The work on surveys, collection and identification of possible stocking materials for the farm is being continued by the Prawn and Fish Seed Survey Team. Samples collected are brought to the office for grouping and measurements. Collection work is presently concentrated at different places in the Ngomeni Lagoon, where the catch is mostly shrimps. From January 1980 to May 1981, some data on the occurrence of mullet fingerlings at the mouth of Sabaki River have been recorded.
A trial run on shrimp culture is being conducted for the first time in the one pond so far completed. Details of preparation and stocking are shown in Tables 1 and 2.
Table 1
Stock composition of Pond 3, Ngomeni Pilot Fish Farm
(1st trial, starting May 1981)
| Species | Percentage (among all crustaceans) | Percentage (among penaeids) | No./ha | Average weight (g) | Estimated total weight/ha (kg) |
| Penaeids | |||||
P. indicus | 59 | 88 | 25 584 | 0.20 | 5.12 |
M. monoceros | 7 | 10 | 3 035 | 0.49 | 1.49 |
P. monodon | 1 | 2 | 434 | 0.36 | 0.15 |
| Total | 67 | 100 | 29 053 | 6.76 | |
| Others | |||||
Carids and Acetes | 33 | 14 309 | No data | ||
| Total | 100 | 43 362 |
Table 2
Management operations of Pond 3, May-August 1981
(1st shrimp culture trial, Ngomeni Pilot Farm)
| Date | |||||
| Activities | May | June | July | August | |
| 1. | Total draining and drying | 28, 31 | |||
| 2. | Flushing | 3, 4, 5 | |||
| 3. | Initial filling; increasing depth | 6, 15, 30 | 30 | ||
| 4. | Water exchange (almost total) | 14, 16, 17 18, 19, 30 | 1, 2, 16 17, 18, 30, 31 | 1, 14, 15, 16, 27, 28 29, 30 | |
| 5. | Stocking | 15–30 | |||
| 6. | Staking of twigs for additional substrate and wave breaks | 1, 17, 27, 28, 29, 30 | |||
| 7. | Introduction of cut grasses | 17, 29 | |||
The shrimps are being reared on natural fertility alone, although the attempt to throw in grasses from time to time is intended not so much to provide organic fertilizers but to act as additional substrate and, hopefully, to attract periphyton and insects.
Due to the high elevation of the pond bottom, water exchange operations are possible only for a maximum of 3 to 4 consecutive days out of each 15-day tide cycle. To allow as much water as possible to come in, ¼-inch mesh screens were set, only to be replaced with ¾-inch chicken wire screens to be able to change water readily within the short time available for this operation. Despite this measure, only about 40 cm of water could be maintained inside the pond.
Meanwhile, on the writer's recommendations, shallow pits were dug near this pond to be used as temporary storage for fresh cow manure. The ready availability of this fertilizer in the vicinity should assure regularly scheduled fertilization operations as would be required later (see Annex I).
