Use of hapas to produce Nile tilapia (Oreochromis niloticus L.) seed in household foodfish ponds: A participatory trial with small-scale farming households in Northwest Bangladesh

Seed production of Nile tilapia (Oreochromis niloticus L.) in nylon mesh net cages (hapas) was tested through a participatory on-farm trial with households in NW Bangladesh. A total of 43 households with small ponds (0.04–0.08ha) located close to the homesteads were sampled from poor to medium social groups in three communities: Tarala Banara (TB), Dewnaghata (DW) and Dola Para (DP). Broodfish of GIFT strain Nile tilapia (12 female and 6 male; 60g size) were stocked in a single spawning hapa (3×2×1m). Swim-up fry were collected from breeding hapas at 15day intervals and stocked alternately in two nursing hapas (1.5×1×1m). With the exception of 15 households at DP in which flooding caused loss of fish, most of the households in TB and DW produced tilapia fry from hapas for 4–5months in addition to the usual production of foodfish/fingerlings in their ponds. Mean swim-up fry production in TB and DW was 5185±3764 and 3415±1536fryhousehold⁻¹, leading to nursed fry production of 2708±1967 and 1380±734fryhousehold⁻¹ respectively. Nursed fry were sold (70%) or re-stocked (30%) for foodfish production in the participants' own ponds. Only households with perennial ponds that were able to hold and rear tilapia broodfish (25% of total households at TB and DW) successfully produced seed in Year 2, but such households started earlier in the season (March) and achieved significantly higher productivity than the previous year. Hapa productivity was impacted by local soil type, presence of shade, depth of mud and level of drainage inputs; more fry were produced in ponds based on sandy and sandy-loam soils with less overhanging vegetation and shade, lower levels of turbidity and benthic mud, and no drainage connections with tube wells or surface run-off. Poorer households were more successful overall and tended to prioritise sale of fry over retention for foodfish culture Households engaged in ancillary fry trading and/or nursery businesses also tended to be relatively successful. Between 8 and 20 customers were supplied by each hapa operator, indicating the broader impacts of local seed production on grow-out for foodfish production.