Variability in First-Year Growth of Yellow Perch (Perca flavescens): Predictions from a Simple Model, Observations, and an Experiment

1994 ◽  
Vol 51 (11) ◽  
pp. 2501-2512 ◽  
Author(s):  
John R. Post ◽  
Donald J. McQueen
Keyword(s):  
Simple Model ◽  
Growth Rates ◽  
Yellow Perch ◽  
Explanatory Power ◽  
Perca Flavescens ◽  
Negative Relationship ◽  
Zooplankton Community ◽  
Prey Abundance ◽  
First Year ◽  
Growth Variability

First-year growth of yellow perch, Perca flavescens, varies by greater than an order of magnitude among populations and among cohorts within populations. The variability in growth rates of natural and enclosure-reared young-of-the-year yellow perch could be explained by the availability of benthic and/or plank-tonic prey (R2 = 0.093–0.098). Mean annual water temperature and cumulative degree-days did not add to the explanatory power of the relationships. The faster growing natural cohorts included more benthos in their diet; however, benthos is not necessary to sustain the highest growth rates because the fastest growth rates were observed in enclosure cohorts that lacked benthic invertebrates. Cohorts in lakes and enclosures that had a high proportion of Daphnia in the zooplankton community also supported higher first-year growth rates. The results of the enclosure experiment suggest that the dominant mechanism creating growth variability is density-dependent intra-age-class competition. Our empirical results, when coupled with a simple model, suggest that the assumption of a negative relationship between energetic costs of foraging and prey abundance, on a daily time scale, is the most appropriate because it acts to amplify growth variability across ranges of prey abundance.

Environmental factors affecting growth of eastern sand darter (Ammocrypta pellucida)

2008 ◽  
Vol 86 (7) ◽  
pp. 714-722 ◽  
Author(s):  
D. A.R. Drake ◽  
M. Power ◽  
M. A. Koops ◽  
S. E. Doka ◽  
N. E. Mandrak
Keyword(s):  
Environmental Factors ◽  
Growth Rates ◽  
First Year ◽  
High Discharge ◽  
Factors Affecting ◽  
Growth Variability ◽  
Substrate Composition ◽  
Structured Population ◽  
Northern Edge ◽  
First Year Of Life

Environmental factors affecting growth of the threatened eastern sand darter ( Ammocrypta pellucida (Putnam, 1863)) were examined using specimens sampled from the northern edge of its range to determine the species’ critical habitat. Length-at-age increments were determined from scale samples as surrogates for growth rates based on back-calculated lengths using the Fraser–Lee method. During the first year of life, 82% of total length is attained, suggesting considerable energetic partitioning towards reproduction following age-0. Positive relationships between age-0 length increments and sand substrates and between age-0 length increments and mean annual channel discharge indicated greatest first-year growth within sand-dominated, high-discharge habitats. Environmental factors that occurred at coarse spatial and temporal levels (i.e., mean annual channel discharge) explained more of the growth variability among eastern sand darters than those occurring at fine levels (i.e., site-level substrate composition). This study indicates that environmental factors can be used to explain variability in cohort-structured population and site-level growth of eastern sand darters.

Changes in Yellow Perch (Perca flavescens) Populations of Lake Michigan, 1954–75

1977 ◽  
Vol 34 (10) ◽  
pp. 1821-1829 ◽  
Author(s):  
LaRue Wells
Keyword(s):  
Population Dynamics ◽  
Growth Rates ◽  
Yellow Perch ◽  
Lake Michigan ◽  
Perca Flavescens ◽  
Commercial Production ◽  
Alosa Pseudoharengus ◽  
Exploitation Competition ◽  
Sport Fishery ◽  
High Production

In the early and mid-1960s the abundance of yellow perch (Perca flavescens) in Lake Michigan declined abruptly. The decline began in the northern part of the lake and spread progressively southward. Circumstantial evidence suggests that the nonnative alewife (Alosa pseudoharengus), by interfering with perch reproduction, was the primary cause of the decline. The alewife was first reported in northeastern Lake Michigan in 1949, and had become extremely abundant throughout the lake before an enormous die-off in 1967 reduced its numbers by an estimated 70%. An intensive fishery hastened the decline of perch. In most areas the decline was immediately preceded by a period of conspicuously high commercial production. This high production appears to have been related in part to increased growth rates of perch resulting from much lower density of younger fish. A sport fishery for perch in shallow water collapsed a few years before the species declined in abundance. The most logical explanation is that heavy concentrations of alewives physically displaced the perch from nearshore areas. Although perch populations increased in some areas in the 1970s, a full recovery is unlikely unless alewife numbers are further reduced. Key words: Percidae, Lake Michigan, Perca, population dynamics, exploitation, competition

Comparison of activity rates of 1+ yellow perch (Perca flavescens) from populations of contrasting growth rates using underwater video observations

1999 ◽  
Vol 56 (6) ◽  
pp. 1122-1132 ◽  
Author(s):  
N Aubin-Horth ◽  
J Gingras ◽  
D Boisclair
Keyword(s):  
Growth Rates ◽  
Yellow Perch ◽  
Perca Flavescens ◽  
Daily Consumption ◽  
Lower Growth ◽  
Average Growth ◽  
Video Observations ◽  
Consumption Rates ◽  
The Difference ◽  
Two Populations

