4 Types Of Aquaculture Systems 

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Fish farming also known as aquaculture involves the controlled culture of aquatic organisms in controlled environments. There are four major systems of aquaculture which include traditional pond farming and recirculation systems, inshore-nearshore cage farms, and offshore cage farming/sea farming. Different systems have unique advantages and constraints in meeting the increasing demand for seafood around the globe.

Wild fish populations are declining steeply. Nearly 90 percent of global sea fish stocks are fully harvested or fished to the brink, requiring more effective policies and enforcement in ‘wild capture’ fisheries. The state of marine biodiversity is intertwined with ocean pollution and its acidification. Plus, according to the WWF, the global fishing fleets are expected to exceed the planet’s capacity by two to three times. If there is no reduction in fishing soon, wild species will face a collapse by mid-century. This emphasizes why the majority of supermarket fish are from fish farms.

What is Aquaculture?

Fish farming commonly referred to as aquaculture is all about cultivating aquatic organisms under controlled conditions. It includes a wide range of methods such as raising fish or shellfish and growing aquatic plants such as seaweeds used in food production. The depletion of wild fish stocks and the increase in global demand for seafood have made this food-producing system gain significant attention and importance over recent years.

Aquaculture mimics natural aquatic habitats that provide optimal conditions necessary for growth and reproduction of different species. In contrast to traditional fishing that relies on harvesting wild populations from oceans, rivers, and lakes; aquaculture offers a more sustainable approach that can be anticipated better to meet global seafood needs.

The history of aquaculture dates back thousands of years with evidence showing early forms of fish farming practiced by ancient civilizations such as Egyptians, Chinese, and the Romans. However, modern techniques in practicing this method have changed considerably through the incorporation of advanced technology and scientific knowledge in a bid to enhance efficiency and minimize environmental impacts.

One of the major advantages of aquaculture is its ability to provide consistent and reliable food sources for millions of people worldwide. Through regulating factors such as feed, water quality, and temperature, farmers can maximize the growth rates of their stocks while ensuring that they remain healthy. This predictability is particularly important for areas where traditional fishing may be limited by factors like overfishing, environmental degradation, or a much-spoken topic today, climate change.

Aquaculture also plays an essential role in food security and poverty alleviation, especially in developing countries where access to nutritious foods is limited, such as in Asia. Through providing job opportunities and fish rich in proteins, aquaculture contributes towards economic growth and stability in these regions.

However, just like any form of agriculture; aquaculture also has its challenges and criticisms. Environmental concerns about water pollution, habitat destruction, or disease spread are possible from intensive farming practices. Moreover, there are ethical issues concerning the welfare of farmed fish and the use of antibiotics as well as chemicals in aquatic operations.

Conventional Pond Aquaculture Systems 

There is already little water in many areas, which will be a major problem right across the globe if we don’t start taking climate change seriously. There is no doubt that a traditional low-input, land-based pond aquaculture system is the wrong way of using freshwater resources. In hot arid climates for example, a one-hectare pond can consume up to 30,000 tons of water every year through seepage and evaporation yielding only about 1-2 tons of fish. It makes sense to start moving towards more water-efficient ‘intensive’ approaches in ponds.

Integrating aquaculture ponds within frameworks of water conservation and management also offers another solution with rainfed aquaculture serving as an alternative strategy for water storage in regions affected by scarcity. This transition would require widespread education, technical support, and dissemination of improved aquaculture methodologies that maximize effective utilization of scarce water resources affecting millions of farmers worldwide.

In certain climates, flow-through systems offer potential gains in efficiency by recycling heat energy which can count against water costs. On the positive side, innovative approaches for managing aquaculture include integration with other agricultural processes including pond systems; water reuse; and the introduction of recirculation technologies. A recirculation system could consume as little as 150 liters per kilogram of fish or even 40 liters per kg with a de-nitrification unit incorporated into it. Nevertheless, it should be noted that most advanced systems may not apply to the majority of fish farmers.

The Integration Of Aquaculture Into Other Systems

For the subsystems within these farming contexts, many outputs are usually called “wastes” or “by-products” but have the potential to become inputs for the next subsystem instead of merely being complementary parts to the overall farm economics.

This concept is illustrated well through integrated systems. For example, in Israel, dual pond systems seamlessly link irrigation reservoirs with fish ponds enabling seasonal transfers based on irrigation requirements and demands for fish culture respectively. Similarly, cages placed within reservoirs and ponds can promote integrative processes at a smaller scale, so that economic use of water resources can be optimized completely. This is yet another way to productively allocate this resource, with aquaculture production doubling up as valuable rainwater storage ponds and stormwater management. For many small-scale systems, the focus will be on aquaculture alongside water storage as a secondary service that aids in other activities such as watering gardens and livestock.

A combination of livestock and aquaculture can be seen in many countries. Nonetheless, ethical issues including public health implications have to be taken into consideration while using animals or industrial effluents (e.g. sewage, heated water, processed water) for fish farming. These are concerns relating to infectious disease transmission and the build-up of harmful substances that demand due care.

Also, there is an alternative source of water supply for fish farms. In Bangladesh e.g., floodwater control offers one option while saline ground or surface waters unfit for irrigation or municipal uses could be used for aquaculture purposes. The vast salty expanses of Asian countries alone underline immense possibilities for expansion into the aquaculture industry that may arise from them.

Recirculation Aquaculture Systems

The applications of recirculating aquaculture systems are very broad, including broodstock management, hatchery and nursery rearing, grow-out operations, and quarantine holding among others. There is an expectation that the use of recirculating systems in intensified commercial aquaculture will grow rapidly over the next few years with various flexibilities for local conditions.

