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Lake suckers of the genus Chasmistes are a unique and important component of the fish assemblages of the western USA. To review recent research, discuss issues, and exchange information, researchers and managers working on the various species participated in a symposium on lake sucker biology as part of the 2010 annual meeting of the Western Division of the American Fisheries Society, held in Salt Lake City, Utah. This special feature of the Western North American Naturalist is dedicated to lake sucker ecology and natural history and provides a central venue for publication of several papers presented in the symposium. To provide a link to the broader peer-reviewed, published literature on lake sucker biology, we have included a bibliography as an (appendix.
The endangered Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) are endemic to the Upper Klamath Basin, Oregon and California. The once very abundant populations have declined drastically due to a combination of habitat loss and impairment, disruption of reproduction and gene flow, intensive harvest, and loss of entire populations. Spawning populations within Upper Klamath Lake are declining and have not had significant recruitment for over a decade. In addition to habitat loss, these populations are threatened by periodic harmful water conditions resulting from massive algal blooms and entrainment of larvae and juveniles into water delivery systems or hydroelectric structures. Populations of shortnose sucker in Clear Lake appear to be relatively healthy and stable, but recruitment of Lost River sucker appears to be sparse. These populations are affected by drought and water management. Other populations are potentially introgressed with Klamath largescale sucker (Catostomus snyderi) or lack sufficient spawning opportunities to be self-sustaining and therefore function as sink populations. Although genetic and ecological similarities between the species are strong, it is important to better understand the needs of both species individually to assure effectiveness and efficiency in recovery efforts. Determination of the factors limiting juvenile survival and recruitment is vital and should be part of a broader program which includes comparison among populations to understand demography and vital rates. Efforts should also include habitat restoration, improvement of water quality conditions, and reduction of entrainment, as well as monitoring to evaluate effectiveness. Lastly, a controlled propagation program should be considered and/or implemented to conserve unique genetic stocks and provide opportunity for augmentation of wild-spawned populations.
Size-structured spatial patterns in larvae of 2 sucker and 3 minnow species are described from fixed-site sampling in Upper Klamath Lake, Oregon, and are used to demonstrate patterns of size-based losses downstream and retention in the lake. The smallest larvae of shortnose suckers (Chasmistes brevirostris), Lost River suckers (Deltistes luxatus), and tui chubs (Siphateles bicolor) were least likely to be found in Lake Ewauna, a downstream catchment; yet the proportion of larger larvae downstream was often substantial, 20%–40% of a size class. In contrast, the smallest larvae of blue chubs (Klamathella coerulea) and fathead minnows (Pimephales promelas) were least likely to be found in restoration marshes. For these 2 species, interannual differences in spatial size-structuring was variable, with larger size classes being found in high proportions in restoration marshes in some years but not in others. These patterns may be indicative of substantial emigration from Upper Klamath Lake, in the case of suckers and tui chubs, and of variable use of restoration marshes by larger blue chubs and fathead minnows. Although this and other approaches can provide insight into larval emigration and movement, spatially intensive sampling and knowledge of circulation patterns may allow for more rigorous estimates of larval movements.
We monitored the response of endangered Lost River sucker (Deltistes luxatus) larvae and shortnose sucker (Chasmistes brevirostris) larvae prior to, and during the first 2 seasons after, restoration of historic wetlands at the mouth of the Williamson River, Upper Klamath Lake, Oregon. In 2006 and 2007 (prerestoration) and in 2009 and 2010 (postrestoration), we used pop nets set in shallow-water (<1-m-deep) wetland habitats to document the distribution and condition of larval fish throughout the Williamson River Delta Preserve, as well as at a reference site along the Goose Ray shoreline in Upper Klamath Lake. From prerestoration to postrestoration, we witnessed significant declines in abundance of larval suckers at the reference site along the Goose Ray shoreline but no similarly significant declines in the 2 pilot restoration projects (t = 9.92, df = 400, P < 0.0001; t = 0.8, df = 400, P = 0.3438). In 2009 and 2010, larvae were documented using the newly restored portions of the delta. Larval suckers captured during pre- and postrestoration in the pilot areas and during postrestoration in the restored areas of the preserve were more likely to have fuller guts than larvae captured at the reference site along the Goose Ray shoreline. Throughout the study, length trends were more variable than gut fullness trends: larvae captured in pilot areas prior to restoration were larger than those captured after restoration, and larvae captured at the reference site postrestoration were on average larger than postrestoration sucker larvae from the restored and pilot areas.
