Effects of Climatic and Density-Dependent Factors on Year-Class Strength of Coregonus lavaretus in Lake Constance

1988 ◽  
Vol 45 (6) ◽  
pp. 1088-1093 ◽  
Author(s):  
Reiner Eckmann ◽  
Ursula Gaedke ◽  
Hans Johst Wetzlar
Keyword(s):  
Thermal Stratification ◽  
Negative Influence ◽  
Meteorological Conditions ◽  
Lake Constance ◽  
Coregonus Lavaretus ◽  
Age Classes ◽  
Final Model ◽  
Density Dependent ◽  
Class Strength ◽  
Stock Recruitment

The influences of density-dependent and density-independent factors on year-class strength (YCS) of Coregonus lavaretus in Lake Constance were studied by multiple linear regression analyses for the period from 1962 to 1982. Meteorological conditions that lead to early thermal stratification of the lake in April are of prime importance for YCS and account for 41% of the total YCS variance. Zooplankton concentration during spring has no significant influence on YCS. The extensive stocking program on the lake (50–200 million larvae stocked per year) significantly supports YCS, but this relationship becomes apparent only after the influence of meteorological conditions are removed from the data. Conspecifics of age-classes 1 and 2 have a negative influence on the age 0 year-class, but the nature of this intraspecific competition remains unknown. No stock–recruitment relationship could be detected in this study. The final model includes five independent variables and accounts for 84% of the total YCS variance.

scholarly journals The influence of eutrophication and population biomass on common whitefish (Coregonus lavaretus) growth — the Lake Constance example revisited

2007 ◽  
Vol 64 (3) ◽  
pp. 402-410 ◽  
Author(s):  
Gregor Thomas ◽  
Reiner Eckmann
Keyword(s):  
Linear Regression Analysis ◽  
Standing Stock ◽  
Nutrient Content ◽  
Multiple Linear Regression Analysis ◽  
Lake Constance ◽  
Coregonus Lavaretus ◽  
Density Dependent ◽  
Stock Biomass ◽  
Evolutionary Response ◽  
The Impact

Accelerated growth of freshwater fish during anthropogenic eutrophication has been attributed almost exclusively to the increased nutrient content, while density-dependent effects have been largely neglected. We evaluated the relative importance of these factors by studying the growth of 43 consecutive year classes of common whitefish (Coregonus lavaretus) from Upper Lake Constance. This prealpine lake underwent eutrophication from the 1950s to 1970s, followed by reoligotrophication. Because whitefish are harvested with gill nets in a strongly size-selective way, we used back-calculated lengths of average fast-growing fish to compare growth among cohorts. Standing stock biomass was estimated based upon virtual year-class strengths. Multiple linear regression analysis revealed that growth of whitefish during their second year was most strongly related to standing stock biomass followed by PO4-P content during spring turnover and by calendar year, which was incorporated as a third independent variable (adjusted R2 = 0.84). The negative correlation between whitefish growth rate and calendar year is interpreted as evidence of an evolutionary response to the highly size-selective fishery during at least four decades. We conclude that density-dependent effects on whitefish growth are more important than had been realized previously and that the impact of eutrophication on growth of whitefish needs to be reconsidered.

Effects of Density-Dependent and Climatic Factors on American shad, Alosa sapidissima, Recruitment: A Predictive Approach

1986 ◽  
Vol 43 (2) ◽  
pp. 457-463 ◽  
Author(s):  
Victor Crecco ◽  
Thomas Savoy ◽  
Walter Whitworth
Keyword(s):  
River Flow ◽  
Climatic Factors ◽  
American Shad ◽  
Connecticut River ◽  
Alosa Sapidissima ◽  
Density Dependent ◽  
Class Strength ◽  
Stock Recruitment ◽  
Parent Stock ◽  
Recruitment Variability

We developed environment-dependent stock–recruitment models for American shad, Alosa sapidissima, in the Connecticut River to forecast recruitment variability and measure density-dependent effects. These models were fitted to the 1966–78 stock–recruitment estimates and to May and June river flow, water temperature, and rainfall data shown previously to affect American shad year-class strength. We also attempted to validate the models by forecasting the 1979–84 year-classes based on juvenile indices, parent stock size, and hydrographic data for these years. The stock–recruitment models without environmental factors explained less than 3% of the recruitment variability, and none of the density-dependent exponents were statistically different from 0. The predictive capability of the Ricker stock–recruitment model improved dramatically (r2 = 0.90) when combined with mean May flows, June flows, and the number of American shad lifted over the Holyoke Dam. The density-dependent exponents of these multiple regression models were highly significant, indicating that density-dependent processes are hidden by climatically induced variability in recruitment. Two environment-dependent stock–recruitment models predicted 80–90% of the American shad recruitment variability from 1979–84.

The Thermal Regime of South Bay, Manitoulin Island

1967 ◽  
Vol 24 (1) ◽  
pp. 101-125 ◽  
Author(s):  
A. M. McCombie
Keyword(s):  
Thermal Regime ◽  
Thermal Stratification ◽  
Yellow Perch ◽  
Lake Trout ◽  
Smallmouth Bass ◽  
Lake Huron ◽  
Vertical Temperature ◽  
Class Strength ◽  
Influence Of Temperature On ◽  
History Of

The thermal regime of South Bay is described from records collected from 1953 to 1962 with thermometers, thermographs, and bathythermographs, the last being cast at 11 stations along the bay and one in Lake Huron. Warming begins in April and thermal stratification is established in June. Shallow areas warm more rapidly than deep in the spring and cool more quickly in autumn. The boundary between the epilimnion and the thermocline becomes sharper as summer advances but the transition from thermocline to hypolimnion remains gradual. The average seasonal trend of surface temperatures is a sine function with a maximum of 66 F in mid August and a minimum of 34 F in late March, though values outside this range occur frequently. At 180 ft the maximum of 47 F is attained in November. At the lake and outermost bay stations there is a temperature slump in June and July which may be due to an upwelling in the lake. Evidence of an exchange of water between the lake and bay is seen in vertical temperature sections and water movements Variations in epilimnial temperatures are correlated with those of the air temperature, but variations in epilimnial and hypolimnial temperatures appear to be unrelated. Finally, literature describing the influence of temperature on the year class strength of smallmouth bass, the distribution of lake trout, the growth of yellow perch, and the life history of Pontoporeia in South Bay is reviewed.

