus) across multiple barriers and over distances up to 227 km in Lake Champlain (USA, Canada) and Lake Ontario (USA, Canada) to determine whether lake populations of sculpin are also highly structured. We predicted that slimy sculpin populations in Lake Champlain would be structured by six causeways as well as by distance, Lake Ontario populations would be structured only by distance, and differences between the lakes would be large relative to within‐lake differences. We examined microsatellite variation among 200 slimy sculpins from Lake Champlain and 48 slimy sculpins from Lake Ontario to evaluate patterns of population connectivity and structure. There was no indication of population substructuring within either lake but sculpin were genetically distinct between lakes. We conclude that there is a single, panmictic population of sculpin present in Lake Champlain and another potentially panmictic population in Lake Ontario, with no indication of genetic isolation by distance. Our results contrast with data from sculpin in streams, suggesting distance and habitat fragmentation exert little influence on population connectivity of benthic fish in lakes.     

Seasonal movement patterns of Credit River brown trout (Salmo trutta)

Zimmer M, Schreer JF, Power M. Seasonal movement patterns of Credit River brown trout (Salmo trutta).
Ecology of Freshwater Fish 2010: 19: 290–299. © 2010 John Wiley & Sons A/S Abstract – Movement habits in riverine populations of brown trout vary among watersheds. Thus it is important to identify factors influencing differences in individual behaviour so as to improve the information resource base available for the design of river‐specific management strategies. Such information is particularly needed in the rapidly urbanising watersheds of eastern North America where relatively little is known about anthropogenic influences on brown trout populations. In this study, we examined the influence of water temperature on brown trout behaviour in the Credit River in south‐central Ontario, Canada with respect to seasonal movement patterns. Observed patterns of movement were also correlated with variations in river discharge and habitat quality. Forty‐three radio‐tagged, adult brown trout were tracked in a confined 39.8 km portion of the Credit River from 15 May 2002 to 28 July 2003. Fish were captured in three sections of the river that differed in distance downstream and habitat quality. Fish size had little impact on movement patterns. However, there was considerable variation in seasonal movement with upstream movements to summer positions, maintenance of summer positions, downstream and often extensive movements in fall. Also observed was maintenance of winter positions and repeated upstream movements in late spring‐early summer to previously used summer positions. The elaborate movement behaviour in the Credit River population was attributed to seasonal changes in thermal habitat quality. Fish tagged in less suitable thermal habitats moved significantly more than fish from more suitable thermal habitats.