Aquacultural Engineering 22 2000 289 – 307
Size economies and optimal scheduling in shrimp production: results from a computer
simulation model
X. Tian
a
, P.S. Leung
b,
, D.J. Lee
c
a
Department of Business, Economic De6elopment and Tourism, HI, USA
b
Department of Molecular Biosciences and Biosystems Engineering, Uni6ersity of Hawaii at Manoa,
3050
Maile Way, Gilmore Hall
111
, Honolulu, HI
96822
, USA
c
Department of Food and Resource Economics, Institute of Food and Agricultural Sciences, Uni6ersity of Florida, FL, USA
Received 10 October 1999; accepted 14 March 2000
Abstract
This paper describes a computer simulation model developed to analyze the economics of shrimp production under different stocking regimes, harvesting schedules, and farm sizes.
The operation examined is ‘closed-market’ where all stages of production occur on-site, and the final product, adult shrimp, are sold in the market. The model was parameterized using
existing market data and secondary production data collected from experimental units at the Oceanic Institute in Hawaii. Results indicated that a weekly stocking and harvesting regime
is more profitable than either a biweekly or 8-week stocking and harvesting regime. Scale economies indicated that the minimum farm size is twenty-six growout ponds and the
optimal farm size is 64 growout ponds. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Shrimp production; Size economies; Optimal scheduling; Simulation model www.elsevier.nllocateaqua-online
1. Introduction
In intensive shrimp production, shrimp L. 6annamei are reared in four distinct stages maturation, hatchery, nursery, and growout corresponding to the four life
Senior authorship is not assigned. Corresponding author. Tel.: + 1-808-9568562; fax: + 1-808-9569269.
E-mail address
:
psleunghawaii.edu P.S. Leung 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 5 5 - 8
phases of the animal nauplii, post-larvae, juvenile, and adult. In a closed-market system, all rearing from nauplii production to adult occurs at the same facility.
Thus, production of the final marketable output, adult animals, is completely dependent on the rearing of all three precursor stages of production. To assure
sufficient input into subsequent stages of production, it may make economic sense to produce an abundance of nauplii, for example, and dispose of the excess. An
illustration of a general, closed-market operation with n-stages and free disposal is shown in Fig. 1.
In producing a desired level of final output, a farmer may wish to determine the amount of intermediate product needed at each stage to generate the least amount
of waste, i.e. the least cost method of production. To find the least cost method, the economic approach specifies a series of production cost functions needed to capture
the scope economies and size economies of the operation. The scope economies are the cost savings derived from producing several products simultaneously from
sharing fixed inputs such as vehicles, buildings, and employees which are used interchangeably in more than one stage of production Baumol et al., 1988. Size
economies occur when average cost total cost per unit of shrimp changes with output level. If shrimp price is constant in output level, then ideally, a farmer may
choose to increase or decrease the size of the operation to minimize average cost. This paper examines operation size and scheduling decisions in shrimp production
using an economic computer simulation model. The remainder of the paper is organized as follows. Section 2 describes the components of the shrimp farm model
and the data used to parameterize the model. Section 3 lays out the scenarios analyzed. Section 4 presents the model results and concludes the paper.
Fig. 1. Closed-market operational production system for aquaculture.
Fig. 2. Relationship between groups of production phases.
2. Shrimp farm model
