Geology topics

M. G. Walsh

Publications and source records attributed to M. G. Walsh.

6 recordsLinked to original sources

USGS2018

Stomach contents and stable isotopes analysis indicate Hemimysis anomala in Lake Ontario are broadly omnivorous

Hemimysis anomala is a recent invader to North American aquatic ecosystems and is spreading rapidly throughout the Great Lakes region. This is the first littoral mysid in the North American Great Lakes; and, as such, the ecosystem effects are unknown and could be substantial. These effects depend on the role of Hemimysis in the food web and, therefore, on its diet. We examined the stomach contents of two life stages of Hemimysis from two sites in Lake Ontario during the growing season (May–November 2010). We also report the relationship between zooplankton hard parts and size for a number of potential prey species to allow the back-calculation of prey lengths from stomach contents. Both juvenile (2–5 mm) and adult Hemimysis (5–11 mm) were omnivorous, consuming phytoplankton, zooplankton, and benthos when available. However, adults appeared slightly more carnivorous and incorporated larger prey in their diets. Hemimysis were able to consume zooplankton prey up to 30% of their own length, including Bythotrephes longimanus and Cercopagis pengoi . Daphnia and Bosmina were selected over other prey by both juvenile and adult Hemimysis and were most common in stomachs during July and September when their abundances in the zooplankton were highest. Measurements of δ 13 C and δ 15 N corroborated stomach content materials, indicating an omnivorous diet which included benthic and pelagic sources. Omnivory by Hemimysis is typical of mysids in general and makes them less sensitive to seasonal dynamics of preferred prey items.

Lake Ontario↗

USGS2007

Occurrence and food habits of the round goby in the profundal zone of southwestern Lake Ontario

Little is known about the ecology of round goby (Neogobius melanostomus), an invasive benthic fish, in the profundal zone of the Great Lakes. In April 2002–2005 we caught increasing numbers of round gobies with a bottom trawl in the 45–150 m depth range of southwestern Lake Ontario. In 2005, we examined gut contents of 30 round gobies from each of three depths, 55, 95, and 130 m, and qualitatively compared gut contents with density of benthic invertebrates determined by Ponar grabs. Round goby guts contained mostly Dreissena spp. and opposum shrimp, Mysis relicta ( Mysis ); the frequency of occurrence of dreissenids in guts decreased with depth, whereas the frequency of occurrence of Mysis in guts increased with depth. Abundance of these invertebrates in the environment followed the same pattern, although dreissenids of optimum edible size (3–12 mm) were still abundant (1,373/m 2 ) at 130 m, where round gobies primarily consumed Mysis , suggesting that round gobies may switch from dreissenids to more profitable prey when it is available. Other food items were ostracods and fish, with ostracods generally eaten by smaller round gobies and fish eaten by larger round gobies. Occurrence and increasing abundance of round gobies in the profundal zone and predation on Mysis by round goby could have far-reaching consequences for the Lake Ontario fish community.

Journal of Great Lakes Research↗

USGS2005

Diet overlap of introduced rainbow trout and three native fishes in an Ozark stream

Private angling groups in Oklahoma have requested permission to stock rainbow trout Oncorhynchus mykiss into streams of northeastern Oklahoma although little is known regarding interactions between introduced rainbow trout and native fishes in these systems. Our study objectives were to assess diet overlap between introduced rainbow trout and native smallmouth bass Micropterus dolomieu, shadow bass Ambloplites ariommus, and bluegill sunfish Lepomis macrochirus in Brush Creek, Oklahoma, a small spring-fed Ozark stream. Rainbow trout diet composition differed from that of all three native fishes in the 2 months of comparison (March and May 2001), and rainbow trout diets contained relatively low numbers of prey. It is unlikely that exploitative competition for food resources occurred between rainbow trout and these three native fishes. ?? 2004 by the American Fisheries Society.

American Fisheries Society Symposium↗

USGS2005

American Fisheries Society 136th Annual Meeting Lake Placid, NY 10-14 September, 2006

The New York Chapter of the American Fisheries Society and the New York State Department of Environmental Conservation invite you to experience the beauty of New York's famous Adirondack Park as the American Fisheries Society (AFS) convenes its 136th Annual Meeting in the legendary Olympic Village of Lake Placid, NY, 10-14 September 2006. Our meeting theme "Fish in the Balance" will explore the interrelation between fish, aquatic habitats, and man, highlighting the challenges facing aquatic resource professionals and the methods that have been employed to resolve conflicts between those that use or have an interest in our aquatic resources. As fragile as it is beautiful, the Adirondack Region is the perfect location to explore this theme. Bordered by Mirror Lake and its namesake, Lake Placid, the Village of Lake Placid has small town charm, but all of the conveniences that a big city would provide. Whether its reliving the magic of the 1980 hockey team's "Miracle on Ice" at the Lake Placid Olympic Center, getting a panoramic view of the Adirondack high peaks from the top of the 90 meter ski jumps, fishing or kayaking in adjacent Mirror Lake, hiking a mountain trail, or enjoying a quiet dinner or shopping excursion in the various shops and restaurants that line Main Street, Lake Placid has something for everyone.

Conference Paper↗

USGS2004

Anchor and visible implant elastomer tag retention by hatchery rainbow trout stocked into an Ozark stream

As part of a study to evaluate the stocking of rainbow trout Oncorhynchus mykiss in an Oklahoma Ozark stream, we tagged 2,542 hatchery-reared rainbow trout (123-366 mm total length) with individually numbered Floy FD-68B anchor tags and visible implant fluorescent elastomer (VIE) tags. We experimentally stocked double-marked rainbow trout into a small northeastern Oklahoma stream from November 2001 to March 2002 and resampled them monthly from December 2001 to October 2002 by electrofishing. Anchor tag retention was 91% through 6 months, and VIE tag retention was 96% through 6 months despite extensive handling of fish within 24 h of tagging. Based on the ease of application, high visibility, and high retention observed in this study, we recommend the use of VIE tags as a batch mark in similarly sized, similarly pigmented fish. The retention of VIE tags was slightly higher than that of anchor tags, and cost per fish was less for VIE than for anchor tags. However, VIE tags would have limited utility if numerous individual tags are necessary; therefore, we recommend anchor tags as individual marks in similarly sized salmonids. Retention for both tag types was relatively high and could be corrected for when estimating population parameters from tagging data.

North American Journal of Fisheries Management↗

USGS2004

Characteristics of smallmouth bass (Micropterus dolomieu) and shadow bass (Ambloplites ariommus) populations in an Ozark stream before and after rainbow trout introduction

We evaluated characteristics of smallmouth bass ( Micropterus dolomieu ) and shadow bass ( Ambloplites ariommus ) populations in a small, northeastern Oklahoma Ozark stream from February 2000 to March 2003 to evaluate potential effects of rainbow trout ( Oncorhynchus mykiss ) introduction on these species. We experimentally stocked rainbow trout into the stream from November 2000 to March 2001 and November 2001 to March 2002. Mark-recapture and telemetry data showed patterns of limited movement among pool habitats by both bass species, and presence of rainbow trout in Brush Creek did not appear to influence movement patterns. We documented recruitment by smallmouth and shadow bass during our study, indicating that rainbow trout introduction did not inhibit spawning. Mean relative weight (Wr) of smallmouth bass ranged from 77 - 80, and we did not detect differences in relative weight among pre-stocking, the first year of stocking, and the second year of stocking. It appears that important population characteristics of these two species in our study stream were not negatively impacted by rainbow trout introduction.

Oklahoma↗