Yellow Perch (Perca flavescens) Biomass Responses to Different Levels of Phytoplankton and Benthic Biomass in Lake Memphremagog, Quebec–Vermont

1975 ◽  
Vol 32 (10) ◽  
pp. 1785-1797 ◽  
Author(s):  
Brian S. Nakashima ◽  
William C. Leggett
Keyword(s):  
Yellow Perch ◽  
Perca Flavescens ◽  
Empirical Support ◽  
Growing Season ◽  
Trophic Levels ◽  
Controlled Systems ◽  
Order Of Magnitude ◽  
Second Year ◽  
The Difference ◽  
Different Levels

Perch biomass in Lake Memphremagog, Quebec was 2.5 times greater in the more productive south than in the less productive north basins. This difference is on the same order of magnitude as biomass differences in the phytoplankton (approximately 1.6×) and benthic (approximately 3×) communities. The difference in perch biomass is attributed to a larger perch population in the south basin. Growth was similar in both basins, and therefore independent of production at these lower trophic levels. Perch growth in both basins is maximal for the Quebec area and probably controlled by the length of the growing season. Abundance levels are fixed by the fourth year and possibly prior to reaching the second year of life. Perch biomass responses to different food levels in Lake Memphremagog provide empirical support to Moore’s (1941) suggestion that at abundant food levels, population size and not growth is enhanced. Previous experiments defining the relation between growth and nutrient concentration and/or primary production did not fully represent the situation in Lake Memphremagog. This may have been due to conditions in simple, controlled systems not usually found in natural, complex ones.

Walleye (Stizostedion vitreum vitreum) and Yellow Perch (Perca flavescens) Populations and Fisheries of the Red Lakes, Minnesota, 1930–75

1977 ◽  
Vol 34 (10) ◽  
pp. 1774-1783 ◽  
Author(s):  
Lloyd L. Smith Jr.
Keyword(s):  
Growth Rate ◽  
Yellow Perch ◽  
Climatic Factors ◽  
Perca Flavescens ◽  
Growing Season ◽  
Commercial Fishery ◽  
Class Strength ◽  
Parent Stock ◽  
Catch Statistics

In an investigation of the commercial fishery of Red Lakes, Minnesota, for the 46-yr period 1930–75, catch statistics were analyzed, and the dynamics of the perch and walleye populations were examined. Mean annual yields of walleye for two statistical periods, 1930–53 and 1954–75, were 309,900 and 245,100 kg, respectively for walleyes, and 96,400 and 109,500 kg for perch. Annual abundance (CPE based on average catches per day per 5-net units of gill nets) varied from 3.8 to 64.6 kg for walleye, and from 2.5 to 34.4 kg for perch. Causes of fluctuations in harvestable stock were directly related to strength of year-classes and to growth rate during the season of capture. Year-class strength was not related to the abundance of parent stock or of potential predators. The respective strengths of year-classes of perch and walleye in the same year were positively correlated (r = 0.859, P < 0.01), and are directly related to climatic factors. Growth rate of walleye in different calendar years varied from +30.7 to −42.2% of mean growth, and that of perch from +13.4 to −8.6% (1941–56). Growing season began in mid-June and was almost over by September 1. Walleye yield could be enhanced by starting harvest July 1 instead of early June. Perch yield could be improved by harvesting small perch. Key words: Percidae, Perca, population dynamics, Stizostedion, long-term yield

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.

Population differences in acid tolerance between yellow perch, Perca flavescens, from naturally acidic and alkaline lakes

1983 ◽  
Vol 61 (1) ◽  
pp. 147-152 ◽  
Author(s):  
Frank J. Rahel
Keyword(s):  
Yellow Perch ◽  
Perca Flavescens ◽  
Acid Tolerance ◽  
Low Ph ◽  
Alkaline Lakes ◽  
Low Salinity ◽  
Ph Tolerance ◽  
Body Sodium ◽  
The Difference ◽  
Laboratory Acclimation

Yellow perch, Perca flavescens, from naturally acidic, Wisconsin brownwater lakes survived longer than perch from alkaline lakes when exposed to a lethal pH in the laboratory. Acclimation to a low but sublethal pH for 3 weeks did not remove the difference in acid tolerance, suggesting it is genetically based. Perch from an acidic, low salinity lake (pH 4.6, 13 μequiv. Na/L, 11 μequiv. K/L) had only slightly lower body sodium and potassium levels than perch from a nonacidic, higher salinity lake (pH 7.6,70 μequiv. Na/L, 18 μequiv. K/L). Perch from both lake types were equally susceptible to a lethal high pH, indicating that acid tolerance is not merely the result of an overall hardiness, but reflects specific adaptation to low pH. The exceptional low pH tolerance of yellow perch from Wisconsin brownwater lakes rivals that reported for tropical blackwater fishes.

