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USGS2018

Fall and winter microhabitat use and suitability for spring chinook salmon parr in a U.S. Pacific Northwest River

Habitat degradation has been implicated as a primary threat to Pacific salmon Oncorhynchus spp. Habitat restoration and conservation are key toward stemming population declines; however, winter microhabitat use and suitability knowledge are lacking for small juvenile salmonids. Our objective was to characterize microhabitat use and suitability for spring Chinook Salmon Oncorhynchus tshawytscha parr during fall and winter. Using radiotelemetry techniques during October–February (2009–2011), we identified fall and winter microhabitat use by spring Chinook Salmon parr in Catherine Creek, northeastern Oregon. Tagged fish occupied two distinct gradient reaches (moderate and low). Using a mixed‐effects logistic regression resource selection function (RSF) model, we found evidence that microhabitat use was similar between free‐flowing and surface ice conditions. However, habitat use shifted between seasons; most notably, there was greater use of silt substrate and areas farther from the bank during winter. Between gradients, microhabitat use differed with greater use of large wood (LW) and submerged aquatic vegetation in the low‐gradient reach. Using a Bayesian RSF approach, we developed gradient‐specific habitat suitability criteria. Throughout the study area, deep depths and slow currents were most suitable, with the exception of the low‐gradient reach where moderate depths were optimal. Near‐cover coarse and fine substrates were most suitable in the moderate‐ and low‐gradient reaches, respectively. Near‐bank LW was most suitable throughout the study area. Multivariate principal component analyses (PCA) indicated co‐occurring deep depths supporting slow currents near cover were intensively occupied in the moderate‐gradient reach. In the low‐gradient reach, PCA indicated co‐occurring moderate depths, slow currents, and near‐bank cover were most frequently occupied. Our study identified suitable and interrelated microhabitat combinations that can guide habitat restoration for fall migrant and overwintering Chinook Salmon parr in Catherine Creek and potentially the Pacific Northwest.

Oregon↗

USGS2018

Migratory behavior and physiological development as potential determinants of life history diversity in fall Chinook Salmon in the Clearwater River

We studied the influence of behavior, water velocity, and physiological development on the downstream movement of subyearling fall‐run Chinook Salmon Oncorhynchus tshawytscha in both free‐flowing and impounded reaches of the Clearwater and Snake rivers as potential mechanisms that might explain life history diversity in this stock. Movement rates and the percentage of radio‐tagged fish that moved faster than the average current velocity were higher in the free‐flowing Clearwater River than in impounded reaches. This supports the notion that water velocity is a primary determinant of downstream movement regardless of a fish's physiological development. In contrast, movement rates slowed and detections became fewer in impounded reaches, where water velocities were much lower. The percentage of fish that moved faster than the average current velocity continued to decline and reached zero in the lowermost reach of Lower Granite Reservoir, suggesting that the behavioral disposition to move downstream was low. These findings contrast with those of a similar, previous study of Snake River subyearlings despite similarity in hydrodynamic conditions between the two studies. Physiological differences between Snake and Clearwater River migrants shed light on this disparity. Subyearlings from the Clearwater River were parr‐like in their development and never showed the increase in gill Na + /K + ‐ATPase activity displayed by smolts from the Snake River. Results from this study provide evidence that behavioral and life history differences between Snake and Clearwater River subyearlings may have a physiological basis that is modified by environmental conditions.

