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USGS1998

Impacts of trapping and banding activities on productivity of Roseate Terns (Sterna Dougallii)

Although Roseate Terns (Sterna dougallii) habituate to many research activities, trapping and handling breeding adults, or repeatedly handling chicks, may affect reproductive success or chick growth. Protocols for trapping adult Roseate Terns that reduce the chances of nest desertion, neglect of chicks, and injury to adults were developed in the early 1980s, but neither short-term nor long-term effects of research activities on this endangered species have been fully investigated. Therefore, this study had the following main objectives: 1) examine long-term data (1978-1996) to determine if trapping activities have had a major effect on annual reproductive success of a Roseate Tern colony, 2) evaluate the effects of trapping adult terns on reproductive success and chick growth, and 3) evaluate the effects of handling chicks on their growth and survival. There were no significant correlations between measures of trapping disturbance and annual reproductive success in 1978-1996 for the Falkner Island (Stewart B. McKinney National Wildlife Refuge, Connecticut) colony, suggesting that trapping from late incubation through chick rearing using the field protocols described herein does not have a major effect on nesting success of Roseate Terns. In 1987-1996, adult trapping did not reduce prefledging survival of first-hatched chicks, and reduced survival of second-hatched chicks only in 1994 and 1995. Results of more detailed research in 1994-1996 suggest that Roseate Terns may be susceptible to trapping effects only when also faced with extreme conditions such as low food availability and/or high predation pressure. Trapping effects did not occur in most years under apparently average or typical conditions, and otherwise seem to be much less important than other factors affecting nesting success (e.g., predation and food availability). Analyses of chick growth data from 1987-1996 showed that while trapping significantly reduced early growth compared to untrapped controls, most of these effects disappeared after controlling for variation due to laying variables and other indices of parental age and quality. Trapping had little or no effect on later growth (indices of fledgling quality) and thus is unlikely to affect postfledging survival and fitness. For chicks whose parents were trapped, the sex of the adult(s), timing of trapping during the nesting stage, and interval between trapping events (if both parents were trapped) had little or no effect on growth. Daily or near-daily handling of chicks did not significantly affect their growth, prefledging survival, or postfledging survival. These results suggest that while trapping adult Roseate Terns can sometimes affect reproductive success and early chick growth and should be taken into account during research, trapping effects tend to be minor, short-lived, and unlikely to affect overall population health. While the full implications for population health and individual fitness are not entirely clear, there appears to be little cause for concern that trapping and banding activities are a significant problem for Roseate Terns. However, this qualitative assessment of the biological significance of trapping effects needs empirical testing. There remains a practical need to explore the ramifications of trapping effects and to consider local conditions when planning trapping activities. We also need to consider how investigator-induced effects might affect research results, and to balance potential effects of research activities against the value of the information gained.

Book↗

USGS2022

Life and death in a dynamic environment: Invasive trout, floods, and intraspecific drivers of translocated populations

Understanding the relative strengths of intrinsic and extrinsic factors regulating populations is a long-standing focus of ecology and critical to advancing conservation programs for imperiled species. Conservation could benefit from an increased understanding of factors influencing vital rates (somatic growth, recruitment, survival) in small, translocated populations, which is lacking owing to difficulties in long-term monitoring of rare species. Translocations, here defined as the transfer of wild-captured individuals from source populations to new habitats, are widely used for species conservation, but outcomes are often minimally monitored, and translocations that are monitored often fail. To improve our understanding of how translocated populations respond to environmental variation, we developed and tested hypotheses related to intrinsic (density dependent) and extrinsic (introduced rainbow trout Oncorhynchus mykiss , stream flow and temperature regime) causes of vital rate variation in endangered humpback chub ( Gila cypha ) populations translocated to Colorado River tributaries in the Grand Canyon (GC), USA. Using biannual recapture data from translocated populations over 10 years, we tested hypotheses related to seasonal somatic growth, and recruitment and population growth rates with linear mixed-effects models and temporal symmetry mark–recapture models. We combined data from recaptures and resights of dispersed fish (both physical captures and continuously recorded antenna detections) from throughout GC to test survival hypotheses, while accounting for site fidelity, using joint live-recapture/live-resight models. While recruitment only occurred in one site, which also drove population growth (relative to survival), evidence supported hypotheses related to density dependence in growth, survival, and recruitment, and somatic growth and recruitment were further limited by introduced trout. Mixed-effects models explained between 67% and 86% of the variation in somatic growth, which showed increased growth rates with greater flood-pulse frequency during monsoon season. Monthly survival was 0.56–0.99 and 0.80–0.99 in the two populations, with lower survival during periods of higher intraspecific abundance and low flood frequency. Our results suggest translocations can contribute toward the recovery of large-river fishes, but continued suppression of invasive fishes to enhance recruitment may be required to ensure population resilience. Furthermore, we demonstrate the importance of flooding to population demographics in food-depauperate, dynamic, invaded systems.

