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M.?S.?Islam A.?MilsteinEmail author M.?A.?Wahab A.?H.?M.?Kamal S.?Dewan 《Aquaculture International》2005,13(6):489-500
Coastal shrimp (Penaeus monodon) aquaculture in Bangladesh is mostly practiced in a special type of field/pond situated by the side of a river -- called
a Gher -- that is used to cultivate rice in winter and shrimp in summer. Ghers of different sizes are managed in different
ways. In order to understand the effects of Gher size and their corresponding management practices on the production and economic
returns of shrimp farming, we conducted an on-farm study in three small (1–5 ha), three medium (6–10 ha) and three large (>10 ha)
Ghers located in the coastal Southwest region of Bangladesh. The mean harvest weight of shrimp was similar in all Ghers, but
survival rates were higher in the small (50%) and medium (37%) ones than in the large (18%) ones. The high mortality in the
large units led to a production that was lower than one-half of that in the small Ghers (about 80 and 200 kg/ha, respectively).
The total variable costs per unit area were similar in all Ghers, but the importance of different items varied with Gher size.
In the small Ghers, there are relatively high investments on inputs and labor. This expenditure results in lower shrimp mortality
and higher production, which in turn results in gross returns that are larger than the total costs -- hence, a positive and
high net return. In large Ghers, the fixed costs are larger than in the small ones simply because of the size of the pond.
Variable costs include higher investments in post-larvae and labor than in small Ghers, and lower inputs applied only at pond
preparation. This results in higher shrimp mortality and lower production, which in turn results in gross returns that are
smaller than the total costs -- hence, a negative or low net return. These findings have positive implications for the future
policy formulation of coastal shrimp aquaculture in Bangladesh. 相似文献
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A.?MilsteinEmail author M.?S.?Islam M.?A.?Wahab A.?H.?M.?Kamal S.?Dewan 《Aquaculture International》2005,13(6):501-518
Coastal shrimp aquaculture in Bangladesh is mostly practiced in an agricultural unit called a Gher, which is a special type
of agricultural field with elevated surrounding embankments/borders situated by the side of a river that is used to grow rice
in winter and shrimp in summer. Ghers of different sizes are managed in different ways. An on-farm project was carried out
to study the effects of Gher size and their related management practices on water quality, shrimp production and the economic
returns of shrimp farming in the Southwest coastal region of Bangladesh. We present here the results of this project with
respect to water quality as explored through factor analysis, which was applied as a way to understand the nature and extent
of the effects of different variables. For the majority of the variables and factors, one-half to two-thirds of their variability
was explained by changes over time (months), and a further one-quarter to one-third was explained by Gher size and associated
management practices. The alternating dry/monsoon season and water management practices determined long-term and large-scale
(annual) water exchange in the Ghers that mainly affected processes related to live and dead particles suspended in the water
column. Processes related to decomposition and nitrification were more dependent on short-term (days) water circulation in
the Ghers, which is turn was reliant on the time span between the exchanges of water in the Ghers and river. Our results show
that improved management leads to higher natural and shrimp productivity in the smaller Ghers and strongly support the argument
put forward by the policy makers and scientific community in Bangladesh that the smaller the Gher, the better they can be
managed and the better the possibility of increased shrimp survival and production. 相似文献
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