Within- and among-population variation in the trophic position of a pelagic predator, lake trout (Salvelinus namaycush)

2000 ◽  
Vol 57 (4) ◽  
pp. 725-731 ◽  
Author(s):  
M Jake Vander Zanden ◽  
Brian J Shuter ◽  
Nigel P Lester ◽  
Joseph B Rasmussen
Keyword(s):  
Body Size ◽  
Total Variation ◽  
Lake Trout ◽  
Prey Size ◽  
Trophic Position ◽  
Feeding Habits ◽  
Salvelinus Namaycush ◽  
Population Variation ◽  
Prey Fish ◽  
Fish Trophic Position

Many aquatic consumers have flexible feeding habits, and the diet and trophic position of a species can be expected to vary both within and among populations. In this study, we quantify the importance of both within- and among-population trophic variation for lake trout (Salvelinus namaycush) using stable isotope designations of trophic position from 13 Ontario and Quebec lakes. Lake-to-lake differences explained 78% of the total variation in lake trout trophic position. Analysis using both stable isotopes and published dietary data demonstrated that the trophic position of lake trout failed to increase appreciably as a function of animal body size. This finding was attributed to weak predator size - prey size relationships as well as to there being no relationship between prey fish trophic position and body size. The variance in trophic position of a population reflects the extent to which individuals forage as trophic specialists; however, we did not identify any one factor that was correlated with within-population trophic variation. Our finding that much of the total variation in trophic position represents among-population differences indicates that considering the average trophic position of a population does not mask substantial within-population trophic variation.

scholarly journals Diet composition and feeding habits of the eyespot skate, Atlantoraja cyclophora (Elasmobranchii: Arhynchobatidae), off Uruguay and northern Argentina

2016 ◽  
Vol 14 (3) ◽  
Author(s):  
Santiago A. Barbini ◽  
Luis O. Lucifora
Keyword(s):  
Body Size ◽  
Diet Composition ◽  
Prey Size ◽  
Prey Availability ◽  
Feeding Habits ◽  
Warm Season ◽  
Cold Season ◽  
The North ◽  
Multiple Hypothesis ◽  
Modelling Approach

ABSTRACT The eyespot skate, Atlantoraja cyclophora, is an endemic species from the southwestern Atlantic, occurring from Rio de Janeiro, Brazil, to northern Patagonia, Argentina. The feeding habits of this species, from off Uruguay and north Argentina, were evaluated using a multiple hypothesis modelling approach. In general, the diet was composed mainly of decapod crustaceans, followed by teleost fishes. Molluscs, mysidaceans, amphipods, isopods, lancelets and elasmobranchs were consumed in lower proportion. The consumption of shrimps drecreased with increasing body size of A. cyclophora. On the other hand, the consumption of teleosts increased with body size. Mature individuals preyed more heavily on crabs than immature individuals. Teleosts were consumed more in the south region (34º - 38ºS) and crabs in the north region (38º - 41ºS). Shrimps were eaten more in the warm season than in the cold season. Prey size increased with increasing body size of A. cyclophora , but large individuals also consumed small teleosts and crabs. Atlantoraja cyclophora has demersal-benthic feeding habits, shifts its diet with increasing body size and in response to seasonal and regional changes in prey availability and distribution.

Ecophysiological determinants of the variation in 137Cs concentrations between and within lacustrine fish populations

2005 ◽  
Vol 62 (12) ◽  
pp. 2727-2739 ◽  
Author(s):  
Marcus Sundbom ◽  
Markus Meili
Keyword(s):  
Body Size ◽  
Trophic Position ◽  
Fish Populations ◽  
Chernobyl Fallout ◽  
Population Means ◽  
Activity Concentrations ◽  
Resource Specialization ◽  
Total Variability ◽  
Biomagnification Factors ◽  
Fish Trophic Position

One decade after the Chernobyl fallout, the variability of 137Cs activity concentrations among fish within a Swedish lake was >20-fold based on 1361 individuals from seven species collected continually during 1996–1999. Of the total variability, 64% was due to differences between species but only 7% due to temporal variation, which was 1.3-fold for the whole community and 1.3- to 2-fold for population means. Contamination increased with body size (0.6- to 6-fold) and decreased with body condition in most species (1.3-fold). Body size and time together accounted for about half of the total variation within populations. Fish 137Cs was related to differences in feeding ecology, both between and within populations. Biomagnification factors ranged from 2.4 to 5.8. Contamination was highest in piscivorous populations and individuals, intermediate in herbivores and zooplanktivores, and lowest in fish specialized in benthic invertebrates despite their association with contaminated sediments. The 137Cs variance within populations was not correlated with their niche width but moderately positively correlated with fish trophic position and strongly positively correlated with functional omnivory (diversity in prey 137Cs). We conclude that individual resource specialization is an important source of variation in 137Cs concentrations within fish populations.

