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

1995 ◽  
Vol 52 (5) ◽  
pp. 925-935 ◽  
Author(s):  
Edward L. Mills ◽  
Connie Adams ◽  
Robert O'Gorman ◽  
Randall W. Owens ◽  
Edward F. Roseman

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 1991–1993. 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.

2006 ◽  
Vol 63 (12) ◽  
pp. 2734-2747 ◽  
Author(s):  
Gideon Gal ◽  
Lars G Rudstam ◽  
Edward L Mills ◽  
Jana R Lantry ◽  
Ora E Johannsson ◽  
...  

Mysis relicta and planktivorous fish feed on zooplankton in Lake Ontario and form a trophic triangle that includes intraguild predation by fish on mysids. Thus, fish affect zooplankton both directly and indirectly. To evaluate the importance of alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), and mysids as zooplanktivores in Lake Ontario, we measured abundances and distributions, assessed diets, and computed mysid and fish consumption rates based on bioenergetics models. We further estimated indirect effects by comparing clearance rates given observed and potential mysid distributions. Estimated consumption rates varied widely with season and water depth and ranged between 2.6 × 10–3 and 1.3 g·m–2·day–1 for mysids and between 1.4 × 10–3 and 0.5 g·m–2·day–1 for fish, representing a daily removal of zooplankton of up to 10.2%·day–1 and 2.0%·day–1 by mysids and fish, respectively. Mysid planktivory exceeded fish planktivory in May and August, but fish planktivory dominated in October. Estimated mysid planktivory rates were 2- to 90-fold lower than the potential rate if mysids moved to temperatures that maximized their predation rates, suggesting an indirect positive effect of fish on zooplankton.


1998 ◽  
Vol 55 (2) ◽  
pp. 307-317 ◽  
Author(s):  
Peter S Rand ◽  
Donald J Stewart

We tested the hypotheses that (1) reductions in individual size and energy density of adult alewife (Alosa pseudoharengus) in Lake Ontario over the past decade have caused reductions in mean size of consumed alewife and compensatory increases in frequency of feeding by salmonines and (2) perceived recent reductions in the alewife and rainbow smelt (Osmerus mordax) prey base in recent years have resulted in shifts in diets of salmonines to less preferred prey items. Data from a diet survey conducted on sport-caught salmonines during 1983-1988 and 1993 indicated significant reductions in the mean size of consumed alewife across all predator species over time and an increased frequency of feeding among some predators (reflected by a decline in the proportion of empty stomachs observed). We found evidence of increased ration levels in coho salmon (Oncorhynchus kisutch) and lake trout (Salvelinus namaycush) and an increase in the number of adult alewife in stomachs of all predator species that was accurately predicted by an earlier bioenergetic model analysis. We found evidence of a shift in diet across years away from rainbow smelt and other fishes to adult alewife. Results point toward possible sources of bioenergetic stress on salmonines in Lake Ontario.


2014 ◽  
Vol 71 (7) ◽  
pp. 1039-1049 ◽  
Author(s):  
Kevin N. McDonnell ◽  
Brian M. Roth

We developed a bioenergetic-based foraging model to evaluate how the composition of the pelagic zooplankton community influences the growth of zooplanktivorous larval walleye (Sander vitreus). Our model incorporates field observations of pelagic zooplankton composition and density as well as size-specific prey preferences of larval walleye to simulate both foraging and consumption rates. The model was evaluated in four lakes in northern Wisconsin: two with invasive populations of rainbow smelt (Osmerus mordax) and two without populations of rainbow smelt. Invasive rainbow smelt are known to alter the composition of pelagic zooplankton communities as well as cause declines in walleye recruitment, thus providing a unique opportunity to evaluate our model. The results suggest that larval walleye growth is slowed in systems that lack high densities of large-bodied Daphnia. Such conditions may create an energetic bottleneck for larval walleye. This approach could easily be applied to other species that are also affected by rainbow smelt or more generally where success of larval foraging is suspected to have a large influence on year-class strength.


