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Salmo salar (Atlantic Salmon) smolts are exposed to predation pressure as they migrate from freshwater into the estuary and near-shore marine environment. In particular, Phalacrocorax auritus (Double-crested Cormorants) are a predator of Atlantic salmon smolts during their estuary and near-shore migration. National Oceanic and Atmospheric Administration's (NOAA) National Marine Fisheries Services’ (NMFS) telemetry data collected prior to this study (1997–2003), suggest that smolts are being removed from the Narraguagus River on their downstream out-migration. This removal may be the result of Cormorant predation. We investigated whether smolt survival could be improved by disrupting normal Cormorant foraging activity by integrating passive smolt tracking and active harassment techniques. Smolt movement and usage of various portions of the estuary according to light condition and tidal stage were explored along with concurrent avian harassment. Although harassment only occurred in approximately 33% of available daylight hours during this study, the impacts were easily recognized. Non-lethal harassment effectively displaced Cormorants from feeding locations and reduced loss of emigrating smolts. In 2004, 83.3% (15 of 18) of all smolt mortalities occurred on days of non-harassment, compared to only 16.7% (3 of 18) on days when harassment occurred. Similarly in 2005, 87.5% (7 of 8) of all smolt mortalities occurred on days of non-harassment, compared to only 12.5% (1 of 8) on days when harassment occurred. Non-lethal harassment appeared to be an effective means to reduce loss of emigrating smolts in the Narraguagus River estuary.
Minimal research has been conducted involving Salvelinus fontinalis (Brook Trout) habitat use and dispersal patterns within Adirondack Mountain headwater streams. Hence, fishery managers are left with information gaps regarding the specific habitat conditions characteristic of sustainable Brook Trout populations in Adirondack flowing waters. Through the use of single-pass electrofishing and markrecapture techniques, size-class specific microhabitat use and reach-scale movement patterns for Brook Trout were examined within two northern Adirondack streams. Water depth, water velocity, and sub strate-size use were observed to be similar among two Brook Trout size classes. Both size classes exhibited use patterns within deeper slowermoving pool habitats; however, larger Brook Trout were found to be associated with smaller-sized substrates within one of our study sites. These habitat-use patterns were also supported by comparison of stream hydrologic condition, including Froude number. Brook Trout movement patterns were found to be dependent on both size class and season. Smaller-sized trout exhibited increased movement during the spring, whereas larger trout were found to be more mobile and move more frequently during early fall. Lastly, we examined the proportion of Brook Trout moving upstream/downstream and found a greater frequency of smaller Brook Trout moving upstream during late summer.
Umbra pygmaea (Eastern Mudminnow) is a freshwater species common in Atlantic slope coastal lowlands from southern New York to northern Florida and is typical of slow-moving, mud-bottomed, and highly vegetated streams, swamps, and small ponds. We examined its seasonal food habits at the Great Swamp National Wildlife Refuge (NWR), NJ and at the Croatan National Forest, NC. A total of 147 Eastern Mudminnow from 35–112 mm TL and 190 Eastern Mudminnow from 22–89 mm TL were examined from these sites, respectively. At both locations, we found it to be a bottom-feeding generalist that consumes cladocerans, ostracods, chironomid larvae, coleopteran larvae, and other insects and crustaceans. Ostracods were most common in the diet at the Great Swamp NWR and occurred in 62% ± 2.5% of the stomachs with food. At Croatan National Forest, chironomid larvae were most common and occurred in 66.7% ± 15.8% of the stomachs. There were no statistically significant differences in diet composition between the sites during the winter, summer, and fall. However, when compared on an annual basis, Jaccard's Index (θJ = 0.636, P = 0.05) suggested that the diet at the two study sites was significantly different. While we identified the same major food groups at both locations, the utilization of these food groups varied seasonally. Detritus was a major stomach content at both locations throughout the year. We also documented cannibalism during the summer season at both locations. The seasonal diet of the Eastern Mudminnow was similar to that of Umbra limi (Central Mudminnow) and Umbra krameri (European Mudminnow). Our findings here are the first quantitative examinations of seasonal differences in the diet of the Eastern Mudminnow within its native North American range.