Idaho, Washington↗

USGS2021

Capacity of two Sierra Nevada rivers for reintroduction of anadromous salmonids: Insights from a high-resolution view

Historically, anadromous steelhead Oncorhynchus mykiss and spring-run Chinook Salmon O. tshawytscha used high-elevation rivers in the Sierra Nevada of California but were extirpated in the 20th century by construction of impassable dams. Plans to reintroduce the fish by opening migratory passage across the dams and reservoirs can only succeed if upstream habitats have the capacity to support viable populations of each species. To estimate capacity in the Tuolumne and Merced rivers of the central Sierra Nevada, we used a high-resolution approach based on remote sensing and dynamic habitat modeling. Our results suggested that for both species in both systems, sediment grain sizes would support widespread spawning and the water temperatures, depths, and velocities would generate ample capacity for fry and juveniles. However, the unregulated Merced River was consistently too warm for adult Chinook Salmon to hold in the dry season prior to spawning, while the regulated Tuolumne River maintained a cooler, more stable thermal regime with a capacity for thousands of holding adults. In our high-resolution approach, we also discovered several specific physical controls on life history expression, including thermal constraints on the timing of spawning, hydraulic prompts for downstream migration of fry, divergence of the hydraulic niches of steelhead and Chinook Salmon, and a key but uncertain role for thermal tolerance in adult Chinook Salmon. Our results suggested that steelhead reintroduction could succeed in either system and Chinook Salmon could succeed in the Tuolumne River if passage strategies account for large numbers of migrant fry and juveniles driven downstream by winter storms and snowmelt. The Merced River appeared too warm for adult Chinook Salmon, which raises questions about the current limited understanding of thermal tolerance in holding adults. Our study shows how a high-resolution approach can provide valuable insights on specific limiting factors that must be addressed for reintroduction to succeed.

California↗

USGS2014

Spring migration ecology of the mid-continent sandhill crane population with an emphasis on use of the Central Platte River Valley, Nebraska

We conducted a 10-year study (1998–2007) of the Mid-Continent Population (MCP) of sandhill cranes (Grus canadensis) to identify spring-migration corridors, locations of major stopovers, and migration chronology by crane breeding affiliation (western Alaska–Siberia [WA–S], northern Canada–Nunavut [NC–N], west-central Canada–Alaska [WC–A], and east-central Canada–Minnesota [EC–M]). In the Central Platte River Valley (CPRV) of Nebraska, we evaluated factors influencing staging chronology, food habits, fat storage, and habitat use of sandhill cranes. We compared our findings to results from the Platte River Ecology Study conducted during 1978–1980. We determined spring migration corridors used by the breeding affiliations (designated subpopulations for management purposes) by monitoring 169 cranes marked with platform transmitter terminals (PTTs). We also marked and monitored 456 cranes in the CPRV with very high frequency (VHF) transmitters to evaluate length and pattern of stay, habitat use, and movements. An estimated 42% and 58% of cranes staging in the CPRV were greater sandhill cranes (G. c. tabida) and lesser sandhill cranes (G. c. canadensis), and they stayed for an average of 20 and 25 days (2000–2007), respectively. Cranes from the WA–S, NC–N, WC–A, and EC–M affiliations spent