Effects of light, prey size, and turbidity on reaction distances of lake trout (Salvelinus namaycush) to salmonid prey

1999 ◽  
Vol 56 (7) ◽  
pp. 1293-1297 ◽  
Author(s):  
Jason L Vogel ◽  
David A Beauchamp
Keyword(s):  
Lake Trout ◽  
Prey Size ◽  
Cutthroat Trout ◽  
Salvelinus Namaycush ◽  
Time Of Day ◽  
Oncorhynchus Clarki ◽  
Natural Environments ◽  
Reaction Distance ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Detection Capabilities

Most studies on visual foraging by fish have focused on reaction distances to invertebrate prey; however, these acuity-based results considerably overestimate reaction distances of piscivores to prey fish. In laboratory experiments, we quantified reaction distance of adult lake trout (Salvelinus namaycush) to rainbow trout (Oncorhynchus mykiss) and cutthroat trout (Oncorhynchus clarki) as a function of light (0.17-261 lx), prey size (55, 75, and 139 mm), and turbidity (0.09, 3.18, and 7.40 NTU). Reaction distances increased rapidly with increasing light from <25 cm at 0.17 lx to about 100 cm at a light threshold of 17.8 lx. Reaction distance declined as a decaying power function of turbidity. By constructing equations that describe the combined effects of light and turbidity on reaction distances, we can begin to model prey detection capabilities of piscivores at any depth at any time of day in natural environments.

A stable isotope evaluation of the structure and spatial heterogeneity of a Lake Superior food web

2000 ◽  
Vol 57 (7) ◽  
pp. 1395-1403 ◽  
Author(s):  
Chris J Harvey ◽  
James F Kitchell
Keyword(s):  
Stable Isotope ◽  
Spatial Heterogeneity ◽  
Food Web ◽  
Lake Trout ◽  
Trophic Position ◽  
Lake Superior ◽  
Salvelinus Namaycush ◽  
Trophic Relationships ◽  
Rainbow Smelt ◽  
Western Lake

We used stable isotope analysis to derive trophic relationships and movement patterns for components of the western Lake Superior food web. Trophic linkages implied by previous gut content studies were only marginally supported by stable isotope data. Siscowet lake trout (Salvelinus namaycush siscowet) were the top predators, and trophic overlap between siscowet and lean lake trout (Salvelinus namaycush) was low. Exotic Pacific salmon (Oncorhynchus spp.) occupied a lower trophic position than native piscivores because the latter relied more on coregonids. To evaluate spatial heterogeneity of the food web, we assumed that the adjacent cities of Duluth and Superior (DS) were a point source of 15N, and we measured isotopes of organisms close to and far from DS. Slimy sculpin (Cottus cognatus) were enriched in the DS area relative to other sites, implying that they are relatively sedentary. Rainbow smelt (Osmerus mordax) showed no differences at any sites, implying high vagility. Other organisms showed differences that could not be attributed to DS, implying that other mechanisms, such as trophic ontogeny, were influencing their isotopic signatures.

Changes in the condition, early growth, and trophic position of lake trout (Salvelinus namaycush) in response to an experimental aquaculture operation

2019 ◽  
Vol 76 (8) ◽  
pp. 1376-1387
Author(s):  
Patrick J. Kennedy ◽  
Paul J. Blanchfield ◽  
Karen A. Kidd ◽  
Michael J. Paterson ◽  
Cheryl L. Podemski ◽  
...  
Keyword(s):  
Energy Use ◽  
Lake Trout ◽  
Trophic Position ◽  
Salvelinus Namaycush ◽  
Early Growth ◽  
Small Scale ◽  
Catch Per Unit Effort ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Mysis Diluviana ◽  
Boreal Shield

We analyzed changes in the condition, early growth, and resource use of lake trout (Salvelinus namaycush) from a Boreal Shield lake in response to an experimental aquaculture operation. Annual small-scale commercial production of rainbow trout (Oncorhynchus mykiss) resulted in increased lake trout body condition during aquaculture operations, which was positively related to minnow catch per unit effort (CPUE). Incremental increases in growth led to larger lake trout following aquaculture. While the littoral energy assimilated by lake trout did not change linearly from 2002 to 2009, we observed a shift towards littoral energy use in the last year of aquaculture and for 2 years after the experiment, coincident with low densities of Mysis diluviana. Lake trout trophic position declined from 2002 to 2009, suggesting increased foraging on secondary versus tertiary consumers. Minnow and slimy sculpin (Cottus cognatus) CPUE increased by 5.2- and 5.5-fold, respectively, and Mysis diluviana densities decreased by 93%. Changes observed in the experimental lake were much greater than those observed in a nearby reference lake. Our results suggest that moderate nutrient enrichment from aquaculture may benefit lake trout in oligotrophic Boreal Shield lakes.

