Abstract:
Ornamental fish farming is one of the important economic activities in Sri Lanka because of its
natural resources. Minerals and nutrients are playing a crucial role in the survival of fishes. Among
the minerals, Calcium (Ca2+) is plays a significant role in the growth and reproduction of
ornamental fishes. Calcium in the form of hardness (CaCO3) in aquifers of Vavuniya (Northern
province) is more enriched than Southern Sri Lanka. This natural resource of water is suitable for
some ornamental fish farming in this region. Therefore, the main focus of this study is to find out
the high propagation probability of live bearer and/or egg layer fish along with varying water
hardness. Virgin Poecilia reticulata (live bearer, n=360) and Betta splendens (egg layer, n =240)
of both sexes were randomly selected and reared for 8 weeks at 150 mg/L (control), 320 mg/L, 540
mg/L & 900 mg/L CaCO3 (hardness) in semi-natural aquaria with 3 replicates. Propagation studies
were conducted to find gonadosometic index (GSI), fecundity, fertility and hatchability of both
species in each set up. Propagation of P. reticulata was significantly greater than (p = 0.016) B.
splendens in hard water (900 mg/L). Supportively, GSI and fecundity were boosted in high water
hardness (540 & 900 mg/L) in P. reticulata. However, B. splendens did not show any significant
variation with increasing water hardness. The bubble nest size and hatchability are the unique
reproduction potential of B. splendens and it was severely affected by increasing hardness (540 &
900 mg/L). Larval growth performance and survival rate also higher in P. reticulata than B.
splendens up to 900 mg/L. Therefore, P. reticulata is the suitable ornamental fish for propagation
compared to B. splendens. As P. reticulata utilize the benefit of water hardness in a positive way,
ornamental trade of live bearers like P. reticulata will aid to uplift the socioeconomic status of the
local people in Vavuniya. However, the fate of egg layers should be monitored in specific hard
waters systems for viable propagation. Thus, the role of Vavuniya Campus is necessary to train the
students for accelerating extension service to the society.