an average of 72, 77, 52, and 53 days, respectively, in spring migration of which 28, 23, 24, and 18 days occurred in the CPRV. The majority of the WA–S subpopulation settled in the CPRV apparently because of inadequate habitat to support more birds upstream, although WA–S cranes accounted for >90% of birds staging in the North Platte River Valley. Crane staging duration in the CPRV was negatively correlated with arrival dates; 92% of cranes stayed >7 days. A program of annual mechanical removal of mature stands of woody growth and seedlings that began in the early 1980s primarily in the main channel of the Platte River has allowed distribution of crane roosts to remain relatively stable over the past 2 decades. Most cranes returned to nocturnal roost sites used in previous years. Corn residues dominated the diet of sandhill cranes in the CPRV, as in the 1970s, despite a marked decline in standing crop of corn residues. Only 14% (10 of 74) of PTT-marked migrant cranes stayed at stopovers for ≥5 days before arriving in the CPRV, which limited the contribution of sites south of the CPRV for fat accumulation needed for migration and reproduction. Body masses of cranes (after adjusting for body size [an index of fat]) at arrival in the CPRV varied widely among years (1998–2006), indicating the importance of maintaining productive habitats on the wintering grounds to condition cranes for migration and reproduction. Average rates of fat gain by adult females while in the CPRV remained similar from 1978–1979 to 1998–1999 but declined among males. Distances cranes flew to feeding grounds in the CPRV increased as the percentage of cropland planted to soybeans increased and as density of cranes on nocturnal roosts increased. These results suggest that as habitats of limited or no value to cranes increase on the landscape, more flight time and higher maintenance costs may reduce fat storage. An estimated 40% of diurnal use occurred north of Interstate 80 (I-80) where ≤5% of lands dedicated to crane conservation are located. Seventy-four and 40% of PTT-marked EC–M and WC–A cranes had spring migrations that included staging in eastern South Dakota for an average of 11 and 10 days, respectively. Cranes of the NC–N, WA–S, and WC–A subpopulations staged an average of 25, 17, and 12 days in central and western Saskatchewan/eastern Alberta. Females in these affiliations increased their fat reserves after leaving Nebraska by an estimated 450, 451, and 452 g, respectively, underscoring the key role of these staging areas in preparing the 3 subpopulations for reproduction. After departing Nebraska, MCP cranes roosted primarily in basin wetlands. Most of these wetlands are in private ownership and lack adequate protection, emphasizing the need for effective laws and policies to ensure their long-term protection. The continued success of the current management goal of maintaining the MCP at approximately its current size and providing diverse recreational opportunities over a wide area of midcontinent and western North America is predicated on the ability of MCP cranes to continue to store large fat reserves in the CPRV in advance of breeding. For the CPRV to remain a key fat storage site, active channel maintenance (e.g., clearing of woody vegetation) likely will need to continue, along with establishing minimum stream flows. These actions would help ensure nocturnal roosting habitat remains sufficiently dispersed to provide cranes with daily intake of high-energy food adequate for major fat storage and limit risk of high mortality from storms and disease. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Nebraska↗

