Why Do Fish Jump?

Sam Mossman ponders the question, "Why do fish jump?"...

Some of the most exciting fish to catch are those that jump clear of the water when hooked. Of New Zealand’s saltwater species – 1,262 of them at last count (2015 figures) – only a handful could be fairly listed as regular aerialists, and then only some of these jump when hooked.

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The most obvious of these, and the most commonly caught, is the kahawai. Found throughout the country’s coastal waters, they certainly live up to their Māori name, a rough English translation of which is ‘strong in the water.’ But they could be fairly called ‘strong in the air’ as well, as they will often blast through the surface when hooked. Although they only grow to a maximum of about 5kg, they are great fighters on light tackle or flyrod, and, contrary to the opinions of some, are a tasty eating fish when bled and chilled promptly. A balmy evening out on the deck with a bottle of chilled pinot gris and a big bowl of fresh kahawai ceviche is a summer favourite in our household.


The billfish: blue, black, and striped marlin (and by extension spearfish, sailfish, and the much more distantly related broadbill swordfish) are renowned for their dynamic aerial displays and the excitement this gives anglers when doing battle. Along with their size, this makes billfish one of the most popular gamefish to catch. Jumping marlin are so iconic that googling ‘jumping marlin image’ will get you over ten million hits.

Some anglers claim that various of the marlin species are better jumpers than others, but I have seen all of the main three Pacific marlins go ballistic on the line, all recording over 30 jumps in a fight. I personally reckon the extent of any given marlin’s aerial performance depends on a wide range of factors. These may include the fish’s physical condition, size (smaller ‘firecrackers’ tend to jump more than bigger, heavier fish), the water temperature (billfish in the tropics seem to put on better displays and these tend to be blues and blacks, inflating these species fighting reputation), oxygen levels in the water, how they are hooked, the individual attitude of the fish, and probably other factors I have not thought of.

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Some shark species are jumpers as well. Notable are the more highly developed ‘game’ species, especially the Lamnidae or mackerel sharks. Many readers will have seen footage of great whites carrying out attacks on seals, charging up from below with their strikes carrying them clear of the water. I once was sitting in a 3.6m dinghy in the Tiri’ Channel, catching a few snapper, when an unexpected thresher shark of about 50kg blasted out of the water about 40m away, clearing the surface by around three metres. The big bronze whalers that move into coastal waters in early summer to feed and have their pups will sometimes take to the air when hooked, being in prime condition and ‘full of beans’ at this time. In popular recreational areas like Auckland’s Takapuna Beach, this behaviour can cause some concern amongst the immersion water sports crowd!

But easily the shark most renowned for its jumping ability is the explosive mako. They are our greatest game shark a powerful, stocky fish with attractive blue, silver and white colouration, they have a sinister beauty and black, soul-less eyes. A number over the old-fashioned 1,000lb (454kg) mark have been caught, and are still being caught, in NZ waters. They have one of the highest brain-to-body-size ratios of any shark and are also warm-blooded, capable of maintaining a body temperature well above that of the surrounding water. This is a big advantage to a predator as warm muscles work better, and this extends their range into cooler, richer waters.

Seasonally, makos are present right through our waters but seem to prefer temperatures over 16°C. Their blood-warming ability helps explain the athleticism of these sharks. They are fast swimmers, and propelled by powerful rigid tails, can put up some tremendous displays of jumping, sometimes reaching an estimated eight metres above the surface. They have been known to jump aboard boats during a fight, and if provoked may also attack boats, sometimes leaving teeth stuck into the hull. Many readers will have seen footage shot last year off Whitianga of a decent-sized mako, hooked and jumping, landing on the bow of a charter boat. Better than in the cockpit, I guess!

Pioneering American angler Zane Grey really rated the mako, calling it New Zealand’s premier gamefish and ensuring its Māori name achieved worldwide usage. This is from his book Angler’s El Dorado:

“He came out slick and fast without a splash and as he swept upward, stiff as a poker, gleaming blue-white, with wide pectorals spread and huge tail curled, his great savage head narrowing to a spear point, he was assuredly a spectacle to fire any angler. I yelled with the rest of them…He shot out so close to our bow that he could have touched, and he went up to half the height of our mast, fifteen feet above the water, and turned in the air to smack down with a resounding roar.”


Another species of jumper, although only an occasional summer visitor to New Zealand waters, is the mahimahi. Although having a mostly tropical distribution, some are caught, most years, in waters around the northern half of the North Island. I have encountered them off the Bay of Islands, Tutukaka, Whakatane, East Cape and wide of the Manukau, in warm summer months when the water temperature is high. Most New Zealand specimens tend to be smaller fish (under 10kg) but several fish of over 20kg have been caught here.