Arizona↗

USGS2022

Differences in population characteristics and modeled response to harvest regulations in reestablished Appalachian Walleye populations

Historically, the Monongahela, Tygart, and Cheat River watersheds in West Virginia were impaired by acidification from acid mine drainage and Walleye Sander vitreus were extirpated from these watersheds by the 1940s. Walleye were reestablished after water quality improvements following passage of environmental legislation and subsequent reintroduction efforts. We compared population characteristics, with emphasis on growth, of Walleye and used modeling to predict the potential effects of harvest regulations in the Monongahela River and two main-stem reservoirs in the Cheat River and Tygart River watersheds. Statistical comparisons of von Bertalanffy growth curves and relative growth indices indicated that Walleye growth significantly differed across all water bodies. Relative growth index results suggested that Walleye growth was above average in Cheat Lake, average in the Monongahela River, and below average in Tygart Lake relative to other North American populations. Growth was negatively correlated with Walleye relative abundance and positively correlated with estimates of productivity (total phosphorus, chlorophyll a ). Walleye diets significantly differed across all water bodies, with diets dominated by Yellow Perch Perca flavescens and Gizzard Shad Dorosoma cepedianum in Cheat Lake, where growth was fastest. Population modeling suggested that effects of exploitation on yield, spawning potential, and size structure were similar under regulations of no length limit and a minimum length limit (381 mm). Models suggested that removing length limits in Tygart Lake could increase angler harvest opportunities and pose minimal threat to the fishery. Models suggested that a protected slot limit could provide increased protection to the spawning potential of Cheat Lake and the Monongahela River populations. Additionally, models predicted that a protected slot limit could increase the number of large (>630-mm) Walleye in these waters. Our findings demonstrate the different characteristics that Walleye populations can develop after reestablishment based on abiotic and biotic conditions and the need for watershed-specific management.

West Virginia↗

USGS2023

Cisco population characteristics in Wisconsin lakes in relation to lake- and landscape-level factors

Objective Declines in Cisco Coregonus artedi populations in some inland lakes have prompted assessments of Cisco occurrence and extirpation risk in relation to various stressors to identify refuge lakes and factors that promote Cisco persistence. However, most previous assessments have focused on presence–absence of Cisco rather than examining how population characteristics, such as relative abundance or growth, might change in relation to lake- and landscape-level environmental factors. Consequently, our specific objectives were to identify important environmental factors explaining variation in Cisco relative abundance and growth and to determine whether population metrics describing size and age distributions were related to relative abundance in Wisconsin inland lakes. Methods Cisco were collected from 48 inland Wisconsin lakes during 2011–2015 using vertical monofilament gill nets and population-specific relative abundance estimates (catch per unit effort [CPUE]) were quantified as the number of individuals per gill-net night. Sagittal otoliths were removed from a subsample of Cisco for age estimation and growth was indexed as mean total length (TL; mm) at age 2. Length and age data were used to develop a suite of metrics describing size and age distributions of each population. Random forest models were used to evaluate relationships between 10 biologically relevant predictor variables representing variation in physical, climatic, catchment, and limnological characteristics and Cisco CPUE and growth. Pearson correlations were used to determine whether population characteristics were related to CPUE. Result Cisco populations exhibited large variation in relative abundance, growth, and size and age distributions. Best-fit random forest models explained approximately 25% of the variation in Cisco CPUE and 46% of the variation in growth. Growing degree-days and variables associated with availability, quality, and quantity of suitable oxythermal conditions were identified as important predictors of both Cisco CPUE and growth; CPUE was also identified as an important predictor of growth. Mean TL and mean TL at age 2 were negatively related to Cisco CPUE, whereas mean age, number of age-classes present, and maximum observed age were positively related to CPUE. Conclusion Our results suggest that maintenance of suitable oxythermal habitat conditions may be critical to conserving abundant Cisco populations. Our assessment also provides insights on how Cisco populations may respond to environmental and anthropogenic stressors, which could aid ongoing and future conservation and management efforts in Wisconsin and elsewhere.