USGS1995

Organochlorine residues in bat guano from nine Mexican caves, 1991

Samples of bat guano, primarily from Mexican free-tailed bats ( Tadarida brasiliensis ), were collected at nine bat roosts in caves in northern and eastern Mexico and analysed for organochlorine residues. DDE, the most abundant residue found in each cave, was highest (0.99 p.p.m. dry weight) at Ojuela Cave, Durango. Other studies of DDE in bat guano indicate that this concentration is too low to reflect harmful concentrations in the bats themselves. The DDE at Ojuela may represent either lingering residues from use of DDT years ago in the Ojuela area of perhaps depuration loss from migrant bats with summer maternity roost(s) in a DDE-contaminated area such as Carlsbad Cavern, New Mexico. Presence of o,p′ -DDT at Tio Bartolo Cave, Nuevo Leon, indicates recent use of DDT, but the concentration of this contaminant was low. Possible impacts on bat colonies of the organophosphorus and carbamate insecticides now in extensive use are unknown.

Ecotoxicology↗

USGS1996

Effects of a legal drain clean-out on wetlands and waterbirds: a recent case history

Repairs to legal drains in the United States may be regulated to protect adjacent wetlands under Section 404 of the Federal Water Pollution Control Act, commonly known as the Clean Water Act (CWA). However, few studies have examined effects of legal drain clean-outs on adjacent wetlands and associated migratory waterbird populations. I compare water regimes, cover-to-open water ratios, and waterbird use on Bruns, Big, Meszaros, and Kraft sloughs (BBMK) in Sargent County, North Dakota before and after the clean-out of Crete-Cogswell Drain No. 11, and relate wetland habitat loss to observed disease-related mortality among staging waterfowl in fall 1990 and spring 1991. Water regimes of BBMK were exceptionally stable, with few records of drawdowns before 1984 when the clean-out began. After the clean-out (1987-90), BBM were dry by mid-summer in all years and open area declined by 96% by 1990, whereas Kraft Slough (a control area) had water throughout all years and percent open area did not change. Numerous species of waterbirds nested in BBMK before the clean-out, and mean ranks of waterbird density were similar. After the clean-out, waterbirds failed to breed successfully in all years at BBM, and use as major waterfowl staging areas and for waterfowl hunting also ended. At Kraft Slough, use by breeding and staging waterbirds continued in all years, as did waterfowl hunting. Reduced access to fresh water after the Drain No. 11 clean-out may have contributed to a dieoff of 487 lesser snow geese (Chen caerulescens) from necrotic enteritis in Kraft Slough in November 1990. Loss of three major staging areas in Sargent County as a result of the drain clean-out has further concentrated migrant waterfowl, particularly during drought periods, increasing the magnitude of risk when epizootics occur in southeastern North Dakota. Ducks and geese banded in Sargent County have been recovered from 34 and 14 states, 7 and 6 provinces of Canada, and 13 and 1 other countries, respectively, indicating waterfowl populations from a wide area are potentially vulnerable to epizootics when crowded into limited roosting habitat. Despite causing the loss of wetland habitat for thousands of midcontinent waterfowl and other waterbirds, a Federal Court in North Dakota ruled that the clean-out of Drain No. 11 met the criteria necessary to be considered maintenance under Section 404 clause (f)(1)(c) and was not recaptured under clause (f)(2). This outcome suggests current law does not protect wetland functions needed to support migratory waterbird populations or associated recreational values when sites have become naturally restored through lack of maintenance of legal drains.

Wetlands↗

USGS1993

Avian communities in riparian forests of different widths in Maryland and Delaware

In agricultural landscapes, much of the remaining forest is in linear tracts along streams. These riparian forests provide habitat for forest birds, but their use by forest interior birds may depend on forest width. We conducted point-count surveys of birds in riparian forests on the Eastern shore of Maryland and Delaware to assess whether the presence of any species was dependent on corridor width. We surveyed 117 corridors that ranged from 25- to 800-m wide. Several area-sensitive neotropical migrants were encountered more frequently in wider riparian forests, and probabilities of occurrence increased most rapidly between 25 and 100 m. Based on these surveys, we recommend that riparian forests be at least 100-m wide to provide some nesting habitat for area-sensitive species. Wider riparian forests would be preferable and should be preserved.

Delaware, Maryland↗

USGS2018

Occurrence of quiescence in free-ranging migratory songbirds

Quiescence is a period of inactivity that occurs before the onset of migratory activity in nocturnally migrating birds. This behavior has been observed in captive birds in migratory disposition, but its occurrence in free-ranging migratory birds has been documented only anecdotally, and causal factors and function(s), if any, are unknown. In this study, we documented and characterized quiescence in three migratory songbird species (red-eyed vireo [ Vireo olivaceus ], Swainson’s thrush [ Catharus ustulatus ], and wood thrush [ Hylocichla mustelina ]) by measuring movement and proportion of time spent inactive prior to departure from a stopover site during fall migration. Individuals of each species displayed a period of inactivity prior to departure which varied from less than 30 min to over 90 min with red-eyed vireos engaged in the longest, most pronounced quiescence. We also examined how quiescence was related to intrinsic and extrinsic factors known to influence the departure of migrating birds, and found some evidence for an effect of age and departure time but no effect of a migrant’s energetic condition, departure direction, atmospheric conditions around departure, or day of year on quiescence. Our novel application of an automated radiotelemetry system yielded a large amount of data to characterize quiescence in free-ranging migratory birds, and we provide guidance for future studies to tease apart the various causal factors and function(s) of this migratory behavior.

