Why do Arctic Grayling (Thymallus arcticus) Get Bigger as You Go Upstream?

1994 ◽  
Vol 51 (10) ◽  
pp. 2154-2163 ◽  
Author(s):  
Nicholas F. Hughes ◽  
James B. Reynolds
Keyword(s):  
Distribution Pattern ◽  
Size Structure ◽  
Habitat Preferences ◽  
Removal Experiment ◽  
Fish Removal ◽  
Actual Distribution ◽  
Small Stream ◽  
Arctic Grayling ◽  
Size Dependent ◽  
Size Gradient

During the summer Arctic grayling in interior Alaskan streams get bigger as you go upstream. We performed a fish removal experiment in a small stream to test two hypotheses about the mechanism that produces this size gradient. The first hypothesis was that all sizes of Arctic grayling prefer positions in the headwaters, but that large fish defend these, forcing smaller ones to occupy positions further downstream (the competition for ranked positions hypothesis). The second hypothesis was that small Arctic grayling actually prefer positions in downstream reaches, and that as they grow their habitat preferences change, and they move to positions further upstream (the size-dependent habitat preference hypothesis). Under this hypothesis, exclusion by other individuals plays no part in producing the whole-stream size gradient. Using the distribution pattern of fish immediately before the removal experiment we developed two sets of rules, one for each hypothesis, to predict how a smaller post removal population, with a different size structure, should be distributed. By comparing these predictions with the actual distribution pattern of the population two years after the removal, we found that the competition for ranked positions hypothesis made much more accurate predictions than the alternative.

Population processes responsible for larger-fish-upstream distribution patterns of Arctic grayling (Thymallus arcticus) in interior Alaskan runoff rivers

1999 ◽  
Vol 56 (12) ◽  
pp. 2292-2299 ◽  
Author(s):  
Nicholas F Hughes
Keyword(s):  
Distribution Pattern ◽  
Distribution Patterns ◽  
Long Distance ◽  
Arctic Grayling ◽  
Sedentary Population ◽  
Thymallus Arcticus ◽  
Population Processes ◽  
Analyse Data ◽  
A Minor ◽  
Size Gradient

During the summer months, Arctic grayling (Thymallus arcticus) in Alaskan streams adopt a larger-older-fish-upstream distribution pattern. In this paper, I analyse data from two large interior Alaskan rivers to determine how population processes maintain this size and age gradient. These analyses support the hypothesis that age-phased recruitment and growth-dependent movement are primarily responsible for this distribution pattern. Age-phased recruitment describes the way that the mean age of fish recruiting to a reach increases upstream, from ages 0-1 in the lower river to ages 3-7 in the headwaters. This process begins with the concentration of spawning fish, and the resultant fry, in the lower reaches of the river. Downstream movement during the first year of life further concentrates young fish in the lower river. Over time, the distribution of this cohort broadens steadily as individuals move further upstream, so that fish recruiting to headwater reaches are 3-7 years old. This process contributes to both size and age gradients. Growth-dependent movement magnifies the size gradient by sorting fast-growing fish into the upper river and slow-growing fish into the lower river. This sorting results from the fact that individuals making long-distance upstream movements tend to have grown particularly rapidly that year, while individuals making long-distance downstream movements tend to have grown especially slowly that year. I rejected the hypothesis that age and size gradients are the result of whole-stream gradients in growth or mortality acting on a sedentary population. However, there was some evidence that fish did grow more slowly in the lowest 40 km of one river, although this made only a minor contribution to the size gradient and growth rates were remarkably constant for the next 120 km. There was no suggestion that spatial variation in mortality rate contributes towards the size or age gradient, but natural and sampling variability could have obscured small but significant differences between reaches.

Effects of nutrient distribution pattern and aboveground competition on size of individuals in Ipomoea tricolor populations

Botany ◽  
2008 ◽  
Vol 86 (11) ◽  
pp. 1260-1265 ◽  
Author(s):  
Ryoji Nakamura ◽  
Naoki Kachi ◽  
Jun-Ichirou Suzuki
Keyword(s):  
Growth Rate ◽  
Distribution Pattern ◽  
Size Structure ◽  
Plant Size ◽  
Nutrient Distribution ◽  
Size Dependent ◽  
Ipomoea Tricolor ◽  
Affected Plant ◽  
Aboveground Competition ◽  
Dependent Growth

