New Zealand’s deep seas are abundant in fish that provide people with healthy nutrition. Fish like hoki live near the seabed, so we fish for them there by bottom trawling. It is the most common commercial fishing method in New Zealand.
What is bottom trawling?
Bottom trawling is a practical and efficient fishing method where a net is towed on very small areas of seabed, where large amounts of target fish species live.
More than 50 per cent of Sealord’s seafood harvest is caught by bottom trawling. Our hoki, jack mackerel, southern blue whiting, squid and ling harvest represents 40 per cent of all fish caught in New Zealand’s seas.
We use technology to precisely find fishing grounds, avoid rocks and to monitor and adjust each trawl. This improves fuel efficiency and how we use our vessels and crew, which helps to lighten our trawling footprint.
Trawling is very limited and highly regulated
Wild fisheries like ours have one of the lowest environmental impacts of any food production, much lower than other animal protein production such as land-based farming1
Like any type of food production, bottom trawling has an impact. But unlike other food production, the area we trawl is very limited.
New Zealand has one of the largest ocean territories (also called our exclusive economic zone, or EEZ) in the world. Less than five per cent of the seabed in our territory is trawled each year, however. Fishers return to the same grounds and use fewer trawls to catch the same amount each year. To replace the amount of food our fisheries provide would require an extra 1.4 million football fields of land cleared for agriculture.
It is important to measure, understand and manage the effects of any type of food production. Using technology such as satellite global positioning systems, our trawling activities are monitored and reported by Fisheries New Zealand. This informs better fisheries management.
Conserving seamount biodiversity
Some bottom trawling occurs on the slopes of seamounts (underwater hills of 1,000m or higher). The total area trawled on the slopes is small and fishers return to the same spot each year, leaving most of the seamount untouched.
The number of seamounts we trawl is also very limited. Of the 142 known seamounts in our ocean territory only 15 have been trawled once or more between 1989 and 2019. 127 seamounts are closed to trawling or have never been trawled.
Find more information about our proposal here:
 Hilborn: The environmental cost of animal source foods, 2018
Commercial and recreational fishers sometimes catch animals they do not intend to. This happens despite using methods and technology to catch a particular species and minimise the risk to others.
Spotlight on sea lions
New Zealand sea lions live mostly in the Auckland and Campbell Islands and are now breeding on Stewart Island and the Otago mainland.
Our squid and southern blue whiting fishing grounds overlap with some sea lion foraging areas, so we use sea lion exclusion devices (SLEDs) in these areas. SLEDs are an attachment in the net that allow sea lions to escape.
Since 2005 the estimated number of sea lions (from fishery observer records) captured annually by deepsea trawlers has reduced by around 80 percent. These efforts contribute to the Department of Conservation’s Sea Lion Threat Management Plan, which is also looking at ways to reduce disease and pup mortality rates. In some years, half of the pups born have succumbed to disease or drowned in mud holes.
As one of the founding members of the Southern Seabird Solutions Trust, we've been at the forefront of issues concerning sustainability. Over the years, we've been involved in several trials, such as different kinds of bird bafflers, configurations of tori lines, as well as participating in information-gathering initiatives.
Seabird Mitigation Measures are an important part of what we do. As well as mitigation equipment, each vessel has a Vessel Management Plant that manages offal discharges into the sea to avoid attracting seabirds.
Solutions for seabirds
Seabirds are attracted to fishing vessels for the potential of an easy feed. Some of the ways we reduce the risk of a bird becoming caught in trawling gear are by:
Sealord is a founding member of the Southern Seabird Solutions Trust, focused on developing further solutions and recognising fishers who excel in minimising seabird bycatch.
Keeping an eye on the catch
Commercial fishing skippers are legally obliged to report their catch. The locations of our deep sea vessels have been monitored by satellite since1994, and our catches have been electronically reported to Fisheries New Zealand since 2010.
We aim for transparency in our reporting and welcome government-appointed observers on our deep sea vessels. We typically have enough observers on board to verify the catch and meet scientific sampling requirements.
Sealord supports the use of cameras on vessels, although plans to put more cameras on New Zealand vessels currently focus on other companies’ inshore fleets. It’s not always practical to host an observer on a small inshore vessel that has a very limited amount of space for crew. It’s not always practical to put a camera on a deep sea fishing vessel either, because the vessels are at sea for several weeks, often in rough weather conditions.
New Zealand’s Quota Management System (QMS) and annual catch limits underpin our global reputation as a leader in sustainable fisheries management. To make the most of the QMS and ensure we can meet consumer demand for healthy seafood, Sealord invests in precision seafood harvesting and is active in industry and government discussions about discards.
Precision seafood harvesting
Precision seafood harvesting (PSH) is a fishing method that helps us target a particular species and let the little fish escape. It also allows fish to be brought alive onto vessels in perfect condition because the fish are transferred from one body of water (the sea) into another body of water (large containers) on deck. This makes it easier to return any undersized fish to the sea in good condition.
The PSH system is a great Kiwi ingenuity story; the technology is the outcome of a Primary Growth Partnership between Sealord, the Ministry for Primary Industries, Aotearoa Fisheries and Sanford.
The deal on discards
Discarding is the process where a small proportion of caught fish is returned to the sea. We can legally discard a fish if it is:
an undersized quota management species (QSM)
a non-QMS fish that we cannot process into fish meal onboard a factory vessel
one of a specific range of shark species (eg spiny dogfish)
one of a small number of species listed in the Fisheries Act (eg kingfish) that are likely to survive when we return them
authorised by a fishery observer.
All other fish must be brought back to shore and reported to a licensed fish receiver at the end of the fishing trip. The QMS fish are then counted towards the total allowable catch limit for the area the fish were caught in.
It is illegal to discard fish in any situation other than those listed. Some fishers may illegally discard fish, arguing that it is uneconomic not to do so. The commercial fishing industry is working with the Ministry of Primary Industries and hopes to find a solution that will incentivise fishers, not penalise them, for bringing unusable fish back to shore.