Intraguild predation between spawning smallmouth bass (Micropterus dolomieu) and nest‐raiding crayfish (Orconectes rusticus): implications for bass nesting success

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The influence of parental care behaviour on localized nest spacing in smallmouth bass, Micropterus dolomieu

Synopsis I examined the consequence of territorial behaviour on localized nest spacing by male smallmouth bass, Micropterus dolomieu in Jones Bay, Lake Opeongo, Ontario. I compared observed nest spacing to that predicted from (i) territory size and shape measured using sonic tracking procedures; and (ii) 1000 simulated, randomly established nesting stocks. The observed spacing between nests (17.52 ± 1.46 m; mean ± standard error) was not different from that predicted from measurements of territory size and shape (17.60 ± 3.20 m) but was significantly greater than that predicted for randomly established nests (9.53 ± 0.06 m). Parental care-associated territorial behaviour influences the spacing between smallmouth bass nests.     

Spawning and Brood Defense of Smallmouth Bass Under the Process of Invasion into a Novel Habitat

Smallmouth bass, Micropterus dolomieu, known as one of the world's most disastrous invasive species, was introduced into Lake Aoki, central Japan in the last 10 years and is of concern for the conservation of the native biodiversity. We investigated spawning and brood defense under novel conditions to devise measures to eradicate a local population of this species. Compared to their native habitat, the size distribution of nesting males was less skewed to the right in this invasive population but rather a skewed normal distribution probably due to prevention of younger cohorts entering the nesting stock. The number of offspring deposited in nests was not positively related to the size of the nesting male. These observations imply that a shortage of suitable nest sites leads to an escalation in male–male competition, followed by a relaxation of female mate choice based on male size. Further, when presented with a model of a potential predator of the offspring, nesting males reacted individually and the intensity of site tenacity was independent of the male size. We propose that the removal of cover accompanied by the use of native predators of young bass can effectively decelerate the expansion of invasive smallmouth bass.     

Snowy plover nest site selection,spatial patterning,and temperatures in the Southern High Plains of Texas

Snowy plover (Charadrius nivosus) populations have declined throughout their range, in part because of habitat degradation and poor nest success, making information regarding regionally specific nest site selection and spatial patterns important when considering habitat conservation and management guidelines. We determined nest site selection characteristics (n = 180) and examined spatial patterns (n = 215) of snowy plover nests in saline lakes in the Southern High Plains (SHP) of Texas. At 104 nests, we examined the influence of substrate type on nest temperatures and heat mitigation. Snowy plover nests were more likely to be found near an object, on pebble substrate, and with fewer plants than random sites. High use areas were generally located in areas with pebble substrate and on human-made or natural islands, berms, and peninsulas. Overall, nests placed on pebble substrate had lower temperatures during the day than nests placed on sand substrates. Nest placement on pebble substrate may be valuable to nesting snowy plovers, providing thermal advantages to incubating adults and depressing potentially high nest predation rates. Management guidelines for this region should emphasize the importance of addressing key elements of snowy plover nesting habitat including the presence of pebble substrate and reducing vegetation encroachment. © 2012 The Wildlife Society.     

Environmental variability influences the structure of benthic algal communities in an oligotrophic lake

Theoretical models suggest that environmental variability can promote biodiversity, both in terms of richness and evenness of species. These findings have been supported experimentally in simplified communities with simplified regimes of environmental variability. Here we test the importance of environmental variability in a more natural setting by comparing the composition of benthic algal communities along a natural gradient of environmental variability created by internal waves in an elongated lake basin. Algal communities were grown on tiles at five upwind and five downwind sites in the lower littoral zone of South Arm, in Lake Opeongo, Ontario, Canada. Upwind sites were 1°C colder, on average, than downwind sites and had more variable water temperatures. The ranges of mean water temperatures and of water temperature variability were greater among upwind sites than among downwind sites. We used water temperature variability as a proxy for environmental variability. Total algal biovolume was similar at all sites, but the composition of these communities varied systematically with temperature variability. An observed shift in the relative dominance between Achnanthidium minutissimum, Surirella sp. and Pinnularia spp. is consistent with what we know about these species. Diatom richness increased from 12 to 15 genera with increasing variability at upwind (p=0.10, r²=0.65) and downwind sites (p=0.11, r²=0.63). Community evenness also increased with increasing variability (p=0.03, r²=0.82 at upwind sites; p=0.0002, r²=0.99 at downwind sites). These relationships were observed despite low nutrient and light availability, as well as the presence of grazers. Furthermore, environmental variability affected diatom communities in the presence of several competing factors (temperature, light, nutrients and disturbance). Our results suggest that increased environmental variability can lead to higher biodiversity in a complex natural system.     

