Marine Aquaculture and Environmental Carrying Capacity

In coastal spatial planning, designated marine areas are often allocated for aquaculture development, or large-scale aquaculture projects are proposed by the fisheries industry. One of the most critical questions is how much of the available area can be sustainably utilized without exceeding the environmental carrying capacity of the surrounding waters. Every aquatic ecosystem has a finite capacity to support cultured organisms while maintaining optimal environmental conditions. This carrying capacity varies from one location to another because each water body has unique physical, chemical, and biological characteristics. Naturally, these environmental processes continuously interact and respond to increasing aquaculture production.

For example, increasing fish biomass requires more dissolved oxygen, which can reduce oxygen availability and negatively affect fish growth and survival. In pearl farming, a larger number of oysters consume more natural food resources, potentially slowing pearl development. Likewise, expanding shrimp farms along the coast generates greater quantities of uneaten feed and organic waste entering the surrounding waters, increasing the risk of shrimp diseases, harmful algal blooms, and water-quality degradation. Similar environmental responses occur in other aquaculture systems and in different aquatic environments.

Aquatic ecosystems possess a natural capacity to absorb and neutralize the environmental impacts generated by marine aquaculture. However, this capacity is limited and differs among water bodies. Large-scale aquaculture operations alter physical, chemical, and biological conditions, including temperature, salinity, dissolved oxygen, phosphate, nitrate, nitrite, silicate, organic and inorganic chemical compounds, and aquatic microorganisms. As long as these parameters remain within their natural resilience limits, the ecosystem can recover and maintain environmental stability. Once these limits are exceeded, environmental quality declines, which ultimately reduces aquaculture productivity and threatens the long-term sustainability of the industry. Therefore, assessing environmental carrying capacity is an essential prerequisite before establishing large-scale aquaculture operations.

Various empirical and statistical methods have been developed to evaluate the relationship between aquaculture production and environmental carrying capacity. While these approaches are useful for management purposes, they often provide only simplified representations of ecosystem processes. A more accurate and reliable assessment can be achieved through process-based numerical modeling that dynamically simulates the interactions among physical, chemical, and biological processes. This approach provides decision-makers with faster, more scientifically robust, and more effective information for sustainable aquaculture planning.