Lake Ontario Salmonids Research Articles

Improving trophic niche and diet resolution of the salmonid community of Lake Ontario using three stable isotopes and multiple tissues

Salmonids are ecologically and economically important fishes in Lake Ontario but declines in Alewife (Alosa pseudoharengus), recently the primary prey item, may cause shifts in salmonid diets. Improving our understanding of salmonid trophic niches and diets and whether these have changed over time will provide insight into salmonid foraging patterns, ecology, and management. Using three stable isotopes (δ13C, δ15N and δ34S) and Bayesian models, we estimated core trophic niches, niche overlaps among species, and diets for six salmonid species from Lake Ontario sampled during 2018. We used fin and muscle tissue with different temporal assimilation periods to assess seasonal variability in diet, and investigated salmonid trophic niches and diets among three major spatial units (East, Central, West). Overall, core trophic niches overlapped across all species, except Lake Trout (Salvelinus namaycush). Consistent with previous lake-wide analyses of Lake Ontario salmonid diets, Alewife were the preferred prey fish, although Lake Trout and Atlantic Salmon (Salmo salar) had more varied diets, particularly based on white muscle. Fin-based isotope mixing models predicted greater consumption of shallow (< 30 m depth) Round Goby (Neogobius melanostomus) for Lake Trout, Brown Trout (Salmo trutta), and Rainbow Trout (Oncorhynchus mykiss) than other salmonids, indicating seasonal variation in diets. Lake Trout and Brown Trout also varied across spatial units with greater Round Goby consumption in western Lake Ontario. Spatially distinct diets suggest that Brown Trout and Lake Trout populations should be monitored regionally. Understanding prey consumption trends are important to effectively manage fish populations, especially considering on-going ecological changes in the Great Lakes.

Patterns in spatial use of land-locked Atlantic salmon (Salmo salar) in a large lake

Understanding the spatial use of reintroduced fish is useful for fisheries management and evaluating restoration success. Atlantic salmon (Salmo salar) were reintroduced into Lake Ontario in the 1990s; however, the movement ecology of these land-locked fish is unknown. Using acoustic telemetry and Floy tag mark-recaptures, we examined seasonal home range and space use of Atlantic salmon in Lake Ontario. Hatchery-raised adult Atlantic salmon were tagged with acoustic transmitters (n = 14; 8 with depth sensors) or Floy tags (n = 1915) and released. Both acoustic telemetry and Floy tag recaptures (n = 90) indicated cross lake movements, and home ranges encompassed nearly the entire lake in summer but was smaller in winter. Movements were nearshore (<2 km from shore) from spring to summer at ∼20 m bathymetric depths, with movements closer to shore in the fall, and further offshore (∼5.5 km from shore and 45 m bathymetric depths) in winter. Depth use was relatively shallow (<4 m) with occasional deeper dives (max = 28.5 m), and small diel vertical movements (1–5 m), moving deeper during daytime, consistent with ocean movements of Atlantic salmon. There appears to be spatial segregation among Atlantic salmon and other Lake Ontario salmonids, however, overlap likely occurs in nearshore waters during the spring. Wide-ranging movements of Atlantic salmon in binational (Canada/USA) waters reflects the importance of government agencies collaborating to ensure sustainable fisheries and the coordination of species restoration activities. This is the first study to provide detailed spatial use of Lake Ontario Atlantic salmon to assist in the management of this reintroduced species.

Diet and trophic niche space and overlap of Lake Ontario salmonid species using stable isotopes and stomach contents

