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Shaun McLennan explains why there’s no simple way to differentiate between the sustainability of various fishing gear types and methods.

Before joining the MSC in February 2016, I spent 3 and a bit years working for the UK government as fishery manager. One of my roles was to assess the impacts that different fishing techniques have on protected marine environments. As with many elements of fisheries management, the answer to the question: “Which fishing method is most environmentally-sound?” isn’t as simple as it may seem.

It’s all about context

Any fishing will have an impact on the environment, but its relative impact depends on a range of factors.

The simple question above leads to many others, for example: Are enough fish being left in the ocean to allow them to reproduce and maintain a healthy population? Are other species being incidentally caught or damaged, and does this threaten their survival? How quickly can impacted habitat recover? Is there enough data to understand the impacts of fishing?

While it is true to say that bottom towed gear such as bottom trawls, scallop dredges and the like, is often associated with impacts on the sea floor, really all fishing techniques have a range of impacts on the environment: rod and line fishing, for example, can have less impact on bottom-dwelling creatures (known as ‘benthos’), but if heavily used, can result in overfishing and the depletion of important fish species. Although not generally thought to create much impact on benthos, lost or discarded long lines, crab pots and gill nets can have lasting impacts on sensitive ecosystems through their legacy of entanglement (known as ‘ghost fishing’).

What about trawling?

Trawling is a common form of commercial fishing as it allows the efficient capture of large volumes of fish living in shoals far below the surface.

Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net is called a trawl. Trawling can be done with various types of equipment (known as fishing gear). There are three main types of trawl:

  • Mid-water trawls make no contact with the seabed. These are often referred to as ‘pelagic trawls’.
  • Semi-pelagic trawls are towed closer to the bottom and may sometimes come into contact with the seabed.
  • Bottom trawls are in contact with the seabed.

The impact on the seabed varies greatly depending on the trawl’s weight and size, the area “swept” by the trawl, and the amount of time it is in contact with the seabed. In addition, the ecological consequences of trawling can vary considerably depending on the type and state of habitat being fished on. For example, trawling on shallow water ‘high energy’ sands will have a completely different impact to trawling on deep water muds or on areas that contain slow growing cold water corals.

Modern technologies, designed to reduce environmental impacts and conserve fuel by reducing drag, mean that trawling gear has been substantially modified in recent years. For example, weighted ropes used to weigh nets down on the seabed are being replaced with ‘rock hoppers’ – rubber wheels which allow the net to skip over the surface of the seafloor, reducing the time the gear is in contact with the bottom.

Other modifications, such as changing the mesh size and including ‘escape hatches’ or sorting grids, help to reduce the level of unintentional catch. This is important to ensure the sustainability of fishing, but also reduces the amount of unwanted, often lower value (from a commercial perspective), fish brought on board.

MSC certified fisheries making improvements

MSC certified fisheries demonstrate how gear modifications and careful fisheries management can result in greater levels of sustainability. The South African hake trawl fishery, for example, only fishes in delimited zones and no fishing is allowed on virgin ground, so that sensitive habitats are protected.

The hake fishery also uses scaring lines which prevent seabirds from becoming entangled in fishing nets, reducing albatross deaths by 99%. It is investing in a science and monitoring programme to map sensitive habitats and understand how the sea floor recovers from trawling.

The MSC certified New Zealand hoki trawl fishery is another example of how bottom trawling can be sustainably managed. Bottom trawling is banned during the spawning season, when mid-water trawls are used instead. Careful monitoring and management of fish stocks have allowed fish populations to more than double since 2001. In 2007, with support from the fishing sector, New Zealand closed 1.1 million km2 (30%) of its waters to bottom trawling, making it the largest area in the world closed to this type of fishing.

Norwegian Barents Sea cod fisheries are another example. MSC certified fisheries in the Barents Sea have extensive monitoring and mapping initiatives in place including the MAREANO programme and PINRO-IMR collaboration. These fisheries actively avoid fishing in areas with sensitive habitats by fishing in predetermined “corridors” when catching fish near the ocean floor.

Requirements for MSC certification

For all the reasons explained above, the MSC does not prejudge the sustainability of different fishing gears. With the exception of those using explosives and cyanide, all types of fishing gear can be assessed to the MSC Fisheries Standard. Assessment focuses on outcomes. Independent assessors consider the impacts of the particular fishing gear on the particular environment and within the confines of the particular regulatory and management system.

To be certified, a fishery must be well managed, fishing in a way that ensures healthy fish populations and not causing irreversible harm to the environment. Where there is room for improvement, fisheries are given conditions of certification requiring them to develop new ways of managing the impact on the marine environment. The MSC is also developing the way in which habitat impacts are assessed by the MSC Fisheries Standard. For example, the newest version of the MSC Standard has specific requirements for very sensitive environments called Vulnerable Marine Ecosystems.

A note on the deep sea

There is no single established definition for ‘deep sea fishing’. The UN FAO considers species below 200m to be ‘deep sea species’; the International Council for the Exploration of the Sea (ICES) puts it below 400m, while the European Commission defines a deep sea fishery using a list of species. Generally, deep sea species are characterised as having low growth rates, slower rates of reproduction and are commonly found in deeper waters.

Rather than defining an assessment approach for specifically exploited depths, the MSC Standard takes an ecosystem based approach, considering the unique fishery, ecosystem and governance characteristics as a whole.

Ensuring continuous improvements

In conclusion, no fishing is free from impacts – it’s the significance of these impacts and their reversibility, and how they are managed, which is important. Government regulation, together with technological advances and demand for more sustainable seafood is helping to evolve and improve the way our fish is caught. By choosing MSC certified seafood, and helping to encourage more fisheries to improve to the robust standard set by the MSC, you can help to ensure healthy oceans for the future.

Find out more about sustainable fishing