Phytoplankton production in integrated fish culture high-output ponds and its status in energy flow

Abstract

Primary productivity of phytoplankton in fish ponds of three different stocking patterns was analyzed. The function and status of primary productivity in the energy flow of the fish ponds was evaluated quantitatively. In ponds subjected to stocking of non-filter-feeding fish, phytoplankton net primary productivity (NPP) was 242–284, 285–292 and 303–330 GJ/ha· year when net fish output was 7.5, 11.2 and 15 t/ha·year, respectively. In ponds subjected to stocking of filter-feeding fish, NPP was 301–384, 388, and 438–493 GJ/ha·year when net fish output was 7.5, 11.2 and 15 t/ha·year, respectively. In the ponds with stocking of 50% non-filter-feeding fish and 50% filter-feeding fish, NPP was between the NPP values observed in the ponds with other stocking patterns. Percent solar efficiency was 1.4–1.5, 1.7–1.8, and 1.4–2.7% for 20%, 50%, and 100% filter-feeding fish stocking, respectively, NPP was equal to 15–27, 30, and 33–46% of energy subsidies, and 30–48, 50, and 51–60% of total energy for phytoplankton and added food. With these inputs, fish production was 2.5–3.4, 3.9–4.2, and 3.1–5.1 t/ha·year, under the three stocking patterns, respectively.