Abstract Lake Ontario supports a diversity of native and non-native salmonids which are managed largely through stocking practices. Ecological changes (e.g., invasive species) altering the food web structure accompanied with shifts in prey abundance, necessitate understanding the trophic niches of Lake Ontario salmonids to aid in management. The objectives of this study were to quantify salmonid (5 species) trophic niches and dietary proportions using stable isotope ratios (δ13C and δ15N) of a large sample set (adult fish (>300 mm; n = 672) and key offshore prey (5 species, n = 2037)) collected across Lake Ontario in 2013. Estimates of prey based on stable isotope ratios were similar to stomach contents. Based on stable isotope ratios, non-native prey dominated salmonid diet; in particular alewife (Alosa pseudoharengus) constituted the majority (0.31 to 0.93) of all salmonid diets, and round goby (Neogobius melanostomus) contributed 0.26 and 0.19 of brown trout (Salmo trutta) and lake trout (Salvelinus namaycush) diets, respectively. Trophic niche overlap was high between all salmonids, except lake trout. The largest trophic niche overlap occurred between Chinook (Oncorhynchus tshawytscha), coho (Oncorhynchus kisutch), and Atlantic salmon (Salmo salar), and their reliance on alewife infers a strong pelagic foraging strategy. Lake, brown and rainbow (Oncorhynchus mykiss) trout had larger and/or more distinct trophic niches indicative of a more variable diet across individuals and utilizing different foraging strategies and/or habitats. Overall, Lake Ontario salmonids maintained a high reliance on alewife, and their potential for plasticity in diet provides important information to management regarding population sustainability.

Evaluation of Lake Ontario salmonid niche space overlap using stable isotopes

Abstract The Lake Ontario ecosystem has undergone substantial ecological change over the past five decades. In this time, an economically important sport fishery developed around non-native salmon and trout species (i.e., Chinook and coho salmon ( Oncorhynchus tshawytscha and Oncorhynchus kisutch ) and rainbow trout ( Oncorhynchus mykiss )). While trying to maintain this economically important recreational fishery, fishery managers are also trying to restore native species to the ecosystem (i.e., lake trout ( Salvelinus namaycush ) and Atlantic salmon ( Salmo salar )). We describe the trophic niche space of five ecologically and socioeconomically important Lake Ontario salmonid species (Chinook and coho salmon and rainbow, brown ( Salmo trutta ) and lake trout) using stable isotopes of carbon and nitrogen ( 13 C and 15 N, respectively). Using a modified standard ellipse analysis, we found a high degree of stable isotope niche space overlap in Lake Ontario salmonid species. Lake trout had the largest trophic niche space and the smallest proportion of overlap relative to the other four salmonid species (14%–28%), whereas coho salmon had the smallest stable isotope niche space and exhibited the highest degree of overlap with the other species (66%–99%). This study identifies and quantifies dietary resource sharing between Lake Ontario salmonids and highlights the importance of other prey fish species to the restoration and sustainability of Lake Ontario salmonid fish stocks.

A Bioenergetics Approach to Modeling PCB Bioaccumulation in Lake Ontario Salmonids

The objective of this paper is to compare the trend of polychlorinated biphenyls (PCBs) bioaccumulation in three species of Lake Ontario salmonids with similar diet patterns and habitat. The concept of bioenergetics, which relates the growth and energy expenditure of a fish directly to its food consumption, is integrated into the study of pollutant accumulation. The resulting bioaccumulation model is a comprehensive approach that combines the physiological information of the fish, such as diet, metabolism, respiration, habitat, age and species, with the environmental conditions in the lake. The three species of salmonids studied are Lake Trout (Salvelinus namaycush), Brown Trout (Salmo trutta), and Chinook Salmon (Oncorhynchus tshawytscha). The model, which relies on a lakewide water quality and fish sampling database from the Ontario Ministry of Environment and Energy, is applied to study the pattern of total body burden of PCBs over the life span of the fish. Results from the model compare favorably to the data, and the observations clearly demonstrate the relative effects of food and water contamination on the time-dependent accumulation of PCBs in the bodies of fish. It is observed that different species sharing the same habitat and exposed to similar water contaminant concentrations are exhibiting marked difference in the body accumulation of PCBs. This difference is successfully reproduced with the model through judicious representation of their diet preferences and generically-governed metabolisms.