We examined laboratory host suitability and assessed the distribution and status of Alasmidonta marginata (Elktoe) in Minnesota. Of the 85 fish species tested, glochidia metamorphosed on 27 species in 6 families (Cyprinidae, Catostomidae, Fundulidae, Poeciliidae, Gasterosteidae, and Cottidae). All catostomid species facilitated metamorphosis, and overall, Catostomidae produced more juvenile mussels per fish. This result, in combination with a previous finding of naturally infested fish, suggests that catostomids are an important host for A. marginata in nature. From extensive surveys, we found extant populations of A. marginata in the St. Croix River, Upper Mississippi River, and Minnesota River systems. Alasmidonta marginata is apparently extirpated or its range has decreased in several interior Minnesota watersheds and the Mississippi River main stem. Barrier waterfalls and habitat degradation have influenced A. marginata's historic and recent distribution more so than the range of its hosts. Further study of naturally occurring and laboratory hosts for A. marginata and other Alasmidonta species is needed in order to improve conservation efforts and elucidate phylogenetic relationships for this group of mussels.
Spatial and temporal dynamics of shore zone fish and Callinectes sapidus (Blue Crab) densities in tidal creeks of the Delaware Coastal Bays were examined during the spring/summer nursery period and in the winter of 2004, 2005, and early 2006 to identify underlying abiotic conditions driving the structure of species assemblages. Distinct spring/summer species assemblages were identified within separate tidal creeks, correlated with dissolved oxygen range. Differences were driven by the dominance of hypoxia-tolerant species in the intensely developed White Creek watershed and hypoxia-sensitive species in the less-developed Miller Creek watershed. In winter, species assemblages were somewhat homogenized and were less influenced by abiotic conditions. Results of this study indicate that the fish and Blue Crab assemblage in the shore zone of tidal creeks in the Delaware Coastal Bays is affected primarily by location-specific influences, such as anthropogenic alteration and associated hypoxia, particularly in the spring and summer.
Monitoring programs using benthic macroinvertebrates are well-used and expanding to areas where communities are species-poor. The sensitivity of these depauperate communities to environmental conditions, however, is not well known. In this study, impoverished benthic invertebrate communities were compared from three climatically and geologically distinct regions of Newfoundland. Differences in community structure were evident among regions at both the genus and family level. These results indicate that widely dispersing and depauperate macroinvertebrate communities can be sufficiently diverse to respond to regional variation in environmental conditions and therefore remain promising for detecting anthropogenic-induced changes.
We investigated ant species richness, interspecific behavioral interactions, and community composition in adjacent forested and open habitat plots in two forest types of the northeastern United States: 1) the more common hemlock-White Pine forest studied at Harvard Forest Long Term Ecological Research Station in central Massachusetts, and T) the rare Pitch Pine barrens of Myles Standish State Forest in southeastern Massachusetts, which also provide habitat for multiple rare and endangered species. Overall, we found that species richness, behavioral interactions, and ecological traits vary between forested and adjacent open habitat plots. The number of species is five times higher per plot in the hemlock-White Pine open habitat (compared to forest habitat), but this pattern (i.e., higher species richness in open vs. forested plots) is not observed in the Pitch Pine barren site. Non-metric multidimensional scaling analyses suggest that community composition is significantly different between forest and open plots at both sites. However, community composition in open plots at both sites did not significantly differ from each other. We show that behaviorally dominant and submissive species mostly occur in open plots while neutrally interacting species are more restricted to forested plots, suggesting that interspecific competitive dynamics may be contributing to the community assembly patterns observed in open habitats. Our findings suggest that conservation and management for both open and forested habitat at either site is extremely important when attempting to maintain optimal ant biodiversity because each habitat type provides suitable conditions for different suites of ant communities.