Size-Selective Mortality in Young-of-the-Year Yellow Perch (Perca flavescens): Evidence from Otolith Microstructure

1987 ◽  
Vol 44 (11) ◽  
pp. 1840-1847 ◽  
Author(s):  
John R. Post ◽  
Andrew B. Prankevicius
Keyword(s):  
Yellow Perch ◽  
Large Body ◽  
Perca Flavescens ◽  
Growing Season ◽  
Otolith Microstructure ◽  
Selective Mortality ◽  
Predator Species ◽  
Piscivorous Fish ◽  
Young Of The Year ◽  
Growing Population

Large body size and high growth rates can strongly influence the survival of larval and juvenile fish during periods of intense predation pressure. Experimental evidence suggests that piscivorous fish often feed size selectively, but direct field evidence of size-selective mortality and of the effect of rapid growth on the intensity of size-selective mortality is limited. We used the growth record from otolith microstructure to test the hypothesis that young-of-the-year yellow perch (Perca flavescens) that survived their first growing season were the larger and faster growing members of their cohort. Strong size-selective mortality was identified within the first growing season for a slowly growing population. During the same year, a faster growing population showed minimal size-selective mortality. In contrasting the two populations, differences in predator species composition confounded the growth rate size-selectivity relationship, but it was clear that size-selective predation could be intense, favouring the survival of the faster growing individuals within a population.

scholarly journals Mode Shape-Based Damage Detection Method (MSDI): Experimental Validation

2021 ◽  
Vol 11 (10) ◽  
pp. 4589
Author(s):  
Ivan Duvnjak ◽  
Domagoj Damjanović ◽  
Marko Bartolac ◽  
Ana Skender
Keyword(s):  
Boundary Conditions ◽  
Damage Detection ◽  
Mode Shape ◽  
Experimental Validation ◽  
Detection Method ◽  
Dynamic Properties ◽  
Damage Index ◽  
Main Principle ◽  
The Difference ◽  
Different Levels

The main principle of vibration-based damage detection in structures is to interpret the changes in dynamic properties of the structure as indicators of damage. In this study, the mode shape damage index (MSDI) method was used to identify discrete damages in plate-like structures. This damage index is based on the difference between modified modal displacements in the undamaged and damaged state of the structure. In order to assess the advantages and limitations of the proposed algorithm, we performed experimental modal analysis on a reinforced concrete (RC) plate under 10 different damage cases. The MSDI values were calculated through considering single and/or multiple damage locations, different levels of damage, and boundary conditions. The experimental results confirmed that the MSDI method can be used to detect the existence of damage, identify single and/or multiple damage locations, and estimate damage severity in the case of single discrete damage.

scholarly journals Six ultraviolet minutes for cleaner operating theatres

2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
R Bosco ◽  
S Gambelli ◽  
V Urbano ◽  
G Cevenini ◽  
G Messina
Keyword(s):  
Cross Sectional Study ◽  
Cross Sectional ◽  
Before And After ◽  
Operating Theatres ◽  
Cleaning Procedures ◽  
The Difference ◽  
Contamination Levels ◽  
Different Levels ◽  
Better Than ◽  
Final Cleaning