Influences on the natural reproduction of whitefish (Coregonus lavaretus) in Lake Constance

2009 ◽  
Vol 66 (4) ◽  
pp. 547-556 ◽  
Author(s):  
Bernd Wahl ◽  
Herbert Löffler
Keyword(s):  
Age Structure ◽  
Lake Constance ◽  
Coregonus Lavaretus ◽  
Low Oxygen ◽  
Stock Size ◽  
Natural Reproduction ◽  
Lake Bottom ◽  
Oxygen Conditions ◽  
Spawning Time ◽  
The Impact

The conditions for the natural reproduction of whitefish ( Coregonus lavaretus ) in Lake Constance have been subject to strong variations during recent decades by the impact of fishing and trophic changes. We analysed fluctuations of stock size, age structure, spawning time, and amount of sampled eggs of this species. The onset of spawning altered because of changes in the age structure of the stock. We found a clear relation of spawning time to the mean age of the annual catch and the November epilimnion temperature. The quantity of eggs sampled from the lake bottom with a dredge is in relation to the number of female spawners and may serve as an early indicator for stock size changes. The proportion of viable eggs on the lake floor correlates with oxygen concentrations in deep water. Extremely low oxygen conditions and an almost total loss of eggs occurred when the nutrient levels were high and oxygen regeneration by vertical winter mixing was weak. A mathematical model serves to interpret the changing abundance of living eggs on the lake bottom over the course of a season and is also used to estimate mortality rates.

scholarly journals Influence of climate variability on whitefish (Coregonus lavaretus) year-class strength in a deep, warm monomictic lake

Oecologia ◽  
2006 ◽  
Vol 151 (3) ◽  
pp. 521-529 ◽  
Author(s):  
Dietmar Straile ◽  
Reiner Eckmann ◽  
Tobias Jüngling ◽  
Gregor Thomas ◽  
Herbert Löffler
Keyword(s):  
Climate Variability ◽  
Coregonus Lavaretus ◽  
Class Strength

Quasi-cycles in crappie populations are forced by interactions among population characteristics and environment

2001 ◽  
Vol 58 (3) ◽  
pp. 594-601 ◽  
Author(s):  
Micheal S Allen ◽  
Leandro E Miranda
Keyword(s):  
Time Series ◽  
Environmental Conditions ◽  
Empirical Data ◽  
Population Model ◽  
Population Characteristics ◽  
Environmental Fluctuation ◽  
Density Dependent ◽  
Stock Recruitment ◽  
Variable Recruitment ◽  
Random Fluctuations

Crappie (Pomoxis spp.) populations have been characterized as cyclic, with strong year-classes recurring at 2- to 4-year intervals. We evaluated the potential for cyclic trends in crappie populations using a population model that included a density-dependent stock recruitment function and random environmental variation. Slow, medium, and fast growth were simulated over 100 years. The model predicted highly variable recruitment that was strongly influenced by environmental fluctuation at low and intermediate stock densities. At high stock density, recruitment was low, even if environmental conditions were favorable. Significant quasi-cycles occurred, but they were not sustained throughout the time series due to random environmental fluctuation. Quasi-cycles occurred because intermediate stock density and favorable environmental conditions occasionally combined to produce a very strong year-class that greatly increased stock density in the following 1–3 years and produced low recruitment, even if environmental conditions were favorable. Empirical data from 32 years of sampling age-0 crappies at Ross Barnett Reservoir showed trends similar to the simulated fluctuations. We conclude that crappie populations likely do not exhibit true cycles but may show quasi-cycles as a result of the interaction between random fluctuations in environment and density-dependent mechanisms. The frequency of such quasi-cycles may be enhanced by rapid growth and high exploitation.

Stock-Recruitment Relationship for Atlantic Salmon (Salmo salar) in Newfoundland Rivers

1982 ◽  
Vol 39 (11) ◽  
pp. 1496-1501 ◽  
Author(s):  
E. M. P. Chadwick
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Winter Temperature ◽  
Supportive Evidence ◽  
Atlantic Salmon Salmo Salar ◽  
Egg Deposition ◽  
Class Strength ◽  
Stock Recruitment ◽  
Indian River

A stock-recruitment relationship was developed for Atlantic salmon (Salmo salar) in Western Arm Brook, a small Newfoundland river. Supportive evidence was also found on Indian and Little Codroy, two other Newfoundland rivers. On Western Arm Brook, year-class strength of smolts was correlated (P < 0.01) with egg deposition. On Little Codroy River, smolt year-class strength was correlated (P < 0.01) with potential egg deposition of adults counted as kelt. On Indian River egg to fry survival was correlated (P < 0.01) with winter temperature and discharge. On the basis of these findings, the current recommended egg deposition of 2.4 eggs∙m−2 of parr-rearing habitat was considered inadequate for Newfoundland rivers.Key words: stock-recruitment, Atlantic salmon

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