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Randall W. Owens

Publications and source records attributed to Randall W. Owens.

11 recordsLinked to original sources
USGS2011

Rediscovery of lake balls in Lake Michigan

For the first time in 70 years, the occurrence of a 'lake ball' in Lake Michigan is here reported in the literature. According to a published system of classification, the object we collected in 1978 was a 'false' lake ball. Dissection revealed that it was colonized by 5 chironomid larvae and 162 oligochaetes. The species and numerical proportions of the oligochaetes indicated that it was formed in or near the mouth of a eutrophic tributary rather than in the open waters of Lake Michigan where it was found. Because of their mobility, false lake balls may be ecologically important, serving as natural vehicles for the dispersal of invertebrates.

Journal of Freshwater Ecology↗
USGS2005

Recovery and decline of lake whitefish in U.S. waters of eastern Lake Ontario, 1980-2001

The lake whitefish (Coregonus clupeaformis) was an important member of the native fish community and a valued commercial species in Lake Ontario. Lake whitefish were common in U.S. waters of the lake until 1965 and very abundant in Canadian waters through the early 1970s, although their numbers declined shortly thereafter. During 1975-1985, lake whitefish stocks remained depressed throughout the lake as a result of the combined effects of degraded water quality, overfishing, and predation. Rainbow smelt (Osmerus mordax) probably preyed on whitefish fry, and sea lamprey (Petromyzon marinus) preyed on adults. During 1985-1987, lake whitefish stocks began to recover in eastern Lake Ontario, and their buildup continued into the mid-1990s. Reasons for the recovery likely included control of the sea lamprey population and a reduction in the number of piscivorous rainbow smelt. By 1997, lake whitefish abundance had declined severely again; some fish appeared to have dispersed from the northeastern to the southeastern regions of the lake, and the depth of capture increased. We believe that the collapse of Diporeia spp. populations during 1992-1999 was responsible for the decline in the lake whitefish populations and the shifts in geographic and bathymetric distribution because lake whitefish fed primarily on Diporeia spp. After the collapse of Diporeia spp. populations, lake whitefish in southeastern Lake Ontario fed on Mysis relicta and quagga mussels (Dreissena bugensis). Changing from a diet of high-lipid Diporeia spp to low-lipid dreissenids and foraging on Mysis relicta at lower temperatures are apparently hampering the rebuilding of lake whitefish stocks.

Technical Report↗
USGS2003

Shifts in the diets of slimy sculpin ( Cottus cognatus ) and lake whitefish ( Coregonus clupeaformis ) in Lake Ontario following the collapse of the burrowing amphipod Diporeia

In Lake Ontario, the diets of slimy sculpin Cottus cognatus and lake whitefish Coregonus clupeaformis shifted from a diet dominated by the burrowing amphipod, Diporeia , and to a lesser extent, Mysis , to a more diverse diet, after Diporeia collapsed, to one dominated by Mysis and prey that were formerly less important or uncommon such as Chironomidae, Oligochaeta, and Ostracoda. Additionally, lake whitefish still preyed on native mollusks like Sphaeriidae and Gastropoda, but also preyed on exotic mollusks, Dreissena spp., which are swallowed intact and subsequently crushed in its muscular stomach. Whether Diporeia was abundant (1992) or scarce (1999), selection indices for Diporeia by slimy sculpins was positive, suggesting that Diporeia was a preferred prey. Unlike lake whitefish, slimy sculpins avoided Dreissena ; therefore, energy diverted to Dreissena production was a real loss for slimy sculpins. The shifts in the diet of these benthic fishes corresponded with drastic changes in the benthic community between 1992 and 1999. The collapse of Diporeia , formerly the most abundant macroinvertebrate in the benthic community, along with sharp declines in the abundance of Oligochaeta and Sphaeriidae, coincided with the establishment and rapid expansion of Dreissena bugensis , the quagga mussel, and to a lesser degree Dreissena polymorpha , the zebra mussel. It appears that the Diporeia population first collapsed at depths >70 m in southeastern Lake Ontario by autumn 1992, at shallower depths in the eastern Lake Ontario by 1995, and along the entire south shore line at depths <100 m, and perhaps in some areas >100 m by 1999. In response to the disappearance of Diporeia , populations of two native benthivores, slimy sculpin and lake whitefish, collapsed in eastern Lake Ontario, perhaps due in part to starvation, because Diporeia was their principal prey. Presently, alternative food resources do not appear sufficient to sustain these two benthivores at their former levels of abundance. We do not expect slimy sculpin and lake whitefish to recover unless Diporeia returns to earlier levels of abundance.