scholarly journals Food Web Structure Informs Potential Causes of Bimodal Size Structure in a Top Predator

2018 ◽  
Vol 11 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Peter C. Searle ◽  
Joshua A. Verde ◽  
Mark C. Belk
Keyword(s):  
Body Size ◽  
Yellow Perch ◽  
Lake Trout ◽  
Large Body ◽  
Somatic Growth ◽  
Salvelinus Namaycush ◽  
Trophic Niche ◽  
Competitive Interactions ◽  
Large Body Size ◽  
Small Lake

Background: Assemblages of fishes in lakes and reservoirs in the western USA are dominated by non-native, large-bodied, piscivorous fishes that lack a shared evolutionary history. Top predators in these crowded systems are often characterized by unstable population dynamics and poor somatic growth rates. One such assemblage is in Fish Lake, located in southern Utah, USA, in which introduced lake trout (Salvelinus namaycush, Walbaum) exhibit a bimodal growth pattern. A few lake trout in Fish Lake grow rapidly to large size typical of the species; whereas, most never grow beyond 600 mm total length. Objective: To inform competitive interactions in this evolutionarily novel fish assemblage that might cause the low recruitment to large body size in lake trout, we characterized trophic niche (from stable isotope analysis of C and N) of all fishes in the lake. Methods: We used a Bayesian mixing model to describe the trophic niche and infer diet of lake trout and their potential prey, and we used Bayesian ellipse analysis to identify potential areas of high competition within the food web. Large lake trout feed mostly on small lake trout and splake (Salvelinus namaycush, Walbaum x Salvelinus fontinalis, Mitchill) despite availability of abundant yellow perch. (Perca flavescens, Mitchill). Small lake trout and splake feed mostly on zooplankton and exhibit substantial overlap of their trophic niche implying competition for food. Yellow perch and Utah chub (Gila atraria, Girard; formerly an important food item for lake trout in Fish Lake) exhibit extreme overlap of their trophic niche implying strong competitive interactions. Results: Our data suggest that lack of recruitment to large body size in lake trout may result from a reduction in availability of Utah chub resulting from competitive interactions with yellow perch, and increased competition from introduced splake for available prey. Conclusion: Management actions that may help ameliorate the poor somatic growth rates of most lake trout include efforts to reduce perch populations or increase vulnerability of perch to predation by lake trout, and removal of splake as a competitor of small lake trout.

Consequences of prey fish community dynamics on lake trout (Salvelinus namaycush) foraging efficiency in Lake Superior

1998 ◽  
Vol 55 (5) ◽  
pp. 1273-1284 ◽  
Author(s):  
Doran M Mason ◽  
Timothy B Johnson ◽  
James F Kitchell
Keyword(s):  
Fish Community ◽  
Community Dynamics ◽  
Lake Trout ◽  
Size Structure ◽  
Lake Superior ◽  
Salvelinus Namaycush ◽  
Foraging Efficiency ◽  
Prey Fish ◽  
Rainbow Smelt ◽  
Lake Herring

We used a size-structured model, indexed by age, that combines bioenergetics and foraging theory to evaluate the effects of prey fish community structure (species dominance, size structure, and density) on the diet and net foraging efficiency of lake trout (Salvelinus namaycush) in Lake Superior. Prey size structure was important for young lake trout but decreased in importance for older lake trout, especially with increasing prey density. The model predicted that rainbow smelt (Osmerus mordax) should dominate the diet of young lake trout due to the size-dependent capture limitations of larger prey. In contrast, lake herring (Coregonus artedi) should dominate the diet of oldest lake trout owing to a higher net energy return than rainbow smelt. Model results are consistent with age-specific diet and size-at-age of lake trout during the last 40 years. Diets of intermediate-sized lake trout do not reflect the recent resurgence of lake herring populations. Absence of a dietary switch is probably due to higher capture probability for rainbow smelt. Lake trout growth and production will likely be highest with a mixed prey species assemblage of young rainbow smelt and older lake herring.