We compared the stereocinematographic (SCG) method to estimate activity rates of yellow perch (Perca flavescens) with the more traditional bioenergetic approach. We also compared activity rates of perch from two populations with contrasting growth rates to test the hypothesis that fish with lower growth rates are characterized by higher activity rates. We attempted to corroborate the SCG method by comparing values of energetic costs obtained with observations of fish movements with estimates obtained using the difference between field-derived consumption and growth rates (bioenergetic method). Independent estimates of consumption and activity rates were obtained for Lakes Hertel (average growth = 172 J·day-1) and Memphremagog (average growth = 595 J·day-1). Daily consumption rates averaged 720 J·day-1 in Lake Hertel and 1457 J·day-1 in Lake Memphremagog. SCG and bioenergetic methods provided similar activity estimates for Lake Hertel (<2.5% difference) and diverged by 0.4-82% for Lake Memphremagog depending on initial values of fish weight or consumption inputted in the bioenergetic equation. Regardless of the method employed, activity rates of fish from Lake Hertel were proportionally higher (24% of consumption rates) than those from Lake Memphremagog (on average 13% of consumption rates). Our work supported the suggestion that populations with slower growth rates may be associated with proportionally higher activity rates.

Trophic interactions between yellow perch (Perca flavescens) and their benthic prey in a littoral zone community

1998 ◽  
Vol 55 (1) ◽  
pp. 28-36 ◽  
Author(s):  
Susan E Cobb ◽  
Mary C Watzin
Keyword(s):  
Growth Rates ◽  
Benthic Community ◽  
Littoral Zone ◽  
Yellow Perch ◽  
Perca Flavescens ◽  
Resource Limitation ◽  
Fish Predation ◽  
High Density ◽  
Density Treatment ◽  
Benthic Prey

Yellow perch (Perca flavescens) growth rates in northern Lake Champlain have declined in recent years while densities have increased, suggesting resource limitation. At high densities, predators have the potential to influence prey communities, but these effects can be highly complex. Using in situ mesh cages in an unmanipulated littoral zone setting, we examined the effects of two densities (0.5 and 1.5/m2) of yellow perch on (i) their growth and (ii) the abundance of major prey groups in the benthic community. Yellow perch growth rates were significantly lower in the high-density treatment than in the low-density treatment. Because site characteristics were not manipulated, measured covariates reflecting sediment and vegetation variation between cages were used to help clarify treatment effects on benthos. Fish predation on invertebrate prey was significant only in the high-density predator treatment for three of the six prey groups examined (predatory chironomids, prey chironomids, and isopods). For this littoral zone community, availability and abundance of benthic prey strongly influenced yellow perch growth rates; but the effect of yellow perch predation on benthic community structure was only moderate.

Among-Population Variability of Fish Growth: I. Influence of the Quantity of Food Consumed

1989 ◽  
Vol 46 (3) ◽  
pp. 457-467 ◽  
Author(s):  
D. Boisclair ◽  
W. C. Leggett
Keyword(s):  
Water Temperature ◽  
Food Consumption ◽  
Growth Rates ◽  
Yellow Perch ◽  
Prey Availability ◽  
Significant Proportion ◽  
Prey Type ◽  
Population Variability ◽  
Fish Growth ◽  
Growth Variability

We assessed the relationship between in situ fish growth and food consumption for a series of yellow perch (Perca flavescens) populations that exhibited a 1.8 to 10-fold range in growth rates on a weight basis. Perch from 12 populations (lakes) and three year–classes (I +, II +, and III +) were sampled at 3–4 wk intervals from late May to late September 1985. On each occasion, water temperature profile and daily ration were determined. Among-lake water temperature differences were minimal (of the 12 lakes studied 10 had mean water temperatures of 19.0 ± 1 °C) and could not explain growth differences. Food consumption covered a four-fold range within each age–class and varied significantly among populations but not among age–classes. Food consumption explained a significant proportion of among-population variability in perch growth rates only for age I + fish (r2 = 0.52). We argue that other factors such as prey type, prey availability, and fish community descriptors are important determinants of among-population growth variability in the lakes we studied, and by implication, in other systems.

Among-Population Variability of Fish Growth: III. Influence of Fish Community

1989 ◽  
Vol 46 (9) ◽  
pp. 1539-1550 ◽  
Author(s):  
D. Boisclair ◽  
W. C. Leggett
Keyword(s):  
Growth Rates ◽  
Yellow Perch ◽  
Fish Community ◽  
Negative Relationship ◽  
Average Density ◽  
Population Variability ◽  
Fish Growth ◽  
Taxonomic Groups ◽  
Food Consumed