The emergence of the fungal disease white-nose syndrome (WNS) among hibernating bats in North America and its causative pathogen, Geomyces destructans, underscores how little is known about fungi associated with bats and their subterranean environments. Investigating 8 caves and mines in New Brunswick, Canada, we cultured a diverse array of fungi from the fur and skin of apparently healthy, hibernating Myotis lucifugus (Little Brown Bat) and M. septentrionalis (Northern Long-eared Bat) in the year prior to the emergence of WNS in the province. Among the 117 isolated fungal taxa, we found an array of psychrophilic, psychrotrophic, keratinolytic, coprophilous, and saprobic fungi. The most common taxa were Geomyces pannorum sensu lato, Penicillium spp., Mortierella spp., Mucor spp., Cephalotrichum stemonitis, Leuconeurospora spp., Penicillium solitum, Cladosporium spp., and Trichosporon dulcitum. Each bat hosted 6.9 ± 3 (SD) fungal taxa, and 30.8 ± 5 taxa were isolated per hibernaculum. Number of taxa isolated per bat was positively correlated with mean and minimum winter temperatures in the dark zones of hibernacula. Forty-seven of the taxa have never been reported in caves, and an additional 31 taxa are new records for North American caves. The presence of Geomyces pannorum sensu lato on 70% of hibernating bats may complicate results of diagnostic techniques used for identifying G. destructans. Bats hibernating in eastern Canada harbor a rich reservoir of fungal species and probably play a role in moving fungal spores into and between hibernacula, as well as onto the landscape.
We investigated nesting success of grassland birds on dry prairie and oak barrens patches embedded within a forested matrix on Fort McCoy Military Installation. We monitored 280 nests of 9 grassland-bird species from mid-May to late July 2000–2002. Pooecetes gramineus (Vesper Sparrow) and Ammodramus savannarum (Grasshopper Sparrow) were the most abundant nesting species. Vesper Sparrow nest densities were highest on smaller grassland patches, while Grasshopper Sparrow nest densities were highest on the largest patches. Probability of fledging at least one young was 0.20 for Vesper Sparrow. For Grasshopper Sparrow, daily nest survival was higher for nests placed away from trees; probability of fledging at least one young was 0.28 for nests away from trees and 0.05 for nests near trees. Maintaining remnant native habitats is important, and management of woody features may help improve habitat quality for some grassland birds in Wisconsin.
A nesting Gavia immer (Common Loon) was discovered incubating 2 rocks on a floating nest platform on the Quabbin reservoir in central Massachusetts for 43 days, well beyond the typical period of 28 days, before we moved in to investigate. The rocks were likely unearthed in the soil and vegetation used on the platform to create a more natural substrate for the nest. We suggest sifting through soil and vegetation to remove rocks before placing material on nest platforms.
Fourteen Alle alle (Dovekie) were recovered from the stomachs of 14 Lophius americanus (Goosefish) caught during winter and spring 2007–2010. All fish were caught in gill nets set at depths of 85–151 m (276–491 ft) 104–150 km (65–94 mi) south of Chatham, MA. Dovekies showed few signs of digestion by the fish, indicating recent capture. Post mortem revealed no cause of mortality. Capture of birds by fish so far from shore and in deep water leads to speculation that the birds were preyed on by Goosefish at or near the surface. Evidence from electronic tagging of Goosefish suggests that Goosefish vertical migrations could bring them into contact with Dovekies feeding offshore. If Goosefish are concentrated during onshore-offshore migrations and Dovekies are concentrated for feeding on prey patches, predation by Goosefish on Dovekies could be episodically important.
Pholis gunnellus (Rock Gunnel) is an amphibious fish found along North Atlantic coastlines. Remaining above the waterline at low tide and breathing air, it is ecologically unusual and is a food source for a variety of seabirds, mammals, and fish. We investigated intertidal and subtidal habitat selection by the Rock Gunnel along the US East Coast. To quantify characteristics of intertidal microhabitats and their usage by the Rock Gunnel, we conducted intertidal quadrat surveys in midcoast Maine and New Brunswick. Using datasets from trawl surveys conducted by state (Massachusetts and Connecticut) and federal fishery management agencies, we investigated how subtidal habitat characteristics influenced the occurrence of Rock Gunnel in trawl yields. Logistic regression and classification and regression tree (CART) analysis showed that Rock Gunnels preferred microhabitats in the lower intertidal zone, with sand/pebble/gravel substrata and overlying cobbles, tidepools, and dense algal cover. The occurrence of Rock Gunnel in trawl yields did not depend upon temperature, salinity, or latitude, but decreased with depth and increased moving eastward. In the intertidal zone, the Rock Gunnel appears to select habitat that minimizes the risks of predation and desiccation at low tide, while allowing access to abundant intertidal prey resources at high tide. The Rock Gunnel's broad physiological tolerances suggest that its selection of habitat in the subtidal zone is driven primarily by the availability of sheltering structure and biotic factors, rather than by temperature or salinity.