An example of this is the PAS system used in American catfish farming. It integrates a highly intensive growth enclosure with a comprehensive network of channels within the pond for water treatment. Its slow circulation and low energy requirements allow precise control of pond environmental parameters while minimizing water usage.

Recirculation does not have to be always high intensity. Thai shrimp farmers utilize closed ponds to avoid water replacement thereby efficiently using brackish water and reducing the risk of introducing diseases into shrimp farms.

Active suspension ponds, demonstrated for tilapia in Israel and USA as well as shrimp culture in Belize reduce the need for water exchange. Hyper-intensive recirculation systems offer myriad advantages including minimal water demand, reduced space requirements, limited discharges, and precise environmental control required to optimize productivity; however, these systems invariably come with high capital costs associated with complexity and potential significant crop loss upon failures necessitating strict management control, feed formulation, health management, and professionalism in operation.

A well-executed recirculating system should be personally affordable focusing mainly on high-value intensive aquaculture at present. Hyper-intensive recirculation systems may be subject to other uses due to changing economic or resource situations especially pertinent in Europe where environmental constraints prevail alongside market demands for high-value species.

Challenges With Recirculation Systems

Firstly, there may be limited knowledge regarding component interactions – for example, biofilters, mechanical filters, and energy flows. An insufficient appreciation of pathogen interaction with benign microbes within biofilters may cause issues. The biofilms potentially could be poorly studied. New feeds may require process modifications. The accumulation of by-products in systems is not yet well understood. Predictive modeling needs to evaluate multifactor interactions for system design and testing. 

The requirement for feeds designed for recycling systems is a trade-off between conversion efficiency and water treatment efficiency. Modern diets may aid in fecal separation from water and slower leaching of nutrients.

Recirculating systems are preferred when culturing exotic species and GMOs because they offer better control over escape to the wild.

Intensification tends to induce stress by disrupting fish social structures while this varies with species therefore more research on behavior is necessary. On the other hand, some species do well at higher stock densities that may require pre-adaptation to a recirculated environment.

Recirculation technology is often specific to a particular species, thus the choice of good-performing species is critical for success. Strains adapted to recirculating systems tend to exhibit superior performance. Welfare concerns as well as increased productivity demands have led to the need for designing systems based on animal requirements.

Sometimes water does not limit the selection of recirculation; rather energy conservation such as heating in hatcheries or grow-out facilities could be a more important consideration.

Fish Cage Aquaculture Systems

The spread of fish cages for breeding around the world is increasing. Europe, parts of South America (especially Chile), and China have adopted advanced technologies. Fish farming based on cage culture is rapidly developing in Southeast Asia with different species of fish. However, major challenges remain such as expensive feeds in limited quantity and seed shortage.

Also, fish seeds and fingerlings are transported widely across borders in Asia mainly to Hong Kong and China markets where live fish are sold and bought. Nevertheless, this trade enhances economic activities, very little is known about its environmental effects except for a few cases of destructive fishing methods used during the capture of fingerlings.

Different countries have distinct species, markets, and problems; therefore they need tailor-made approaches to cage culture development. Nonetheless, future projections indicate that there will be more expansion of this type of farming.

Inshore-Nearshore Cage Farms

Environmental degradation can be avoided or even turned into positive experiences through the establishment of these kinds of cage farms within the coastlines or near them. For example, a combination of fish cages and seaweed or bivalve cultivation could reduce nutrient loading as well as organic matter levels in water bodies. Additionally, using cages together with artificial reefs could lead to stock enhancement and provide opportunities for future sustainable aquaculture.

Several technical points should be emphasized here:

Nets quality improvement against fouling agents/predators versus a reduction dependence upon antifouling paints;

Designing new types especially deepwater/large size/submersible ones;

Scaling up necessitates more stringent risk management strategies;

Equipment for grading, handling, counting offloads, and biomass estimates must be improved.

Cage culture’s future requires good environmental control by managers who consider several things: mortality within survival rates; accuracy when estimating fish population inside a particular pond; feeding regimes that minimize wastage due to overfeeding; material balances inside an enclosed system; models focusing on nutrient release including sedimentation, dispersion, and benthic deposition; understanding of recovery mechanisms to find optimum following periods; rotation schemes for sites and improved mooring equipment for easy management; remote sensing in areas without infrastructure and connections among aquaculture facilities.

Countries that are likely to expand their coastal aquaculture must manage their coastal zones effectively, and define clearly property rights and access rights.

Offshore Cage Farming/Sea Farming

Though it requires advanced surveillance technologies and far-off feeding controls, open sea aquaculture has some advantages like increased dispersal of wastes and exchanges, as well as safe designing. Nevertheless, such merits are outweighed by the costs of production being prohibitive while all other existing initiatives are still at the stage of prototypes. On top of this, fish performance may not be similar in inshore against offshore environments thus more research is needed on this matter.

Different from near-shore cage systems there are infrastructure requirements for open sea farming. This means that offshore systems can work for long periods without going back to the shore for repairs which present specific challenges related to repairing nets. In addition, they may need various support structures (platforms) used during operations such as sorting, harvesting, handling, checking, and treatment.

In the short-term period, high-value species will most likely determine whether open sea aquaculture is a feasible enterprise.

Summary 

Aquaculture constitutes an important part of the global food system contributing towards sustainable seafood provision as a way of catering to population explosion. The type of farming taking place on the farm and its location will dictate what kind of aquaculture system is appropriate given the amount of yields required.

To find out more about aquaculture or the equipment we have to offer for monitoring aquaculture systems feel free to reach out to the world-class team at Atlas Scientific

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