We investigated whether the distribution pattern of soil nutrients interacted with aboveground competition to affect plant size in Ipomoea tricolor Cav. populations. Six plants per pot were grown in a factorial experiment with combinations of heterogeneous or homogeneous nutrient distribution pattern and presence or absence of aboveground competition. Plants were harvested and ranked by their aboveground biomasses. In analyses of plant sizes in all ranks simultaneously, mean plant size was significantly affected by nutrient distribution pattern, aboveground competition, and their interaction. In analyses of plant sizes of each rank, aboveground competition affected plant size, which was found in all ranks. Nutrient distribution pattern affected plant size in the higher ranks, but not in the lowest rank. Selective root placement into nutrient-rich patches under heterogeneous conditions was observed. Our results suggest that the magnitude of the effect of nutrient distribution pattern on plant size changed among ranks owing to changes in aboveground competition and size-dependent growth rate. Size-dependent growth rate could explain the significant effect of nutrient distribution pattern independent of the effect of aboveground competition. Nutrient distribution pattern would then interact with aboveground competition and consequently affect size structure in a population.

scholarly journals Temporal Variation in the Niche Partitioning of Lake Michigan Salmonines as it Relates to Alewife Abundance and Size Structure.

2021 ◽  
Author(s):  
Benjamin A. Turschak ◽  
Charles R. Bronte ◽  
Sergiusz J. Czesny ◽  
Brandon S. Gerig ◽  
Austin Happel ◽  
...  
Keyword(s):  
Ecological Niche ◽  
Lake Michigan ◽  
Nitrogen Isotopes ◽  
Size Structure ◽  
Prey Availability ◽  
Habitat Preferences ◽  
Niche Partitioning ◽  
Niche Overlap ◽  
Isotopic Niche ◽  
Resource Gradient

Stable isotope analyses offer a useful means for quantifying ecological niche dimensions, though few studies have examined isotopic response of an ecological community with respect to resource gradients such as fluctuations in prey availability. Stable carbon and nitrogen isotopes were measured for Lake Michigan salmonines and their prey collected from 2014 to 2016. Bayesian ellipse and mixing model analyses were used to quantify isotopic niche characteristics and diets, respectively, among species and years. During the three-year study period, abundance and size structure of preferred alewife prey changed substantially and offered an opportunity to explore predator isotopic niche response and diet shifts along a prey resource gradient. Results suggested increased reliance on alewives, especially small alewives, over the study period and were consistent with greater availability of this prey. However, differential use of alewife size classes and alternative prey sources by salmonine predators was apparent, which suggested possible resource partitioning. Characterization of ecological niche overlap using stable isotopes likely requires consideration of shared resource availability as well as specific prey and habitat preferences.

Emergence of size-structured dominance hierarchies through size-dependent feedback

2022 ◽  
Vol 377 (1845) ◽  
Author(s):  
Ian M. Hamilton ◽  
Macie D. Benincasa
Keyword(s):  
Size Structure ◽  
Dynamic Game ◽  
Optimal Investment ◽  
Growth Suppression ◽  
Pecking Order ◽  
Dominance Hierarchies ◽  
Size Dependent ◽  
Current State ◽  
Dominance Structure ◽  
Competition For Food

Size-based dominance hierarchies influence fitness, group size and population dynamics and link dominance structure to evolutionary and ecological outcomes. While larger individuals often gain dominance, social status may influence growth and size in return, resulting in feedbacks among status, growth and size. Here, we present two models evaluating how these feedbacks influence the emergence of size structure in a dominance hierarchy. In the first, size influences competition for food and investment in suppressing growth of groupmates. Stable size differences emerged when suppression was greatest for similarly sized individuals and size had little effect on competition for food. The model predicted size divergence when size strongly affected competition for food. In the second model, we used a dynamic game to solve for optimal investment in growth suppression as a function of size structure. Investment in growth suppression was favoured only when dominants and subordinates were similar in size, generating size ratios different than those expected by chance. Variation in the feedbacks among growth, size and status can explain variation in emergent size structure of dominance hierarchies and its consequences for conflict within groups. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’.

