Fig. 21. Female Tench. Length 22 cm., 3 summers. In the male the 

 ventral fins are more strongly developed and reach almost to the anal fin. 



As already indicated, the culture of tench is generally in bad repute. Only in 

 the pond fishery in Quolsdorf, has systematic selection and constant separation of age 

 classes brought forth outstanding growth results: The Quolsdorf tench which under good 

 circumstances attains portion weight even after two years. According to Nordquist, a 

 good growing race introduced into Sweden surpassed in the second year the old race by 

 70 to 100 percent. Systematic breeding of rapid growing tench races, according to the 

 same basic principles as with the carp, is therefore the most important task for the 

 tench grower. 



The tench, as already stated, is hardly ever grown alone, but rather is used mostly 

 always as secondary stock in carp ponds. At present no conclusive Judgement can be 

 formed on the value of this procedure, because it must be also practically assumed that 

 it can be of a different character in individual ponds in accordance with local con- 

 ditions . 



Since the food of the tench is practically the same as that of the carp, the 

 advantage of secondary stock lies only in the increase of fish stock density. Walter 

 rightly emphasizes that this can just as well be attained by the addition of small 

 carps. Not more tench than 10 percent of the number of carps may be added, or else 

 the individual growth of the carps will suffer appreciably. Stronger additions of 

 tench will suppress the individual growth of the carps. However, the growth increase 

 per hectar rises thereby. At the customary intensity of tench additions the number of 

 the carps must be decreased. It has been shown to be advisable in practice, that to a 

 certain number of two-j'ear-carps not more than an equal number of two year tench be 

 added. I have repeatedly found that many pond operators have had special success by 

 setting in only half as many tench as carp, both of the two year age class. To yearling 

 carps there should be added not more than 100 to 200 percent of yearling tench if both 

 fish species are to have satisfactory individual growth. 



Formerly, there was a good market for tench, weighing l/^ ^° 1/3 of a pound, but to- 

 day the demand is mostly for 1/2 to 3/A pounds fish. They bring better prices than carp, 

 but the fishbreeder will make a real profit only then when he properly adjusts his fish- 

 ery to the necessary alterations. 



A 2 years old tench should reach a weight of from 50 to 100 grams. Smaller fish 

 would not reach the proper weight in the third year, while larger ones would increase the 

 costs of upkeep. The percentage individual grov/th would eventually become too small. 

 Von Milkau has recommended — in order to achieve such results — to stock the ponds with 

 about 200 carp (2 years old) and 200 tench (2 years old) per hectar, or 1,000 carps 

 (jnearlings) and 2,800 tench (yearlings) per hectar. 



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