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Geology topics

D. S. Dropkin

Publications and source records attributed to D. S. Dropkin.

At least 19 recordsLinked to original sources
USGS2011

Diel feeding chronology of six fish species in the Juniata River, Pennsylvania

We examined diel feeding chronology of six fish species in the Juniata River, Pennsylvania. Ephemeropteran nymphs were the major prey of redbreast sunfish ( Lepomis auritus ; 70.5%) and smallmouth bass ( Micropterus dolomieu ; 59.7%) during each of six 4-h intervals over a 24-h period. The main dietary component of mimic shiner ( Notropis volucellus ) was chironomids (42.3%), whereas spotfin shiner ( Cyprinella spiloptera ) mainly ate terrestrial invertebrates (50.2%). Juvenile white sucker ( Catostomus commersoni ) exhibited substantial diel variation in diet composition with some prey taxa composing the entire diet during some 4-h intervals and being completely absent from the diet during other periods. Bluntnose minnow ( Pimephales notatus ) contained mostly detritus (75.5%). Interspecific diel diet overlap (Cγ) was low among the six species except for smallmouth bass-redbreast sunfish (0.735). Mimic shiner ([xbar] = 0.302) had the highest diet overlap with other species and bluntnose minnow ([xbar] = 0.134) had the least similar. Smallmouth bass, redbreast sunfish, white sucker, and spotfin shiner all had diurnal feeding peaks. Peak food consumption of mimic shiner and bluntnose minnow occurred at midnight. Our results indicate that because of diel variation in diet composition and feeding periodicity for these six species, dietary analysis conducted at only one interval would not provide an accurate representation of the diet of these species.

Pennsylvania↗
USGS2011

Ontogenetic and diel variation in stream habitat use by brook trout ( Salvelinus fontinalis ) in a headwater stream

Although considerable information exists on habitat use by stream salmonids, only a small portion has quantitatively examined diurnal and nocturnal habitat variation. We examined diel variation in habitat use by age-0 and age-1+ brook trout ( Salvelinus fontinalis ) during summer and autumn in a headwater stream in northern Pennsylvania. Habitat variables measured included cover, depth, substrate, and velocity. The most pronounced diel variation occurred in the use of cover during both seasons. Both age-0 brook trout and age-1+ trout were associated with less cover at night. Age-0 brook trout occupied swifter water during the day than at night during both seasons, but the difference was not significant. Increased cover, depth, and substrate size governed the habitat of age-1+ brook trout. Our findings support the need for a better understanding of diel differences in habitat use of stream salmonids when considering habitat enhancement and protection.

Journal of Freshwater Ecology↗
USGS2009

Prioritizing removal of dams for passage of diadromous fishes on a major river system

Native diadromous fishes have been extirpated from much of the Susquehanna River system for nearly a century. Recent restoration efforts have focused on removal of dams, but there are hundreds of dams and presently there is no biologically based system to assist in prioritizing their removal. We present a new method that uses existing habitat suitability index models (HSI) for American shad Alosa sapidissima, alewife A. pseudoharengus, blueback herring A. aestivalis, and American eel Anguilla rostrata to prioritize the removal of non-hydropower dams within the Susquehanna River system. We ranked HSI scores for each of the four species, association between a landscape-scale factor and HSIs, length of river opened by removing a dam, and distance from the mouth at Chesapeake Bay for each dam and then calculated a mean rank prioritization for dam removal by averaging the ranks for the seven criteria. This prioritization method is resistant to outliers, is not strongly affected by somewhat arbitrary decisions on metrics included in the analysis, and provides a biologically based prioritization for dam removal that can be easily amended to include other metrics or adapted to other river systems and that complements other social and economic considerations that must be included in decisions to remove dams.

River Research and Applications↗
USGS2009

Biology of the caddisfly oligostomis ocelligera (Trichoptera: Phryganeidae) inhabiting acidic mine drainage in Pennsylvania

