Under the scenarios and assumptions simulated here,
inclusion of Australian redclaw crayfish in tilapia
culture can have potentially positive economic outcomes.
A polyculture strategy using redclaw with tilapia
can help to increase profitability, shorten investment
return time and attenuate risk from changes in tilapia
sale price and production costs, especially when
relatively short return periods are used.
Polyculture substantially improved profitability at
the three studied time horizons in comparison to tilapia
monoculture. Tilapia mortality and the consequent
decrease in biomass were compensated for by income
from crayfish sales and a reduction in production costs.
Tilapia monoculture at the 5-year time horizon was not
profitable.
Production costs decreased in the polyculture
scenarios because culture cycles were shorter as a
result of greater tilapia weight gain over a shorter time
period. Gross income was higher from polyculture
largely due to the commercial value of the crayfish,
which is comparable to the price of freshwater prawn
and some marine shrimp species. Time horizon plays a
determinant role in the consolidation of rural aquaculture
companies, meaning it is vital and necessary to
research and propose alternative production strategies
that allow for rapid return of investment capital. All the
polyculture scenarios simulated here attained a yield
rate higher than the discount rate, which is required for
an investment's net present value to be positive.
Greater profits were obtained with medium crayfish
densities. The polyculture scenarios analyzed here
Table 3
Sensitivity analysis
33/0 33/10 33/20
Year Tilapia Tilapia Crayfish Tilapia Crayfish
Sale price
5 616.92 22.97 1.97 56.68 5.93
10 22.89 12.84 1.07 13.59 1.83
15 17.73 10.83 0.89 11.45 1.54
Feed cost
5 −346.45 −13.05 −0.36 −23.87 −1.12
10 −23.69 −7.28 −0.20 −7.78 −0.36
15 −9.87 −6.13 −0.17 −6.55 −0.31
Seed cost
5 −106.88 −4.78 −1.21 −8.61 −4.35
10 −4.23 −2.70 −0.68 −2.79 −1.41
15 −3.33 −2.28 −0.58 −2.37 −1.19
Percentage change in IRR versus a percentage unit increase in sale
price and main production costs
156 D. Ponce-Marbán et al. / Aquaculture 261 (2006) 151–159
meet the yield, risk and investment capital period
objectives of rural aquaculture companies in Yucatan,
Mexico.
The sensitivity analysis suggested that diversifying
Nile tilapia polyculture with high commercial value
species like Australian redclaw crayfish can attenuate
the risk implicit in the market. Model results encourage
field testing with mean densities in a pilot tilapia–
redclaw polyculture system in Yucatan, Mexico before
advising producers. Until such time, these simulations,
based on experimental data, suggest that a polyculture
strategy may be an option for increasing production,
mitigating risk in the tilapia market and improving
producer income.