Published in Divelog Australasia February 2023

by Nigel Marsh

I had been enjoying a wonderful dive at Flying Fish Cove, Christmas Island, marvelling at the amazing variety of fishes when I suddenly spotted a tiny little fish that I had never seen before. I slowly approached the small fish as it weaved its way between the corals, and when it stopped, I quickly snapped several photos before the tiny fish got nervous and disappeared under a ledge. I knew this lovely little fish was a toby, a type of pufferfish, but it took me a while to discover that it was a Tyler's Toby, one of the rarest members of this family of small pufferfish.

The pufferfish family, or Tetraodontidae, contains around 193 species that are slow swimmers and as such have a range of defences to deter predators. All pufferfish have poisonous flesh and skin, which generally keeps them safe from most, but not all, predators. These fish also have rough prickly skin, and most members of the family can also inflate their bodies by sucking in seawater to make themselves larger, so they are harder to eat.


My favourite group of pufferfish are the tobies. These small fish generally don’t inflate themselves to deter predators, instead they try to avoid them all together by being shy and elusive, and are quick to hide if a potential predator gets too close.

Toby is an Australian name to describe members of the Canthigaster genus, but in some countries they are call sharpnose puffers. These little fish are mainly found in tropical and subtropical waters throughout the Indo-Pacific region, but a few also venture into warm temperate waters and a limited number are found in the Atlantic Ocean. There are 37 toby species so far described, and all are small, pretty and colourful little reef fish.

Most tobies only grow to 10cm long, but a few larger members of the group can reach 25cm in length. They almost all have colourful decorative skin patterns of spots and wavy lines, but a few also have stripes or bands. It is thought that these colourful skin patterns formed as a warning to other fish that they are poisonous and shouldn’t be messed with.


Tobies are bottom feeders, consuming a wide variety of benthic organisms. They are often seen slowly swimming across the bottom, nipping at anything edible they can find. Their broad diet includes small molluscs, echinoderms, worms, algae, tunicates, corals, sponges and bryozoans.

Little is known about the biology and behaviour of most tobies. However, studies of the very common Blacksaddle Toby (Canthigaster valentine) found that this species lives in small groups, which consists of a male and his harem of females. Each of the females has her own patch of turf within the male’s territory. They breed year-round, every four to ten days, when the male comes to visit and fertiliser his ladies’ eggs.


The female lays anywhere from 15 to 800 eggs, which are attached to the bottom. The eggs are left unguarded, as they are toxic and rarely touched by other fish, and when they are consumed by some silly fish they are generally spat straight out. Larval tobies hatch after three to five days, and are only 1.4mm long. They then drift with ocean currents with the plankton for between 65 and 113 days, at which point they are large enough to settle on a reef.

Beside the male and female harem groups, there are also individual bachelor male Blacksaddle Tobies that roam between territories. These poor lonely guys may battle with established males and claim their territory, but mostly wait for an embedded male to die and then take over their harem of females.


Little is known about most other tobies. Some also seem to live in small groups, but many are observed singular or in pairs. But as most of these tobies are shy, observing them is quite difficult.

The Blacksaddle Toby is one of the more conspicuous members of the family, often seen out in the open. They also occasionally gather in large groups of up to one hundred. Why they do this is unknown. As they are common, and left alone by most predators, they have a few fishy fans that have found success copying them. Juvenile Bluespotted Coral Trout (Plectropomus laevis), have a similar colour pattern, but only when they are young.


However, the Blacksaddle Filefish (Paraluteres prionurus) has gone to extremes, being a complete mimic of the Blacksaddle Toby. This fish looks almost identical to the toby, being a similar size and having the same colour pattern. They even hang out with the tobies, for the ultimate deception. But they do have a different fin arrangement, and being a member of the leatherjacket family, they also have a dorsal spine. So, on close inspection they can be told apart.


In Australia fifteen species of tobies have been recorded, but I have only seen half of them, as most are rarely seen. Across tropical Australia the Blacksaddle Toby is quite common, but two timid tobies to look for on the Great Barrier Reef are the Netted Toby (Canthigaster papua) and the Honeycomb Toby (Canthigaster janthinoptera). You mostly see these little fish around ledges, where they can quickly escape when a diver gets too close.


I have actually found southern Queensland is the best place to see a good variety of tobies. While the Blacksaddle Toby is seen at almost every dive site, most other tobies seem to like more sheltered spots, and even estuaries, like the Seaway and Tweed River. In these areas I have seen the Honeycomb Toby and regularly see the Pacific Crowned Toby (Canthigaster axiologus) and the Blackspot Toby (Canthigaster bennetti). The Clown Toby (Canthigaster callisterna), which is more common in New South Wales, is also occasionally encountered, and recently I even spotted a rare Ambon Toby (Canthigaster amboinensis).


Encountering the Tyler's Toby (Canthigaster tyleri) at Christmas Island (as mentioned in the introduction) was quite a surprise as this species is rarely seen, and is not found off mainland Australia. This species is also found in parts of Southeast Asia, but in this area you are more likely to see the Compressed Toby (Canthigaster compressa), especially at muck sites. The only other toby species I have seen in Southeast Asia is the Ocellate Toby (Canthigaster rivulata) when muck diving at Manado, Indonesia. This species is also recorded off northern Australia, but is rarely seen.


Tobies are fascinating little pufferfish that are always fun to encounter and photograph.