Wisconsin↗

USGS2006

Variation in the establishment of a non-native annual grass influences competitive interactions with Mojave Desert perennials

Competition between native and non-native species can change the composition and structure of plant communities, but in deserts, the highly variable timing of resource availability also influences non-native plant establishment, thus modulating their impacts on native species. In a field experiment, we varied densities of the non-native annual grass Bromus madritensis ssp. rubens around individuals of three native Mojave Desert perennials-Larrea tridentata, Achnatherum hymenoides, and Pleuraphis rigida-in either winter or spring. For comparison, additional plots were prepared for the same perennial species and seasons, but with a mixture of native annual species as neighbors. Growth of perennials declined when Bromus was established in winter because Bromus stands had 2-3 months of growth and high water use before perennial growth began. However, water potentials for the perennials were not significantly reduced, suggesting that direct competition for water may not be the major mechanism driving reduced perennial growth. The impact of Bromus on Larrea was lower than for the two perennial grasses, likely because Larrea maintains low growth rates throughout the year, even after Bromus has completed its life cycle. This result contrasts with the perennial grasses, whose phenology completely overlaps with (Achnatherum) or closely follows (Pleuraphis) that of Bromus. In comparison, Bromus plants established in spring were smaller than those established in winter and thus did not effectively reduce growth of the perennials. Growth of perennials with mixed annuals as neighbors also did not differ from those with Bromus neighbors of equivalent biomass, but stands of these native annuals did not achieve the high biomass of Bromus stands that were necessary to reduce perennial growth. Seed dormancy and narrow requirements for seedling survivorship of native annuals produce densities and biomass lower than those achieved by Bromus; thus, impacts of native Mojave Desert annuals on perennials are expected to be lower than those of Bromus. ?? 2006 Springer Science+Business Media B.V.

Biological Invasions↗

USGS2023

Investigating effects of climate-induced changes in water temperature and diet on mercury concentrations in an Arctic freshwater forage fish

The amount of mercury (Hg) in Arctic lake food webs is, and will continue to be, affected by rapid, ongoing climate change. At warmer temperatures, fish require more energy to sustain growth; changes in their metabolic rates and consuming prey with potentially higher Hg concentrations could result in increased Hg accumulation. To examine the potential implications of climate warming on forage fish Hg accumulation in Arctic lakes, we quantified growth and Hg accumulation in Ninespine Stickleback Pungitius pungitius under different temperature and diet scenarios using bioenergetics models. Four scenarios were considered that examined the role of climate, diet, climate × diet, and climate × diet × elevated prey Hg. As expected, annual fish growth increased with warmer temperatures, but growth rates and Hg accumulation were largely diet dependent. Compared to current growth rates of 0.3 g⋅y −1 , fish growth increased at least 200% for fish consuming energy-dense benthic prey and decreased at least 40% for fish consuming pelagic prey. Compared to baseline levels, the Hg burden per kilocalorie of Ninespine Stickleback declined up to 43% with benthic consumption – indicating strong somatic growth dilution – but no more than 4% with pelagic consumption; elevated prey Hg concentrations led to moderate Hg declines in benthic-foraging fish and Hg increases in pelagic-foraging fish. Bioenergetics models demonstrated the complex interaction of water temperature, growth, prey proportions, and prey Hg concentrations that respond to climate change. Further work is needed to resolve mechanisms and rates linking climate change to Hg availability and uptake in Arctic freshwater systems.

Alaska↗

USGS2004

Improved spatial resolution for U-series dating of opal at Yucca Mountain, Nevada, USA, using ion-microprobe and microdigestion methods