Motivations and Satisfactions of Lake Ontario Boating Salmonid Anglers

Declines in populations of forage fish are leading fisheries management agencies to predict declining growth and survivorship of some Lake Ontario salmonids in coming years. These expectations have stimulated additional interest in research that can help managers predict how changes in fish populations or other fishing conditions may influence participation in the open lake fishery. Managers need additional understanding of angler motivations and satisfactions to effectively predict rates of fishing participation. We utilized a study of Lake Ontario salmonid anglers to test hypotheses about the relative importance of catch-related motivations and satisfactions within two angler subgroups (fishing tournament and salmon snagging participants) and among anglers at two levels of personal investment (i.e., high and low). Anglers were identified through a randomized sample of boat registrants in five New York State counties bordering Lake Ontario. Data on motivations and satisfactions were gathered through a self-administered mail-back questionnaire. Tournament anglers, salmon snaggers, and highly invested anglers were found to hold a range of motivations and satisfactions. Nevertheless, results also led to acceptance of our hypotheses that tournament anglers, salmon snaggers, and highly invested anglers all place high personal importance on catch-related motivations and satisfactions. Based on these results it is reasonable to expect some decrease in fishing participation by these angler subgroups if fish size or abundance decreases. Findings related to highly invested anglers are particularly noteworthy, given the fact that this group accounts for the majority of angler days and angler expenditures on Lake Ontario.

Modelling Bioaccumulation of Organic Pollutants in Fish with an Application to PCBs in Lake Ontario Salmonids

A model describing passive accumulation of organic chemicals from the aqueous environment and contaminated food in fish is developed. This model considers both biological attributes of the fish and physicochemical properties of the chemical that determine diffusive exchange across gill membranes and intestinal mucosa. Important biological characteristics addressed by the model are the fish's gill morphometry, feeding and growth rate and fractional aqueous, lipid, and nonlipid organic composition. Relevant physicochemical properties are the chemical's molar volume and n-octanol/water partition coefficient (Kow), which are used to estimate the chemical's aqueous diffusivity and partitioning to the fish's lipid and nonlipid organic fractions respectively. The model is used to describe and to analyze the bioaccumulation of polychlorinated biphenyls (PCBs) in Lake Ontario alewife (Alosa pseudoharengus), coho salmon (Oncorhynchus kisutch), rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and lake trout (Salvelinus namaycush).

Assessment of relative toxicity of chlorinated dibenzo- [formula omitted]-dioxins, dibenzofurans, and biphenyls in Lake Ontario salmonids to mammalian systems using toxic equivalent factors (TEP)

Concentrations of chlorinated dibenzo-p-dioxins and dibenzofurans were measured in four species of Lake Ontario salmonids and related to congener-specific PCB analyses for the same fish reported in a previous study. The toxicity of these chemical concentrations to mammalian systems were evaluated using toxic equivalent factors (TEF), based on composite, AHH induction, and thymic atrophy indices. The results indicated the PCB levels monitored in these species are potentially 5 to 10-fold, or more, toxic to mammals than the levels of dioxins or furans.

Distribution of polychlorinated biphenyl congeners and other halocarbons in whole fish and muscle among Lake Ontario salmonids

Distribution of polychlorinated biphenyl congeners and other halocarbons in whole fish and muscle among Lake Ontario salmonids

Cadmium and lead in Lake Ontario salmonids.

Currently, there are data documenting the existence of cadmium and lead in Lake Ontario salmonids. Investigators recently reported the absence of detectable residues of either element in edible fillets of coho and chinook salmon from Michigan tributaries to the other four laurention Great Lakes. However, flame atomic absorption spectrometry was used and the reported detectability limit (10 ppm) was greater than the trace levels that may likely have been present. The present investigation was initiated to (1) establish the existence and magnitude of cadmium and lead content of Lake Ontario salmonids, and (2) to assess the potential impact of their consumption on human dietary cadmium and lead intake.

Content and Chemical Form of Mercury and Selenium in Lake Ontario Salmon and Trout

The content and chemical form of mercury and selenium were determined in the edible tissue of salmon (coho, chinook) and trout (lake, brown) taken offshore from Lake Ontario near Rochester, New York. For all fish species, total mercury content ranged from 0.3 to 0.8 μg/g (fresh-weight), which is similar to concentrations commonly found in canned tuna. Most of the total mercury (63 to 79 percent) was present as methylmercury, the remainder being divalent inorganic mercury. For all species, 6 to 45 percent of the total selenium content was present as selenate (SeVI), the remainder being selenite (SeIV) and selenide (Se-11). On a molar basis, total selenium content usually exceeded that of total mercury. Samples of smoked and unsmoked brown trout fillets were also examined. Based on the results of this study there is no immediate human health hazard from mercury and selenium. However, there is a need to report specific chemical forms of these metals in Lake Ontario salmonid fishes so that elevated concentrations can be better evaluated.

