Also known as greenbone because of, you guessed it, their bright green bones, butterfish are a special shallow reef species. Eaten fresh, they truly live up to their name with a buttery texture that melts in your mouth.

They are commonly caught by set net and, more recently, have become a sought-after catch for spearfishers in the Marlborough Sounds.

Sadly, butterfish populations at the top and west coast of the South Island are in trouble. Fisheries NZ recently reviewed their management. In response, the Minister for Oceans and Fisheries has introduced a recreational daily bag limit of five butterfish per person. The new limit applies from 1 November.

To understand why, we need to look at what we know about their stock status, their ecology and how they are fished.

Stock Status

Butterfish around the top and west coast of the South Island are part of Quota Management Area 7. There isn’t enough data to say whether they are overfished, but anecdotal evidence suggests butterfish numbers are declining and the fishery needs a break. 

A lack of information is no reason to delay or avoid action. The Fisheries Act requires caution when information is uncertain, unreliable or inadequate. As Minister, Shane Jones has a legal obligation to ensure sustainability and prevent or mitigate the long-term damage to the marine environment. 

The only logical decision was to reduce pressure on butterfish populations by leaving more fish in the water. 

Ecology of Butterfish

Fishing isn’t the only factor. Habitat loss is likely a major driver too. 

Butterfish love kelp. They depend on healthy kelp forests for food and shelter, so the loss of kelp in some areas has left them more vulnerable to both environmental and fishing pressures. 

Studies indicate that as our oceans warm, herbivorous fish such as butterfish are likely to fare worse, because kelp is sensitive to marine heatwaves and rising temperatures. In the Marlborough Sounds, giant kelp has undergone a long-term retreat, with sedimentation and kina overgrazing compounding the loss.

Fisheries NZ estimates that 20-40% of historical commercial butterfish catch was taken from areas now affected by kelp loss.

We have little control over warming waters. What we can control is how we fish. Leaving more fish in the water builds resilience against environmental change that no catch limit can itself manage.

We can also control the size at which butterfish are harvested. It’s disappointing that the current minimum legal size (MLS) of 35 cm does not reflect their biology. 

All butterfish begin life as females, and around half the population changes to male between 37 cm and 45 cm. With the MLS set at 35 cm, fish can be taken before they have a chance to breed. Our July submission supported a review of the MLS to reflect this unique trait and help populations recover.

Changes to Catch Limits

Our submission also supported giving butterfish in this area their own daily bag limit of seven per person, rather than leaving them in the mixed finfish bag of 20.

Whenever we support a cut to our bag limit, it’s because we are genuinely concerned about the state of the fishery and want to see abundance return. Alongside the commercial cut, this is recreational fishers doing their part. 

A species-specific limit makes sense for a stock of unknown status. Cutting the de facto limit of 20 helps provide for the reasonably foreseeable needs of future generations while delivering a meaningful reduction.

A limit of seven also recognises that butterfish are taken by two very different methods. Spearfishing is selective, so a diver can take a precise number. Set netting is less so, and a single lift may bring up multiple fish.

The Minister opted instead for a limit of five. That may work for spearfishers, but for set netters it risks forcing the return of fish already caught, increasing wastage.  

The same review also looked at commercial fishing. The Minister decides the annual Total Allowable Commercial Catch (TACC), which is divided up between quota holders. In late 2025, the quota holders voluntarily agreed to shelve some of their TACC, leaving it uncaught.

The Minister has now cut the TACC from 38 to 14 tonnes, locking in the level the industry had already agreed to. We’re concerned this arrangement merely formalises the status quo rather than adding any margin for precaution. Given how little is known about these populations, it’s unclear whether this reduction goes far enough.

Depletion Breeds Conflict

Butterfish don’t tend to move far from their home reef, which makes them especially vulnerable to localised depletion. 

Recreational spearfishing appears to be growing in popularity in the Marlborough Sounds. It’s great to see more people getting in the water. But if that growth continues, pressure on the most accessible reefs will build.

Commercial spearfishing adds to the pressure. LegaSea backs small-scale, low-impact commercial operations that deploy selective techniques rather than bulk harvesting. Spearfishing has a negligible impact on the seafloor and little to no bycatch. 

The difficulty is that commercial spearfishers work the same accessible reefs favoured by recreational spearos, creating an overlap between the two fisheries. This concentrates harvesting effort on the same discrete areas, heightening the risk of localised depletion to which butterfish are particularly susceptible.

As butterfish populations come under more pressure, there is a growing risk for conflict in the water as people chase a shrinking resource. That’s why we submitted strongly in support of officials facilitating cross-sector engagement and a review of where these fisheries overlap.

Managing for Abundance

Catch reductions like this are often the ambulance at the bottom of the cliff. By the time they arrive, the damage is done. The better approach is to manage stocks like butterfish at higher levels from the start.

Rebuilding our inshore fish stocks to at least half the estimated biomass that existed before industrial fishing began means the good stuff follows: better fishing, healthier ecosystems and a more resilient ocean.

It all comes back to restoring fish populations. Like many Kiwis, we’re tired of dealing with the fallout of poor management. We’d rather see meaningful action now, – to keep people safe in the water, and so our future generations can enjoy an abundant and thriving coastal marine environment.

References:

1. Joint recreational submission. BUT 7 review. 24 July 2026.
2. Hay, C. H. (1990). The distribution of Macrocystis (Phaeophyta: Laminariales) as a biological indicator of cool sea surface temperature, with special reference to New Zealand waters. Journal of the Royal Society of New Zealand, 20(4), 313–336;
3. Williams, B. M. (2025). Status, values, and restoration potential of Macrocystis pyrifera kelp forests in Aotearoa New Zealand [Embargoed PhD thesis]. University of Otago.
4. Tait, L. W., Thoral, F., Pinkerton, M. H., Thomsen, M. S., & Schiel, D. R. (2021). Loss of giant kelp, Macrocystis pyrifera, driven by marine heatwaves and exacerbated by poor water clarity in New Zealand. Frontiers in Marine Science, 8, 721087;
5. Bunting, I., Kok, Y. Y., Krieger, E. C., Bury, S. J., D’Archino, R., & Cornwall, C. E. (2024). Marine heatwave intensity and duration negatively affect growth in young sporophytes of the giant kelp Macrocystis pyrifera. Frontiers in Marine Science, 11, 1423595.
6. Wing, S. R., Shears, N. T., Tait, L. W., & Schiel, D. R. (2022). The legacies of land clearance and trophic downgrading accumulate to affect structure and function of kelp forests. Ecosphere, 13(12), e4303.
7. Doheny, B., Davis, J. P., & Miller, B. (2023). Fishery-induced trophic cascades and sea urchin barrens in New Zealand: a review and discussion for management (New Zealand Aquatic Environment and Biodiversity Report No. 324).
8. Lafont, D. J., & Shears, N. T. (2025). Assessing drivers of variation in the distribution of macroalgal forests across a complex marine environment in Central New Zealand. Marine Environmental Research, 209, 107171.
9. Review of sustainability measures for butterfish (BUT 7) for 2026/27, Fisheries New Zealand Discussion Paper No 2026/18. June 2026.