Aquatic Ecosystem Health & Management↗
USGS2003

Establishment of dreissenids in Lake Ontario: implications for the endemic fish community

Coincident with the establishment of dreissenids in Lake Ontario, the depth distribution of alewife, a non-native predator of larval fishes, shifted deeper and the abundance of burrowing amphipod, Diporeia, declined sharply. The alewife distribution shift was followed by increased reproductive success of two native fishes, lake trout and yellow perch whereas the decline of Diporeia was followed by the appearance of emaciated lake whitefish and slimy sculpin, two native fishes that eat Diporeia.

Conference Paper↗
USGS2000

Age and growth of pike ( Esox lucius ) in Chivyrkui Bay, Lake Baikal

The purpose of this study was to describe age and growth of pike ( Esox lucius ) in Lake Baikal. Pike were collected with gill nets and by angling in Chivyrkui Bay in late July-early August 1993 and by gill nets in June 1995. Total length (mm), weight (g), and sex were recorded and scales and cleithra were collected for aging. In 1993, pike, ages 1 to 3, ranged in length from 331 to 810 mm and in 1995 , pike, ages 2 to 10, ranged in length from 365 to 1,111 mm but only three percent were age 7 or older. Most growth in length occurred during the first two years of life. The length-weight relation for pike from Chivyrkui Bay was similar to that of pike from the St. Lawrence River. Calculated total length of pike from Lake Baikal equalled or exceeded the lengths of pike from lakes Erie or Ontario. Good agreement was found between ages from cleithra and from scales. Lengths at age in June 1995 (N=108) varied widely among pike. Females were generally larger than males at a given age among fish age-3 and older. When compared with the circumpolar growth standard, based on the von Bertalanffy growth curve, growth of Lake Baikal pike exceeded all other Asian populations, and equalled or exceeded many other northern hemisphere populations.

Journal of Great Lakes Research↗
USGS2000

Shifts in depth distributions of alewives, rainbow smelt, and age-2 lake trout in southern Lake Ontario following establishment of Dreissenids

In the mid-1990s, biologists conducting assessments of fish stocks in Lake Ontario reported finding alewives Alosa pseudoharengus , rainbow smelt Osmerus mordax , and juvenile lake trout Salvelinus namaycush at greater depths than in the mid-1980s. To determine if depth distributions shifted coincident with the early 1990s colonization of Lake Ontario by exotic Dreissena mussels, we calculated mean depth of capture for each of the three species during trawl surveys conducted annually during 1978&ndash;1997 and examined the means for significant deviations from established patterns. We found that mean capture depth of alewives, rainbow smelt, and age-2 lake trout shifted deeper during the build up of the dreissenid population in Lake Ontario but that timing of the shift varied among seasons and species. Depth shifts occurred first for rainbow smelt and age-2 lake trout in June 1991. In 1992, alewives shifted deeper in June followed by age-2 lake trout in July&ndash;August. Finally, in 1993 and 1994, the distribution of lake trout and alewives shifted in April&ndash;May. Reasons why the three fishes moved to deeper water are not clear, but changes in distribution were not linked to temperature. Mean temperature of capture after the depth shift was significantly lower than before the depth shift except for alewives in April&ndash;May. Movement of alewives, rainbow smelt, and age-2 lake trout to colder, deeper water has the potential to alter growth and reproduction schedules by exposing the fish to different temperature regimes and to alter the food chain, increasing predation on Mysis relicta in deep water and decreasing alewife predation on lake trout fry over nearshore spawning grounds in spring.

Transactions of the American Fisheries Society↗
USGS1998

Blueback herring ( Alosa aestivalis ) in Lake Ontario: First record, entry route, and colonization potential

Two juvenile blueback herring ( Alosa aestivalis ) were caught in Lake Ontario in October 1995, the first record of this anadromous marine clupeid in the Great Lakes. Blueback herring most likely gained entry to Lake Ontario via the Erie Barge Canal, a navigation canal that links the Mohawk-Hudson rivers, which drain to the Atlantic Ocean, to Oneida Lake, which drains to Lake Ontario through the Oneida-Oswego rivers. Blueback herring ascend the Hudson River to spawn and were first reported from the upper Mohawk River in 1978. They currently spawn in several of the upper Mohawk's tributaries, including one about 430 km from the ocean but only 25 km from Oneida Lake. They were first found in Oneida Lake in 1982 and, in fall 1994, large numbers of juvenile blueback herring were found moving down the Oswego River. In the southern United States, blueback herring established self-reproducing populations in several reservoirs, and thus they have the potential to colonize Lake Ontario. If blueback herring became established in Lake Ontario, they could spread to other Great Lakes and impede recovery of depressed populations of indigenous fishes, like lake herring ( Coregonus artedi ) and lake trout ( Salvelinus namaycush ), through competition with, or predation on, their larvae.