2003 ◽  
Vol 29 (2) ◽  
pp. 205-212 ◽  
Author(s):  
Tara M. Bushnoe ◽  
David Michael Warner ◽  
Lars Gösta Rudstam ◽  
Edward L. Mills

1987 ◽  
Vol 44 (S2) ◽  
pp. s390-s403 ◽  
Author(s):  
Robert O'Gorman ◽  
Roger A. Bergstedt ◽  
Thomas H. Eckert

The size of hatchery-reared brown trout (Salmo trutta) and coho salmon (Oncorhynchus kisutch), 1 yr after release in Lake Ontario, declined when the stocking of salmonines was increased between 1978 and 1984. The principal prey species, alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax), failed to show the expected, predator-induced downturn in abundance. Instead, rainbow smelt remained moderately abundant and alewives very abundant. During this period, alewife year-classes were small, survival of yearling alewives was poor, growth of young-of-the-year of both alewives and rainbow smelt was slow (growth of most older alewives ceased), and rainbow smelt numbers gradually increased (the much larger alewife population presumably buffered older rainbow smelt from predation by large piscivores). When adult alewife numbers were halved by a winter die-off, the subsequent year-class of alewives was large and growth of brown trout during their first year in the lake increased. This suggested a causal relation between abundance of young alewives and brown trout growth. In the first year coho salmon were at liberty, their growth was related to abundance of young-of-the-year alewives; in their second year it was related to the abundance of yearling alewives and the condition of adult alewives. We hypothesize that abundant adult alewives suppressed production of young-of-the-year fish (necessary prey for salmonines during their first year in the lake) through competition for limited zooplankton production, and thus impeded the transfer of energy from the lowest trophic level to young salmonine predators.


1987 ◽  
Vol 44 (S2) ◽  
pp. s37-s52 ◽  
Author(s):  
W. J. Christie ◽  
K. A. Scott ◽  
P. G. Sly ◽  
R. H. Strus

During the past 10 yr there have been dramatic increases in piscivorous populations of walleye (Stizostedion vitreum) in the Bay of Quinte and of planted lake trout (Salvelinus namaycush) and double-crested cormorants (Phalacrocorax auritus) in the Kingston basin of Lake Ontario. This paper documents changes in the prey stocks shared by these piscivores, including reduction in size and abundance of the slimy sculpin (Cottus cognatus) with subsequent stock equilibration and unabated reduction in the size and abundance of rainbow smelt (Osmerus mordax), both owing to predation pressure from the lake trout. The third primary prey species, alewife (Alosa pseudoharengus), has not yet suffered severely from the depredations of the piscivores. Symptoms of the effects are discernible, however, and the implications of a possible collapse are discussed. Lake trout survival and growth have not yet been affected by the changes in prey availability, but their diet has shifted both in response to their own expanded size composition and relative abundance of the three prey species. Increased utilization of alewife makes the hunting of the trout more pelagic. Problems of obtaining representative samples of the prey are discussed.


1981 ◽  
Vol 38 (6) ◽  
pp. 662-668 ◽  
Author(s):  
Larry B. Crowder ◽  
John J. Magnuson ◽  
Stephen B. Brandt

The potential for ecological segregation of Lake Michigan fishes was examined by comparing diets and thermal habitat use of common species. Samples were collected by bottom trawling (N = 68) off Grand Haven, Michigan, September 7–13, 1977. Five common species exhibited complementarity in the use of food and thermal habitat resources. During the day, adult alewife (Alosa pseudoharengus), and rainbow smelt (Osmerus mordax) had similar diets but occupied somewhat different thermal habitats. Young-of-the-year (YOY) alewives segregated from adult alewife and rainbow smelt on both habitat and food. Spottail shiner (Notropis hudsonius), YOY alewives, and yellow perch (Perca flavescens) used similar thermal habitats but fed on different prey. Trout-perch (Percopsis osmiscomaycus) tended to segregate from the others based on both food and thermal habitat but may experience diffuse competition. Adults of the three native species consume entirely different prey than exotic alewife and rainbow smelt. The native species which declined during the invasion of alewife and rainbow smelt were those with apparently similar habitat and food requirements to the exotics. These data suggest that competition is important in maintaining the structure of the Lake Michigan fish community.Key words: competition, fishes, food, habitat, Lake Michigan, predation, temperature