Behavioral Ecology and Sociobiology↗

USGS2014

Risks of avian influenza transmission in areas of intensive free-ranging duck production with wild waterfowl

For decades, southern China has been considered to be an important source for emerging influenza viruses since key hosts live together in high densities in areas with intensive agriculture. However, the underlying conditions of emergence and spread of avian influenza viruses (AIV) have not been studied in detail, particularly the complex spatiotemporal interplay of viral transmission between wild and domestic ducks, two major actors of AIV epidemiology. In this synthesis, we examine the risks of avian influenza spread in Poyang Lake, an area of intensive free-ranging duck production and large numbers of wild waterfowl. Our synthesis shows that farming of free-grazing domestic ducks is intensive in this area and synchronized with wild duck migration. The presence of juvenile domestic ducks in harvested paddy fields prior to the arrival and departure of migrant ducks in the same fields may amplify the risk of AIV circulation and facilitate the transmission between wild and domestic populations. We provide evidence associating wild ducks migration with the spread of H5N1 in the spring of 2008 from southern China to South Korea, Russia, and Japan, supported by documented wild duck movements and phylogenetic analyses of highly pathogenic avian influenza H5N1 sequences. We suggest that prevention measures based on a modification of agricultural practices may be implemented in these areas to reduce the intensity of AIV transmission between wild and domestic ducks. This would require involving all local stakeholders to discuss feasible and acceptable solutions.

Poyang Lake↗

USGS2023

Drivers and timing of grass carp movement within the Sandusky River, Ohio: Implications to potential spawning barrier response strategy

Understanding the timing and drivers of migration can be beneficial for improving response efforts aimed at reducing invasive species densities. Efforts by management agencies to remove grass carp ( Ctenopharyngodon idella) , an invasive species to the Laurentian Great Lakes, have been ongoing in Lake Erie tributaries since 2018. To bolster efforts, deployment of a non-physical barrier has been proposed downstream of a known grass carp spawning location near Brady’s Island (BI) in the Sandusky River, OH, USA to limit recruitment. However, knowledge of grass carp migratory timing, the environmental variables that cue carp migration, and the potential effects the barrier might impose on native fish [e.g., walleye ( Sander vitreus )] movements would help inform barrier deployment and scheduling. We used detection data from grass carp ( n = 29) and walleye ( n = 84) tagged with acoustic transmitters to address four objectives: (1) quantify interannual variation (years = 2015–2021) of grass carp migration timing to BI; (2) evaluate timing of different grass carp movement modalities (residents and migrants); (3) assess overlap in migration timing with native walleye, and (4) evaluate environmental cues of grass carp migration to BI. Median grass carp arrival at BI occurred within a three-week period (148–165 Julian days), suggesting that deploying a barrier immediately prior to this time frame may be effective for deterring grass carp spawning. Temperature, photoperiod, and discharge influenced grass carp migration timing given that most arrival events occurred at daylengths > 14.5 h, temperatures exceeding 18 °C, and low discharge events (< 3,000 cubic feet second −1 [CFS]). Minimal interannual variability in migration timing existed for grass carp and walleye over a six-year period. However, the median departure time of walleye was more than 45 days before the median arrival time of grass carp, suggesting a spawning barrier may minimally affect walleye spawning. No differences in arrival timing at BI were observed between grass carp migratory contingents, indicating that if a barrier were deployed in the spring, it would likely affect all grass carp spatial contingents. This work highlights management implications of barrier control efforts of aquatic invasive species and provides insight into the environmental cues that grass carp use for upstream migration.

Ohio↗

USGS2011

Population genetic structure and conservation genetics of threatened Okaloosa darters (Etheostoma okaloosae)

