Iron Fertilization Can Enhance the Mass Production of Copepod, Pseudodiaptomus annandalei, for Fish Aquaculture

Copepods are proven nutritious food sources for the mariculture/larviculture industry, however, unreliable methods for mass production of copepods are a major bottleneck. In this study, we modified a previously reported inorganic fertilization method (N: 700 μg L(−1) and P: 100 μg L(−1)) by the addition of iron (Fe: 10 μg L(−1), using FeSO(4)·7H(2)O) (+Fe treatment) and compared its suitability for copepod culture (Pseudodiaptomus annandalei) to the original method (control). The experiment was conducted outdoors in 1000 L tanks for 15 days. The addition of iron prolonged the growth phase of the phytoplankton and resulted in the production of significantly more small phytoplankton (0.45–20 μm, average 2.01 ± 0.52 vs. 9.03 ± 4.17 µg L(−1) in control and +Fe, respectively) and adult copepods (control: 195 ± 35, +Fe: 431 ± 109 ind L(−1)), whereas copepodid-stage was similar between treatments (control: 511 ± 107 vs. +Fe: 502 ± 68 ind L(−1)). Although adding iron increased the cost of production by 23% compared to the control, the estimated net profit was 97% greater. We concluded that inorganic fertilization, with the addition of iron (Fe: 10 μg L(−1)), could be an effective method for the mass production of copepods for larviculture.