<em>Abstract</em>.—Thiamine concentrations in representative Great Lakes prey fish, including alewives <em>Alosa pseudoharengus</em>, rainbow smelt <em>Osmerus mordax</em>, slimy sculpin <em>Cottus cognatus</em>, bloater chub <em>Coregonus hoyi</em>, and lake herring <em>Coregonus artedi</em>, and their major dietary items, including mysids <em>Mysis relicta</em>, amphipods <em>Diporeia hoyi</em>, and net macroplankton, were measured to assess their potential involvement in depressed thiamine concentrations in lake trout <em>Salvelinus namaycush </em>of the Great Lakes. Mean thiamine concentrations in all biota were greater than the recommended dietary intake of 3.3 nmol/g for prevention of effects on growth, although the adequacy of these concentrations for reproduction is not known. Mean thiamine concentrations decreased in the order alewives > bloater chub, herring > smelt and differed from the order of associated egg thiamine concentrations published for lake trout feeding on these species (herring > alewives, smelt). As a result, these data strongly implicate the high thiaminase content, rather than the low thiamine content, of alewives and smelt as being responsible for the low egg thiamine concentrations of Great Lakes lake trout stocks that feed heavily on these species. Variations in thiamine content among prey species did not appear to be related to levels in their diet, because thiamine concentrations in <em>Mysis</em>, <em>Diporeia</em>, and macroplankton showed little consistency between group or between lake variation. There was no lake to lake variation in mean thiamine concentrations of prey species, but considerable within species variation occurred that was unrelated to size.


<i>Abstract</i>.—Fish population recoveries can result from ecosystem change in the absence of targeted restoration actions. In Lake Ontario, native Deepwater Sculpin <i>Myoxocephalus thompsonii</i> were common in the late 1800s, but by the mid-1900s the species was possibly extirpated. During this period, mineral nutrient inputs increased and piscivore abundance declined, which increased the abundance of the nonnative planktivores Alewife <i>Alosa pseudoharengus</i> and Rainbow Smelt <i>Osmerus mordax</i>. Deepwater Sculpin larvae are pelagic and vulnerable to predation by planktivores. Annual bottom trawl surveys did not capture Deepwater Sculpin from 1978 to 1995 (<i>n</i> = 6,666 tows) despite sampling appropriate habitat (trawl depths: 7–170 m). The absence of observations during this time resulted in an elevated conservation status for the species, but no restoration actions were initiated. In 1996, three individuals were caught in bottom trawls, the first observed since 1972. Since then, their abundance has increased, and in 2017, they were the second most abundant Lake Ontario prey fish. The food-web changes that occurred from 1970 through the 1990s contributed to this recovery. Alewife and Rainbow Smelt abundance declined during this period due to predation by stocked salmonids and legislation that reduced nutrient inputs and food web productivity. In the 1990s, proliferation of nonnative, filter-feeding dreissenid mussels dramatically increased water clarity. As light penetration increased, the early-spring depth distribution of Alewife and Rainbow Smelt shifted deeper, away from larval Deepwater Sculpin habitat. The intentional and unintentional changes that occurred in Lake Ontario were not targeted at Deepwater Sculpin restoration but resulted in conditions that favored the species’ recovery. While standard surveys documented the recovery, more diverse information (e.g., observations in deep habitats and early-life stages) would have improved our understanding of why the species recovered when it did. Annual Lake Ontario trawl surveys have collaboratively expanded their spatial extent and diversified habitat sampled, based on lessons learned from the Deepwater Sculpin recovery.


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