An evaluation of triploidy as a potential solution to the problem of precocious sexual maturation in common carp, Cyprinus carpio, in Karnataka, India

Precocious maturation and unwanted reproduction have been identified as potential constraints on yields of common carp in aquaculture and culture-based fisheries in Karnataka state, southern India. Both males and females can attain sexual maturation well before reaching a marketable size. Even if fish do not spawn and produce fry, the gonadosomatic index (GSI) can exceed 20% of the harvested weight of an individual fish. The use of sterile triploids may provide a solution to this problem. Based on modifications to previously published protocols, triploidy was induced using heat shocks (40 degreesC for 1.5 min starting 1-3 min post-fertilization). The culture performance of diploid and triploid fish was compared in a series of trials involving separate or communal stocking and monoculture or polyculture (with catla and rohu). Gonad development in triploids was typical of that seen in other species (very much reduced in females, rather less reduced in males, while diploid counterparts were mature). Diploid fish were generally heavier than triploid fish at the end of most of these trials, and female fish were generally heavier than male fish. However, when gutted weight was considered, the significant differences between diploid and triploid fish were removed, although females were still heavier than males in most trials. Thus, although these trials continued for several months beyond the typical time of first maturation in diploid common carp, triploid fish did not show any improvement over diploids apart from higher dressout percentages. (C) 2002 Elsevier Science B.V. All rights reserved.