Two novel methods of in situ isotope analysis, ion microprobe and microdigestion, were used for 230Th/U and 234U/238U dating of finely laminated opal hemispheres formed in unsaturated felsic tuff at Yucca Mountain, Nevada, proposed site for a high-level radioactive waste repository. Both methods allow analysis of layers as many as several orders of magnitude thinner than standard methods using total hemisphere digestion that were reported previously. Average growth rates calculated from data at this improved spatial resolution verified that opal grew at extremely slow rates over the last million years. Growth rates of 0.58 and 0.69 mm/m.y. were obtained for the outer 305 and 740 ??m of two opal hemispheres analyzed by ion microprobe, and 0.68 mm/m.y. for the outer 22 ??m of one of these same hemispheres analyzed by sequential microdigestion. These Pleistocene growth rates are 2 to 10 times slower than those calculated for older secondary calcite and silica mineral coatings deposited over the last 5 to 10 m.y. dated by the U-Pb method and may reflect differences between Miocene and Pleistocene seepage flux. The microdigestion data also imply that opal growth rates may have varied over the last 40 k.y. These data are the first indication that growth rates and associated seepage in the proposed repository horizon may correlate with changes in late Pleistocene climate, involving faster growth during wetter, cooler climates (glacial maximum), slower growth during transition climates, and no growth during the most arid climate (modern). Data collected at this refined spatial scale may lead to a better understanding of the hydrologic variability expected within the thick unsaturated zone at Yucca Mountain over the time scale of interest for radioactive waste isolation. ?? 2004 Elsevier Ltd.

Geochimica et Cosmochimica Acta↗

USGS1998

Understory vegetation in old and young Douglas-fir forests of western Oregon

We studied understory composition in thinned and unthinned Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco)/western hemlock ( Tsuga heterophylla (Raf.) Sarg.) stands on 28 sites in western Oregon. These stands had regenerated naturally after timber harvest, 40–70 years before thinning. Commercial thinning had occurred 10–24 years previously, with 8–60% of the volume removed from below with the intent to homogenize spacing among trees. Undisturbed old-growth Douglas-fir stands were present for comparison on 18 of these sites. Total herbaceous cover was greater in thinned (25% cover) stands than in unthinned (13% cover) or old-growth (15% cover) stands. Species richness was also greater in thinned (137) than in unthinned (114) and old-growth (91) stands ( P =0.05). Part of the increased richness was caused by the presence of exotic species in thinned stands, but there were also more native grass and nitrogen-fixing species in thinned stands than in unthinned or old-growth stands. Groups of species differed among stand-types. For example, the frequency of tall cordate-leaved species was greater in old-growth stands ( P =0.009), but their relative cover was different only between old-growth and unthinned stands ( P =0.08). Both the cover and frequency of grasses and sedges in thinned stands were greater than in unthinned or old-growth stands ( P ≤0.002). Ordination of shrub cover showed differences among old-growth and unthinned stands compared to thinned stands, mainly because of the amount of Gaultheria shallon Pursh and Polystichum munitum (Kaulf.) Presl in heavily thinned stands. Ordination of herbaceous community data showed that there were much stronger differences among sites than among stand-types. The lack of difference among stand-types demonstrates the resiliency of herbaceous communities to disturbance associated with past and current forest management.

Oregon↗

USGS2009

Ecology of stream fish: Insights gained from an individual-based approach to juvenile Atlantic salmon

Using data from an ongoing study of juvenile Atlantic salmon growth and survival in tributaries of the Connecticut River, USA, we compare standard population-level approaches to those focusing on individuals. We highlight the potential benefits of resampling individually tagged stream fish as compared to standard approaches. Specifically we focus on growth, survival, movements and population estimation. The advantages of estimating sizes and growth rates from individual size trajectories include obtaining growth histories and the ability to perform retrospective analysis of the consequences of different life-history strategies. An example might be the patterns of growth leading to either early maturity or migration. Resampling known individuals is the only way we know to chart both short-term and long-term movements and to assign growth and mortality consequences to such movements. Finally, individual-level data permit robust estimation of survival and density/abundance using methods such as Cormack/Jolly-Seber. The results indicate that population estimates were about 10% lower using individual data than using population data, that survival from sample to sample was typically >90%, that the majority of recaptured fish did not move during the summer, that growth was rapid during spring and most fish lost mass during the summer and that growth trajectories for maturing and non-maturing fish showed substantially different patterns. An individual-based approach to stream fish ecology provides the opportunity to explore the mechanisms responsible for population-level patterns but comes at the cost of significant field effort. Tradeoffs between increased data resolution and the effort required to obtain the data must be considered before undertaking individual-based field studies of stream fishes.

