Mariculture is the practice of cultivating aquatic organisms within a saltwater environment, including the open ocean, sheltered coastal areas, and land-based facilities that utilize pumped seawater. This involves the controlled breeding, rearing, and harvesting of various marine species such as finfish, shellfish, and seaweeds. Mariculture represents an expanding sector designed to meet the growing global demand for seafood while reducing pressure on wild fish stocks. The practice requires deliberate intervention in the natural production cycle, differentiating it from traditional capture fisheries.
Mariculture Versus General Aquaculture
Mariculture is a subset of the broader field known as aquaculture, which is the farming of aquatic organisms in any water body. The primary difference is the environment: aquaculture encompasses cultivation in freshwater, brackish water, and marine environments, while mariculture is strictly limited to marine or high-salinity habitats. This environmental constraint means mariculture operations must manage the unique challenges of a saltwater setting, including high salinity levels and the dynamic conditions of the ocean. Maintaining a stable environment is inherently more complex in marine settings due to the variability of tides, currents, and water quality in open systems. This specialized nature addresses the need to farm organisms, like Atlantic salmon or oysters, that require the specific mineral content and salinity profile of the sea to thrive.
Species and Products of Mariculture
The marine environment supports the cultivation of a diverse array of organisms, categorized into finfish, shellfish, and marine algae.
Finfish represent a significant product, with species such as Atlantic salmon, cod, and sea bass commonly raised in large-scale operations. These species are typically carnivorous and require formulated feed to achieve commercially viable growth rates, making them a high-value product in the seafood market.
Shellfish, including oysters, mussels, and clams, are a major focus of mariculture, often grown using simple, low-impact methods. These organisms are filter feeders, meaning they derive their nutrition by filtering naturally occurring plankton from the water, eliminating the need for external feed inputs. This extractive quality positions them as environmentally sound products, as they can help remove excess nutrients from the surrounding water.
Marine algae, or seaweeds like kelp and nori, constitute a rapidly growing category of mariculture products. These macroalgae are cultivated for human consumption and for use in pharmaceuticals, cosmetics, and feed additives. Like shellfish, seaweed is an extractive crop that absorbs inorganic nutrients such as nitrogen and phosphorus from the water, contributing to local water quality improvement.
Major Cultivation Techniques
Mariculture operations use a variety of specialized techniques, which are primarily dictated by the target species and the proximity to the coast.
Open Ocean Systems
Open ocean systems, often called offshore mariculture, involve placing large, submersible net pens or cages in deeper water, far from the coastline. This location benefits from high water exchange and strong currents, which help to disperse waste and maintain optimal water quality for finfish like tuna or cobia.
Nearshore Systems
Nearshore systems utilize the relatively sheltered conditions of bays, lagoons, and protected coastal areas for cultivation. For filter feeders like mussels and oysters, techniques such as longlines or raft systems are used, where the organisms are suspended from floating structures. These methods allow the shellfish to feed efficiently on the naturally occurring plankton without disturbing the seabed.
Land-Based Systems
Land-based systems are the most technologically controlled form of mariculture, often employing Recirculating Aquaculture Systems (RAS) or flow-through tanks. These facilities pump in and treat seawater to create a highly regulated environment for species like shrimp or specialized finfish. RAS minimizes water usage and waste discharge by continuously filtering and reusing the water, offering a biosecure environment that is independent of local ocean conditions.