Study of Recirculation Semi Intensive Seed Production (RESISP) 1207

Study of Recirculation Semi Intensive Seed Production (RESISP) 1207

Masatoshi FUTAGAWA / CORDUNAP

September 7, 2012

Based on SISP (semi intensive seed production) operation on October 2010, the method had disadvantages of difficulty of larva estimation. The method improved to RESISP that culture water at copepoda tank recirculates to separated larva tank.

The trials are conducting from July 2012 and 2^nd trial is running now. There are some observations found and information below.

RESISP1207

1^st trial was conducted 23 days from July 28 to August 13, 2012. The system consist copepod tank (20 m³), two larva tanks (1 m³) and pump (0.85kw, 3.8A). Copepod tank equip three air stones at 50 cm depth due to low air pressure, two airlifts (lift up water from bottom) and submersible light (400W). Bottom water was supplied to Larva tank1 and return to copepod tank. Surface water was supplied to Larva tank 2 and drain to outside of the system. Submersible light enhance growth of phytoplankton during cloudy and the night, operated 18:00 to 7:00.

Initial water was introduced with 120 µm bag-net on July 21 and fill up to 20 m³ until 3^rd days culture (DC). Filter water was supplied 3 to 5 % per day basically and increased 20 to 24 % when pH rose to over 8.2. Fertilizer, potassium nitrate (15-0-14, 3ppm) and triple superphosphate (0-14-0, 0.5 ppm), were applied after soaking in water by blender every day until 18 DC. Water temperature (WT) and pH were read every morning at 10 AM.

Average WT was 17.1±0.3 ºC and pH was 8.0±0.2 during culture. Water color turned to green at 5 DC and turned to brown after that. Skeletonema spp. and Chaetoceros spp. were abundant and pH rise to 8.6 on 11 DC. Recirculation system was not operated due to over capacity of pump, the motor became hot because of too much closed outlet.

However, the planktons corrupted due to strong sunlight on 19 DC and culture water turned to transparent. There were very few plankton observed, dead ones accumulated on bottom and rot, mold grew. The operation was terminated at 23 DC and drained totally on August 23.

 

Observations

There are several observations that improve phytoplankton and copepod production as below.

• Intensive cultured phytoplankton like T-Isochrysis inoculated during initial water supply and culture useful phytoplankton to produce copepod easily.
• Fertilizers apply until water has color, until 3 to 5 DC usually.
• Filter water until water color turn to brown and remove bag-net to introduce copepod with supply water. In addition to that, inoculate copepods that come from intensive culture was ideal.
• Feed artificial feeds powder (1g/m³/day) when supply water without bag-net to enhance copepod propagation.
• Capacity of pump related to copepod multiplication and larva growth that 10 to 20 % of copepod biomass per day, equivalent 20 to 30 % of copepod tank volume approximately.
• Centrifuge pump is not ideal to moving water that damage plankton and copepod. Ideally, the water carries by airlift but it can’t lift more than 3 cm. It needs to invent how to lift higher.