The recovery program for the endangered June sucker (Chasmistes liorus) relies on population augmentation to overcome recruitment deficits. Successful recruitment of artificially propagated individuals is affected by release timing, release size, and rearing techniques. We examined the effect of release timing and release size (total length [TL] and a relative condition factor [Wr]) on recruitment probability of hatchery-reared June sucker (Utah Division of Wildlife Resources Fisheries Experiment Station [FES]) and captive-reared June sucker (Red Butte Reservoir [RBR] refuge population) stocked across multiple years. Because source and year effects were confounded, we assessed the probability of recruitment individually for each major stocking event (i.e., source × year combination). Successful recruitment occurred if an individual was recaptured or detected at least once during annual spawning runs up Utah Lake tributaries. For stocking events from RBR, probability of recruitment was highest in individuals stocked during spring and early summer but decreased as summer progressed. No difference existed between spring and fall stocking events. June sucker from the FES stocked in October had lower overall probability of recruitment than those stocked in August. The relationships between recruitment probability and TL and Wr for stocking events from RBR were hump shaped, with peaks at approximately 375 mm TL and 100%, respectively. For FES individuals, a positive relationship existed between recruitment probability and TL for individuals stocked during August only; no relationship existed between the recruitment probability and Wr. Release timing and release size affected the recruitment success of captive-reared June sucker; therefore, recovery plans should incorporate these factors in augmentation efforts to maximize augmentation efficiency and success.
One of the fundamental determinants of survival and growth of individuals is population density. Typically, individuals exhibit negative density dependence, but positive density dependence (Allee effect) may occur. Understanding patterns of density dependence is important for conservation and management of species that have low densities as a result of recent population declines. June sucker (Chasmistes liorus) is an endangered species that was formerly abundant but now is found at low densities in Utah Lake. We tested the hypothesis that young June sucker exhibit positive density dependence (i.e., Allee effects) in growth and survival at low densities. In addition, we tested the hypothesis that patterns of density dependence in growth and survival of young June sucker are consistent across years. We conducted a series of 5 experiments in 5 separate years. All 5 experiments included similar levels of density manipulations of young June sucker. June sucker exhibited Allee effects in both growth and survival in some years, but patterns of density dependence varied widely among years. Growth exhibited consistent patterns of negative density dependence, especially at higher densities. Survival was less affected by density, exhibiting no response to density in about half of the experimental comparisons. Overall, intermediate densities around 50 individuals · m-2 seemed to provide the best tradeoff between growth and number produced.
The endangered June sucker, Chasmistes liorus, is a long-lived, zooplanktivorous sucker endemic to Utah Lake, Utah. Habitat degradation both in the tributaries, where adults spawn, and in the lake has contributed to near complete mortality of larval and juvenile fish within the first few weeks after hatching, leading to a long-term lack of recruitment to the adult population. Recovery of June sucker depends on habitat restoration in the river and the lake that will increase the survival of young fish. Thus, it is important to understand how habitat heterogeneity within the lake will influence the survival and growth of young June suckers. To this end, we compared the survival and growth of juvenile June suckers at 2 spatial scales: (1) large regions across the lake and (2) habitats within regions, namely, open water versus vegetated habitats. We related patterns of survival and growth to food availability (zooplankton density). Growth, but not survival, differed significantly among sites at the landscape scale. Sites with higher zooplankton density had higher mean growth. At the habitat scale, survival was greater in vegetated habitats, whereas growth was higher in the open water. Again, increased growth occurred in the area where zooplankton density was greatest. The density of small zooplankton (e.g., Brachionus rotifers) is a good indicator of habitat suitability for young June suckers at both the regional scale and the habitat scale. Future restoration activities should focus on submersed macrophytes and the spawning tributaries (e.g., Hobble Creek) that transport larval fish into the most productive regions of Utah Lake with the highest zooplankton densities (e.g., Provo Bay).
