Various fed aquaculture systems
also match the most efficient forms of terrestrial animal husbandry, and trends
suggest that carnivores in the wild have been transformed in aquaculture to
omnivores, with impacts on resource use comparable to conventional, terrestrial
agriculture systems, but are more efficient. Production efficiencies of edible
mass for a variety of aquaculture systems are 2.54.5 kg dry feed/kg edible
mass, compared with 3.017.4 for a range of conventional terrestrial animal
production systems. Beef cattle require over 10 kg of feed to add 1 kg of edible
weight, whereas tilapia and catfish use less than 3 kg to add a kg of edible
weight.
Energy use in unfed and low-trophic-level aquaculture systems (e.g.
seaweeds, mussels, carps, tilapias) is comparable to energy use in vegetable,
sheep and rangeland beef agriculture. Highest energy use is in fish cage and
shrimp aquaculture, comparable to intensive animal agriculture feedlots, and
extreme energy use has been reported for some of these aquaculture systems
in Thailand.
Capture fisheries are energy intensive in comparison with pond
aquaculture of low-trophic-level species. For example, to produce 1 kg of catfish
protein about 34 kcal of fossil fuel energy is required; lobster and shrimp
capture fisheries use more than five times this amount of energy. Energy
use in intensive salmon cage aquaculture is less than in lobster and shrimp
fishing, but is comparable to use in intensive beef production in feedlots.
Life
Cycle Assessment of alternative grow-out technologies for salmon aquaculture
in Canada has shown that for salmon cage aquaculture, feeds comprised 87
percent of total energy use, and fuel/electricity, 13 percent. Energy use in landbased recirculating systems was completely opposite: 10 percent of the total
energy use was in feed and 90 percent in fossil fuel/electricity. Freshwater use
remains a critical issue in aquaculture. Freshwater reuse systems have low
consumptive use comparable to vegetable crops.
Freshwater pond aquaculture
systems have consumptive water use comparable to pig/chicken farming and the
terrestrial farming of oil seed crops. Extreme water use has been documented
in shrimp, trout, and striped catfish operations. Water use in striped catfish
is of concern to Mekong policy-makers, as it is projected that these catfish
aquaculture systems will expand and even surpass their present growth rate to
reach an industry of approximately 1.5 million tonnes by 2020.
Water, energy and land usage in aquaculture are all interactive. Reuse and
cage aquaculture systems use less land and freshwater but have higher energy
and feed requirements, with the exception of no feed cage and seawater
(e.g. shellfish, seaweeds) systems. Currently, reuse and cage aquaculture
systems perform poorly in overall life cycle or other sustainability assessments
in comparison to pond systems. Use of alternative renewable energy systems
and the mobilization of alternative (non-marine) feed sources could improve the
sustainability of reuse and cage systems considerably in the next decade.
Resource use constraints on the expansion of global aquaculture are different
for fed and non-fed aquaculture. Over the past decade for non-fed shellfish
aquaculture, there has been a remarkable global convergence around the
notion that solutions to user (space) conflicts can be solved not only through
technological advances, but also by a growing global consensus that shellfish
aquaculture can fit in, not only environmentally but also in a socially
responsible manner, to many coastal environments worldwide, the vast majority
of which are already overcrowded with existing uses.
For fed aquaculture, new indicators of resource use have been developed and
promulgated. Before this resource use in fed aquaculture was being measured
in terms of feed conversion ratios (FCRs) followed by FIFO (fish in fish out)
ratios. First publications a decade ago measured values of FIFO in marine fish
and shrimp aquaculture. More comprehensive indicator assessments of fish
feed equivalencies, protein efficiency ratios and fish feed equivalences will allow
more informed decision-making on resource use and efficiencies. Over the past
decade, aquafeed companies have accelerated research to reduce the use of
marine proteins and oils in feed formulations, and have adopted indicators
for the production efficiencies in terms of marine protein and oil dependency
ratios for fed aquaculture species. Current projections are that over the next
decade, fed aquaculture will use less marine fishmeals/oils while overall
aquaculture production will continue its rapid growth.
Over the past decade, new, environmentally sound technologies and resourceefficient farming systems have been developed, and new examples of the
integration of aquaculture into coastal area and inland watershed management
plans have been achieved; however, most are still at the pilot scale commercially
or are part of regional governance systems, and are not widespread. These
pilot-scale models of commercial aquaculture ecosystems are highly productive,
water and land efficient, and are net energy and protein producers which follow
design principles similar to those used in the fields of agroecology and agroecosystems. Good examples exist for both temperate zone and tropical nations
with severe land, water and energy constraints.
Increasing technological efficiencies in the use of land, water, food, seed and
energy through sustainable intensification such as the widespread adoption
of integrated multi-trophic aquaculture (IMTA) and integrated agricultureaquaculture farming ecosystems approaches will not be enough, since these will
improve only the efficiency of resource use and increase yields per unit of inputs
and do not address social constraints and user conflicts. In most developing
countries, an exponentially growing population to 2050 will require aquaculture
to expand rapidly into land and water areas that are currently held in common.
Aquaculture expansion into open-water freshwater and marine waters raises
the complex issues of access to and management of common pool resources,
and conflicts with exiting users that could cause acute social, political and
economic problems. The seminal works of 2009 Nobel Laureate Elinor Ostrom
could provide important insights for the orderly expansion of aquaculture into a
more crowded, resource-efficient world striving to be sustainable, and rife with
user conflicts.
Presented in the Aquaculture 2010 conference proceedings, published in 2012 by the Food and Agriculture Organisation of the United Nations (FAO) and the Network of Aquaculture Centres in Asia-Pacific (NACA)
June 2012
Further ReadingYou can view the full report and full list of authors by clicking here. |