These fish are highly valued for their bright colours, powerful fights (including considerable aerial work), and exceptional quality as table fish. They are surface-oriented and are attracted to floating debris and structures. With warming ocean temperatures, we may see more of them in local waters in the future.

Get forked

So, what do marlin, makos, mahimahi, and kahawai have in common that helps account for their tendency to jump when hooked? An obvious common feature is (for their size) large, deeply forked tails. At a pinch, the mako’s large lunate tail with near even-sized upper and lower lobes fits roughly into this mould. Tails of this design can provide the large amount of speed and power required for a fish to clear the water. Another local species, the grey mullet, while seldom caught on a hook, is a commonly observed free-jumper and also has a large, deeply forked tail.

But deeply forked tails are not a diagnostic feature of jumpers. Many fish have deeply forked tails but are not known to jump when hooked. And what about sunfish? They have sort of big sculls top and bottom of the body and no real tail. I had always considered them to be sluggish old waddlers who could hardly get out of their own way until I saw several of them jump clear of the water!

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Hot blooded

What about the musculature and blood circulation systems of these fish? Sharks of the Lamnidae family, such as makos, are known to have what is called ‘regional endothermy’ – elevated body core temperatures. This allows these sharks to hold a body temperature well above that of the surrounding water via a clever heat transfer system in their circulatory system.

Marlin, too, have the ability to heat blood through specialised organs. This warmer blood is largely directed to the marlin’s brain and eyes, allowing it to hunt more successfully in cooler waters which, in the NZ context, can mean both being able to penetrate further into cooler southern waters or to feed successfully in deeper, cooler water (under the thermocline). But the billfish version of blood heating would seem to be a less effective system than that of makos, which are commonly encountered much further south than billfish.

Mahimahi, to the best of my knowledge, don’t have specialised blood-heating systems but, as mentioned, the core of their range is in the tropics and we only see them in local waters in midsummer when our ocean temperatures reach their peaks, so it is a reasonable deduction that they are dependent on staying in hot water to keep their body temperatures high, rather than developing an internal blood heating system.

What about kahawai? I know of no research that shows any clever blood-heating mechanisms in these fish but what they do have is a lot of blood, and a pretty decent pump (heart) to drive it quickly around their bodies, as anyone who has bled one can confirm – if you are not careful, this can be a messy business! Lots of blood, delivered quickly, carries lots of oxygen: fuel for powerful muscles.

For the high jump

The time of year seems to be related to how much fish will jump, as well. Some fish build up condition with the approach to spawning and the better their condition, the more airtime they get. A good example is kahawai. In my neck of the woods (or should that be weeds?) kahawai are as fat as mud and chocka with roe and milt around Easter until they spawn around May. They are like jumping jacks at this time of year.

Some fish jump freely in the normal course of their usual activities, but rarely when hooked. I have mentioned grey mullet and sunfish already. Salmon are well known for jumping obstacles like small waterfalls when running to spawn but seldom take to the air when hooked.

Hot pursuit

Flying fish use the air as a refuge when being pursued by predators and can glide long distances on their hang glider-like wings with just the tip of their elongated lower tail lobe dipping into the water to give a bit of extra drive. Other baitfish will jump, too, when herded against the surface by predators – nowhere to go but up!

I have seen large yellowfin tuna jumping clear of the water when chasing smaller skipjack tuna that are themselves leaving the water, trying to escape. The skippies themselves will take to the air in pursuit of baitfish, but neither species are known to jump on the line.

Attempting to rid themselves of parasites may be another reason for fish to take to the air and it is a fair bet that this is one reason why makos, marlin and sunfish are seen free jumping.

There are some fish that I have seen take to the air when hooked, that are not known as jumpers. Over the years I have seen a couple of kingfish do this, but reckon it was just because they happened to be pointing upwards when they spooked and took off.

A final, important link between kahawai, makos, marlin, and mahimahi is that they are used to interacting with the surface film and the realm above it and may consider jumping into the air as an important escape tactic when they find themselves in trouble – such as when attached to a line.

All these fish regularly feed at the surface and use it as a barrier to herd their prey against, or as an escape route when they are under attack themselves. They seem to be aware of what is happening above the surface too. For example, I have watched mahimahi in close hot pursuit of aerial flying fish either leap into the air to nail them or smash them the second they re-enter the water. It’s a fish-eat-fish world out there and it pays to get the jump on the opposition!

November 2023 - Sam Mossman
New Zealand Fishing News Magazine.
Copyright: NZ Fishing Media Ltd.
Re-publishing elsewhere is prohibited

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