Effects of Large-Scale Predator Reduction on Nest Success of Upland Nesting Ducks

ABSTRACT Population growth for mallards (Anas platyrhynchos), and presumably other upland nesting ducks, in the Prairie Pothole Region of the United States and Canada is most sensitive to nest success, and nest success is most strongly influenced by predation. We evaluated the efficacy of reducing predator populations to improve nest success of upland nesting ducks on township-sized (93.2 km²) management units in eastern North Dakota, USA, during 2005–2007. We monitored 7,489 nests on 7 trapped and 5 nontrapped sites. Trappers annually removed an average of 245 predators per trapped site, and we found nest success to be 1.4–1.9 times greater on trapped sites than nontrapped sites, depending on year. Nest success was greater on both trapped and nontrapped sites when compared with a study conducted in the same areas in the mid-1990s, likely because of changes in red fox (Vulpes vulpes) and coyote (Canis latrans) population dynamics. Nests initiated midseason had higher daily survival rates (DSR) than those initiated earlier or later in the season. Daily survival rates for nests in the middle of the nesting cycle were higher than for nests that were early in laying or late in incubation. Nests near the periphery of trapped sites had slightly higher DSRs than nests in the center of trapped sites. Predator reduction at the township scale provides managers with an effective tool to improve nest success at large spatial scales.     

The role of progeny quality and male size in the nesting success of smallmouth bass: integrating field and laboratory studies

Smallmouth bass display size-specific variation in reproductive success with larger brood-guarding males in a population more likely to rear offspring to independence than smaller individuals. The exact mechanisms responsible for this size-specific increase in reproductive output have yet to be identified. To assist in this process, we investigated the relationship between the size of brood-guarding male smallmouth bass and offspring quality (in this case, egg physiology, egg morphology, egg size, hatching success and lab survival). Further, we examined how factors such as egg physiology, egg morphology and egg size influenced reproductive success in the wild and hatching success in a controlled laboratory environment. Nesting male smallmouth bass that successfully reared their offspring to independence spawned earliest in the nesting period were the largest individuals, and guarded eggs with greater concentrations of cortisol compared to males that abandoned their offspring prematurely. Offspring survival in the laboratory was not correlated with offspring survival in the wild, indicating that caution should be used interpreting studies that attempt to relate laboratory-derived survival metrics to the wild. Together, results demonstrate size-specific differences in offspring quality for nesting smallmouth bass, which are correlated with higher concentrations of cortisol in eggs. However, hatching success under laboratory conditions was dissimilar to nesting success in the field relative to cortisol concentrations.     

Increased parental care cost for nest-guarding fish in a lake with hyperabundant nest predators

Although parental care increases offspring survival, providingcare is costly, reducing parental growth and survival and, thereby,compromising future reproductive success. To determine if anexotic benthic predator might be affecting parental care bynest-guarding smallmouth bass (Micropterus dolomieu), we comparednest-guarding behavior and energy expenditures in two systems,one with a hyperabundant recently introduced predator, the roundgoby (Neogobious melanostomus). In Lake Erie, USA, smallmouthbass vigorously defended their nests from benthic round gobies.In Lake Opeongo, Canada, smallmouth bass were exposed to fewerand predominantly open-water predators and were less activein their nest defense. From scuba and video observations, wedocumented that nest-guarding smallmouth bass chased predators(99% of which were round gobies) nine times more frequentlyin Lake Erie than in Lake Opeongo. This heightened activityresulted in a significant decline in weight and energetic contentof guarding males in Lake Erie but no change in Lake Opeongomales. Bioenergetic simulations revealed that parental careincreased smallmouth bass standard metabolic rate by 210% inLake Erie but only by 28% in Lake Opeongo. As energy reservesdeclined and offspring became increasingly independent, malesin both lakes consumed more prey and spent more time foragingaway from their nests; however, nest-guarding smallmouth bassconsumed few prey and, in Lake Erie, rarely consumed round gobies.Therefore, increased parental care costs owing to the presenceof round gobies could affect future growth, reproduction, andsurvival if smallmouth bass approach critically low energy reserves.     

