Blue Cod
This species guide was written by experienced saltwater angler, and Black Magic Brand Ambassador, Dan Govier. Dan is based in Nelson, New Zealand, and regularly spends his weekends fishing around the beautiful Marlborough Sounds with his wife and daughter.
DESCRIPTION
Blue cod are only found in New Zealand waters and can live for up to 30 years. They are often thought of as a South Island fish; however, they are present throughout the North Island. They can change sex from female to male as they grow older to ensure that breeding populations continue to exist. The adults are bluish green to blue-black on the upper half of their bodies, with white towards the body. They can have a range of pigments in their skin, including brown and orange spotted through their main colours. Their colours can change as they grow and develop.
Their heads are prominent and rounded with a plump shaped body covered in firm scales. Their large lateral eyes can rotate independently, which allows them to see almost everywhere around them.
Blue cod don’t have a swim bladder which means they will sink to the sea floor if they stop swimming. Therefore, they are classed as a bottom dwelling species, which is why they also have a flat abdomen.
They‘re opportunistic carnivores, who stalk their ‘prey’. Their diets include pilchards, sprats, mullet, mussels, crabs and other blue cod, all of which they are known to eat whole.
Blue cod are very inquisitive and extremely territorial – they’re known to approach divers and nip their fingers! These factors, combined with their voracious appetite and lack of fear – can make them susceptible to over-fishing, leading to special limits and fishing closure periods during their spawning season being implemented in parts of New Zealand. You’ll find if you’re fishing in an area that has not had a lot of fishing pressure, you will generally catch the big males first.
Please check your local fishing regulations for more information.
Spawning takes place in late winter and spring each year, as a continuous event where their eggs are released over time into the water column. These eggs remain pelagic within the water column for about five days before settling to the seabed. Young fish, once hatched, are found below 20 metres, then move to shallow water in summer. Juvenile cod between 100-150 mm are white with a broad brown band along each side, but when they are adults, they become more distinctly blue with green sides.
SIZE AND WEIGHT
Blue cod can grow up to 60cm in length and weigh up to 4kg. However, most blue cod are commonly caught around 0.8 – 1.5kg.
Growth is believed to be rapid during the first year, after which it slows down, as fish tend to increase in weight rather than length.
The average size of blue cod varies with locality (larger in the southern region) and also with sex, where males tend to be larger than females.
Growth rates and size at sexual maturity is dependent on location; Northland cod are mature at 10-19cm at two years old, Marlborough Sounds at 21-26cm at three to six years and Southland at 26-28cm at four to five years.
WHEN AND WHERE TO FISH
Blue cod are endemic to New Zealand and are a bottom dwelling species. Juveniles are found in the shallow waters around the rocky coastlines, and adults (over 25cm) are found in water depths up to 150 metres. Despite this, they are predominately an inshore bottom-dwelling domestic fish commonly found near reefs and around rocky bottoms with patches of sand and weed.
They can be found all around New Zealand but are more common south of the Cook Strait and are an iconic species in the South Island.
Home range and movement patterns of blue cod are poorly understood, but it’s believed that movements may be size related and fish in enclosed areas (e.g. Marlborough Sounds) move less than those in open areas (e.g. Foveaux Strait). This supports the theory that fisheries in sheltered waters should be managed separately as we are now seeing with blue cod fisheries management, as fish in enclosed waters have little intermixing between fish stocks which can make them susceptible to overfishing.
FISHERIES MANAGEMENT
The stocks of blue cod around most of New Zealand have decreased compared to what they used to be, but the Marlborough Sounds has seen a significant decline in blue cod numbers and size, and the fishery has come under considerable stress compared to 30 years ago.
Following the significant decline in blue cod numbers and increasing concerns from many, a working group was formed to develop objectives and increase public engagement to ensure everyone had an opportunity to provide input to developing a Blue Cod Strategy. The strategy recognises that the blue cod fishery is unique, and that management of the fishery needs to incorporate the life cycle and broader ecological needs. All of this was implemented to ensure that there is an abundant and sustainable fishery for all to enjoy in the future.
In 2020, the Blue Cod Strategy introduced a traffic light system for the South Island blue cod fishery where recreational daily limits were based on the health of the local fish stock to achieve stock sustainability. A colour rating system was designated for each of the different blue cod management areas in the South Island to provide a management framework that enables the colour rating to be changed based on available information that may support whether that the fish stock is improving or declining.
The traffic light system is comprised of three components, as listed below, but for further information please visit the MPI website:
- Green – these areas have the healthiest blue cod stocks, and have a daily limit of 15 blue cod;
- Orange – these areas are rebuilding or possibly declining, and have a daily limit of 10 blue cod; and
- Red – the blue cod in these areas are in trouble and have a daily limit of two blue cod.
The blue cod fishery in the Marlborough Sounds is closed from 1 September to 20 December each year to prevent targeting of blue cod during their breeding season.
A range of different management measures have been in place for the Marlborough Sounds Area now for over several years and the blue cod fishing is starting to show some recovery.
So, make sure you check and understand the rules and regulations for catching blue cod in your area in terms of size limits, daily takes, and closed seasons, particularly if you fish in the South Island to ensure we can continue to catch this iconic species into the future.
HOW TO FISH
Blue cod would be one of the easier fish species to catch, given they are primarily scavengers. They will eat almost anything you throw at them and almost any rig will work well around reef and rocky structures.
FLASHER RIGS
Flasher rigs baited with pilchard, mackerel, squid or any fresh bait you have caught works well. When a blue cod is hooked it will twist and spin a lot on the line, so you need to have a strong trace to prevent the line from breaking or being twisted beyond repair. Snapper Snatchers® or Snapper Snacks®, despite the name, work very well for blue cod. These rigs are tied using [Black Magic] 80lb Tough Trace which is durable against the reef areas that are often fished, and also makes it much easier to untwist the trace if you hook a blue cod. You can catch a lot of smaller blue cod when fishing an area, so the recurve hooks rigged into Snapper Snatchers® and Snapper Snacks® help ensure the cod are hooked in the mouth and any released fish stand the best chance of survival. However, if you don’t want to use flasher rigs, you can make your own ledger rig using [Black Magic] 80lb Tough Trace and KLT® or KL hooks. It’s recommended to not use hooks smaller than 5/0 to avoiding catching the smaller fish.
SLOW JIGS
Slow jigs also work very well for catching blue cod. They can be much easier to use given you don’t need a sinker and bait, so the gear feels lighter when using it, and I often find slow jigs attract the bigger more aggressive fish given their territorial nature. Some people are tempted to put bait on slow jigs; however, don’t fall into that trap, as it will often attract the smaller fish.
[Black Magic] Sunakku® slow jigs are a great slow jig for chasing blue cod, as it’s a very clean way of fishing, and they produce the results. Make sure you work the full range of the water column where you can see fish on your sounder. This is because some of the bigger fish can be cruising higher in the water column, so if you work the jig slightly off the bottom, you’ll often find the bigger fish. Using colour marked braid such as [Black Magic] Rainbow Braid Elite 8x (which has indicators for every 1 metre and 5 metre) is a good way of knowing how far off the bottom you are.
The recent release of 200g Sunakku® jigs will allow you to fish slow jigs in deeper waters or areas where there is strong current to ensure you can still get to the bottom. However, a trick to remember is that you want to fish the lightest jig possible that will still get you to the bottom, as this jig will provide the best action and entice more fish to take your line.
