Aquacultural Engineering 22 2000 243 – 254
Optimizing multi-stage shrimp production systems
Jaw-Kai Wang
a,
, Junghans Leiman
b
a
Department of Biosystems Engineering, Uni6ersity of Hawaii,
3050
Maile Way c
111
, Honolulu, HI
96822
USA
b
Jalan Taman Kebon Sirih c
6
, Jakarta
10250
, Indonesia Received 9 September 1999; accepted 10 January 2000
Abstract
Multi-stage penaeid shrimp grow-out systems have considerable advantage over conven- tional single-stage grow-out systems. A multi-stage shrimp grow-out system has more than
one production stage wherein the shrimp stocking density changes as the shrimp grow in size and are moved from one production stage to the next. The shrimp stocking density
shrimpm
2
is at its highest when the shrimp post larvae enter the first production stage and is reduced each time the shrimp are transferred to subsequent stages. The use of multi-stage
instead of single-stage production systems has been considered by numerous authors. This paper presents a methodology by which to select the optimum number of stages for a
production system and, using available data, demonstrates that optimum efficiency can be achieved, in most cases, by using a two-stage production system consisting of a prolonged
nursery stage followed by a grow-out stage. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Shrimp; Aquacultural engineering; Shrimp production www.elsevier.nllocateaqua-online
1. Introduction
A multi-stage shrimp grow-out system has more than one production stage wherein the shrimp stocking density changes as the shrimp grow in size and are
moved from one production stage to the next. The shrimp stocking density, defined as the number of shrimp per m
2
of water surface area, is highest when the shrimp
Corresponding author. Tel.: + 1-808-9568154; fax: + 1-808-9569269. E-mail address
:
jawkaihawaii.edu J.-K. Wang 0144-860900 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 1 4 4 - 8 6 0 9 0 0 0 0 0 3 8 - 8
enter the first production stage and is reduced each time the shrimp are transferred to subsequent stages.
The advantages of multi-stage production systems have been well identified by Cao and Jiang 1990, Fast 1991, Sandifer et al. 1991, Sturmer et al. 1991,
Samocha and Lawrence 1992, Stern and Letellier 1992. In general, these authors feel that a multi-stage shrimp production system can improve stock inventory
control and disease treatment, reduce predator damage and feed waste, alleviate the difficulty of monitoring survival rate, provide more efficient use of land, and
potentially lead to increased numbers of crops per year.
On the other hand, Stern and Letellier 1992 reported increased shrimp stress in a multi-stage production system due to the transfer of animals which may cause
increased mortality. Let us assume that identical mechanical oxygenation and pumping efficiencies
prevail and that biological efficiencies such as growth rate, mortality rate, feed conversion ratio, and final average weight of shrimp produced are constants that
do not vary in the production systems under consideration. The annual operating cost of a shrimp production system is then approximately a function of the number
of shrimp produced, since the number of shrimp targeted for production will dictate the number of postlarvae required, feed and electrical costs, and other expenses.
The annual operating cost per kg of shrimp produced, therefore, should not vary with the number of stages in a production system. Thus, the financial return of a
multi-stage shrimp production system, given the above assumptions, must be approximately a function of land and construction costs Chong, 1990. If we
further assume that construction cost is proportional to the water surface area of the specific system, we can then compare the expected financial returns of shrimp
production systems by comparing their land use efficiency.
By adopting the above simplifying assumptions, the problem of optimizing a multi-stage shrimp production system is reduced to the following:
Min
j
A
pr
j,i =
i
[N j,iA j,i] 1
where: A
pr
j,i is total water surface area of pondstanks in phase configuration j and phase i m
2
; N j,i is number of pondstanks in phase configuration j and phase i integer c ; A j,i is water surface area of individual pondtank in phase
configuration j and phase i m
2
.
2. Shrimp size, density, growth rate and mortality