Oligostomis ocelligera (a phryganeid caddisfly) is reported for the first time from a degraded lotic systema first-order stream in north-central Pennsylvania that was severely impacted by acid mine drainage. Although uncommonly collected and poorly known, O. ocelligera maintained a substantial population in the mine discharge, free of competition from Plecoptera, Ephemeroptera, and other species of Trichoptera. It thrived under conditions of very low pH (2.583.13), high concentrations of sulfate (542 mg/L) and heavy metals (Fe 12 mg/L, Mn 14 mg/L, Al 16 mg/L), and a nearly uniform springbrook-like temperature regime. More than 350 larvae were collected from deposits of leaves and woody detritus in a pool 0.32 km downstream from the mine entrance over a two-year period. Measurement of head-capsule widths yielded a multimodal distribution with five peaks, corresponding to five instars, in conformity with Dyar's Law. Eighty-three egg masses were observed along the stream channel from 3 June to 12 November at a mean distance of 6.1 cm above the water surface in moist, protected locations such as under moss mats or in crevices of logs. Eggs began hatching by mid-summer, first-instar larvae were present in samples from AugustOctober, all five instars were represented in October, instars IIV were still present in December, but only instars IV and V were represented in samples collected from March to July. The extended periods of oviposition and larval recruitment, together with a remarkably protracted flight period of six months (29 April30 October), led to the conclusion that the population of O. ocelligera at the mine site exhibited an asynchronous univoltine life cycle. Measurement of the width of the anterior border of the frontoclypeal apotome confirmed Wiggins' proposal that this metric is useful for distinguishing final instar larvae of O. ocelligera from its only Nearctic congener, O. pardalis. Occupied pupal cases were found embedded in sodden logs from 8 April to 10 June. Pupae had mandibles reduced to membranous lobes. A silken mesh closing the anterior end case of the pupal case is reported for the first time in O. ocelligera, representing the third evolutionary reversal for this behavioral character in the phylogeny of phryganeid genera proposed by Wiggins. Adults exhibited only diurnal flight, and were absent from light traps deployed on five nights. Females displayed more cryptic behavior, and their wing pattern was distinctly duller in color than males.

Northeastern Naturalist↗
USGS2008

Seasonal habitat use by brook trout, Salvelinus fontinalis (Mitchill), in a second-order stream

Seasonal habitat use by over-yearling and under-yearling brook trout, Salvelinus fontinalis (Mitchill), was examined in a second-order stream in north-central Pennsylvania, USA. The habitat occupied by brook trout and available habitat were determined in a 0.5-km stream reach during the spring, summer and autumn of 1989 and the spring and summer of 1990. Cover, depth, substrate and velocity were quantified from over 2000 observations of individual brook trout. Habitat used by under-yearling brook trout was more uniform between seasons and years than that used by over-yearling brook trout. Over-yearling brook trout occupied areas with more cover and greater depth than did under-yearling brook trout, suggesting ontogenetic shifts in these variables. Differences for velocity and substrate were not as great as those for cover and depth. The selection of areas with low water velocities governed trout habitat use in spring, whereas cover and depth were the most important habitat variables in summer and autumn. Principal component analysis showed that available habitat and trout habitat centroids diverged most in spring, indicating that habitat selection by brook trout may be greatest at this time.

Fisheries Management and Ecology↗
USGS2008

Linking landscapes and habitat suitability scores for diadromous fish restoration in the susquehanna river basin

Dams within the Susquehanna River drainage, Pennsylvania, are potential barriers to migration of diadromous fishes, and many are under consideration for removal to facilitate fish passage. To provide useful input for prioritizing dam removal, we examined relations between landscape-scale factors and habitat suitability indices (HSIs) for native diadromous species of the Susquehanna River. We used two different methods (U.S. Fish and Wildlife Service method: Stier and Crance [1985], Ross et al. [1993a, 1993b, 1997], and Pardue [1983]; Pennsylvania State University method: Carline et al. [1994]) to calculate HSIs for several life stages of American shad Alosa sapidissima, alewives Alosa pseudoharengus, and blueback herring Alosa aestivalis and a single HSI for American eels Anguilla rostrata based on habitat variables measured at transects spaced every 5 km on six major Susquehanna River tributaries. Using geographical information systems, we calculated land use and geologic variables upstream from each transect and associated those data with HSIs calculated at each transect. We then performed canonical correlation analysis to determine how HSIs were linked to geologic and land use factors. Canonical correlation analysis identified the proportion of watershed underlain by carbonate rock as a positive correlate of HSIs for all species and life stages except American eels and juvenile blueback herring. We hypothesize that potential mechanisms linking carbonate rock to habitat suitability include increased productivity and buffering capacity. No other consistent patterns of positive or negative correlation between landscape-scale factors and HSIs were evident. This analysis will be useful for prioritizing removal of dams in the Susquehanna River drainage, because it provides a broad perspective on relationships between habitat suitability for diadromous fishes and easily measured landscape factors. This approach can be applied elsewhere to elucidate relationships between fine- and coarse-scale variables and suitability of habitat for fishes. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗
USGS2008

