New Zealand Sea Fishes

Blue Shark – Prionace glauca – also Blue Pointer, Blue Whaler

Blue sharks are viviparous – their young are born fully formed and swimming

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The blue shark is easily distinguished from the mako by its more slender body. The pectoral fins are also much longer. The blue shark, also known as a blue whaler or blue pointer, lives up to its name with the upper body colouring a strikingly vivid cobalt blue. The blue fades darker after capture becoming almost black. The undersides are bright white. The large black eye has a circle of white around it and a nictitating membrane that closes over the eye to protect it from struggling prey. Its eyes close each time it takes a bite out of something!

Unlike the Mako, the blue shark has no keel where the body joins the tail. The blue shark is more slender than the mako. However, when blues reach about 9 feet in length they tend to become heavier in the body rather than growing much longer. They reach a maximum fork length of 10 feet.

Howard Lewis of Canterbury with a blue shark taken on SWF gear. Note the Alvey Saltwater Fly Reel. This is a relatively inexpensive saltwater fly reel well capable of landing big sea fish.

Also unlike the mako blue sharks doesn’t jump clear of the water when hooked. A really big blue shark can weigh as much as 500 pounds (230kg). The range of the blue shark is vast. It can be found close to shore as well as in the deep sea. It ranges widely across the world in tropical, subtropical and cooler temperate waters. It is found anywhere in waters between 10 degrees C to 22 C. In years past this species was much more common in New Zealand inshore waters than it is today.

Rob Gray and a 57.4kg blue shark – Canterbury Sport Fishing Club.

In the 1970s blue sharks were occasionally captured during surfcasting competitions held along the Canterbury coast. This is also true of other species; with groper also being caught at such events by surfcasters. Such a catch would be unknown today!

Pictured is a blue shark caught about a decade ago surfcasting at Gentle Annie Beach, Mokinui, north of Westport, on the South Island’s West Coast. In the United States, blue sharks are known to come into very shallow water. In 1996 a person wading in shallow water in Truro, Massachusetts, required 46 stitches to close a leg wound inflicted by a blue shark.

Typical Deceiver pattern or Berley fly for targeting blue sharks. You need a good supply if you are tagging and releasing your fish. Size 5/0 hooks and the fly needs to be at least 100mm in length.

The name blue whaler comes from its habit of following whaling ships to feed on the constant supply of waste product associated with such an enterprise. The rotting carcasses of dead sea mammals are eaten when available. It also feeds on schools of fish and squid which it follows in its migrations across the oceans. It is estimated that as many as 20 million blue sharks are caught by fishermen every year. Most of these are taken as accidental bycatch when targeting more sort after species.

This small blue shark was taken surfcasting at Gentle Annie Beach on the South Island’s West Coast.

Although eatable the flesh of the blue shark is quite watery. It is essential to process the flesh quickly after capture before the onset of urea decomposition which makes it un-eatable with a strong ammonia smell.

Blue sharks are viviparous (their young are born fully formed and swimming). They can have very large litters with as many as 135 being recorded. However, the average is between 25 to 60 pups. This species is one of the easiest game fish to catch found in the southern waters of New Zealand. It is targeted by southern anglers in search of Saltwater Fly and light-line record International Game Fish Association New Zealand and world records.

The usual method, from my own experience off Canterbury and Otago, is to head five miles or so offshore and then start a berley trail. Typical berley being blood and minced fish. We would mix this with seawater in 20-litre buckets and ladle it at a constant rate of about a litre per minute on to the surface. A surprisingly small amount of blood will colour a lot of seawater! Twenty litres of blood tipped straight over the side, depending on sea conditions, seems to turn acres of ocean pink!

This would be supplemented by a large mesh onion bag containing fish heads, frames, offal, and so on, tossed over the side and secured to the boat by a rope. How long it would take for blue sharks to arrive would depend perhaps on the quality and quantity of the berley. In my experience, it takes anywhere from one to five hours. However, on the half dozen or so occasions I have done this I have never known the sharks not to show up! When the sharks do arrive it is important to keep the berley slick going at a constant rate should they otherwise lose interest. It is a good idea to assign a crew member to the task otherwise in all the excitement it is easy to forget.

Blue shark weighing 71 kg caught by Howard Lewis off the Canterbury Coast.

