Blue Cod

Blue Cod

For all their modest size and undistinguished looks, blue cod have long been an important species to the New Zealand fishery. And no wonder. They can be found right up into shallow water, making them easy to access; they are easy to catch and will accept a wide range of baits and lures; and are definitely one of the tastier species in our waters. Sam Mossman gives a run-down on this popular table fish.

Archaeologist Foss Leach, in his definitive book Fishing in Pre-European New Zealand lists blue cod as making up 16.6% of fish remains found in excavated pre-European middens, making them the second most important species to early Maori.

The commercial fishery for blue cod also has a long history. It is predominantly an inshore domestic fishery with very little deep-water catch. The major commercial blue cod fisheries in New Zealand are off Southland and the Chatham Islands, with smaller but locally significant fisheries off Otago, Canterbury, the Marlborough Sounds and Wanganui. National landings of up to 3000 tonnes were being reported over ninety years ago and catches of 2500 tonnes were sustained for many years in the 1950s and 1960s.

Traditionally, the commercial catch was taken by handline, but these days it mostly comes from cod potting, which is considered much more ecologically sound. Since 1994-95, total landings still exceeded 2000t annually, peaking at 2500t in 2003-04. The Total Allowable Commercial Catch currently stands at 2,332 tonnes and in some fisheries regions the TACC is a little overfished, while in others it comes in a little under. Overall, commercial catches have remained stable at this level in recent years.

By contrast, while ranked as the third most popular species for recreational anglers (after snapper and kahawai), amateur fishers only take around 300 tonnes (12%) of the total blue cod catch from South Island and Chatham Island waters. Recreational blue cod fishing is probably at its most popular in the Marlborough Sounds and with a decline in the fishery there, considerable tinkering with regulations and management has been going on in recent years.

Chatham Islands fisherman Sam Lanauze with a ripper cod.

Chatham Islands fisherman Sam Lanauze with a ripper cod.

The recreational fishing effort in other southern areas has historically been relatively low (largely because the numbers of recreational marine fishers in the South Island are much lower than those in the North). The latest survey results suggest participation in recreational fishing is trending downwards.

Blue cod, although a southern icon and the predominant reef species in South Island waters, are found right throughout the country. I grew up fishing in Hawkes Bay waters, a sort of fishy Mason-Dixon line with more snapper to the north and blue cod increasing to the south. Over the years I have caught solid two-kilo plus specimens of cod as far north as Spirits Bay and even the Three Kings Islands, but there is no doubt that southern regions are their spiritual home and the best cod fishing I have experienced has been off Fiordland, Stewart Island and the Chathams.

When are cod not cod?

Blue cod (Parapercis colias) are not actually related to the true cods, such as red cod. Rather, they’re weevers, which places them in the wider sandperch family, joining about 50 other species internationally under this umbrella. Three of these have been recorded in NZ waters and two of them, the uncommon yellow cod and the blue cod, are endemic to our waters. Another, the redbanded grubfish, is also found in Australia. Most sandperch species are small in size, with our blue cod amongst the biggest of the bunch and one of the few with enough growth potential to support a commercial fishery.

A chunky, pugnacious-looking fish with tasty white flaky flesh, the colour of blue cod changes with size. Juveniles have a whitish body with two brown stripes running their entire length and maturing fish darken to brown and then a mottled grey. When they reach about 30cm a further change to green or blue occurs, from which the species draws its name. I have also encountered jet-black coloured specimens at Stewart Island and Fiordland. Early European explorer James Cook referred to blue cod as ‘coalfish’, perhaps because this species reminded him of the coalfish (pollock) of Atlantic waters, or maybe he encountered some of the jet-black specimens which reminded him of the colour of mineral coal.

A cod’s life

Blue cod are a moderately long-lived species, although ages over 20 years are relatively uncommon in research surveys, making up just 2% of the records. The oldest recorded age for blue cod is 32 years (a 58cm male) and was caught offshore from the Banks Peninsula in 2002. Of course, we are talking age here, not size, and growth rate may be influenced by a range of factors, including sex, genetics, habitat quality, available feed and fishing pressure relative to location. It is a bit like humans: growth rate does not necessarily equate to age. You can get big young blokes and little old blokes.

Size-at-sexual maturity also varies according to location. In Northland, maturity is reached at 10-19cm at an age of two years, while in the Marlborough Sounds it is reached at 21-26cm at 3-6 years. In Southland, the fish become mature between 26-28cm at an age of 4-5 years.

Most blue cod don’t get around too much. While tagging programs have shown occasional individual movement records of up to 156km, around two-thirds of the fish moved less than a kilometre.

Blue cod spawning seems to occur towards the second half of the calendar year but varies between areas, from August to November in the north; August to October in the Marlborough Sounds, August to December around Stewart Island, November to January at Chatham Islands, October in Otago and November to January in Southland. Eggs are pelagic for about five days after spawning and larvae are pelagic for about five more days before settling onto the seabed.

Gender benders

Blue cod are hermaphrodites, with individuals over a large length range changing sex from female to male, but the presence of some large, older females suggests that not all blue cod undergo sex change. Blue cod males grow faster and are larger than females. Large males tend to defend a territory around a group of females, and this aggressive territorial behaviour of large males may suppress sex change in smaller females.

What’s for dinner?

