The Complete Guide to New Zealand Flounder — Pātiki | Fish Species Guide

The Complete Guide to New Zealand Flounder — Pātiki

Everything you need to know about our iconic flatfish: their secret life cycle, where to find them, when to fish, and the rules you need to follow.

New Zealand's harbours, estuaries and coastlines are home to one of the country's most popular — and most mysterious — fish. The flounder, or pātiki as they're known in te reo Māori, have been feeding Kiwi families for generations. But how much do we really know about these masters of disguise lying beneath our feet?

Whether you're setting a net in the Kaipara, wading the mudflats of the Manukau, or gigging off a west coast beach, understanding your quarry makes you a better fisher — and helps keep our fishery healthy for the next generation.

👉 Browse our full range of NZ-made flounder nets →

Meet the Family: New Zealand's Four Flounder Species

New Zealand is home to four native flounder species, all belonging to the genus Rhombosolea:

Yellow-belly Flounder (Rhombosolea leporina) — Pātiki-tōtara

The star of this guide. Oval-shaped with a greenish-brown back and distinctive yellow underside that develops as the fish matures (juveniles start out white). Grows up to 50 cm. Most abundant around the North Island and the most common flounder in harbours like the Kaipara, Manukau and the Firth of Thames.

Sand Flounder (Rhombosolea plebeia) — Pātiki

Diamond-shaped with a greenish-brown back and white belly. Grows up to 45 cm. Prefers sandier habitats in harbours and open coastline. Very common in the Hauraki Gulf, Bay of Plenty, Canterbury Bight and Tasman/Golden Bay.

Black Flounder (Rhombosolea retiaria) — Pātiki-mohoao

Oval-shaped with brick-orange spots on a dark back. Grows up to 45 cm. The only species that can live entirely in fresh water — found in estuaries, coastal lakes, rivers and the open coast. Common in Canterbury and Southland, especially Lake Ellesmere/Te Waihora.

Greenback Flounder (Rhombosolea tapirina)

Oval-shaped with a dark green back and white belly. Grows up to 50 cm. Often confused with the yellow-belly. More common in the South Island, particularly Canterbury Bight and Southland.

The Secret Life Cycle of a Flounder

The life of a flounder is one of remarkable transformation — from a tiny, upright-swimming fish with eyes on both sides of its head, to the flat, camouflaged bottom-dweller we know.

Stage 1: Eggs & Larvae (Winter–Spring)

Adult flounder migrate offshore during winter to spawn in deeper coastal waters, typically 18–50 metres deep. In the Hauraki Gulf, yellow-belly flounder spawn during September and October in a belt from Tapu on the eastern Firth of Thames, north-west towards Ponui Island. The spawning season can extend from June to December.

A single female can produce a staggering number of eggs — a 45 cm yellow-belly flounder can release up to 1.25 million eggs in one spawning event. Smaller 30 cm females produce around 250,000. The eggs are fertilised externally in the water column, and larvae hatch after about 4–5 days.

Here's where it gets interesting: newly hatched flounder look nothing like the flat fish we know. They swim upright, like any normal fish, with one eye on each side of their head. They drift with the currents and tides, carried from offshore spawning grounds towards the sheltered estuaries and harbours.

Stage 2: Metamorphosis — The Big Transformation

As the larva grows, something extraordinary happens. The left eye begins to migrate across the head to the right side. The fish transforms from an upright swimmer into a side-lying bottom-dweller. The right side (now facing up) darkens to match the seafloor, while the underside stays pale. This metamorphosis happens as the larva moves from open water into shallow inshore areas.

Stage 3: Juvenile Life (First 2 Years)

Once both eyes are on the right side, juvenile flounder settle onto the seafloor in shallow estuaries, harbours and inlets. They prefer the very shallowest areas — warm, sun-heated mudflats and sandflats, sometimes in water just inches deep.

As they grow from 5–20 cm, juveniles start venturing into slightly deeper inshore channels, moving out with the ebb tide. They're not fussy eaters at this stage — they'll hoover up amphipods, small crustaceans, worms, molluscs and detritus from the mudflat floor.

Stage 4: Adulthood & Spawning (2+ Years)

Yellow-belly flounder reach maturity at about two years old. Males mature at around 15–24 cm, while females need to grow larger — typically 26–29 cm before they're ready to spawn.