Abstract Background Sanitizing the operating theatres (OT) is important to minimize risk of post-operative infections. Disinfection procedures between one operation and another is less aggressive than final cleaning procedures, at the end of the day. Aim was assessing the difference of contamination: i) between different levels of disinfection; ii) before and after the use of a UVC Device (UVC-D). Methods Between December 2019/February 2020 a cross sectional study was conducted in OT in a real clinical context. 94 Petri dishes (PD) were used in 3 OT. Three different sanitation levels (SL1-3) were compared pre- and post-use of UVC-D: i) No cleaning after surgery (SL1); ii) after in-between cleaning (SL2); iii) after terminal cleaning (SL3). UVC-D was employed for 6 minutes, 3 minutes per bed side. PD were incubated at 36 °C and colony forming unit (CFU) counted at 48h. Descriptive statistic, Wilcoxon and Mann-Whitney tests were performed to assess the contamination levels in total, pre/post use of UVC-D, and between different sanitation levels, respectively. Results In total we had a mean of 3.39 CFU/PD (C.I. 2.05 - 4.74) and a median of 1 CFU/PD (Min. 0 - Max. 39), after UVC-D use we had a mean of 2.20 CFU/PD (C.I. 0.69 - 5.09) and a median of 0 CFU/PD (Min. 0 - Max. 133). The UVC-D led to a significant reduction of CFU (p &lt; 0.001). Without UVC-D we had a significant CFU drop (p &lt; 0.05) between SL1 and SL3. Using UVC-D, we observed significant reductions of contamination (p &lt; 0.05) between SL3 and SL1. Comparing SL1 (median 0) post UVC-D use vs SL2 pre UVC-D use (median 0.5), and SL2 post UVC-D use (median 0) vs SL3 pre UVC-D use (median 1) we had a significant reduction of contamination (p &lt; 0.05). Conclusions UVC-D improved environmental contamination in any of the three sanitation levels. Furthermore, the use of UVC-D alone was better than in-between and terminal cleaning. Although these encouraging results, the cleaning procedures executed by dedicated staff has to be considered. Key messages UVC are efficient to decrease contamination in operating theatres regardless of sanitation levels. The additional use of UVC technology to standard cleaning procedures significantly improves sanitation levels.

Insertion of vowels in English syllabic consonantal clusters pronounced by L1 Polish speakers

2021 ◽  
Vol 7 (1) ◽  
pp. 331-341
Author(s):  
Urszula Chwesiuk
Keyword(s):  
Language Learning ◽  
Teaching Methodology ◽  
English Studies ◽  
Vowel Reduction ◽  
Potential Influence ◽  
English System ◽  
The Difference ◽  
Practical Implications ◽  
Different Levels

Abstract The aim of this study was an attempt to verify whether Polish speakers of English insert a vowel in the word-final clusters containing a consonant and a syllabic /l/ or /n/ due to the L1–L2 transfer. L1 Polish speakers are mostly unaware of the existence of syllabic consonants; hence, they use the Polish phonotactics and articulate a vocalic sound before a final sonorant which is deprived of its syllabicity. This phenomenon was examined among L1 Polish speakers, 1-year students of English studies, and the recording sessions were repeated a year later. Since, over that time, they were instructed with regard to phonetics and phonology but also the overall practical language learning, the results demonstrated the occurrence of the phenomenon of vowel insertion on different levels of advanced command of English. If the vowels were inserted, their quality and length were monitored and analysed. With regard to the English system, pronouncing vowel /ə/ before a syllabic consonant is possible, yet not usual. That is why another aim of this study is to examine to what extent the vowels articulated by the subjects differ from the standard pronunciation of non-final /ə/. The quality differences between the vowels articulated in the words ending with /l/ and /n/ were examined as well as the potential influence from the difference between /l/ and /n/ on the occurrence of vowel reduction. Even though Polish phonotactics permit numerous consonantal combinations in all word positions, it proved to be challenging for L1 Polish speakers to pronounce word-final consonantal clusters containing both syllabic sonorants. This result carries practical implications for the teaching methodology of English phonetics.

scholarly journals An experimental and theoretical investigation of diffusion in a two-phase alloy

1948 ◽  
Vol 192 (1031) ◽  
pp. 575-592 ◽  
Keyword(s):  
Free Energy ◽  
Single Phase ◽  
Phase State ◽  
Theoretical Treatment ◽  
Research Association ◽  
Essential Difference ◽  
Two Phase ◽  
Two Factors ◽  
Order Of Magnitude ◽  
The Difference

