Water hardness influenced reproductive dynamics in two freshwater fish species; Poecilia reticulata and Betta splendens
Abstract Objective: Hardness of water in the form of CaCO3 affect reproductive potential in various fish species, differently. The study evaluates the effect of water hardness on growth and reproduction of two aquarium fishes, Poecilia reticulata (Ovo-viviparous sp.) and Betta splendens (Oviparous sp.) by growing them under 150 (control), 320, 540 and 900 ppm CaCO3 levels in semi natural aquaria. Results: Growth increased with increasing water hardness, reporting a significant growth of P. reticulata (p = 0.005) at 900 ppm. Similarly, the reproductive potential of P. reticulata was improved significantly, recording the highest fecundity (16.22 ± 3.90) and Gonadosomatic Index (GSI-2.48 ± 0.597) at 900 ppm. However, in B. splendens water hardness adversely affected the reproduction by reporting a significantly low hatchability and disturbed bubble nests at 900 ppm, compared to the largest bubble nest formed at the control (108.58 ± 16.19 cm2). Thus, study revealed differential effects of water hardness on reproductive potential of the test species, by increasing the potential of P. reticulata while decreasing that of B. splendens. Though larval survival was affected in both species, larval growth was improvement significantly in P. reticulata at 900 ppm level. Understanding reproductive dynamics in natural waters are crucial for propagation and conservation perspectives of freshwater fishes.