The Population Density of Four Species of Freshwater Fish, Roach (Rutilus rutilus (L.)), Bleak (Alburnus alburnus (L.)), Dace (Leuciscus leuciscus (L.)) and Perch (Perca fluviatilis L.) in the River Thames at Reading

10.2307/2374 ◽  
1965 ◽  
Vol 34 (1) ◽  
pp. 173 ◽  
Author(s):  
W. P. Williams
Keyword(s):  
Population Density ◽  
Freshwater Fish ◽  
Perca Fluviatilis ◽  
Rutilus Rutilus ◽  
Roach Rutilus Rutilus ◽  
Perch Perca Fluviatilis ◽  
River Thames ◽  
Bleak Alburnus Alburnus

Fecundity of Two Cyprinid Fishes in the River Thames, Reading, England

1969 ◽  
Vol 26 (11) ◽  
pp. 2795-2805 ◽  
Author(s):  
I. Mackay ◽  
K. H. Mann
Keyword(s):  
Population Density ◽  
Egg Production ◽  
Rutilus Rutilus ◽  
Confidence Limits ◽  
Roach Rutilus Rutilus ◽  
Spawning Period ◽  
Cyprinid Fishes ◽  
River Thames ◽  
The Relationship ◽  
Bleak Alburnus Alburnus

Egg production by two cyprinids in the River Thames at Reading, England, was studied quantitatively from January to June 1966. Roach (Rutilus rutilus) had a short spawning period, shedding all their eggs in one batch, whereas bleak (Alburnus alburnus) had a protracted spawning period and produced two or three batches of eggs. The relationship between egg numbers (Y) and age (X) for roach was given by log Y = 0.0840X + 3.2085; the estimated fecundity of a 6-year-old fish was 5157 with 95% confidence limits at 4725 and 5631. For bleak the relationship was log Y = 0.0564X + 3.5221, and the estimated fecundity of a 5-year-old fish was 6356 with 95% confidence limits at 5987 and 6776. Combining previously obtained data on population density with new data on sex ratio and percentage breeding in each age class, the population fecundity for roach was about 600 eggs/m2 and for bleak about 3000 eggs/m2.The roach population had lower fecundity than roach populations in other studies and there was some evidence that a proportion of females ceased egg production during the period of the study. The possibility that low fecundity was a response to food shortage is discussed.

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