Although roundtail chub (Gila robusta) is generally considered a riverine species, 6 natural lakes in the upper Green River basin, Wyoming, have resident populations of this fish. In 2 of the lakes, Halfmoon and Little Halfmoon, we investigated the ecology of resident roundtail chub, including their habitat use, diet, weight—length relationships, growth, and reproduction. Lentic roundtail chub used littoral and mid-depth benthic habitats most often, with the highest catch rates in littoral habitats. Roundtail chub were rarely caught in pelagic or deep benthic habitats. Opportunistic foraging was observed in both lakes, with roundtail chub consuming terrestrial and aquatic insects, vegetation, and fish. Roundtail chub from both lakes had weight—length relationships similar to those reported for lotic populations but slower annual growth rates. Fish in spawning condition were captured from mid-June to late July when water temperatures ranged from 8.7 to 18.3 °C and snowmelt runoff was at its maximum. Knowledge of roundtail chub ecology in lentic systems will influence management decisions and conservation actions important to preserving this species in the Colorado River basin.
Ectoparasite infestation has been implicated in increased physiological costs and reduced fitness of several animals. The semiaquatic habit of muskrat (Ondatra zibethicus) restricts its ectoparasites to small mites. We assessed variation in muskrat reproductive effort and fat content in response to relative abundance of parasitic mites. There were no significant correlations between total number of placental scars, number of litters, or percent body fat and the relative abundance of ectoparasitic mites. Our results suggest that these measures of muskrat reproduction and physiology are generally unaffected by arachnid ectoparasites.
Insect exclusion from the flowers of Penstemon caryi showed that fruits are not produced unless pollen is moved between flowers by pollinators. We recorded over 30 species of bees visiting the flowers, and about a third of the bee species were common. Flower visitors were primarily pollen-collecting female bees, most of which also carried pollen on areas of the head that strongly implicated them as pollinators. While larger bees were generally more common on the flowers than smaller bees, there appeared to be no difference between size groups in (1) the percent of females collecting Penstemon pollen, (2) the percent of collected pollen that was Penstemon pollen, or (3) the percent of individuals that carried pollen in areas likely to effect pollination. Two long-tongued species, Anthophora ursina (Apidae) and Osmia brevis (Megachilidae), dominated the collections. These 2 species have very different host associations with Penstemon flowers: the specialist O. brevis collects pollen only from species of beardtongues in the western United States, while the generalist A. ursina uses a wide spectrum of plant species for pollen and seems to express fidelity to Penstemon flowers only when those flowers are abundant. There was no evidence that specialists are superior to generalists as pollinators of P. caryi.
The distribution and geographic range of Greater Sage-Grouse (Centrocercus urophasianus) have been reduced by 56% since European settlement. Although loss and fragmentation of sagebrush (Artemisia spp.) habitats have been cited as the primary causes for the decline of the species, degradation of existing habitat also has been considered an important factor. Guidelines for protection and management of breeding and winter habitat have been developed for land managers, but winter habitat use has not been thoroughly described throughout the species' range, particularly for the western portion of its range in Oregon. We examined vegetation-type selection and use by Greater Sage-Grouse during winter (Nov–Feb) at 3 study areas in southeastern Oregon (1989–1992). Elevation gradients and vegetative communities differed among these 3 areas. Our objective was to examine the geographic variation in the selection and use of various vegetation types during winter, when sage-grouse distributions may be most restricted. We described differences in vegetation structure at the microhabitat scale among 3 areas and differences in vegetation-type selection at the macrohabitat scale. We found that the use of mixed sagebrush (basin big sagebrush [Artemisia tridentata tridentata]) and other shrubby vegetation types by sage-grouse was greater than expected at all 3 study areas. At the low- and high-elevation study areas, low sagebrush (Artemisia longiloba) vegetation types were selected more often than expected at random, which was contrary to our original hypotheses. Basin big sagebrush vegetation types were used in proportion to their availability at the 2 low-elevation study areas, and big sagebrush steppe was used less than available (avoided) at the low-elevation areas; these results were contrary to our original predictions. Such differences in selection among the study areas in southeastern Oregon create additional challenges for land managers, who are charged with managing habitats for sage-grouse use during autumn and winter in this portion of the species' geographic range.