Spatial and annual variation in the diets of juvenile smallmouth bass, Micropterus dolomieu

Synopsis We measured macroinvertebrate densities and abundance, size, and diet of juvenile smallmouth bass, Micropterus dolomieu, at five sites located at varying distances from a metalimnetic release dam. We used these data to determine the influence of high prey abundances on stomach fullness and age-0 year-class strength. Summer diets of juvenile smallmouth bass (27.7–107.7 mm total length) were dominated by Ephemeroptera (primarily Baetidae) but diet composition was highly variable among years and sites. A linear index of prey selection showed that Ephemeroptera were preferred and Trichoptera were avoided at all sites in all years; but, selection indices were not consistent for Chironomidae or Amphipoda and Isopoda. In two of three years, stomach fullness (gut content mass relative to predicted maximum) of juvenile smallmouth bass decreased with distance downstream of the dam, which reflected patterns observed in benthic macroinvertebrate densities. However, in 1989 when flooding and increased turbidity reduced abundances of juvenile smallmouth bass, no differences in stomach fullness were found among sites. High stomach fullness of juvenile smallmouth bass was attributed to high prey abundances near the dam in years of low or normal streamflow. However, patterns in juvenile smallmouth bass abundances in mid-summer could not be attributed to longitudinal variation in prey abundance.     

Do Cory’s shearwaters Calonectris diomedea synchronize laying among close neighborhoods? A reappraisal using data from artificial nest sites

Previous studies of Cory’s shearwater nesting biology suggest that pairs nesting at very close range to one another lay their eggs more synchronously than the colony as a whole. However, such apparent synchrony could be confounded by the existence of spatial structure in the quality of nesting sites and, hence, quality of the birds occupying the nests. If laying dates differ between sites of different quality, then synchrony is just a by-product of the spatial arrangement of nest sites. In this study, we show that when studying laying dates in artificial nests of uniform quality, no local synchronization of laying could be detected. We point to other shortcomings of previous analyses and conclude that, although Cory’s shearwaters show remarkably synchronized attendance behaviors at the nesting sites, there is no conclusive evidence showing that laying dates are influenced by the behavior of near neighbors.     

Environmental influences on annual variation in nest success of smallmouth bass,Micropterus dolomieui,in Long Point Bay,Lake Erie

Synopsis Successful production of young in smallmouth bass,Micropterus dolomieui, nests varied between 33 and 88 percent over two years. Six variables were measured at each successful smallmouth bass nest. Discriminant analysis indicated that the combined influences of these variables differed between years. Canonical coefficients determined that hours of strong wind followed by degree-days contributed to the observed difference. Nest success was higher when the total hours of wind stronger than Beaufort force 4 was low during offspring development. Higher degree-day values during offspring development were recorded in the more successful year.     

Red-breasted goose colonies on the Taimyr Peninsula: Factors responsible for the proximity of goose nests to nests of peregrine falcons,rough-legged buzzards,and snowy owls

Red-breasted goose colonies have been studied near Medusa Bay (73°21′N, 80°32′E), on the northwestern Taimyr Peninsula, and along the Agapa River (70°11′N, 86°15′E) down to its mouth (71°26′N, 89° 13′E), in the central Taimyr Peninsula. Red-breasted geese nesting near peregrine falcons are protected by the falcons from arctic foxes; however, they are sometimes attacked by the falcons themselves. In the colonies near peregrine falcon nests, the vast majority of goose nests were situated no farther than 100 m from the falcon nest. When food is abundant, falcons protect a larger area around their nest. The distance between the falcon nest and the surrounding goose nests is inversely related to the falcon’s activity. In years of higher falcon activity, falcons prevent red-breasted geese from nesting as close to their nest as in years of lower falcon activity. Additional stimuli are required for red-breasted geese to form colonies near rough-legged buzzard nests. The distance between snowy owl nests and red-breasted goose nests was smaller when arctic foxes were abundant than when they were scarce.     