The success of annual migrations for songbirds is greatly affected by habitat quality at stopover sites, particularly in relation to food needed for rapid refueling. The abundance and nutritional quality of important food resources may be linked to the presence of deciduous shrub species that provide seasonal fruits in the fall and support insects in the spring. The objective of this study was to determine whether migrating songbirds benefit from resources provided by native or invasive fruit-bearing shrubs found at 2 bird-banding stations in Rochester, NY. We conducted nutritional analyses (energy density, fat content, total soluble solids) on the fruits of common shrub species at the study sites, monitored removal of the fall fruits of focal native and invasive shrub species in the field, and measured the abundance of midges—a common insect resource for migrating songbirds— supported by the focal shrub species in the spring. The highest fat content and energy densities were found in fruits of native shrubs, ranging from 6.57 to 48.72% fat and 18.83 to 28.68 kJ/g of energy. All invasive fruits had ≤0.99% fat and ≤17.17 kJ/g of energy. We also found a significant positive correlation between fat and energy content of the fruits. Native dogwood fruits were consumed by migrating songbirds at higher rates than invasive fruits over the fall migration period. However, there was no clear pattern of midge abundance between native and invasive shrub species during the spring migration period. Our results suggest that fruits of native shrubs are of greater nutritional value to migrating songbirds than the fruits of invasive shrubs during fall migration, which is supported by the higher removal rates by songbirds of native dogwood fruits than fruits of the 4 other invasive fruit species. This finding suggests that removal of invasive fruit-bearing shrubs or plants will not negatively impact migrating birds when high-quality native fruit-bearing shrubs are available. However, additional study on the relative value of these shrubs in the spring and over multiple seasons is needed to provide insight into their overall value for birds during annual migrations.
A new cave population of sculpin fish from Central Pennsylvania is described that, if confirmed to be cave adapted, would become the second northernmost cave-adapted fish in the world. The Tytoona Cave fish lack the suite of modifications typical of troglomorphic populations. Their eyes, pectoral fins, and mouths appear to be as large as those of their surface counterparts, they have the same number of cephalic lateralis pores, and their pigmentation levels do not appear to be much lower. Nonetheless, they are considered to be cave adapted due to the presence of ovigerous females, a lack of evidence for starvation, and primarily because the cephalic lateralis pores (part of the lateral line system) are significantly larger than those of similar-sized surface fish. It may be that the Tytoona Cave population only has some emergent cave adaptations because in high latitudes the extent of polar ice sheet migration during the Pleistocene era restricted colonization by fish at least until 12 ka ago, when the ice age ended.
Ixodes scapularis (Black-legged Tick) has expanded its range in recent decades. To establish baseline data on the abundance of the Black-legged Tick and Borrelia burgdorferi (the causative agent of Lyme disease) at the edge of a putative range expansion, we collected 1398 ticks from five locations along the Connecticut River in Vermont. Collection locations were approximately evenly distributed between the villages of Ascutney and Guildhall. Relative abundance and distribution by species varied across sites. Black-legged Ticks dominated our collections (n = 1348, 96%), followed by Haemaphysalis leporispalustris (Rabbit Tick; n = 45, 3%), and Dermacentor variabilis (American Dog Tick; n = 5, <1%). Black-legged Tick abundance ranged from 6198 ticks per survey hectare (all life stages combined) at the Thetford site to zero at the Guildhall site. There was little to no overlap of tick species across sites. Phenology of Black-legged Ticks matched published information from other regions of the northeastern USA. Prevalence of B. burgdorferi in adult Black-legged Ticks was 8.9% (n = 112).