Productivity and profitability model for Mithraculus forceps aquaculture

Background/Question/Methods The demand for marine ornamentals has increased exponentially in the past decade. However, most trade in marine ornamentals comes from wild-caught stock; their culture is still limited to few species. Interest from the governments in promoting the culture and trade of non-food aquatic species, particularly ornamentals, has been spurred by their growing potential for increasing rural employment and generating income. Therefore, there is a widespread interest in predicting product yield as well as culture profitability.
Marine ornamental red-clinging crabs Mithraculus forceps are popular in the aquarium industry for its ability to control nuisance algae. The effect of different culture conditions (temperature, stocking density  and prey density, and number and volume of tanks) in the processes of larval and juvenile mortality, metamorphosis to juvenile, and larval and juvenile growth were modeled, and their implementation costs (feed, labor and maintenance costs) and final profit (considering sell rate and market price)  were predicted. 
The objective of the model is to yield a better management plan and be used for decision support; the model aims contributing to reduce production costs, and maximize product quality and profitability of raising one batch of M. forceps larvae to market size in an aquaculture facility.

Results/Conclusions Overall, the model was able to integrate previously collected data and produce expected forecasts of M. forceps larval and juvenile culture. According to the model, a batch of 1500 larvae reared in ten 10 L tanks in optimal conditions (10 prey.mL^-1 and 28^oC) and then, as juveniles, in a 3 m² water table at 28ºC, is expected to reach commercial size in 122 days. Sensitivity analysis revealed that temperature is the most important factor regulating survival and growth, and consequently profit: lower temperatures cause an increase in mortality and increase culture time; higher temperatures are more deleterious but promote a faster growth. Although productivity per tank is higher at higher stocking densities, survival and growth decrease with increasing stocking density, so the productivity increases as the animals are distributed to the greater number of tanks. However, productivity increase is followed up by an increase in feeding, labor and maintenance costs, which can reduce profit. The model simulations will allow managers to find the most profitable culture combination to the characteristics of aquaculture facility.
The implementation of predictive models to wider range of species culture would allow improvement of aquaculture efficiency and profitability and therefore, protect environment by minimizing wild collection.