Effect of fish removal on the abundance and size structure of the sea urchinDiadema antillarum: A field experiment

2015 ◽  
Vol 11 (10) ◽  
pp. 1100-1107 ◽  
Author(s):  
Ruber Rodríguez-Barreras ◽  
Alain Durán ◽  
Julián Lopéz-Morell ◽  
Alberto M. Sabat
Keyword(s):  
Field Experiment ◽  
Size Structure ◽  
Fish Removal

Size- and sex-based habitat partitioning by Lepetodrilus fucensis near hydrothermal vents on the Juan de Fuca Ridge, Northeast Pacific

2008 ◽  
Vol 65 (11) ◽  
pp. 2332-2341 ◽  
Author(s):  
Amanda E. Bates
Keyword(s):  
Hydrothermal Vents ◽  
Size Structure ◽  
Environmental Gradients ◽  
Cost Of Reproduction ◽  
Juan De Fuca Ridge ◽  
Habitat Partitioning ◽  
Northeast Pacific ◽  
Juan De Fuca ◽  
One Year ◽  
Size Gradient

This study examines habitat partitioning by a hydrothermal vent limpet, Lepetodrilus fucensis, along environmental gradients and among vents with differing levels of flux. To test for spatial patterns in size structure, two distances from isolated vent flows were sampled (0–25 cm and 51–75 cm). Lepetodrilus fucensis displays a size gradient: juveniles are rare in flow (relative abundance < 5%, density = 56 ± 46 individuals·dm–2) and abundant peripherally (>95%, 2616 ± 2002 individuals·dm–2). Next, sex-based habitat partitioning was examined. High flux locations are female-biased (proportion male = 0.34 ± 0.07), whereas males are overrepresented peripherally and at waning vents (0.64 ± 0.08). The spatial mismatch between the sexes within a vent is driven by differential habitat occupation at decimetre scales. One hypothesis to explain this pattern is that females suffer a higher cost of reproduction and outcompete males for habitats with high food availability. Indeed, relatively higher percentages of females in waning vents had empty gonads in comparison with males (32%–78% vs. 0%–16%, respectively). Furthermore, females transplanted to the vent periphery for one year displayed much lower survivorship than males (2% vs. 27%). This finding suggests that differential survivorship between the sexes when food is limited can yield male-biased populations at waning vents.

The structure of plankton communities

1977 ◽  
Vol 280 (976) ◽  
pp. 485-534 ◽  
Keyword(s):  
Trophic Level ◽  
Size Structure ◽  
Food Limitation ◽  
Relative Size ◽  
Size Composition ◽  
Trophic Levels ◽  
Total Biomass ◽  
Size Dependent ◽  
First Feeding ◽  
Determining Modes

Interactions of herbivorous copepods with their phytoplankton food depend on the size composition of organisms in both trophic levels. A simulation model is used to analyse these size-dependent relations with the following conclusions. 1. Relative size structure of herbivores and their food is more important than total biomass of each trophic level in determining modes of transfer from plants to herbivores. In nearly all cases, in the model, food limitation affects reproduction or the first feeding stage of the nauplii. 2. No single factor emerges as predominant in determining the size structure of both populations. 3. The nature of predation on the herbivores is at least as important in determining both phytoplankton and herbivore size composition as physical or nutrient parameters. 4. The magnitude of the population of the larger herbivores such as Calanus , important as food for fish, depends on their coexistence with the smaller copepod species which control the smaller phytoplankton. 5. Stress on the system, if it affects adversely the smaller herbivores, can lead to the breakdown of the Calanus -diatom component. 6. Prediction of the population structure for both plants and herbivores may be a more attainable objective of theory and more practically important than prediction of total biomass at each trophic level.

scholarly journals Potential for climate effects on the size-structure of host–parasitoid indirect interaction networks

2012 ◽  
Vol 367 (1605) ◽  
pp. 3018-3024 ◽  
Author(s):  
Dominic C. Henri ◽  
David Seager ◽  
Tiffany Weller ◽  
F. J. Frank van Veen
Keyword(s):  
Size Structure ◽  
Weather Conditions ◽  
Optimal Foraging Theory ◽  
Apparent Competition ◽  
Interaction Networks ◽  
Host Size ◽  
Indirect Interaction ◽  
Weather Patterns ◽  
Size Dependent ◽  
The Common

