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Despite a robust literature, there is little consensus on a definition of ‘sustainability’, nor on systems and farming practices that are ‘sustainable’. While US aquaculture is practiced in a highly sustainable way, the pressure from continuous population growth requires that resources be used in increasingly efficient ways. Encouraging farms to include efficiencies of resource use and cost in their annual review of farm productivity and financial performance would also encourage farms to increase efficiency of resource use as an incentive to reduce production costs.
An emerging focus in the literature has been on resource-use efficiency. A number of studies have shown that natural resource use and negative environmental impacts were concentrated at the farm level. Thus, while sustainability concepts tend to be broader than just resource-use efficiency, a growing body of literature suggests that attention to the efficiency of use of resources at the farm level may be a practical approach to enhancing sustainability by reducing negative environmental impacts. To be measurable at the farm level, however, metrics must be well aligned with farm recordkeeping systems.
The main contribution of this paper is to show how the incorporation of metrics that are well aligned with a common farm-level management tool such as enterprise budgets can shed light on comparative resource- use efficiencies as well as the associated resource-cost efficiencies.
Materials and Methods
Scenarios
Scenarios selected included a variety of ponds, raceways, and RASs, with an emphasis on the major species raised in the USA. The scenarios for this analysis included the most common management practices and degree of production intensity as determined by previous surveys of US aquaculture farms. RAS scenarios were developed despite the lack of sufficient numbers of commercial RAS in the USA from which to obtain sufficient farm-level data.
Resource-use and resource-cost metrics
Sets of resource-use efficiency metrics were developed based on the types of resources essential to aquaculture production and to previous empirical work. Resources that are essential inputs for food production generally include: land, labor, capital, water, and energy. The resource-use metrics selected included total land area, water footprint, energy use (electricity and fuel), and feed use in aquaculture.
- Land-use efficiency was calculated based on total land used for the farm. Land-cost efficiency was calculated by dividing the annualized value of land by the weight (kg) of fish produced for each scenario.
- Water-use efficiency was measured by the weight (kg) of fish produced divided by the water footprint.
- Energy-use efficiency was measured by the kg of fish produced divided by the energy use in giga- joules (GJ).
- Labor and management use efficiencies were measured by dividing the weight (in kg) of fish sold by the full-time equivalents (FTEs) in labor and management, respectively. The management-cost efficiency was measured by dividing the sum of wages paid for management by the weight of fish sold.
- The productivity of capital used was measured as the weight (in kg) of fish sold divided by the annualized cost of total investment capital. The capital cost efficiency was calculated by dividing the annualized cost of total investment capital by the weight (in kg) of fish sold.
- Feed efficiency was measured as the feed conversion ratio, calculated as the kg of feed fed divided by the kg of fish sold. The feed-cost efficiency was calculated by dividing the total expenditures on feed by the weight (in kg) of fish sold.
- The enterprise budgets were developed with standardized values (national averages) for key items, including land values, labor wages, management salaries, and interest rates. Feed costs, however, were not standardized across the budgets.
Results
Land
The RASs exhibited the greatest productivity of land use with the greatest values of weight of fish produced per unit area of land used (in kg of fish ha-1 of land). Raceway production of trout was the second most productive use of land and was followed by that of ponds.
Resource-cost efficiency of total land for the various farm scenarios showed that the scenarios with the lowest fish yield (kg . ha-1) had the greatest annualized land cost per kg of fish produced. The lowest land cost per kg of fish produced was that of RAS production.
Water
The farm scenario that demonstrated the greatest water-use efficiency was that of intensively aerated hybrid cat fish production, followed by RAS tilapia (45400 kg . yr-1), multiple-batch channel catfish, the other RAS scenarios, largemouth bass in ponds, and the other pond species.
“The cost of water per kg of fish produced was greatest for those farm scenarios with the lowest productivity (kg of fish . l-1 of water) except for trout produced in raceways.”
Overall, the water-cost efficiency was lowest for fathead minnows, followed by sportfish and golden shiners, goldfish, largemouth bass produced for food- fish, the RAS systems, and then hybrid catfish with intensive aeration.
Feed
Feed conversion ratios were greatest for the sportfish, largemouth bass for food fish, and minnow farms. Feed prices in this analysis were not standardized, however, because feed prices vary across species due to different nutritional requirements and costs of ingredients. As a result, the feed-cost efficiencies calculated were affected by varying feed prices for different species.