Response of macroinvertebrate communities to remediation-simulating conditions in Pennsylvania streams influenced by acid mine drainage

We compared naturally alkaline streams with limestone lithology to freestone streams with and without acid mine drainage (AMD) to predict benthic macroinvertebrate community recovery from AMD in limestone-treated watersheds. Surrogate-recovered (limestone) and, in many cases, freestone systems had significantly higher macroinvertebrate densities; diversity; taxa richness; Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa; EPT/chironomid ratios; scraper/collector - gatherer ratios; herbivores; collector - filterers; and scrapers. AMD-influenced systems had significantly greater numbers of Diptera and collector - gatherers. An entire trophic level (herbivores) was 'restored' in surrogate-recovered streams, which also showed greater trophic specialization. Indicator analysis identified seven taxa (within Crustacea, Diptera, Nematoda, Trichoptera, and Ephemeroptera) as significant indicators of limestone systems and six taxa (within Ephemeroptera, Plecoptera, Tricoptera, Coleoptera, and Mollusca) as significant freestone indicators, all useful as biological indicators of recovery from AMD. ?? Springer Science+Business Media B.V. 2007.

Environmental Monitoring and Assessment↗
USGS2006

Behavioral changes associated with suboptimal prey densities for larval American shad

Laboratory studies were conducted to determine the effects of suboptimal prey density and length of prey-deprivation period on swimming, feeding, and social behavior in larval American shad. Alosa sapidissima. Replicated prey-density treatments of 1,000, 500, and 0 Artemia nauplii/liter and deprivation periods of 0,2, and 4 days were established for an 8-day period. The duration or frequency of 11 behavior patterns was quantified with an event recorder during the experiment. Exposure to suboptimal prey densities affected three categories of larval behavior: swimming activities (pivot and dart), interaction with other larvae (escape or avoid), and stereotypical feeding responses (sigmoid and lunge). Location of a food patch, simulated by the sudden introduction of prey to aquaria, affected the frequency of feeding responses more than other categories of behavior. The patch model was supported as a foraging strategy in larvae. The ontogeny of prey deprivation was evidenced primarily by changes in swimming activity (reduced pivot and dart frequencies), though feeding responses (particularly fixate) were also diminished. Deprivation-induced loss of pivot and fixate was an irreversible, pathological effect of starvation. Deprivation also resulted in greater vertical orientation (head up, 42°) of larvae than non-deprived larvae (21–29°). These changes in behavior may result in less effective escape from predators, location of food patches, or pursuit and capture of prey items in riverine habitats.

Ecology of Freshwater Fish↗
USGS2005

Effects of prey density and short term food deprivation on the growth and survival of American shad larvae

Growth and survival of 16-and 18-day-old American larvae ( Alosa sapidissima ) increased with prey density (0, 500, and 1000 Artemia l −1 ), though differences were not always significant. Significant differences were not observed in growth parameters and survival for larvae fed 500 v . 1000 Artemia 1 −1 in laboratory experiments. Food deprivation for as little as 2 days had significant effects on survival but growth effects were not detectable until 4 days of starvation. These findings have application to the Susquehanna River where c . 11 million 2.5-week-old shad larvae are released annually as part of a basin wide effort to restore the species. Larvae released at upriver sites where food may be limiting would drift for 2–3 days to reach reservoirs with higher prey densities. Based on these laboratory findings, survival of shad may be reduced significantly if larvae do not feed prior to reaching reservoir environments.

Journal of Fish Biology↗
USGS1997

Food and prey selection of recently released American shad (Alosa sapidissima) larvae

We examined the diet composition and prey selection of 1,875 recently released American shad ( Alosa sapidissima ) larvae (approximately 18-d old). Larvae were collected in the Juniata River, Pennsylvania, during June in 1991 and 1992. Chironomid pupae were selected by shad larvae and were the major component in the diet in 1991 (50%) and 1992 (96%). Chironomid larvae, the second-ranked prey in the diet, were less preferred both years. Less than one percent of the shad larvae contained riverine prey 2 to 3 hr after release, and only about 4% contained natural food 24 to 30 hr following release. At least for the 30 hr following release, feeding activity of stocked shad appears to be much reduced compared to that of wild populations.