Communities of insect herbivores are thought to be structured mainly by indirect processes mediated by shared natural enemies, such as apparent competition. In host–parasitoid interaction networks, overlap in natural enemy communities between any pair of host species depends on the realized niches of parasitoids, which ultimately depend on the foraging decisions of individuals. Optimal foraging theory predicts that egg-limited parasitoid females should reject small hosts in favour of future opportunities to oviposit in larger hosts, while time-limited parasitoids are expected to optimize oviposition rate regardless of host size. The degree to which parasitoids are time- or egg-limited depends in part on weather conditions, as this determines the proportion of an individual's lifespan that is available to foraging. Using a 10-year time series of monthly quantitative host–parasitoid webs, we present evidence for host-size-based electivity and sex allocation in the common secondary parasitoid Asaphes vulgaris. We argue that this electivity leads to body-size-dependent asymmetry in apparent competition among hosts and we discuss how changing weather patterns, as a result of climate change, may impact foraging behaviour and thereby the size-structure and dynamics of host–parasitoid indirect interaction networks.

scholarly journals Protection of large predators in a marine reserve alters size-dependent prey mortality

2017 ◽  
Vol 284 (1847) ◽  
pp. 20161936 ◽  
Author(s):  
Rebecca L. Selden ◽  
Steven D. Gaines ◽  
Scott L. Hamilton ◽  
Robert R. Warner
Keyword(s):  
Size Structure ◽  
Sea Urchins ◽  
Marine Reserves ◽  
Marine Reserve ◽  
Mortality Rates ◽  
Kelp Forests ◽  
Size Dependent ◽  
Predator Size ◽  
Top Predators ◽  
Large Predators

Where predator–prey interactions are size-dependent, reductions in predator size owing to fishing has the potential to disrupt the ecological role of top predators in marine ecosystems. In southern California kelp forests, we investigated the size-dependence of the interaction between herbivorous sea urchins and one of their predators, California sheephead ( Semicossyphus pulcher ). Empirical tests examined how differences in predator size structure between reserve and fished areas affected size-specific urchin mortality. Sites inside marine reserves had greater sheephead size and biomass, while empirical feeding trials indicated that larger sheephead were required to successfully consume urchins of increasing test diameter. Evaluations of the selectivity of sheephead for two urchin species indicated that shorter-spined purple urchins were attacked more frequently and successfully than longer-spined red urchins of the same size class, particularly at the largest test diameters. As a result of these size-specific interactions and the higher biomass of large sheephead inside reserves, urchin mortality rates were three times higher inside the reserve for both species. In addition, urchin mortality rates decreased with urchin size, and very few large urchins were successfully consumed in fished areas. The truncation of sheephead size structure that commonly occurs owing to fishing will probably result in reductions in urchin mortality, which may reduce the resilience of kelp beds to urchin barren formation. By contrast, the recovery of predator size structure in marine reserves may restore this resilience, but may be delayed until fish grow to sizes capable of consuming larger urchins.

Digenean trematodes moderately alter Hydrobia ulvae population size structure

2003 ◽  
Vol 83 (2) ◽  
pp. 297-305 ◽  
Author(s):  
Xavier de Montaudouin ◽  
Hugues Blanchet ◽  
Isabelle Kisielewski ◽  
Céline Desclaux ◽  
Guy Bachelet
Keyword(s):  
Population Size ◽  
Size Structure ◽  
Seasonal Pattern ◽  
Shell Height ◽  
Parasite Prevalence ◽  
Primary Host ◽  
Size Dependent ◽  
Hydrobia Ulvae ◽  
Population Size Structure ◽  
Structure Changes

The mudsnail Hydrobia ulvae, primary host to a number of digeneans, was studied to check whether parasite effects on individual hosts could have repercussion on population size structure and dynamics. Three different mudsnail populations were monitored monthly in Arcachon Bay, south-west France. Arguin is a moderately sheltered oceanic sandflat and a bird reserve, La Canelette is a sheltered sandflat near a harbour and Lette Douce is a sheltered salt marsh. Parasite prevalence differed among the three stations, with no obvious seasonal pattern: 0–16% at Arguin, 0–6% at La Canelette and 1–5% at Lette Douce. Between four and five digenean species were identified, with Haploporidae dominating at Arguin and Notocotylidae dominating at Lette Douce. Prevalence increased with snail shell height. Large snails from Arguin were heavily parasitized, but suddenly disappeared between December 1998 and January 1999. The snail size distribution was consequently modified. To test whether digenean-induced mortality could be involved, a 50-d laboratory experiment was performed. Mudsnails hosting digeneans with rediae (as Haploporidae or Heterophyidae) displayed significantly higher mortality rates than mudsnails hosting sporocysts (as Microphallidae) or healthy mudsnails. The present study demonstrates that digenean parasites induce population structure changes and shorten lifespan of mudsnails, through increasing size-dependent mortality.

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