Imperiled Okaloosa darters ( Etheostoma okaloosae ) are small, benthic fish limited to six streams that flow into three bayous of Choctawhatchee Bay in northwest Florida, USA. We analyzed the complete mitochondrial cytochrome b gene and 10 nuclear microsatellite loci for 255 and 273 Okaloosa darters, respectively. Bayesian clustering analyses and AMOVA reflect congruent population genetic structure in both mitochondrial and microsatellite DNA. This structure reveals historical isolation of Okaloosa darter streams nested within bayous. Most of the six streams appear to have exchanged migrants though they remain genetically distinct. The U.S. Fish and Wildlife Service recently reclassified Okaloosa darters from endangered to threatened status. Our genetic data support the reclassification of Okaloosa darter Evolutionary Significant Units (ESUs) in the larger Tom’s, Turkey, and Rocky creeks from endangered to threatened status. However, the three smaller drainages (Mill, Swift, and Turkey Bolton creeks) remain at risk due to their small population sizes and anthropogenic pressures on remaining habitat. Natural resource managers now have the evolutionary information to guide recovery actions within and among drainages throughout the range of the Okaloosa darter.

Florida↗

USGS2012

Puerto Rico and Florida manatees represent genetically distinct groups

The West Indian manatee ( Trichechus manatus ) populations in Florida ( T. m. latirostris ) and Puerto Rico ( T. m. manatus ) are considered distinct subspecies and are listed together as endangered under the United States Endangered Species Act. Sustained management and conservation efforts for the Florida subspecies have led to the suggested reclassification of the species to a threatened or delisted status. However, the two populations are geographically distant, morphologically distinct, and habitat degradation and boat strikes continue to threaten the Puerto Rico population. Here, 15 microsatellite markers and mitochondrial control region sequences were used to determine the relatedness of the two populations and investigate the genetic diversity and phylogeographic organization of the Puerto Rico population. Highly divergent allele frequencies were identified between Florida and Puerto Rico using microsatellite (F ST = 0.16; R ST = 0.12 (P < 0.001)) and mitochondrial (F ST = 0.66; Φ ST = 0.50 (P < 0.001)) DNA. Microsatellite Bayesian cluster analyses detected two populations (K = 2) and no admixture or recent migrants between Florida (q = 0.99) and Puerto Rico (q = 0.98). The microsatellite genetic diversity values in Puerto Rico (H E = 0.45; N A = 3.9), were similar, but lower than those previously identified in Florida (H E = 0.48, N A = 4.8). Within Puerto Rico, the mitochondrial genetic diversity values (π = 0.001; h = 0.49) were slightly lower than those previously reported (π = 0.002; h = 0.54) and strong phylogeographic structure was identified (F ST global = 0.82; Φ ST global = 0.78 (P < 0.001)). The genetic division with Florida, low diversity, small population size (N = 250), and distinct threats and habitat emphasize the need for separate protections in Puerto Rico. Conservation efforts including threat mitigation, migration corridors, and protection of subpopulations could lead to improved genetic variation in the endangered Puerto Rico manatee population.

Florida↗

USGS2014

Spatial genetic structure of bristle-thighed curlews (Numenius tahitiensis): Breeding area differentiation not reflected on the non-breeding grounds

Migratory birds occupy geographically and ecologically disparate areas during their annual cycle with conditions on breeding and non-breeding grounds playing separate and important roles in population dynamics. We used data from nuclear microsatellite and mitochondrial DNA control region loci to assess the breeding and non-breeding spatial genetic structure of a transoceanic migrant shorebird, the bristle-thighed curlew. We found spatial variance in the distribution of allelic and haplotypic frequencies between the curlew's two breeding areas in Alaska but did not observe this spatial structure throughout its non-breeding range on low-lying tropical and subtropical islands in the Central Pacific (Oceania). This suggests that the two breeding populations do not spatially segregate during the non-breeding season. Lack of migratory connectivity is likely attributable to the species' behavior, as bristle-thighed curlews exhibit differential timing of migration and some individuals move among islands during non-breeding months. Given the detrimental impact of many past and current human activities on island ecosystems, admixture of breeding populations in Oceania may render the bristle-thighed curlew less vulnerable to perturbations there, as neither breeding population will be disproportionally affected by local habitat losses or by stochastic events. Furthermore, lack of migratory connectivity may enable bristle-thighed curlews to respond to changing island ecosystems by altering their non-breeding distribution. However, availability of suitable non-breeding habitat for curlews in Oceania is increasingly limited on both low-lying and high islands by habitat loss, sea level rise, and invasive mammalian predators that pose a threat to flightless and flight-compromised curlews during the molting period.

