You may have seen recent news  around the sustainability of harvesting from rock pools and the use of bottom trawls. Making sustainable seafood choices is one of the most important things we can do to help prevent overfishing and protect our marine ecosystems. Navigating information on sustainable seafood can sometimes be tricky.  

On 16 April we held a free interactive workshop hosted by Sir Peter Blake MERC to build skills and knowledge around choosing, harvesting and preparing kaimoana that’s healthier for us and for our ocean as a part of Auckland’s EcoFest. 

A major reason all three of these were showcased at the event is their position in the marine food web. All of these species sit near the ‘bottom’ of the food chain feeding directly on algae and plankton.

Sea urchins are considered a delicacy around the world. Called uni in Japanese or Riccio di mare in Italian, there are a variety of popular recipes. Many people believe that it is best eaten raw right out of the test, but it can be prepared on rice as uni sushi or in a dish called Spaghetti ai Ricci di Mare where the kina roe is mixed with garlic and olive oil to make a rich ocean-flavoured sauce.

It is important to note that sea urchins that live on tropical coral reefs help protect corals by eating algae that can overgrow them. We recommend avoiding eating urchins and herbivorous from these areas.

Both of these bivalve molluscs can form important reef structures layering on top of rocks and then each other! Farmed GreenshellTM mussels all start out as wild spat (baby kūtai) from 90 mile beach in Northland and are grown to adult size on farms across the country. The preferred tio for farming are the introduced Pacific Oyster because they grow faster than the native species.

Tio are best eaten raw with various sauces like mignonette or a cocktail sauce with horseradish and ketchup. If you’re adventurous, putting tio on the BBQ for a few minutes and using a garlic-parmesan butter is a favourite preparation. Kūtai can be eaten raw, but it is best to cook them before eating. You can boil or steam them (you can flavour the water with spices or other liquids) until their shells open. Avoid overcooking, or they get chewy. Simply serve with butter, or with finely diced onion and capsicum with a can of coconut milk and pour over the cooked kūtai for a nice Thai spin on this delicious kaimoana.

Did you know?

Ocean food chains tend to be much longer than most of the land-based food we eat? Most food from the land only involves one or two steps from the energy source, the sun (ex. Sun -> grass -> cow). In the ocean, most fish people eat involves 4 or 5 steps up the food chain (ex. Sun -> phytoplankton -> zooplankton -> small fish -> large fish). With each step, there is an overall loss of energy leaving each higher step with less overall biomass. So even though the top predators are larger animals, there are a lot less of them!

Seafood is a major source of protein, fats, and nutrients in many places around the world and is increasingly used to make dietary supplements. There are, however, important human health concerns in addition to consequences for ocean health. Pollutants we release on land and at sea are absorbed and consumed by marine life. These become more concentrated in the bodies of animals higher up in the food web. Plastics further concentrate many chemical pollutants, adding even higher pollutant loads. Plastic waste, from nanoplastics to large pieces, are found in every marine habitat including the most remote polar and deep sea environments. These can be consumed by animals at every level of the marine food web, sometimes to the point of filling up their stomachs. 

There is a wide range of chemical pollutants including heavy metals, PCBs, dioxins, PFAS and more, largely coming from industrial processes, fertilizers, pesticides, and herbicides. These can have negative effects on marine life and people that eat seafood. These pollutants can affect endocrine, reproductive, immune, nervous systems, and more, altering the health and productivity of populations and ecosystems. While risks of heavy metals are more widely known and have resulted in guidelines limiting the consumption of certain fish species like tuna, swordfish, and sharks, several other pollutants are less well known.

Many factors are considered when evaluating the sustainability of fisheries, aquaculture farms, and seafood products. A key factor includes having effective management and regulation in place. For both wild caught and farmed seafood, minimising environmental impacts is important. In fisheries, low bycatch levels and avoiding overfishing are also important. Bycatch includes any marine life caught in addition to the target species when fishing. Overfishing means removing more of the population than can be reproduced by the wild population resulting in declines. Globally, over 35% of fisheries are considered overfished.

Fisheries & bycatch

Different types of gear result in different levels of target catch and bycatch and can have other environmental impacts. Bottom trawl is the most common commercial gear used in New Zealand accounting for 69% of commercial catch in 2023-2024. Bycatch can either be landed and sold, donated for research/education or disposed of, or it is discarded and released at sea. The chance of survival when released alive depends on several things including the type of gear used, where and when they were caught, how they were handled, any injuries sustained, and the biology of the species.

Fisheries can be managed on species and ecosystem levels. There are typically regulations for species and for different gears used.

While this system works relatively well, there is always room for improvement! As of 2025, 493 stocks including 14% of commercial catch still need to be assessed, and some assessments have not been repeated in several years. Currently, 13% of assessed stocks are considered overfished or collapsed. There is an even greater need to invest in frequent stock assessments as pressure from climate change, pollution, and coastal development continue to influence the productivity of our marine species and ecosystems. It is also vital to continue to identify and protect more of our important marine areas.

Seafood farming and aquaculture are a fast growing and opportunity rich area of food production and export for New Zealand. There are ways fish farming can be done well to supplement or replace wild caught seafood, but there are also several important concerns and considerations. Mussles, oysters, salmon and kingfish are some of the key species that are actively being farmed in New Zealand. 

Choosing local New Zealand seafood will have a lower carbon footprint than imported options and is also more reliably well-managed than seafood originating from many other places. Fishing methods differ in their impact on the environment as well as their levels of bycatch. Species caught by pot or line tend to have lower levels of bycatch and habitat damage. Gear contacting the bottom (like bottom trawls and dredges) can damage seafloor habitats and stir up sediment releasing carbon and smothering sedentary species. Learn about your local operators like Moana NZ that strive to embody a values based, intergenerational approach and have invested in technologies to improve selectivity and quality of catch and reduce bottom contact. 

Another option is ‘catch to order’. Groups like the Tora Collective take orders and deliver what you want when you want it, a great alternative to harvesting yourself.

Other resources for making sustainable choices include the Ministry of Primary Industries (MPI) Stock Status Table, Marine Stewardship Council labels, and Seafood Watch. 

DIY harvesting is the clearest way for you to know where your seafood came from and how it was collected! There are many things to consider in addition to the official rules to make sure you are harvesting sustainably. 

Recreational harvesting in New Zealand allows many more gears to be used than in other countries, some of which are highly destructive, both in terms of habitat damage and bycatch levels. Recreational fisheries can have just as much and in some cases more of an impact on fish populations than commercial fishing. Additionally, legal limits for some species are higher than populations can realistically support depending on the number of people collecting.

There are many ways to engage in citizen science where you can contribute important information toward understanding and tracking patterns and changes in our ocean and marine life. Tindale Marine Charitable Trust runs a fish tagging programme where you can get a kit to measure, tag and release fish to find out more about their survival and movement. You can submit sightings of wildlife through iNaturalist on your own or through participating in bioblitz events. Taking our survey is another great way to engage in citizen science right from your home! Check out events through Seaweek and local organisations to get involved in your area!