High density rearing of rohu, Labeo rohita (Hamilton) from spawn to fry in concrete tanks: effect of daily feed ration and soil base on fry growth and survival

摘要

Rearing of rohu spawn to fry size was carried out at high density (2000 spawn m(-2)) in large concrete nursery tanks (10 m x 5 m x 1.2 m) to standardize the daily ration of supplementary feed and to assess the impact of soil base on the fry performance. In Set-1, supplementary feed was provided at 100% (control), 75% and 50% of the daily ration that is commonly used in earthen carp nursery ponds and named as the three treatments T-1, T-2 and T-3 respectively. Although in Set-II, performance of fry were evaluated in tanks provided with and without soil base. The fry survival was to the tune of 45-59% at this high density of 2000 spawn m(-2), indicating the efficacy of the concrete nursery system for high density seed rearing. In Set-I, T-2 receiving 75% of the control ration exhibited similar fry growth as that of T-1, but its fry survival (58.8%) was 10% higher than the latter. This indicated that supplementary feed in a concrete nursery can be reduced up to 25% of that provided in earthen nursery system while ensuring a higher fry yield. However, further reduction up to 50% of the control ration in T-3 yielded lower fry survival and growth (P < 0.05) revealing inadequacy of the available feed. In Set-II, treatment without soil base (T-ns) yielded similar fry growth but 10% higher survival compared to that with the soil base (T-s) revealing non-essentiality of soil base in concrete tanks for such short-term nursery rearing of rohu.