Adults move into deeper waters and begin the seasonal pattern that will define the rest of their lives: spending summer in harbours and estuaries to feed, then migrating offshore in winter to spawn.

How Long Do They Live?

Yellow-belly flounder typically live 3–4 years, with some reaching 5 years. This means most will only spawn once or twice in their lifetime. The oldest known flounder in New Zealand was a 10-year-old greenback, found off the south-east coast of the South Island.

You can't tell a flounder's age by its size — scientists use the fish's ear bones (otoliths), which grow rings like a tree, one per year.

Where to Catch Flounder

Flounder are found right around New Zealand's coastline, but yellow-belly flounder are most abundant in the North Island.

Prime Habitat

The golden rule: look where freshwater meets saltwater. Flounder love the brackish zones where streams and rivers flow into harbours and estuaries. These areas are rich in crabs, shrimp, whitebait and small shellfish — everything a flounder wants to eat.

Best structure to look for:

• Mudflats and sandflats with channels running through them
• Creek and stream mouths entering estuaries
• Cockle beds (full of crabs and worms)
• Flat papa rock shelves (they hold heat from the sun)
• Eelgrass beds
• Edges of mangrove areas
• Worm beds on surf beaches (especially west coast)

Famous flounder spots include:

• Kaipara Harbour — one of NZ's best flatfish grounds
• Manukau Harbour — huge flats with excellent channel structure
• Firth of Thames — key yellow-belly habitat
• Hauraki Gulf — both sand and yellow-belly
• Raglan / Kāwhia / Aotea harbours — west coast gems
• Whangarei Harbour — prolific Northland estuary
• West coast surf beaches — big yellow-belly on the worm beds
• Canterbury Bight and Lake Ellesmere — South Island strongholds
• Otago Harbour — good populations of all species

Best Times to Fish

Flounder feed primarily on the incoming tide, moving up from the deeper channels onto the shallow flats to hunt. The last three hours of the incoming tide are usually the most productive.

Best months: November through May, with January to April being peak season for spearing and gigging. However, good catches can be taken year-round, especially with nets set in channels.

Time of day: Flounder are largely nocturnal feeders. Night fishing with a spotlight (floundering/gigging) is a Kiwi tradition — calm, dark nights on an incoming tide are ideal.

Pro tip: Scout your spot during the day at low tide. Look for channels, soft mud, crab holes and creek mouths. Mark them, then come back at night on the incoming tide.

Choosing the Right Flounder Net

Getting the right net makes all the difference. Action Outdoors manufactures all our flounder nets right here in Auckland — designed specifically for New Zealand conditions and regulations.

Set Nets

Set nets are the classic flounder fishing method — set them across a channel or along a mudflat edge and let the fish swim into the mesh. Our set nets come in 20m, 30m, 40m and 60m lengths with 100mm mesh (the legal minimum for flatfish).

• Flounder Net Mono Mesh Floating Top Rope (20m–60m) — Monofilament mesh with floating top rope. Great all-rounder.
• Flounder Net Multi-Mono Floating Top Rope (30m–60m) — Multi-mono mesh for extra durability and fish-holding ability.
• Flounder Net Mono Mesh Floats on Rope (30m–60m) — Mono mesh with floats threaded on the top rope.
• Flounder Net Multi-Mono Floats on Rope (30m–60m) — Multi-mono with floats on rope for maximum visibility and buoyancy.
• South Island Flounder Nets (20m–60m) — Designed for South Island conditions and species mix.

Drag Nets

Drag nets (also called beach seine nets) are hauled by hand through shallow water — perfect for sandy beaches and surf flats.

• NZ Made Flounder Beach Drag Nets (15m–40m) — NZ-made beach drag nets for floundering on the sand.

👉 View all flounder nets →

When and Where Do Flounder Breed?

Yellow-belly flounder spawn during winter and spring — primarily June through December, with the peak typically September to October.

Adults migrate offshore from harbours and estuaries into deeper coastal water (18–50 m) to spawn. After spawning, they head back inshore during summer to feed and fatten up for the next cycle.

Key spawning areas:

• Hauraki Gulf — September–October, in waters 18–27 m deep between the Firth of Thames and Ponui Island
• Avon-Heathcote Estuary — short breeding season in winter/spring
• Throughout mainland NZ coastal waters, Stewart Island and the Chatham Islands

Flounder are in their best eating condition over summer (December–April) when they're fat and feeding hard. By late winter/early spring they're thin and depleted after spawning.