Biological soil crust ecology in the hot Mojave Desert is poorly understood with regard to crust distribution and abundance, as well as the impacts of trampling disturbance on crust development. Our objective was to study biological soil crusts in 2 areas of differing disturbance pressures in the high desert region of Joshua Tree National Park, California, with respect to visible crust cover and frequency, chlorophyll a, and soil stability. Impacts on biological soil crusts from 2 disturbance regimes, historic grazing and recent high foot traffic, were compared using a disturbance indicator. In addition, we measured a suite of abiotic and biotic soil parameters commonly associated with crust abundance and distribution and characterized occurrence with respect to 3 geomorphic features (pockets, slopes, and wash banks).
Individual physical and chemical soil parameters historically have been associated with crust development. In contrast, this study demonstrates that geomorphic features with a suite of soil properties clearly impacted crust development. In both study areas, wash banks showed the best crust development (51%–52% total crust cover) and slopes showed the poorest crust development (<37% total crust cover). Lichens and mosses were best developed in the pocket areas (1.1% and 1.5% cover, 25%–30% frequency), which can accumulate and retain moisture during and following precipitation events.
Our disturbance index suggested that the high-foot-traffic area, being associated with a reduction in visible crust cover, has experienced more recent disturbance than the historically grazed sites. However, despite the reduction in cover, the high-foot-traffic area had more lichen and moss crusts, indicating that the crusts in this area are more successionally mature. In contrast, the historically grazed area showed clear signs of recovery from past grazing disturbance, with a higher visual cover of biological soil crusts. However, crusts also had lower biomass values, supporting an earlier successional stage. Overall, we conclude that biological soil crusts of the Mojave Desert are very different in composition, form, and ecology than crusts of other desert regions of North America.
Northern flying squirrels (Glaucomys sabrinus) are found in boreal forests of northern and northwestern North America, but a small population is isolated to the Black Hills of South Dakota and Wyoming. Few micro satellite primers have been developed for this species, though they are needed to examine the genetic structure of these populations. Thus, we isolated and characterized 5 micro satellite loci in northern flying squirrels through a series of steps involving microbiology, molecular biology, and genetic techniques. Data analyses with these primers indicated that the northern flying squirrel population found in the Black Hills may have low heterozygosity and significant departure from Hardy-Weinberg equilibrium. The development of these primers not only provides additional data for analyzing a small, disjunct population but also serves as a mechanism for understanding population dynamics and assisting with overall management and conservation of unique populations.
We analyzed the effects of a second-entry prescribed fire in a mixed conifer forest in Grand Canyon National Park, Arizona, 14 years after the initial burn to assess whether restoration and management objectives were achieved. The surface fire had little effect on large overstory ponderosa pine, Douglas-fir, and white fir trees and did not change total tree density or basal area. The fire reduced the overall density of conifer seedlings <30 cm tall by 87%, but had a smaller effect on seedlings >30 cm tall and on sapling density. The fire reduced litter depths by 33%, duff depths by 23%, fine woody debris by 21%, and coarse woody debris by 44%. These effects were mostly consistent with restoration goals in mixed conifer forests and continue to move this forest toward reference conditions. Grand Canyon National Park staff now considers this forest to be in “maintenance burning,” meaning that they plan to allow natural ignitions to maintain forest structure in the future. This forest is now more resilient to projected increases in fire size and/or frequency under conditions of a warming climate. This example illustrates that use of prescribed fire in a ponderosa pine—dominated mixed conifer forest can be consistent both with restoring historical conditions and with managing for resilience under altered disturbance regimes accompanying a changing climate.
We examined the diets of 3 species of bufonids from northern Mexico (Anaxyrus debilis, Anaxyrus punctatus, and lncilius mazatlanensis) with the objective of better understanding the diets of amphibians in this region of Mexico, which is currently undergoing environmental change. The diet of A. debilis was numerically and volumetrically dominated by termites, followed by ants. In A. debilis, some aspects of prey size were correlated with toad head width but were not related to head length or body size (i.e., snout—vent length [SVL]). Ants were numerically the most important prey item in the diet of A. punctatus, but beetles were volumetrically the most important prey item. Prey size was not related to toad head size or body size in A. punctatus. The diet of I. mazatlanensis numerically consisted of ants, beetles, and bugs; however, volumetrically, its diet was dominated by beetles. In I. mazatlanensis, only prey length was correlated with toad head width and SVL. The diets of these 3 species generally fit our previous understanding of the diets of bufonids.