Massachusetts↗

USGS2012

Effect of Feeding-Fasting Cycles on Oxygen Consumption and Bioenergetics of Yellow Perch

We measured growth and oxygen consumption of age-1 yellow perch Perca flavescens subjected to ad libitum (control) or variable feeding cycles of 2 (i.e., 2 d of feed, 2 d of deprivation), 6, or 12 d for a 72-d period. Individual, female yellow perch (initial weight = 51.9 ± 0.9 g [mean ± SE]) were stocked in 110-L aquaria to provide six replicates per treatment and fed measured rations of live fathead minnow Pimephales promelas . Consumption, absolute growth rate, growth efficiency, and oxygen consumption were similar among feeding regimens. However, growth trajectories for fish on the 2-d cycle were significantly lower than other feed–fast cycles. Hyperphagia occurred in all treatments. Bioenergetics model simulations indicated that consumption was significantly underestimated ( t = 5.4, df = 4, P = 0.006), while growth was overestimated ( t = −5.5, df = 4, P = 0.005) for fish on the 12-d cycle. However, model errors detected between observed and predicted values were low, ranging from −10.1% to +7.8%. We found that juvenile yellow perch exhibited compensatory growth (CG), but none of the feed–fast treatments resulted in growth overcompensation. Likewise, we found no evidence that respiration rates varied with CG, implying that yellow perch bioenergetics models could be used to predict the effects of feeding history and CG response on food consumption and fish growth.

Transactions of the American Fisheries Society↗

USGS2023

Identifying mechanisms underlying individual body size increases in a changing, highly seasonal environment: The growing trout of West Brook

As air temperature increases, it has been suggested that smaller individual body size may be a general response to climate warming. However, for ectotherms inhabiting cold, highly seasonal environments, warming temperatures may increase the scope for growth and result in larger body size. In a long-term study of individual brook trout Salvelinus fontinalis and brown trout Salmo trutta inhabiting a small stream network, individual lengths increased over the course of 15 years. As size-selective gains and losses to the population acted to reduce body sizes and mean body size at first tagging in the autumn (<60 mm) were not observed to change substantially over time, the increase in body size was best explained by higher individual growth rates. For brook trout, increasing water temperatures during the spring (when both trout species accomplish most of their total annual growth) was the primary driver of growth rate for juvenile fish and the environmental factor which best explained increases in individual body size over time. For brown trout, by contrast, reduction in and subsequent elimination of juvenile Atlantic salmon Salmo salar midway through the study period explained most of the increases in juvenile growth and body size. In addition to these major trends, a considerable amount of interannual variation in trout growth and body size was explained by other abiotic (stream flow) and biotic (population density) factors with the direction and magnitude of these effects differing by season, age-class and species. For example, stream flow was the dominant growth rate driver for adult fish with strong positive effects in the summer and autumn, but flow variation could not explain increases in body size as we observed no trend in flow. Overall, our work supports the general contention that for high-latitude ectotherms, increasing spring temperatures associated with a warming climate can result in increased growth and individual body size (up to a point), but context-dependent change in other factors can substantially contribute to both interannual variation and longer-term effects.

Massachusetts↗

USGS2009

Forecasting the combined effects of urbanization and climate change on stream ecosystems: from impacts to management options

Streams collect runoff, heat, and sediment from their watersheds, making them highly vulnerable to anthropogenic disturbances such as urbanization and climate change. Forecasting the effects of these disturbances using process-based models is critical to identifying the form and magnitude of likely impacts. Here, we integrate a new biotic model with four previously developed physical models (downscaled climate projections, stream hydrology, geomorphology, and water temperature) to predict how stream fish growth and reproduction will most probably respond to shifts in climate and urbanization over the next several decades. The biotic submodel couples dynamics in fish populations and habitat suitability to predict fish assemblage composition, based on readily available biotic information (preferences for habitat, temperature, and food, and characteristics of spawning) and day-to-day variability in stream conditions. We illustrate the model using Piedmont headwater streams in the Chesapeake Bay watershed of the USA, projecting ten scenarios: Baseline (low urbanization; no on-going construction; and present-day climate); one Urbanization scenario (higher impervious surface, lower forest cover, significant construction activity); four future climate change scenarios [Hadley CM3 and Parallel Climate Models under medium-high (A2) and medium-low (B2) emissions scenarios]; and the same four climate change scenarios plus Urbanization. Urbanization alone depressed growth or reproduction of 8 of 39 species, while climate change alone depressed 22 to 29 species. Almost every recreationally important species (i.e. trouts, basses, sunfishes) and six of the ten currently most common species were predicted to be significantly stressed. The combined effect of climate change and urbanization on adult growth was sometimes large compared to the effect of either stressor alone. Thus, the model predicts considerable change in fish assemblage composition, including loss of diversity. Synthesis and applications . The interaction of climate change and urban growth may entail significant reconfiguring of headwater streams, including a loss of ecosystem structure and services, which will be more costly than climate change alone. On local scales, stakeholders cannot control climate drivers but they can mitigate stream impacts via careful land use. Therefore, to conserve stream ecosystems, we recommend that proactive measures be taken to insure against species loss or severe population declines. Delays will inevitably exacerbate the impacts of both climate change and urbanization on headwater systems.