MPI Rules: What You Need to Know

Fishing rules are set by Fisheries New Zealand (part of MPI) and apply to all recreational fishers. Breaking them can result in fines up to $20,000, so it's worth knowing the basics.

Minimum Legal Sizes

• Yellow-belly flounder: 25 cm (measured nose to the V of the tail)
• Sand flounder: 23 cm (most areas; 25 cm in the Challenger FMA)
• Black flounder: 25 cm
• Greenback flounder: 25 cm

At 25 cm, a yellow-belly flounder is approximately 2 years old and may have spawned once — but research shows only about 15% of females are sexually mature at this size. The legal limit is designed to let the majority of fish breed at least once.

Daily Catch Limits

Flounder are counted within the combined daily finfish limit:

• Auckland/Kermadec FMA: 20 finfish total per person per day
• Central FMA: 20 finfish total
• South-East FMA: 30 finfish total

There's no separate species limit for flounder — just stay within your combined bag.

Net Rules for Recreational Fishers

Set Nets:

• Maximum length: 60 metres
• Must have a surface float at each end, marked with your surname, initials and phone number
• Must not be baited
• Only one set net per person (plus one bait net up to 10 m with ≤50 mm mesh)
• Nets must be at least 60 metres apart from other set nets
• Cannot block more than one quarter of any river, stream, channel, bay or waterway
• Must not strand fish by the falling tide
• Nets can only be hauled by hand — no winches

Drag Nets:

• Maximum length: 40 metres
• Only one per person
• Must be hauled by hand

Minimum Mesh Sizes:

• Flatfish (including yellow-belly, black and greenback flounder): 100 mm mesh
• Sand flounder: 100 mm mesh
• These minimums ensure undersized fish can swim through. The bigger the mesh, the bigger the fish you keep.

Mesh is measured across two opposing knots when the mesh is pulled tight — not corner to corner across the diamond.

Set Net Bans & Restricted Areas

This is the big one — and it's worth checking your specific area before you go:

North Island West Coast (Māui Dolphin Protection): Set netting is banned from Maunganui Bluff to Pariokariwa Point (north of New Plymouth), extending out to 7 nautical miles offshore. Additional bans apply in the Kaipara, Waikato, Raglan and Manukau harbour entrances. This is to protect the critically endangered Māui dolphin.

South Island East Coast (Hector's Dolphin Protection): Set netting is banned out to 4 nautical miles along most of the east coast from Clarence Point to Slope Point. Limited exemptions exist for flounder nets in some areas with specific conditions (smaller nets, winter-only, close to shore).

Marine Reserves: No netting of any kind — including Kāpiti, Taputeranga, Long Island, and others.

Specific closed areas exist in most regions — Pāuatahanui Inlet (no set netting), parts of Otago Harbour, and many others. Always check the MPI website or the free NZ Fishing Rules app for your area.

How to Stay Legal

1. Download the free NZ Fishing Rules app — it uses your GPS to show local rules
2. Text a species name to 9889 for a free rules reply
3. Check signs at your fishing spot
4. Visit mpi.govt.nz/fishingrules for full regional details
5. When in doubt, release the fish

A Fish Worth Protecting

Flounder have been feeding New Zealanders since long before European arrival. In Māori tradition, pātiki are taonga (treasured) — a vital mahinga kai (food resource) for iwi across the country. The diamond-shaped pātikitiki weaving pattern, inspired by the sand flounder's shape, is one of the most recognisable designs in Māori art.

Today our pātiki face challenges: habitat degradation in estuaries, sedimentation, invasive species like the Asian paddle crab, and fishing pressure. By following the rules, using the right mesh size, and releasing undersized fish carefully, we can all play a part in keeping this fishery strong.

Quick Reference Card

Action Outdoors is New Zealand's largest fishing net manufacturer, producing over 350,000 metres of ready-to-use nets every year from our factory in Auckland. Browse our full range of flounder nets, set nets and drag nets →

Always check the latest MPI rules for your area before heading out: mpi.govt.nz/fishingrules

Sources: NIWA Taonga Species Series — Pātiki; Fisheries New Zealand (FLA reports); MPI Recreational Fishing Rules; Wikipedia — Yellowbelly flounder; University of Waikato research; University of Canterbury research.