Conservation Genetics↗

USGS2018

Genetic diversity, effective population size, and structure among black bear populations in the Lower Mississippi Alluvial Valley, USA

Multiple small populations of American black bears Ursus americanus , including the recently delisted Louisiana black bear subspecies U. a. luteolus , occupy a fragmented landscape in the Lower Mississippi Alluvial Valley, USA (LMAV). Populations include bears native to the LMAV, bears translocated from Minnesota during the 1960s, and recently reintroduced and colonizing populations sourced from within the LMAV. We estimated population structure, gene flow, and genetic parameters important to conservation of small populations using genotypes at 23 microsatellite markers for 265 bears from seven populations. We inferred five genetic clusters corresponding to the following populations: White River and western Mississippi, Tensas River and Three Rivers, Upper Atchafalaya, Lower Atchafalaya, and Minnesota. Upper Atchafalaya was suggested as the product of Minnesota-sourced translocations, but those populations have since diverged, likely because of a founder effect followed by genetic drift and isolation. An admixture zone recently developed in northeastern Louisiana and western Mississippi between migrants from White River and Tensas River, resulting in a Wahlund effect. However, gene flow among most populations has been limited and considerable genetic differentiation accumulated (global F ST = 0.22), particularly among the three Louisiana black bear populations that existed when federal listing occurred. Consistent with previous bottlenecks, founder effects, and persisting isolation, all LMAV bear populations had low genetic diversity ( A R = 2.08–4.81; H E = 0.36–0.63) or small effective population size ( N E = 3–49). Translocating bears among populations as part of a regional genetic restoration program may help improve genetic diversity and increase effective population sizes.

Lower Mississippi Alluvial Valley↗

USGS2023

Genetic analysis of federally endangered Cape Sable seaside sparrow subpopulations in the Greater Everglades, USA

The federally endangered Cape Sable seaside sparrow ( Ammospiza maritima mirabilis ) is endemic to the Greater Everglades ecosystem in southern Florida, inhabiting fragmented marl prairies in six individual subpopulations. The subspecies is threatened by loss of breeding habitat from fire and water management. Genetic information is severely limited for the subspecies but could help inform decisions regarding subpopulation protections and potential translocations for genetic rescue. To provide genetic data and inform management efforts, feather samples were collected across five subpopulations (designated A–E) and protocols were tested to optimize DNA extraction yields. We assessed four mitochondrial DNA markers (N = 36–69) and 12 nuclear microsatellite loci (N = 55) in 108 sparrows. Mitochondrial DNA sequences revealed low haplotype diversity, with NADH dehydrogenase-2 haplotypes matching to most other extant subspecies and to the Atlantic coast subspecies. Nuclear diversity was low compared to other subspecies, but similar across subpopulations. Samples grouped as one population when analyzed by Principal Component Analysis, Bayesian modelling and genetic distance metrics. Limited genetic emigration was detected from one putative migrant. Relatedness was significantly different for sparrows in the most geographically distant subpopulation (A), likely reflecting high self-recruitment and natal site fidelity ( P = 0.003). The low to moderate effective population size (N E = 202.4; N E :N C = 0.06) and generation time estimates indicated that unique genetic variation could be lost quickly during stochastic events. The sample sizes were limited, which reduced the power to comprehensively address recent population size reductions and any subsequent loss of genetic diversity.