Journal of Applied Ecology↗

USGS2000

The use of coded microwire tags mark-recapture studies of juvenile Caribbean spiny lobster, Panulirus argus

To evaluate the suitability of using coded microwire tags (CWTs) to mark early-benthic-stage Caribbean spiny lobster, Panulirus argus , we compared the survival, growth, and feeding of tagged and untagged lobsters held in the laboratory through the first five juvenile molts. We also examined the growth of 65 microwire-tagged lobsters released into the wild as early-benthic-stage juveniles. Tag retention rates of lobsters held in the laboratory were 86% for those tagged as first-stage juveniles and 96% for those tagged as second-stage juveniles; virtually all tag loss was confined to the first post-tag molt. Survival and growth rates of tagged second-stage juveniles in the laboratory did not significantly differ from those of untagged lobsters, but first-stage-tagged juveniles had lower growth rates than untagged lobsters did and a 25% post-tagging mortality rate. The mean growth rate of juveniles released into the wild was 0.82 mm CL/wk, but growth differed by season; no sex- or habitat-specific differences in growth were observed. Data obtained from these recaptured lobsters provide the first detailed estimates of growth of P . argus under natural conditions during the earliest part of their benthic life and illustrate the potential usefulness of coded microwire tags in mark-recapture investigations of juveniles for this and other species.

Florida↗

USGS2011

Development of a bioenergetics model for humpback chub and evaluation of water temperature changes in the Grand Canyon, Colorado River

The construction of Glen Canyon Dam above the Grand Canyon (Arizona) has reduced the water temperature in the Colorado River and altered the growth rate and feeding patterns of the federally endangered humpback chub Gila cypha. A bioenergetics model for humpback chub was developed and used to examine how warmer water temperatures in the lower Colorado River (achieved through a temperature control device [TCD] at Glen Canyon Dam) might influence their growth rate and food requirements. Parameter values for humpback chub were developed by Monte Carlo filtering and fitting to laboratory growth. Parameter bounds were established from the literature for Gila species, random parameter sets were selected within these bounds, and the growth of modeled humpback chub was compared with criteria from a laboratory growth experiment at 24??C. This method of parameter estimation could be applied to other imperiled fishes where physiological studies are impractical. Final parameter values were corroborated by comparison with the growth rates of humpback chub from independent field and laboratory studies. Simulations indicated that increasing water temperatures from approximately 9??C to 16??C during summer and fall, the change expected from the TCD, may have a minimal effect on humpback chub growth rate unless food availability also increases with temperature. To evaluate the effects of increased temperatures on humpback chub in the lower Colorado River, it will be essential to monitor their growth rate, the invertebrate community, and the predators of humpback chub, which are also influenced by temperature changes. Bioenergetics models for humpback chub and their predators should be helpful tools for identifying potential scenarios and evaluating the complex interactions resulting from a TCD. ?? Copyright by the American Fisheries Society 2005.

Transactions of the American Fisheries Society↗

USGS2005

A novel approach to fitting the von Bertalanffy relationship to a mixed stock of Atlantic sturgeon harvested off the New Jersey Coast

We examined the growth characteristics of 303 Atlantic sturgeon, Acipenser oxyrinchus , caught in the commercial fishery off the New Jersey coast from 1992 to 1994 (fork length range: 93–219 cm). Sections taken from the leading pectoral fin ray were used to age each sturgeon. Ages ranged from 5–26 years. Von Bertalanffy growth models for males and females fit well, but test statistics (t-test, maximum likelihood) failed to reject the null hypothesis that growth was not significantly different between sexes. Consequently, all data were pooled and the combined data gave L ∞ and K estimates of 174.2 cm and 0.144, respectively. Our growth data do not fit the pattern of slower growth and increased size in more northernly latitudes for Atlantic sturgeon observed in other work. Lack of uniformity of our growth data may be due to (1) the sturgeon fishery harvesting multiple stocks having different growth rates, and (2) size limits for the commercial fishery having created a bias in estimating growth parameters.

