Optimization of stocking density of seabass (Lates calcalifer) in brackish- and freshwater earthen ponds under monoculture in South-west coastal zone of Bangladesh

Abstract

The Asian seabass (Lates calcarifer) is a fast-growing, euryhaline fish capable of withstanding
wide environmental fluctuations and fetch higher market price due to its good taste. For semi-intensive and
intensive aquaculture, it is important to optimize stocking density. The present study was undertaken to
compare and standardize production and stocking density of seabass in earthen ponds. Seabass fingerlings
were collected from natural sources and stocked both in coastal brackishwater and freshwater ponds with the
stocking density of 20, 25 and 30 individual/decimal in T1, T2 and T3, respectively. The seabass feed
prepared with 40% crude protein, 8% crude lipid, 10.00% ash and 3.00% crude fibre was applied as
supplementary feed. Water quality parameters were not significantly different among the treatments. In
brakishwater ponds, average survival rates (%) were 59.31±3.08%, 53.75±2.78% and 39.99±2.09% in
T1, T2 and T3 respectively while in freshwater ponds the survival rates were 58.81±3.90%, 51.82±5.84%
and 39.59±2.06% in T1, T2 and T3 respectively. The specific growth rates (SGR) of seabass in
brackishwater was somewhat higher in T2 without significant difference among the treatments. The SGR of
seabass in freshwater pond was significantly higher in T2 and T3 than that of T1. But the highest SGR was
recorded in T2 where stocking density was 25 individual/decimal. Average net yields in treatments T1, T2
and T3 under brackishwater were estimated as 1043.06±34.13 kg/ha, 1255.55±58.63 kg/ha and
1115.18±70.29 kg/ha respectively. Average net yields in treatments T1, T2 and T3 under freshwater were
946.96±93.73kg/ha, 1186.79±113.46kg/ha and 1069.86±33.04kg/ha respectively. The highest net yields in
T2 were 1255.55±58.63 kg/ha and 1186.79±113.46 kg/ha in brackish water and freshwater environment,
respectively with significant difference among the treatments. According to the findings of the present study,
it may be concluded that the culture of seabass at stocking density of 25 individual/decimal in earthen pond of
brackishwater environment with artificial feed has profound impacts on SGR which ultimately increases the
yield of seabass.