Journal of Great Lakes Research↗
USGS1995

Predation on Mysis relicta by slimy sculpins (Cottus cognatus) in southern Lake Ontario

Mysis relicta and Diporeia dominated the diet of slimy sculpins ( Cottus cognatus ) caught at depths of 55, 75, and 95 m at two locations in southern Lake Ontario. Length of prey was positively correlated with length of slimy sculpin. At a given depth, mean length of slimy sculpins was greater at Rochester than at Nine Mile Point, and mean length increased with depth at both locations. Frequency of occurrence of Mysis in the stomachs of slimy sculpins increased with depth, whereas frequency of Diporeia generally decreased with depth. Diporeia dominated the slimy sculpin diet at 55 m, whereas Mysis dominated the diet at 95 m. Slimy sculpins, some as small as 30 mm long, fed successfully on Mysis in Lake Ontario. We suggest that extirpation of the deepwater sculpin ( Myoxocephalus thompsoni ) and perhaps the coregonines ( Coregonus spp.) in Lake Ontario allowed slimy sculpins to expand into deeper areas where they could exploit Mysis . We also suggest that at depths ≥75 m in Lake Ontario, the current Mysis -benthivore link with slimy sculpins may be similar to the past when deepwater sculpins were present.

Journal of Great Lakes Research↗
USGS1995

Planktivory by alewife ( Alosa pseudoharengus ) and rainbow smelt ( Osmerus mordax ) on microcrustacean zooplankton and dreissenid (Bivalvia: Dreissenidae) veligers in southern Lake Ontario

The objective of this study was to describe the diet of young-of-the-year and adult alewife ( Alosa pseudoharengus ) and rainbow smelt ( Osmerus mordax ) in nearshore waters coincident with the colonization of Lake Ontario by Dreissena . Laboratory experiments and field observations indicated that alewife and rainbow smelt consumed dreissenid veligers and that the veligers remained intact and identifiable in the digestive tract for several hours. Dreissenid larvae were found in field-caught alewife and rainbow smelt in August 1992, even though veliger densities were low (<0.1/L). Zooplankton dominated the diet of all fish and veliger larvae were <0.1% of the biomass of prey eaten by these fish. Density of veligers and the distribution of settled dreissenids declined from west to east along the south shore of Lake Ontario. Based on veliger consumption rates we measured and the abundance of veligers and planktivores, we conclude that planktivory by alewife and smelt in the nearshore waters of Lake Ontario did not substantially reduce the number of veligers during 1991&ndash;1993. However, our results indicate that if the density of veligers in Lake Ontario decreases, and if planktivores remain abundant, planktivory on veliger populations could be significant.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1994

Energy density and size of pelagic prey fishes in Lake Ontario, 1978-1990: Implications for salmonine energetics

We describe dynamics of energy density and size of Lake Ontario alewife Alosa pseudoharengus and rainbow smelt Osmerus mordax , and we use a bioenergetics model of a common pelagic piscivore, chinook salmon Oncorhynchus tshawytscha , to demonstrate the effect of these factors on piscivore daily ration during 1978&ndash;1990. The energy density of alewives varied more than twofold between peaks in September (age 1) or October&ndash;November (age &ge;2) and the lows in May (age 1) or July&ndash;September (age&ge;2). The previously described seasonal pattern of energy density of Lake Michigan alewives was similar except that energy density of older alewives (age&ge;3) was markedly higher in Lake Michigan. During 1978&ndash;1990, the spring energy density of Lake Ontario alewives peaked in 1979 (6,259 J/g wet weight), declined irregularly until 1985, and then remained stable through 1990 (at approximately 4,600 J/g). The initial decline may have been a density-dependent response to a burgeoning alewife population, but the lack of an increase in alewife condition in the late 1980s, when alewife biomass fell, suggests a decline in lake productivity. Energy density of rainbow smelt increased with age in Lake Ontario and condition was invariant during 1978&ndash;1990 despite a threefold change in rainbow smelt biomass. Rainbow smelt energy density was lower and fluctuated less seasonally in Lake Ontario than in Lake Michigan. Mean weight of alewives aged 2 and older dropped from 41 g in 1978 to 19 g in 1989 in Lake Ontario. Rainbow smelt aged 2 and older showed a drop in mean weight from 13&ndash;17 g in 1978&ndash;1982 to 8 g in 1990. This downward trend in mean size of alewives was correlated with the sizes of alewives consumed by Lake Ontario chinook salmon during 1983&ndash;1987. For adult chinook salmon to maintain a constant growth rate during 1978&ndash;1990, mean individual daily ration during June&ndash;October had to increase from a low of 2.2% body weight/d (or 1.5 prey fish/d) in 1979 to 3.1% body weight/d (3.7 prey fish/d) in 1988. This increase in forage demand may have caused the observed declines in individual condition of salmonines over this period.

Transactions of the American Fisheries Society↗