Feeding habits of a large endangered skate from the south-west Atlantic: the spotback skate, Atlantoraja castelnaui

2012 ◽  
Vol 63 (2) ◽  
pp. 180 ◽  
Author(s):  
Santiago A. Barbini ◽  
Luis O. Lucifora
Keyword(s):  
Body Size ◽  
Prey Size ◽  
Feeding Habits ◽  
Warm Season ◽  
Cold Season ◽  
The South ◽  
The North ◽  
South West ◽  
Multiple Hypothesis ◽  
Modelling Approach

Elasmobranch predation has important effects on marine ecosystems. Identifying the main correlates of the feeding habits of skates is of paramount importance for determining their ecological role. We tested the hypotheses that the diet of the spotback skate, Atlantoraja castelnaui, off Uruguay and northern Argentina, changes with increasing body size, between seasons and regions and that prey size increased with predator’s size using a multiple-hypothesis modelling approach. A. castelnaui preyed mainly on teleosts, followed by cephalopods, elasmobranchs and decapods. Small individuals of A. castelnaui consumed decapods and large individuals ate elasmobranchs and cephalopods. The consumption of teleosts was constant along the ontogeny but differed between seasons; more demersal-benthic teleosts were consumed in the cold season, whereas more benthic teleosts were eaten in the warm season. Also, A. castelnaui consumed more cephalopods in the warm season than in the cold season. Benthic teleosts were consumed more in the south region, whereas decapods were eaten more in the north region. A. castelnaui is able to consume larger teleosts as it grows. We conclude that A. castelnaui is a versatile, mainly piscivorous, consumer that shifts its diet with increasing body size and in response to seasonal and regional changes in prey abundance or distribution.

Accumulation of PCBs by Lake Trout (Salvelinus namaycush): An Individual-Based Model Approach

1993 ◽  
Vol 50 (1) ◽  
pp. 97-109 ◽  
Author(s):  
Charles P. Madenjian ◽  
Stephen R. Carpenter ◽  
Gary W. Eck ◽  
Michael A. Miller
Keyword(s):  
Uncertainty Analysis ◽  
Lake Michigan ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Prey Fish ◽  
Age Classes ◽  
Individual Based Model ◽  
Trout Population ◽  
Different Levels ◽  
Model Approach

To explain the variation in growth and in concentration of polychlorinated biphenyls (PCBs) among individual fish, an individual-based model (IBM) was applied to the lake trout (Salvelinus namaycush) population in Lake Michigan. The IBM accurately represented the variation in growth exhibited by the different age classes of lake trout. Uncertainty analysis of the IBM revealed that mean PCB concentration for the lake trout population was most sensitive to PCB concentration in their prey. The variability in PCB concentration among lake trout individuals was not adequately explained by the IBM, unless variation in prey fish PCBs was included in the model. To accomplish this, the simulated lake trout population was divided into subsets subjected to different levels of PCB concentration in the prey fish. Thus, model results indicated that variability in prey fish PCB concentration was an important component of the variation in PCB concentration observed among individual lake trout comprising the Lake Michigan population.

Multiple Trophic Level Structuring in Salvelinus–Coregonus Assemblages in Boreal Forest Lakes

1993 ◽  
Vol 50 (7) ◽  
pp. 1442-1455 ◽  
Author(s):  
Edward A. Trippel ◽  
F. William H. Beamish
Keyword(s):  
Body Size ◽  
Lake Trout ◽  
Zooplankton Community ◽  
Salvelinus Namaycush ◽  
High Conductivity ◽  
Top Down ◽  
Mysis Relicta ◽  
Northwestern Ontario ◽  
Coregonus Artedi ◽  
Forest Lakes

Hypolimnetic trophic interactions were examined among lake trout (Salvelinus namaycush), cisco (Coregonus artedi), zooplankton, and macroinvertebrates in six northwestern Ontario lakes varying sevenfold in conductivity. Faster growth and larger body size of lake trout in high-conductivity lakes were associated with larger meal sizes, earlier entry of cisco into their diet, and consumption of relatively few, large-bodied prey. Cisco preyed on zooplankton and macroinvertebrates. Cisco were abundant, large bodied, and fast growing in high-conductivity lakes. In one low-conductivity lake (Greenwich Lake), lake trout were 12 times as abundant as cisco whereas in all other lakes, lake trout to cisco ratios were ~ 1:1 or less regardless of conductivity. In Greenwich Lake, lake trout consumed large quantities of age-0 cisco and Mysis relicta, which was associated with "top-down" trophic structuring. Food web analyses strongly suggest that in Greenwich Lake the high abundance of piscivores resulted directly in a low abundance of planktivores and indirectly in a large-bodied zooplankton community and planktivores with rapid growth rates.

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