Reproductive ability of endemic species of Lake Ajamaru Melanotaenia ajamaruensis Allen & Cross, 1980 on spawning at various sex ratio

Abstract

Melanotaenia ajamaruensis or Ajamaru Rainbowfish is endemic species of Lake Ajamaru, Papua, Indonesia. It belongs to Rainbowfish group, with data deficient status. They have attractive color, especially on male and has potential as an ornamental fish, but the percentage of male is low. A study was conducted to find out their reproductive ability at various sex ratios (male:female = 1:1; 1:2; or 1:3) with two replications for 40 days (January-February 2021) at Research Center for Limnology, LIPI. Observations were also conducted on sexual maturity age, egg diameter, size at a certain age. The ratio of 1:3 have the highest value on number of spawning (NoS): 25 times, number of eggs (NoE)/female: 54 eggs, number of larvae (NoL)/female: 49 larvae, fertilization rate/FR (%): 97.16; hatching rate/HR (%): 97.93; larvae survival at seven days /SR7 (%): 90.34, and eggs incubation time/EIT (days): 5.24. The sexual maturity on 8 months old. Egg diameter (mm): 0.98±0.043, larvae size (mm) at (0 day), and at 1, 2, 4, 8, 12 weeks old were: 3.2±0.68; and 6±0.74; 11.70±1.77; 19.48±1.86; 21.65±2.64; 25.0±2.94 respectively. Daily growth rate 0.26 mm/day That is indicates that M ajamaruensi could adapted well to ex-situ habitat and the reproduction could takes place with a small number of males (1:3).