Nest site preference and success in a gregarious, ground-nesting bee Dieunomia triangulifera

1. The characteristics of preferred nest sites of the solitary bee Dieunomia triangulifera, which nests gregariously in alluvial soil, were investigated. Nest presence was used as an indication of preference. In those cases where nests were more than a few days old, therefore, this study also investigated nest success. 2. Independent variables tested were soil surface moisture, presence of nesting conspecifics, smooth vs. irregular soil surface, distance to visual landmarks, percentage of vegetation cover, soil compaction, vehicular traffic, soil surface temperature, and light intensity. 3. Bees preferred to nest in moist, compact soil with an irregular surface. More bees nested near visual landmarks and in places with little or no vegetation. They preferred nesting in areas with warmer soil surface temperatures and brighter illumination. The presence of nesting conspecifics did not influence nesting decisions. Vehicular traffic also seemed to have no impact on nest initiation but did seem to have a negative impact on nest success. 4. Although it might seem that ground-nesting bees should not be limited by nesting sites, relatively little of the study area met all their apparent criteria. This might account, in part, for gregarious nesting in this species.     

The Distribution of Tardigrades Upwind and Downwindof a Missouri Coal-Burning Power Plant

Significant differences occurred in the density of tardigrades, rotifers, and nematodes and the diversity of tardigrades between collecting sites located upwind and downwind from a coal-burning power plant in Missouri. The oak tree species and lichen genera also varied in the two areas. Tardigrade and rotifer densities were greater in upwind sites, whereas nematode density was higher in downwind samples. One tardigrade species (Ramazzottius sp.) was found only at the upwind sites, and one species (Echiniscus sp.) was only in the downwind samples. In contrast, three species (Macrobiotus sp., Minibiotus sp., and Milnesium tardigradum) were found both upwind and downwind but in different densities in the two areas. The study presents baseline data for long-term monitoring of the effects of environmental factors on nematode and rotifer densities as well as tardigrade density and diversity.     

Aspects of the biology of Tilapia mossambica Peters (Pisces: Cichlidae) in a natural freshwater lake (Lake Sibaya, South Africa)

An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1–7 m deep. Adult fishes (over 8 cm standard length) are usually absent from water deeper than 12m and shallower than 0–5 m, whereas juveniles may occur at all depths, and fry only in very shallow water.
T. mossambica inhabits the littoral and sublittoral in the warm and transition periods (August–April) but moves into deep water in the cool season (May–July). Exposed and sheltered areas are utilized for different purposes by adult fishes, the former for nesting, and latter for feeding and mouth–brooding. Habitat selection by males is governed by the availability of suitable nest sites. Nests are most common in sparsely–vegetated sheltered areas. Brooding females preferred sheltered littoral areas but ventured onto the terrace to release the fry. Juveniles and fry inhabited exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour is described. The biology of T. mossambica in Lake Sibaya is compared to data on the same, and similar species, in other systems. The utilization of available resources in the lake by T. mossambica is discussed and reference is made to the importance of the retention of generalized characters for the successful habitation of the cyclically–renewed habitat of the littoral.     

Stable isotope-based determinations of the average temperatures experienced by young-of-the-year Svalbard Arctic charr (Salvelinus alpinus (L.))