We assessed the relationship between in situ fish growth and fish community descriptors in 12 yellow perch (Perca flavescens) populations that exhibited a 1.8 to 10-fold range in growth rates depending on age class. Data on the quantity and quality of food consumed were used to assess the mechanisms by which fish community composition influences in situ growth rates. Among-population variability in growth rates of the 12 perch populations was most strongly and consistently explained by the average density of the total fish community and/or the average density of cyprinids. A multivariate model involving fish average density and perch feeding levels explained 90% of the variance in perch growth. Perch growth rates decreased as fish average density increased (r2 = 0.60) and increased as feeding levels increased (r2 = 0.30). We found no significant relationship between the quantity of food consumed by perch and fish average density. The percent contribution of prey taxonomic groups to perch diet was not related to fish average density. We suggest that nonexploitative interactions (operating through increased activity costs) provides a more credible explanation for the negative relationship between perch growth and fish average density than does exploitative competition (decreased total quantities of food consumed or prey quality).

scholarly journals Examining GDP Growth and Its Volatility: An Episodic Approach

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 890
Author(s):  
Jakub Bartak ◽  
Łukasz Jabłoński ◽  
Agnieszka Jastrzębska
Keyword(s):  
Economic Growth ◽  
Genetic Algorithm ◽  
Time Series ◽  
Human Capital ◽  
Growth Rates ◽  
Structural Breaks ◽  
Negative Relationship ◽  
Gdp Per Capita ◽  
Gdp Growth ◽  
Per Capita

In this paper, we study economic growth and its volatility from an episodic perspective. We first demonstrate the ability of the genetic algorithm to detect shifts in the volatility and levels of a given time series. Having shown that it works well, we then use it to detect structural breaks that segment the GDP per capita time series into episodes characterized by different means and volatility of growth rates. We further investigate whether a volatile economy is likely to grow more slowly and analyze the determinants of high/low growth with high/low volatility patterns. The main results indicate a negative relationship between volatility and growth. Moreover, the results suggest that international trade simultaneously promotes growth and increases volatility, human capital promotes growth and stability, and financial development reduces volatility and negatively correlates with growth.

scholarly journals Genre Knowledge and Writing Development: Results From the Writing Transfer Project

2019 ◽  
Vol 37 (1) ◽  
pp. 69-103 ◽  
Author(s):  
Dana Lynn Driscoll ◽  
Joseph Paszek ◽  
Gwen Gorzelsky ◽  
Carol L. Hayes ◽  
Edmund Jones
Keyword(s):  
General Education ◽  
Institutional Design ◽  
Explanatory Power ◽  
Theoretical Work ◽  
Writing Development ◽  
First Year ◽  
Writing Courses ◽  
Key Factor ◽  
Genre Knowledge ◽  
Audience Awareness

Using a mixed-methods, multi-institutional design of general education writing courses at four institutions, this study examined genre as a key factor for understanding and promoting writing development. It thus aims to provide empirical validation of decades of theoretical work on and qualitative studies of genre and the nature of genre knowledge. While showing that both simplistic and nuanced genre knowledge promote writing development, our findings suggest that nuanced genre knowledge correlates with writing development over the course of a semester. Based on these findings, we propose an expanded view of Tardy’s four genre knowledge components and argue for their explanatory power. We recognize these genre components can be cultivated by using three particular strategies: writing for nonclassroom audiences, using source texts explicitly to join existing disciplinary conversations, and cultivating two types of metacognitive awareness (awareness of the writing strategies used to complete specific tasks and awareness of one’s levels of proficiency in particular types of writing knowledge). Findings can be used to enrich first-year or upper-division writing curricula in the areas of genre knowledge, audience awareness, and source use.

scholarly journals Spatial Disparities of COVID-19 Cases and Fatalities in United States Counties

2021 ◽  
Vol 18 (16) ◽  
pp. 8259
Author(s):  
Sarah L. Jackson ◽  
Sahar Derakhshan ◽  
Leah Blackwood ◽  
Logan Lee ◽  
Qian Huang ◽  
...  
Keyword(s):  
United States ◽  
Great Plains ◽  
Explanatory Power ◽  
Temporal Trends ◽  
The United States ◽  
First Year ◽  
Significant Case ◽  
Urban Rural ◽  
Spatial And Temporal Trends ◽  
Mitigation Policies

This paper examines the spatial and temporal trends in county-level COVID-19 cases and fatalities in the United States during the first year of the pandemic (January 2020–January 2021). Statistical and geospatial analyses highlight greater impacts in the Great Plains, Southwestern and Southern regions based on cases and fatalities per 100,000 population. Significant case and fatality spatial clusters were most prevalent between November 2020 and January 2021. Distinct urban–rural differences in COVID-19 experiences uncovered higher rural cases and fatalities per 100,000 population and fewer government mitigation actions enacted in rural counties. High levels of social vulnerability and the absence of mitigation policies were significantly associated with higher fatalities, while existing community resilience had more influential spatial explanatory power. Using differences in percentage unemployment changes between 2019 and 2020 as a proxy for pre-emergent recovery revealed urban counties were hit harder in the early months of the pandemic, corresponding with imposed government mitigation policies. This longitudinal, place-based study confirms some early urban–rural patterns initially observed in the pandemic, as well as the disparate COVID-19 experiences among socially vulnerable populations. The results are critical in identifying geographic disparities in COVID-19 exposures and outcomes and providing the evidentiary basis for targeting pandemic recovery.

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