The current human population is set to continue growing, requiring increased food production to accommodate. One-third of the population is defined as having food insecurity, calling for long-term sustainable food production and innovative solutions. Aquaculture, one of the fastest-growing sectors in food production, can expand farming to the vast expanses of underutilised aquatic environments which make up 70% of Earth's surface. However, the fast development within the aquaculture sector is leading to intensified practices and increased quantities of feed, waste, and therapeutants discharged into the environment. This can lead to accelerated algae growth which impacts the water quality and diminishes oxygen levels causing determinantal effects in aquatic organisms including illness and mass mortality events. Habitat destruction has also been documented as a result of water contamination. Furthermore, certain algal blooms pose health risks to humans due to the production of toxins and increased bacterial presence, potentially causing illness through contact or ingestion of contaminated water or fish.
Integrated Multitrophic Aquaculture (IMTA) when implemented effectively, can provide a more environmentally conscious form of fish farming. It involves the cultivation of species from various trophic levels, combining extractive species such as seaweeds and shellfish which recycle waste produced by fish. Thus, promoting an ecological balance and a long-term reduction in running costs.
In Sungo Bay, China, it is estimated 300 tonnes of nitrogen are released into the water through intensive aquaculture farming cycles. The integration of farming with seaweed and abalones has largely mitigated these effects by utilising the large amounts of inorganic nitrogen. Instead of causing environmental degradation, evidence suggests the long-term practice of IMTA has improved the conditions within the bay. The abalones are grown in lantern nets suspended from lines of seaweed which the abalones directly feed off, removing feed cost and reducing nitrogen and phosphorous input. During the harvest cycle of the seaweed, scraps are fed into the abalone nets to maintain the self-sustaining cycle.
Research from Bangladesh suggests IMTA enables faster regeneration of coastal aquatic ecosystems from natural perturbation, whilst cultivating robust species that increase the profit stability of small-scale farms.
In The Bay of Fundy, Canda, abalones that utilise salmon waste show up to 50% increase in growth rate then at abalone monoculture sites. Even when insignificant growth rate is shown, the farm is still able to capitalise off the high market value of abalones increasing financial security of the farm by providing additional stock.
Since the 1970s wild fish stocks have continued to collapse or decrease in yield size. The quantity of fish needed to keep up with market demand and accommodate a larger population can be achieved through aquaculture. However, the practice often produces large amounts of waste that can disrupt the surrounding environment and therefore not be sustained. IMTA prevents extreme disruption to allow for intensive farming over sustained periods.
One of the biggest problems with practical application of IMTA is the complex multifaceted interaction. Different species combinations may result in diverse species-species interactions, impacting farm efficiency and reducing IMTA success. Furthermore, offshore sites have greater technical difficulty in implementing IMTA systems, such as securing seaweed to withstand strong currents, which requires specific techniques. Farm specific assessments are needed for IMTA to be successfully implemented which can be costly and time-consuming. The initial investments make convincing stakeholders to undertake IMTA at already profiting farms difficult. However, economic modelling has demonstrated that the higher overall net productivity at IMTA farms has the potential to enhance profitability in comparison to monoculture farms at the same site. A study by John Ellis and Rachel Tiller from SINTEF, assessed the relationship between stakeholders from the Norwegian salmon industry and the use of IMTA. Participants recognized IMTA could enhance sustainable aquaculture practice, however, they identified opposition from policymakers, regulatory challenges, and resistance from the salmon industry focused solely on conventional salmon production. Similar results were found in Europe by researchers from St Andrews.
It is almost guaranteed without ecologically concise farming practice, long-term farming will not be able to keep up with the increasing demand without increasing damage to the environment and eventually leading to farm collapse. Active government participation and policy creation could catalyse more sustainable farming practice. By employing IMTA practices, aquaculture farms have the potential to generate greater profit whilst causing ecological uplift.
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