Features Connected with the Spawning of British Coarse Fish

British Coarse fish can be divided into two groups according to date of spawning, March-June and May-July. When these are tabled it is clear that the species in each category have certain features in common and differ from those of the other categories, although with some overlap.

 

Spawning Season

 

March-June

 

May-July

 

Day lengthIncreasingLong, increasing
TemperatureRising (10-15 degrees C)Warm (above 16 degrees C)
Condition of rooted plantsGrowingFully grown
Location of eggs:  
Laid amongst stones  
Stuck to stones          
Minnow, Barbel, Chub, Loach,
Gudgeon, Bullhead
 
In nests in gravel         Grayling 
Among weeds               PerchRuffe
Stuck to weeds            
      
Pike
Roach, Rudd, Carp, Bream,
Tench,
In a nest of weeds         Stickleback
Diameter of Eggs1.3 to 3.2 mm0.5 to 1.7mm
Length of fry when ready to feed4 to 8mm2.5 mm plus
Time between laying and:  
hatching of eggs4 to 28 days3 to 20 days
fry ready to feed  3 to 7 weeks1 to 4 weeks
Food of young fryDiatoms, water fleas and rotifers (different from food of older fish)

 

Important features are the size of the eggs and where they are laid, the time taken to develop and the early habits of the fry.
For all fishes, the number of eggs laid each year is relative to the size of the female parent; the bigger she is, the more eggs she'll lay. Larger females may lay slightly larger eggs but the size of the eggs varies very little and is a characteristic of the species. Fish producing small eggs lay much larger numbers than fish of the same size belonging to another species which produces large eggs.
The eggs always contain some yolk which is used by the developing embryos. The little fish that hatches from the egg usually still has a yolk sac attached to it's ventral surface and is called an alevin. When all the yolk has been consumed, the little fish must seek food for itself and it is then called a fry.

Examples of the size and numbers of eggs in relation to the size of the parent fish are:

 

Species
Diameter of egg (mm)
Number laid per pound of
female body weight
Grayling3.2 - 4.0 mm3000 - 4500
Pike2.5 - 4.0 mm10,000 - 20,000
Perch2.0 - 2.5 mmapprox 100,000
Tench1.2 mmapprox 275,000
Carp0.9 - 1.2 mmup to 550,000

 

The small eggs of May-July spawning cyprinids are usually attached to water weeds. They contain very little yolk and develop quickly, hatching after a few days into very small alevins. The tiny, delicate fry can eat only minute organisms such as diatoms, rotifers and water fleas and their food is generally different from that of adults.
These small food organisms are very abundant in summer in still water or in the shallow weedy areas of rivers where there is little or no flow. In some species such as Carp and Bream, the fry have adhesive organs and attach themselves to plants.
Most of the March-June spawners lay their eggs among or attached to stones but perch and pike need rooted plants. The eggs are of medium size and develop in a few weeks into fry which are small and able to feed on only small organisms. Like the fry of the later spawners, these must find diatoms, rotifers and water fleas and must change their diet later to that of the adults.
The fry are bigger and slightly less delicate than those of the May-July spawners and the females lay generally fewer eggs.

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