Aquaculture – A Solution to Ghost Gear?

First, let’s define what is aquaculture and what practices are being used.

The practice of aquaculture, the controlled breeding, rearing and harvesting of marine organisms, is rapidly growing contrasting branch to commercial capture fisheries.

Aquaculture has been practiced all over the globe for centuries. However, it was not until the 1980s, the tremendous decline in global fish stocks and the emerging “Blue Revolution” that aquaculture was used as a major source of fish supply. Besides crustaceans, molluscs and aquatic plants, fish contribute a major part of cultivated marine organisms in aquaculture. Today, more seafood on our plates come from aquaculture than from fisheries. Generally, aquaculture can be distinguished by practices in artificial facilities (onshore), in inland waters (inshore) and in marine waters (offshore).

Fig. 1: Offshore aquaculture facility. Source : https://foodtank.com/news/2014/10/whats-up-with-organic-fish-in-the-united-states/

Even though initially proposed to counteract declining fish populations, over the years the biological and environmental concerns of aquaculture such as pollution, invasive species, genetic modification, fish diseases and deforestation of coastal areas have risen. Further, common predatory fish such as salmon need other fish products in their nutrition, resolving in a vicious circle. The fish in/fish out (FIFO) ratio defines how much weight of wild fish is needed to produce a similar weight of farmed fish. Even though, some farmed fish may have low FIFO ratios of low as 0.3 such as for carp, for other fish such as salmon FIFO rates go up to 5 (it takes 5 kg of wild fish to produce 1 kg of farmed salmon).

But, is aquaculture important anyways…?

Aquaculture production has been increasing by over 500% since 1990 and today, represents a major source of fish supply for human consumption.

Fig. 2: Aquaculture and fish production. Source : FAO 2020

One might think that with the controlled aquaculture systems, various ecological and environmental problems from commercial fisheries might be solved. Especially the plastic pollution from commercial fishing might be tackled as the aquaculture tanks are controlled, stationary and used gear does not get lost as easy as commercial fishing nets. But, is that so…?

What about plastics in aquaculture..?

Ghosts gear that constitutes a major part to global ocean plastic comes from fisheries. It ends up in the ocean being discarded, lost and abandoned. So, well managed aquaculture with stationary tanks might be a solution to this problem, right?
The truth is that aquaculture industry makes huge use of plastics. From aquaculture gear such as nylon fish cages and -nets, buoys, pond liners, shellfish farming bags to tools and materials such as bags, bottles and buckets, plastics can be found in every processing level in aquaculture. Unfortunately, the plastics are lost very easily into the ocean by storms, poor waste management and even intentional discharge. In some cases, heavy storms associated with high waves and heavy rainfall can flush coastal aquaculture facilities and wash all gear out in the ocean. The magnitude of plastics in the ocean originated from aquaculture is very poorly understood and estimations are extremely difficult to make as no monitoring of aquaculture facilities is conducted. A study from Sherrington et al. 2016 summarizes and compares the magnitude of waste from fisheries and aquaculture in the European Economic Area. They found that 130,000 – 500,000 tonnes of ocean debris is originated from fisheries and 95,000 – 655,000 tonnes come from aquaculture. As the aquaculture sector is the fastest growing food sector in the world, one might argue that waste from aquaculture may exceed waste from fisheries many times over. Plastic pollution originated from aquaculture is gaining attention just in recent years with the extensive growth of the sector, however, the issue needs to be dealt with urgently. With the continuous growth of the sector it needs to be made sure that the plastic pollution from aquaculture does not grow simultaneously.

Fig. 3: A diver controls the aquaculture equipment under water. Source : https://www.sueddeutsche.de/wissen/aquakultur-muschelzucht-zwischen-muelltueten-1.3159782

So, are there any good news?

The problem of plastic pollution from aquaculture is slowly gaining attention in recent years. In 2019, the Aquaculture Stewardship Council (ASC) has published a paper addressing the issue of plastics, litter and ghost gear in aquaculture. In this paper they are reviewing additional criteria for ASC certified farms to address the issues of plastic pollution from aquaculture and the need to set new standards. They propose a responsible use of plastics in aquaculture using the ‘5 R’s’ approach – Reduce, Re-use, Recycle, Recover, Refuse. Further, just this year, the GGGI (Global Ghost Gear Initiative) has released the “Best Practice Framework for the Management of Aquaculture Gear”, an extensive document guiding aquaculture stakeholders how to prevent and reduce gear loss from aquaculture. This framework provides guidance addressing the issue of plastic pollution in various aquaculture sectors, from gear manufacturers to aquaculture operations, being the first document of its kind. Also, research on biodegradable products in the fishing- and aquaculture sector is growing. For instance, the European project BIOGEARS have developed compostable aquaculture ropes that are currently being tested aiming for a sustainable aquaculture in the future.

But, what can we do now?

It is fundamental to know about how the choices we make affect the environment. Even though, both the aquaculture and the capture fisheries sector might reduce the usage of plastics in the future, it is crucial to know that other problems such as bycatch and decline in fish stocks in fisheries and organic pollution and eutrophication of coastal waters in aquaculture are taken place. In that sense, we should be conscious about the fact that every fish on or plate comes with certain costs. Especially in countries that are not reliant on fish as basic nutrition, we should be aware of the costs that come with it, reduce our fish consumption, consume consciously and don’t support products from aquaculture that are not proven to be a part of the solution but instead are part of the problem.