Energy
The farm scenarios with the most efficient energy use were the 2 catfish scenarios, hybrid catfish with intensive aeration and multiple-batch channel catfish. These were followed by trout in raceways and largemouth bass pond production, and then RASs and the other pond-based farm scenarios.
The energy cost per kg of fish produced was greatest for pond production of goldfish, sportfish, fathead minnows, and golden shiner scenarios, followed by RASs, trout in raceways, largemouth bass food fish, and multiple-batch channel catfish.
Labor and management
The 2 catfish scenarios demonstrated by far the greatest labor productivity, as measured in kg of fish sold per FTE of labor. Given that labor wages and costs were standardized across the production scenarios analyzed, the labor costs per kg of fish sold showed that the farm scenarios with the lowest labor productivity values had the greatest labor costs per kg of fish sold.
Capital
Capital-use efficiency was substantially greater in the 2 catfish farm scenarios as compared to the other scenarios, followed by the largemouth bass food fish and trout raceway scenarios. The lowest capital use efficiency values were those of the smaller pond and RAS scenarios.
Discussion
As expected, the cost per kg metrics calculated generally mirrored (inversely) the quantities of resources used per kg. This was true for land, energy, labor, management, and investment capital. Despite a few exceptions, cost-efficiency metrics could be used interchangeably with resource- use efficiency in terms of discussions related to the relative sustainability of aquaculture production systems. With water use, the same relationship between cost efficiency and resource-use efficiency was found among all scenarios except for trout production in raceways.
The metrics presented in the present study did not account for or adjust for total water requirements as opposed to water ‘consumed’, nor consider the value of water in areas in which scarcity has created markets for use of scarce water resources. Monitoring water use on any type of farm is the first step in the search for ways to reduce water volumes used, particularly in those systems that previous research has shown to ‘consume’ greater quantities of water, as in RASs.
“Feed use was the second exception to the close relationship between physical efficiencies (quantity of resource used per kg of aquatic animal product) and cost efficiencies.”
Results of this analysis highlight the importance of Results of this analysis highlight the importance of examining resource-use efficiencies of key resources when discussing relative sustainability. Different production systems in this study demonstrated varying levels of efficiency for the resources analyzed.
Aquaculture production technologies continue to evolve rapidly as research continues to identify and develop improved production practices.
Therefore, estimates of resource use on farms will continue to change as production practices evolve. In terms of economic sustainability, the scenarios analyzed in this study reflect business realities of segments of US aquaculture that have been economically sustainable for many years.
The exception to this is, of course, RASs, for which there are only a few commercial examples of successful RAS businesses. Regions where land and water are less expensive can support more extensive production systems, such as that of minnows and sportfish. Clearly, in regions with very high land values, RASs would be expected to be more competitive economically due to its more efficient use of land. While some production systems use some resources more efficiently than do others, existing aquaculture businesses in the USA, regardless of species or production system, are managed as sustainable food production systems.
Conclusions
More intensive production systems were found to use resources (land, water, energy, labor, management, and capital) more efficiently per kg of fish produced than less intensive production systems with lower yields (kg .ha-1). Except for land and feed use, however, intensive pond production of catfish resulted in the most efficient use of resources overall, demonstrating the overall highest degree of sustainability of catfish pond production as compared to other systems and species.
RAS production was the most efficient in terms of land and feed use among all scenarios evaluated. The metrics used in this analysis were those that can be calculated in a fairly simple fashion on farms. While these metrics do not capture the full effects of embodied energy resources in feed, tanks, equipment, and sources of energy, among others, they offer a practical way for farm owners and managers to monitor resource use as a way to both control costs and improve farm profitability by seeking to use resources in the most efficient manner possible.
This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “RESOURCE-USE EFFICIENCY IN US AQUACULTURE: FARM-LEVEL COMPARISONS ACROSS FISH SPECIES AND PRODUCTION SYSTEMS” developed by: C. R. ENGLE – Virginia Polytechnic Institute and State University, G. KUMAR – Mississippi State University, J. VAN SENTEN – Virginia Polytechnic Institute and State University, Hampton.The original article was published on July 2021, through AQUACULTURE ENVIRONMENT INTERACTIONS under the use of a creative license. The full version can be accessed freely online through this link: https://doi. org/10.3354/aei00405.
