The market carps are fished out in the autumn of the thiird or fourth growth year, and 

 are either sold at once or after a shorter or longer time of storage. The main demand 

 occurs in the Christmas and New Year season and increases considerably during the Lenten 

 season of the following calendar year. The commercial size classes are designated as 20'3, 

 25's, 30's, /iO's, etc., which means that 30 or 40, etc., carps -weigh 50 kilograms. 



It must be emphasized that the general industry of carp culture as described above 

 is not always completely and purely of that type. Many fisheries sell a part of their 

 fish stock, that is, they only partly rear these fishes. Others again must buy additional 

 carp stock and then keep them only one or two years until they have grown to market sized 

 fishes. The general and partial industry frequently work together. 



It is only a small step to the purely specialized industry. The larger special 

 industry is fully equal in its specialty to a corresponding growth division of the general 

 industiy. These specialties may be pure fish stock production of carp alevins, yearling 

 carps, or two year carps; or the growing of yearling carps to two year agej or the main- 

 tenance and growing of carps for market size production and a corresponding stock pro- 

 duction with one or two i'ear rotations; or a maturing industry with a one or twD year 

 rotation, A special treatment is not necessary. Only the basic principles of the small 

 pond industry are specially compiled. 



C. Side-lines in carp culture . 



Value and disadvantages of secondary fishes. 



Modern trout fisheries hardly ever go in for side lines, nowadays. On the other 

 hand, few carp fisheries raise carp exclusively. Almost all of them go in for side lines. 

 The underlying idea is to increase business, that is, make more profits, but it must be 

 kept in mind that the culture of side lines makes the raising of carp more difficult and 

 more complicated. Like in agriculture, "mixed crops" increase the returns but complicate 

 the harvesting at the same time. For small fisheries, run upon a simple scale the 

 culture of side lines is hardly to be recommended. 



The Tench (Tinea vulgaris) 



The most common side line of carp fisheries is tench breeding. So common is this 

 custom that some fisheries are known as "carp and tench fisheries". The tench is (Tinea 



vulgaris Guv.) (Fig. 21) 



The raising of tench is usually done in the carp developnent and maturing ponds. 

 Several spawning tench are simply placed with the carp. A great evil, justly called 

 "tench mischief by the tench industry, is the great over-production of small tench brood. 

 The brood is mostly set out year after year and much too abundantly, so that finally from 

 over-aging it again spawns before it has grown to market size. 



Because tench are native fishes they are extraordinarily easily propagated, and there- 

 fore only one female per hectar shoxild be placed so as to avoid production of too many and 

 too small yearling tench. The females are distinguished from the males by far weaker and 

 shorter developed ventral fins and weaker appearing pelvic bones, (see Fig. 21). 



Great difficulties are caused if they are allowed to spawn in special spawning ponds 

 (after the carp in the same Dubisch ponds), because the brood is difficult to fish out. 

 Cn the other hand, Schaeperclaus (1930) has recently developed another "two pond method" 

 for producing yearling tench: Spawning tench in greater numbers are set in carp nursing 

 ponds (or special tench nursing ponds). By a late fishing out of the nursing ponds in 

 the first days of August, nursling tench about 3 cm. long can be fished out and separated 

 on micro-sorting tables from the carp and tadpoles, and set out in brood nursing ponds. 

 They remain in these ponds until the following spring. This is a great advantage on 

 account of the unusual difficulties of fish ins-out tench which like to creep into the 

 mud (use special sieve boxes) and they have verj' sensitive skins. 



