11-year cycle of spawning time and growth of the whitefish (Coregonus lavaretus) of Lake Constance

1984 ◽  
Vol 46 (1) ◽  
pp. 163-170 ◽  
Author(s):  
J. Hartmann
Keyword(s):  
Lake Constance ◽  
Coregonus Lavaretus ◽  
Spawning Time

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 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 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.

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