Is Trypanoplasma Salmositica Present in Lake Ontario Salmonids?

During the period June-October 1981, fish, including lake trout (Salvelinus namaycush), brown trout (Salmo trutta), rainbow trout (Salmo gairdneri) and coho salmon (Oncorhynchus kisutch), were collected from four locations on Lake Ontario. In addition, juvenile coho salmon reared from Lake Ontario fish eggs and maintained in a hatchery were collected. Subsequently, air-dried blood smears were stained with Leishman-Giesma and examined under oil emersion for Trypanoplasma salmositica. In this study of 131 fish, no T. salmositica were found. From these findings it may be assumed that T. salmositica are either rare or not present in Lake Ontario salmonids.

Elimination of Hexachlorobenzene (HCB) by Rainbow Trout (Salmo gairdneri), and an Examination of its Kinetics in Lake Ontario Salmonids

Subadult rainbow trout (Salmo gairdneri) were fed diets containing hexachlorobenzene (HCB) to establish mean body burdens of 225 and 440 μg HCB per fish. They were sampled after 0, 24, 55, and 110 d to estimate the rate of elimination. The biological half-life or T[Formula: see text] of HCB for trout under the prescribed laboratory conditions was estimated to be at least 7 mo, and perhaps as long as several years. T[Formula: see text] was calculated using body burden or μg HCB per fish, and tissue concentrations or μg/kg HCB. Estimates of T[Formula: see text] derived from tissue concentrations ranged from 61 to 117 d, but this was shown to be due to a relative increase in body weight over the study period. The implications of increasing body weight on kinetics measurements are discussed, and an equation is presented that adjusts for changes in body weight where estimates of T[Formula: see text] are calculated using tissue concentrations.The results of this and other studies on HCB were used to examine the kinetics of HCB in salmonids collected from Lake Ontario. Using the information derived from laboratory studies on rainbow trout, good agreement was achieved between the expected level and that monitored in field samples of rainbow trout, but only a fair agreement was suggested for lake trout (Salvelinus namaycush) and coho salmon (Oncorhynchus kisutch). Differences in the HCB kinetics of these species may be attributed to body weight, age, and perhaps feeding habits. Concentrations of HCB reported in field sampling programs generally range from 1 to 100 μg/kg in fish, and it is suggested that these levels are primarily due to the limited availability of HCB in the Lake Ontario environment.Key words: contaminants, hexachlorobenzene (HCB), half-life, elimination, depuration, rainbow trout, Salmo gairdneri; Lake Ontario

Hexachlorobenzene (HCB) levels in Lake Ontario salmonids.

Hexachlorobenzene, C6CI 6, has been used as an agr icul tural fungicide unt i l the early 1970's. HCB is also used as a peptizing agent for rubber products, a wood preservative, and a p last ic izer for polyvinyl chloride (QUINLIVAN et al. 1975, PLIMMER & KLINGEBIEL 1976). HCB is also formed as a by-product during the manufacture of industr ia l chemicals, especially those products containing chlorine and chlorinated hydrocarbons, and the incineration of domestic and industr ia l waste (EPA 1973).

The Roles of Research and Extension Education in the Developing Lake Ontario Salmonid Fishery

Abstract Resource management agencies involved in developing a sport fishery often lack the resources to deal with associated problems and potentials. As a result, the economic and social impacts on small communities affected by the fishery may be neglected. In New York State, the development of the Great Lakes salmonid fishery by the New York State Department of Environmental Conservation (DEC) has occurred with the cooperation of New York Sea Grant research and extension efforts. The following case study documents research and extension efforts designed to cope with diverse fishery development problems.