Florida↗

USGS2011

Migration of Sakhalin taimen (Parahucho perryi): Evidence of freshwater resident life history types

Sakhalin taimen ( Parahucho perryi ) range from the Russian Far East mainland along the Sea of Japan coast, and Sakhalin, Kuril, and Hokkaido Islands and are considered to primarily be an anadromous species. We used otolith strontium-to-calcium ratios (Sr/Ca) to determine the chronology of migration between freshwater and saltwater and identify migratory contingents of taimen collected from the Koppi River, Russia. In addition, we examined taimen from the Sarufutsu River, Japan and Tumnin River, Russia that were captured in marine waters. Transects of otolith Sr/Ca for the Sarufutsu River fish were consistent with patterns observed in anadromous salmonids. Two fish from the Tumnin River appeared to be recent migrants to saltwater and one fish was characterized by an otolith Sr/Ca transect consistent with marine migration. Using these transects as benchmarks, all Koppi River taimen were classified as freshwater residents. These findings suggest more work is needed to assess life history variability among locations and the role of freshwater productivity in controlling migratory behavior in taimen.

Tumnin River, Koppi River, Sarufutsu River↗

USGS2011

Individual condition and stream temperature influence early maturation of rainbow and steelhead trout, ncorhynchus mykiss

Alternative male phenotypes in salmonine fishes arise from individuals that mature as larger and older anadromous marine-migrants or as smaller and younger freshwater residents. To better understand the processes influencing the expression of these phenotypes we examined the influences of growth in length (fork length) and whole body lipid content in rainbow trout ( Oncorhynchus mykiss ). Fish were sampled from the John Day River basin in northeast Oregon where both anadromous ("steelhead") and freshwater resident rainbow trout coexist. Larger males with higher lipid levels had a greater probability of maturing as a resident at age-1+. Among males, 38% were maturing overall, and the odds ratios of the logistic model indicated that the probability of a male maturing early as a resident at age-1+ increased 49% (95% confidence interval (CI) = 23-81%) for every 5 mm increase in length and 33% (95% CI = 10-61%) for every 0.5% increase in whole body lipid content. There was an inverse association between individual condition and water temperature as growth was greater in warmer streams while whole body lipid content was higher in cooler streams. Our results support predictions from life history theory and further suggest that relationships between individual condition, maturation, and environmental variables (e.g., water temperature) are shaped by complex developmental and evolutionary influences.

Oregon↗

USGS2015

Seasonal cues of Arctic grayling movement in a small Arctic stream: the importance of surface water connectivity

In Arctic ecosystems, freshwater fish migrate seasonally between productive shallow water habitats that freeze in winter and deep overwinter refuge in rivers and lakes. How these movements relate to seasonal hydrology is not well understood. We used passive integrated transponder tags and stream wide antennae to track 1035 Arctic grayling in Crea Creek, a seasonally flowing beaded stream on the Arctic Coastal Plain, Alaska. Migration of juvenile and adult fish into Crea Creek peaked in June immediately after ice break-up in the stream. Fish that entered the stream during periods of high flow and cold stream temperature traveled farther upstream than those entering during periods of lower flow and warmer temperature. We used generalized linear models to relate migration of adult and juvenile fish out of Crea Creek to hydrology. Most adults migrated in late June – early July, and there was best support (Akaike weight = 0.46; w i ) for a model indicating that the rate of migration increased with decreasing discharge. Juvenile migration occurred in two peaks; the early peak consisted of larger juveniles and coincided with adult migration, while the later peak occurred shortly before freeze-up in September and included smaller juveniles. A model that included discharge, minimum stream temperature, year, season, and mean size of potential migrants was most strongly supported ( w i = 0.86). Juvenile migration rate increased sharply as daily minimum stream temperature decreased, suggesting fish respond to impending freeze-up. We found fish movements to be intimately tied to the strong seasonality of discharge and temperature, and demonstrate the importance of small stream connectivity for migratory Arctic grayling during the entire open-water period. The ongoing and anticipated effects of climate change and petroleum development on Arctic hydrology (e.g. reduced stream connectivity, earlier peak flows, increased evapotranspiration) have important implications for Arctic freshwater ecosystems.

Alaska↗