New Jersey↗

USGS2017

Evaluating land-use change scenarios for the Puget Sound Basin, Washington, within the ecosystem recovery target model-based framework

The Puget Sound Basin, Washington, has experienced rapid urban growth in recent decades, with varying impacts to local ecosystems and natural resources. To plan for future growth, land managers often use scenarios to assess how the pattern and volume of growth may affect natural resources. Using three different land-management scenarios for the years 2000–2060, we assessed various spatial patterns of urban growth relative to maps depicting a model-based characterization of the ecological integrity and recent development pressure of individual land parcels. The three scenarios depict future trajectories of land-use change under alternative management strategies—status quo, managed growth, and unconstrained growth. The resulting analysis offers a preliminary assessment of how future growth patterns in the Puget Sound Basin may impact land targeted for conservation and how short-term metrics of land-development pressure compare to longer term growth projections.

Washington↗

USGS1981

Dendroclimatic estimates of a drought index for northern Virginia

A 230-year record of the Palmer drought-severity index (PDSI) was estimated for northern Virginia from variations in widths of tree rings. Increment cores were extracted from eastern hemlock, Tsuga canadensis (L.) Carr., at three locations in northern Virginia. Measurements of annual growth increments were made and converted to standardized indices of growth. A response function was derived for hemlock to determine the growth-climate relationship. Growth was positively correlated with precipitation and negatively correlated with temperature during the May-July growing season. Combined standardized indices of growth were calibrated with the July PDSI. Growth accounted for 20-30 percent of the PDSI variance. Further regressions using factor scores of combined tree growth indices resulted in a small but significant improvement. Greatest improvement was made by using factor scores of growth indices of individual trees, thereby accounting for 64 percent of the July PDSI variance in the regression. Comparison of the results with a 241-year reconstruction from New York showed good agreement between low-frequency climatic trends. Analysis of the estimated Central Mountain climatic division of Virginia PDSI record indicated that, relative to the long-term record (1746-1975), dry years have occurred in disproportionally larger numbers during the last half of the 19th century and the mid-20th century. This trend appears reversed for the last half of the 18th century and the first half of the 19th century. Although these results are considered first-generation products, they are encouraging, suggesting that once additional tree-ring chronologies are constructed and techniques are refined, it will be possible to obtain more accurate estimates of prior climatic conditions in the mid-Atlantic region.

Water Supply Paper↗

USGS1981

Factors influencing methionine toxicity in young Bobwhite quail

Young Bobwhite quail ( Colinus virginianus ) were fed low and adequate protein purified diets with and without excess methionine to evaluate factors affecting methionine toxicity. Growth of quail fed an adequate protein (27%) diet, without supplemental glycine, was depressed by 1.75% and 2.25% excess methionine. Supplemental glycine (.3%) alleviated growth depression caused by 2.25% excess methionine. Quail fed 1.75% and 2.25% excess methionine developed signs of toxicity characterized by weakness, a lowered, outstretched neck when moving, and ataxia. In addition, quail would fall on their sides when disturbed and spin with their heads retracted. These conditions were transient in nature. Growth of quail fed a low protein (18.9%) diet was depressed by 1% and 1.5% excess methionine and DL -homocystine. Quail fed 1% and 1.5% excess methionine in this diet also developed signs of toxicity, the incidence of which was greater and the duration longer than occurred with quail fed adequate protein. Supplementing a low protein (20.15%) diet with .3% or .6% glycine or threonine or a combination of these amino acids did not alleviate growth depression caused by 1.5% excess methionine; however, 2% and 3% supplemental glycine were somewhat effective. Supplements of glycine (2%, 3%) and threonine (1%) completely reversed growth depression from 1% excess methionine but did not influence growth of controls, indicating that both amino acids counteract methionine toxicity. Both glycine and threonine alone improved growth by about the same extent in diets with 1% or 1.5% excess methionine; however, these amino acids alleviated less than 30% of the growth depression resulting from 1.5% excess methionine. The effectiveness of glycine in alleviating methionine toxicity in a low protein diet was decreased, and hemoglobin levels were depressed with 1.5% excess methionine compared to less amounts.

Poultry Science↗