The present paper describes an investigation of diffusion in the solid state. Previous experimental work has been confined to the case in which the free energy of a mixture is a minimum for the single-phase state, and diffusion decreases local differences of concentration. This may be called ‘diffusion downhill’. However, it is possible for the free energy to be a minimum for the two-phase state; diffusion may then increase differences of concentration; and so may be called ‘diffusion uphill’. Becker (1937) has proposed a simple theoretical treatment of these two types of diffusion in a binary alloy. The present paper describes an experimental test of this theory, using the unusual properties of the alloy Cu 4 FeNi 3 . This alloy is single phase above 800° C and two-phase at lower temperatures, both the phases being face-centred cubic; the essential difference between the two phases is their content of copper. On dissociating from one phase into two the alloy develops a series of intermediate structures showing striking X-ray patterns which are very sensitive to changes of structure. It was found possible to utilize these results for a quantitative study of diffusion ‘uphill’ and ‘downhill’ in the alloy. The experimental results, which can be expressed very simply, are in fair agreement with conclusions drawn from Becker’s theory. It was found that Fick’s equation, dc / dt = D d2c / dx2 , can, within the limits of error, be applied in all cases, with the modification that c denotes the difference of the measured copper concentration from its equilibrium value. The theory postulates that D is the product of two factors, of which one is D 0f the coefficient of diffusion that would be measured if the alloy were an ideal solid solution. The theory is able to calculate D/D 0 , if only in first approximation, and the experiments confirm this calculation. It was found that in most cases the speed of diffusion—‘uphill’ or ‘downhill’—has the order of magnitude of D 0 . * Now with British Electrical Research Association.

Survival to hatching of fishes in sulfate-saline waters, Devils Lake, North Dakota

1995 ◽  
Vol 52 (3) ◽  
pp. 464-469 ◽  
Author(s):  
Todd M. Koel ◽  
John J. Peterka
Keyword(s):  
North Dakota ◽  
Sodium Sulfate ◽  
Yellow Perch ◽  
Hatching Success ◽  
Perca Flavescens ◽  
White Sucker ◽  
Catostomus Commersoni ◽  
Devils Lake ◽  
Common Carp Cyprinus Carpio ◽  
Species Survival

Laboratory-based bioassays were conducted to determine concentrations of sodium-sulfate type salinities that limit the hatching success of several fish species. Survival to hatching (SH) was significantly lower (P < 0.05) in sodium-sulfate type waters from Devils Lake, North Dakota, of ≥ 2400 mg/L total dissolved solids (TDS) than in fresh water of 200 mg/L. In waters of 200, 1150, 2400, 4250, and 6350 mg/L TDS, walleye (Stizostedion vitreum) SH was 41, 38, 7, 1, and 0%; northern pike (Esox lucius) SH was 92, 68, 33, 2, and 0%; yellow perch (Perca flavescens) SH was 88, 70, 73, 0, and 0%; white sucker (Catostomus commersoni) SH was 87, 95, 66, 0, and 0%; common carp (Cyprinus carpio) SH was 71, 69, 49, 63, and 25%.

Trapping Effect on the Kinetic Critical Radius in Nucleation and Growth Processes

2014 ◽  
Vol 790-791 ◽  
pp. 97-102
Author(s):  
Zoltán Erdélyi ◽  
Zoltán Balogh ◽  
Gabor L. Katona ◽  
Dezső L. Beke
Keyword(s):  
Critical Nucleus ◽  
Solid Phase ◽  
Kinetic Monte Carlo ◽  
Mean Field ◽  
Transformation Process ◽  
Nucleus Size ◽  
Critical Nucleus Size ◽  
Acta Mater ◽  
Order Of Magnitude ◽  
The Difference

The critical nucleus size—above which nuclei grow, below dissolve—during diffusion controlled nucleation in binary solid-solid phase transformation process is calculated using kinetic Monte Carlo (KMC). If atomic jumps are slower in an A-rich nucleus than in the embedding B-rich matrix, the nucleus traps the A atoms approaching its surface. It doesn’t have enough time to eject A atoms before new ones arrive, even if it would be favourable thermodynamically. In this case the critical nucleus size can be even by an order of magnitude smaller than expected from equilibrium thermodynamics or without trapping. These results were published in [Z. Erdélyi et al., Acta Mater. 58 (2010) 5639]. In a recent paper M. Leitner [M. Leitner, Acta Mater. 60 (2012) 6709] has questioned our results based on the arguments that his simulations led to different results, but he could not point out the reason for the difference. In this paper we summarize our original results and on the basis of recent KMC and kinetic mean field (KMF) simulations we show that Leitner’s conclusions are not valid and we confirm again our original results.

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