Mean ambient water temperatures experienced by individual young-of-the-year (YOY) Arctic charr, Salvelinus alpinus (L.), from a Svalbard lake were estimated using measurements of oxygen stable isotopes (δ¹⁸O) derived from fish otoliths. Otolith-derived water temperatures differed significantly from temperatures recorded at the outlet river of the Dieset watercourse but were consistent with temperatures previously recorded in shallow littoral areas of other Svalbard lakes where YOY charr are commonly found. This indicates that fixed-point monitoring does not necessarily represent the temperatures and thermal habitats used by individual fish. Otolith-derived water temperatures were also positively related to fish length-at-capture and otolith size, although much of the variation remained unexplained. Differences among individuals could be related to variability in food availability and food intake as well as variation in the initial fish size at hatching. Implications for subsequent investigations into how YOY charr respond and adapt to future climate change are discussed.     

Year-long assessment of airborne endotoxin at a concentrated dairy operation

In this study, we monitored total airborne endotoxins at upwind and downwind sites at a large open-lot dairy each month for a year. At the upwind site, the average airborne concentration was 28.5 endotoxin units (EU) m⁻³, while at the downwind edge of the lot and 200 m from the lot edge, the average concentrations were 169 and 72 EU m⁻³, respectively. At the downwind edge of the lot, there was a significant correlation between the airborne endotoxin concentration and wind speed or air temperature. A comparison between total and inhalable airborne endotoxin concentrations, near the end of the study, revealed no significant differences between the two endotoxin collection methods. Our data suggest that endotoxin exposure can be reduced as one increases their distance from the open-lot dairy.     

Quantifying the potential effects of climate change and the invasion of smallmouth bass on native lake trout populations across Canadian lakes

Climate change and invasive species are two stressors that should have large impacts on native species in aquatic and terrestrial ecosystems. We quantify and integrate the effects of climate change and the establishment of an invasive species (smallmouth bass Micropterus dolomieu ) on native lake trout Salvelinus namaycush populations. We assembled a dataset of almost 22 000 Canadian lakes that contained information on fish communities, lake morphologies, and geography. We examined the pelagic-benthic and littoral forage fish community available to lake trout populations across three lake size classes in these aquatic ecosystems. Due to the decreased presence of alternate prey resources, lake trout populations residing in smaller lakes are more vulnerable to the effects of smallmouth bass establishment. A detailed spatially and temporally explicit approach to assess smallmouth bass invasion risk in Ontario lakes suggests that the number of Ontario lakes with vulnerable lake trout populations could increase from 118 (~1%) to 1612 (~20%) by 2050 following projected climate warming. In addition, we identified nearly 9700 lake trout populations in Canada threatened by 2100, by the potential range expansion of smallmouth bass. Our study provides an integration of two major stressors of ecosystems, namely climate change and invasive species, by considering climate-change scenarios, dispersal rates of invasive species, and inter-specific biotic interactions.     

Correlates of reproductive success in stream-dwelling male rock bass,Ambloplites rupestris (Centrarchidae)

Synopsis Reproductive success was determined for individual male rock bass, Ambloplites rupestris, inhabiting the Middle Thames River near London, Ontario. Successful males produced numbers of young similar to rock bass breeding elsewhere, but the probability of males producing any young at all was comparatively small. Flooding, predation, and fouling of nests by algae were the major causes of brood mortality. Brood vulnerability was greatest within the egg, when nests were probably most conspicuous to predators. Male reproductive success was positively correlated with large size, early nesting, warm water conditions, and minimal flow rates. Larger males were chosen preferentially by females, and renested more often.     

The role of ecotones as feeding grounds for fish fry in a Bohemian water supply reservoir

The food composition of young-of-the-year (YOY) roach, common bream and perch, the dominant fish species in ímov reservoir, was investigated during 1989 and 1990. The littoral fry assemblages were dominated by roach and perch, while bream larvae migrated into deeper water early in their development. The YOY roach fed opportunistically. Up to 15 mm length they remained close to the shoreline, preferring periphyton, Chydoridae and larval Chironomidae. Perch larvae between 10–15 mm long gradually became demersal but their diet continued to consist of the planktonic Cyclops spp. and Diaptomus spp. Resource partitioning was a characteristic feature of the littoral fry assemblages. The only significant overlap in diet occurred with Polyphemus pediculus, which was positively selected by both roach and perch fry.