It is a somewhat eerie experience to be surrounded by large sharks; particularly in a smaller boat. The blue sharks always seem to arrive first or at least are the first to be seen. They swim in slow sinuous motion right up to the boat where they inspect the berley bag and appear to me to be quite unafraid. It has been my experience for there to be a mixture of sizes from quite small ones or perhaps just over a metre to much bigger specimens of over three metres. Unlike, say kahawai, for example, that school by size.

In my view, blue sharks are sluggish fighters and seem to be especially dumb fish. They can be hooked in the jaw, but will totally ignore the hook and swim back to the berley bag for another look, at the same time continuing to feed on other baits in the water! Apparently the heads of very large specimens, in excess of 400 pounds, become bigger and broader. The current all-tackle world record for blue shark is a 528 lbs specimen caught by Joe Seidel at Montauk, New York, on 9 August 2001. Many of the record line class captures of blue sharks have taken place along the eastern seaboard of the United States particularly off Massachusetts. However, this may simply be because of the higher concentration of big game fishing vessels and anglers on this coast.

The Blue Shark with Gary Wilson

The Blue Shark is a wide-ranging shark found throughout most of the world’s warm and temperate oceans. It is especially abundant around the New Zealand coastline and is probably the most commonly caught game shark in the South Island.

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Although similar in appearance to the mako, the blue is as its name suggests is a brilliant cobalt blue in colour while its lower body is a snowy white. lt is a relatively slender-bodied shark that is easily identified by its long pectoral fins, pointed snout and small triangular teeth which unlike the teeth of a mako, are not visible when its mouth is closed.

Being such a slender shark, a blue will weigh lighter than a mako of an equivalent length. For instance, a 3-metre blue shark could be expected to weigh around 400 lb whereas a mako of a similar size would
pull the scales down to around the 800 lb mark.

A blue shark inspects the berley bucket.

This species of shark is known to grow over 3.5 metres long and weighed over 450 lb (205kg). The current IGFA all-tackle record is for a fish caught off Catherine Bay, Australia back in 1976 which weighed in at 437 lb (198.22kg) generally though in our waters they are a lot smaller with a fish of over 176 lb (80kg) being classed as a good one.

The blue is a true pelagic shark, more commonly found in the open ocean than in waters closer to land although at times it will venture in quite close to shore sometimes coming into surprisingly shallow water, in fact, one was speared a few years back, in of all places, the Christchurch estuary.

Blue sharks are more abundant in waters between 7-18 degrees, which in the South Island means that they are found fairly close to the surface of the ocean whereas in warmer tropical waters they are found deeper down where the water is cooler only venturing up to the surface to investigate any possible disturbance which may indicate food.

Tagging has shown that the blue shark is a great wanderer and it will cover great distances in its travels, at times crossing entire oceans. The record at the moment is held by a shark that was tagged off the New York coast and later recovered over 3,666 miles (5900 km) away in Brazil.

Many blue sharks are captured with bite marks on the body, these fish are almost always female. The bites are caused by the somewhat aggressive behaviour of the male

shark during mating. Over centuries the female blue has evolved a skin several times thicker than that of the male, this thicker skin is located at strategic points along the body and is there to reduce the damage caused during “lovemaking”. A male blue can be identified from the female by a set of claspers located on the underside of the shark’s belly near the vent. They are actually extensions of the pelvic fins and are used by the male during mating to deliver sperm into the female reproductive tract.

A female blue shark will give birth to an unusually high number of young for a shark. Litters have been known to contain over 120 pups but the usual litter size is a lot smaller with half that number being more common, once born the young are abandoned by their mother and are left to fend for themselves. The blue shark is an opportunistic feeder and it will feed on most small sharks, fishes and squids. It also responds well to burley, at times swimming right up to the back of a boat to take a baited hook.

The first sighting of blue shark in a burley slick is often a reddy-brown smudge moving up the trail toward the boat, though in areas like Kaikoura, they are often sighted on calm days free swimming with their dorsal fins sticking out of the water and are fished for only if they are considered large enough for capture.

The blue shark is reputed to be a relatively poor fighter. In some instances, it will swim around the boat after being hooked while still feeding on items in the burley trail and, at times like these, a small tap on the head with the burley masher can work wonders in motivating a hooked fish to fight as it should! Most of the blue’s reputation as a poor fighter can be put down to the fact that they are usually taken on tackle which is far too heavy for them to show their stuff. If lines are kept under 10kg (20lbs), your average blue puts up quite a good account of itself and although not in the league of a mako, it will certainly keep the angler busy for a while!

 

This post was last modified on 17/10/2021 12:42 pm

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