Journal of Freshwater Ecology↗
USGS1997

Food habits of Atlantic sturgeon off the central New Jersey coast

Limited information exists on the marine diet of the Atlantic sturgeon Acipenser oxyrinchus oxyrinchus . We examined the food habits of 275 Atlantic sturgeon (total length, 106–203 cm) caught in the commercial fishery off the coast of New Jersey. Stomachs were provided by fishermen. Significantly more stomachs were empty in the spring than in the fall. Sand and organic debris were a major component in the stomachs (26.3–75.4% by weight). Polycheates were the primary prey group consumed, although the isopod Politolana concharum was the most important individual prey eaten. Mollusks and fish contributed little to the diet. Some prey taxa (i.e., polychaetes, isopods, amphipods) exhibited seasonal variation in importance in the diet of Atlantic sturgeon. Identification of the offshore diet of Atlantic sturgeon is an important step in developing a better understanding of the life history requirements and marine ecology of this species.

New Jersey↗
USGS1996

Feeding ecology of larval and juvenile American shad (Alosa sapidissima) in a small pond

Release ponds are used as part of a multifacet effort to restore American shad ( Alosa sapidissima ) in the upper Susquehanna River basin. Little information exists, however, on the feeding ecology of young shad in small ponds. Consequently, we examined feeding ecology and prey selection of 299 larval and 299 juvenile American shad in a small pond during spring and summer. Larval shad mainly consumed copepods (37.7%) and cladocerans (37.4%) whereas juvenile shad ate chironomids (43.1%) and ostracods (28.4%). Larval and juvenile shad exhibited diel variation in diet composition and feeding periodicity. Food consumption by shad was minimal at night; feeding activity was highest during the day, peaking at 2000 h for both larvae and juveniles. Electivity values of shad larvae for prey taxa were highest for cladocerans (+0.27) and lowest for ostracods (−0.07). Electivity values of juvenile shad were highest for chironomids (+ 0.21) and ostracods (+ 0.09), and lowest for copepods (− 0.08) and baetids (− 0.14). Our data indicate differences in diet composition, prey preference and, to a lesser extent, feeding patterns between larval and juvenile American shad in small pond environments.

Journal of Applied Ichthyology↗
USGS1996

Comparative diets of hatchery and wild Atlantic salmon smolts in the Merrimack River

We examined diets of smolts of 224 “wild” and 150 hatchery Atlantic salmon Salmo salar ; wild smolts had been released as fry from the hatchery 2 years before collection, whereas hatchery fish were released as smolts from the hatchery 3–15 d before. Smolts were collected from 1991 to 1993 at trapping facilities at dams in the Merrimack River during spring outmigration. About 50% of the hatchery smolts and 50% of the wild smolts examined had empty stomachs. For smolts containing food, terrestrial invertebrates were the major prey of both hatchery and wild salmon. Adult aquatic dipterans (i.e., chironomids, culicids, and simuliids) also composed a large portion of the diet of both groups of salmon. Hydropsychid and chironomid larvae were the main benthic taxa consumed. Surface‐oriented prey dominated the diet of hatchery (73.7%) and wild (62.4%) smolts. The coefficient of dietary overlap ( C λ) between hatchery and wild smolts was high during all years and ranged from 0.83 to 0.93. Stomach fullness of hatchery smolts was significantly less than that of wild smolts. Further research is needed to determine if the low food consumption of hatchery smolts affects survival.

Massachusetts, New Hampshire↗
USGS1993

Dieldrin variation in diet composition of a riverine fish community

Although diel food habit studies have been undertaken on a number of individual species, few studies have examined diel variation in the diets of fish communities. We examined the diel diet variation and feeding periodicity of a fish community in the Juniata River, Pennsylvania. Nine species, totalling 1,098 fish, were collected at 4-h intervals over a 24-h period in October 1989, in numbers sufficient to describe their diel variation in diet composition. Diel variation in diet composition was evident in all species, as no single prey taxon was dominant in the diet of any species during any 4-h interval. Ephemeropterans were the most important prey taxa for four species of centrarchids, whereas chironomids were the main prey of banded killifish, mimic shiners, and spotfin shiners. Algae was the major component in the diet of spottail shiners, whereas bluntnose minnows contained mostly detritus. Feeding activities of rock bass, redbreast sunfish, and pumpkinseed occurred at low levels throughout the day; peak feeding occurred from 2000 to 0400 hours. Food consumption of smallmouth bass increased throughout the day with peak consumption occurring at 2000 hours. Non-centrarchids fed little during daylight hours and showed peak activity at 2000–2400 h. Construction of a 24-hour diet from six 4-h interval estimates and feeding periodicity data provided a comprehensive representation of the diel feeding ecology of all species collected.

Hydrobiologia↗