Cod are voracious feeders and will take just about any small animal or fish they can get their jaws around. They mostly feed on the bottom, preying on a wide variety of small fish (including juvenile blue cod), as well as worms, crabs, small octopus and so on. Over 50 different items were identified from the stomach contents of blue cod in one area. A lot of the cod I have caught at the Chatham Islands had small whole paua (30mm) in their stomachs, and paua gut (hua) is a great bait for them.

Sometimes they will come up off the bottom to feed, most notably in southern waters when there are huge concentrations of salps or krill higher in the water column. On one occasion, we berleyed an aggregation of blue cod to the surface out of 30m of water using a gory mix of paua hua and chicken gut favoured by cod potters there. The fish were so switched on that I caught a number of big specimens by sight-casting saltwater flies to them.

Fishing for cod

Blue cod can hardly be regarded as a sport fish unless you get to the ends of the scale – very big fish on light tackle. In some of the blue cod Valhalla’s like the Fiordland coast, Stewart Island or the Chathams, we regularly caught blue cod of 3-5kg, and on 4kg tackle such fish can pull a bit. However, this sort of gear is regarded as pretty “soft” by the hard-bitten locals. No finesse is required for cod in remote areas. A bit of 8mm rope with several large long-shanked hooks spliced in and half a sash weight or a dive weight added to the bottom serves to harvest a feed of cod. And the bait? Why blue cod of course!

Blues are absolute suckers for a baited ledger rig and will take most baits. They are not picky about old smelly bait either, sometimes seeming to prefer it to fresher stuff. If there is a ‘secret weapon’ bait for blues, it is probably small whole octopus or paua gut. Add these to one of Black Magic’s fluoro-green ‘Snapper Snatchers’, and you have a rig that will catch pretty much any cod that swims.

Research has shown high (25%) mortality in released fish that are deep-hooked, but mouth-hooked fish survive release well. It is suggested that circle hooks or J-hooks size 6-0 and above can be used to avoid deep hooking undersized fish.

Cod on jigs

But I can seldom bring myself to fish for blue cod with baits anymore. Jigging holds much more attraction. It is a simple technique – just drop the lure to the bottom and yo-yo it up and down. As a long-time advocate of soft-plastic lures, I can vouch for the fact that they are absolutely lethal on cod. I started catching cod on Mr Twister soft-baits way back in 1981, and the new designs of scented tails fished on light braid are even more effective. Perhaps too effective even, as cod can be very aggressive biters and are pretty hard on the tail supplies. The tougher brands of soft-baits, such as Z-Man or Black Magic’s Dartspin lures, are recommended.

Many modern lure styles that were initially introduced into northern fisheries for snapper are equally effective on cod. Kabura (sliders), inchiku types and slow-pitch metal types all work well and are best rigged with single hooks for easier unhooking. Jigs nearly always mean mouth hook-ups, too, so there is no drama with deeply hooked fish. Using medium-sized jigs (80g or so) will weed out a lot of the smaller fish, reducing the need to deal with undersized specimens which have to be returned.

If drift fishing is employed, this method will crop the larger adult males (the ones you want) without hitting any one group too hard. The next senior fish (if it is a female, it will change sex to a male) will then take over management of the group in the tradition of ‘dead man’s shoes’ promotion.

The advantages of this style of fishing are many: no bait is required, so there are no problems getting and storing it, there is no time wasted, less mess to clean up afterwards, no anchor pulling to be done and prospecting different areas is quick and easy. I also reckon that lure fishing is more fun than bait, especially if lighter tackle, four or six kilo line, is used.

How big?

Some of the ‘official’ data list blue cod as having a maximum length of 55cm and weight of 5kg. However, for some areas I reckon this is a bit conservative. On one trip along the wild southern Fiordland coast some years ago, we stopped to jig a shallow off-shore bank for a couple of hours. We kept 10 of the best cod. On the scales, six of these made the old-fashioned ten-pound mark and a couple of the heaviest were over five kilos. They reminded me a bit like Staffordshire bull terriers with fins! And that was just a quick stop to catch a feed on a single trip – not trying too hard.

Blue cod are available to anglers from the shallows, right out to 150m-plus.

Blue cod are available to anglers from the shallows, right out to 150m-plus.

Occasional cod probably grow even bigger than this. Foss Leach reports cod remains from a Chatham Islands midden with a derived length of 68.5cm. There is a length-weight conversion equation for cod, and using it, a fish of this length equates to 8.1kg (17.85 old-fashioned pounds).

I have a couple of mates with whom I used to fish for southern bluefin tuna off the Fiordland coast: long-time Fiordland cray fishermen Mark Harris and Ron Grant. I once asked them just how big blue cod grew. Now bear in mind, these are reticent southern men who habitually understate things. The question was cause for reflection. A rollie was carefully constructed and lit before a considered opinion was given. “I reckon we’ve caught them to 16 or 17 pounds over the years,” said Mark, and Ron nodded his agreement.

I like to muse that, somewhere in the Southern Ocean, hanging around a deep, remote rocky pinnacle, maybe somewhere off the Snares, is an ancient, scarred, gnarly twenty-pound blue cod that eats eight-inch paua for breakfast and could rip the throat out of any barracouta that intruded on his turf.

   This article is reproduced with permission of   
New Zealand Fishing News

May 2020 - Sam Mossman
Re-publishing elsewhere is prohibited

Rate this

Fishing bite times

Major Bites

Minor Bites

Major Bites

Minor Bites

  • Fishing Reports, News & Specials