Poor Knights marine reserve
fish, fish and more fish: the legendary fish schools of the Poor Knights
by Dr J Floor Anthoni (2007)
New Zealand is famous for its schools of surface-feeding fish, the demoiselles, blue maomao, trevally and pink maomao. If watching them from the surface is spectacular, being near them in the water becomes a challenge to describe.
  • blue maomao: the most spectacular schooling fish of the Poor Knights
  • trevally: liquid silver, always hasty and hungry
  • demoiselles: little darlings, the swallows of the sea 
  • pink maomao: graceful beauties of the deep
  • koheru: a pillar of the food chain, silver and yellow
  • golden snapper: visitors from the dark deep

Begin your study of the sea at the Seafriends home page or our sitemap. Find more about the Poor Knights.
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f052629: A mixed school of trevally and blue maomao at 25m depth, Fred's Pinnacle.

blue maomao
Blue Maomao (Scorpis violaceus) are the ambassadors for the Poor Knights. They are a New Zealand species, occurring in the warmer waters around the North Island, and at the Kermadec Islands. When old (up to 40cm and 10-20 years) they are iridescent blue, a coloration that develops with age, from the pale blue young. Juvenile blue maomao even have a yellow anal fin.
Although blue maomao are found swimming in open water, they are not truly pelagic because they return to their sleeping spots on the rock at night. Visitors to the Poor Knights delight in seeing schools of blue maomao, numbering hundreds to thousands, feeding on the surface. Schools of young fish then colour the water light blue, whereas old fish cause a deep blue iridescence. Blue maoamo have their eyes set right in the front of their heads, right above their small but flexible mouths. When they collectively ruffle the water's surface while feeding in a frenzy, they actually see their prey (fast moving shrimps), as their mouths snap left, front and right, without their bodies needing to move likewise. With their large breast fins and disc-like shape, these fish are very agile, a necessity for zooplankton feeding.
tourists observing a school of blue maomao.
f990135: divers on charter boat Pacific Hideaway observing a surface-feeding school of blue maomao.
blue maomao school suddenly dives
f013003: the moment of woosh when the school decides to dive, as if attacked from above by sea birds.
blue maomao (Scorpis violaceus) school
f024623: the old blue maomao are no longer found on the poor knights. This young school stopped feeding to inspect the photographer.
blue maomao (Scorpis violaceus) school
f011922: a school of young blue maomao.
blue maomao (Scorpis violaceus) school
f049031: even during daytime, after a good breakfast, blue maomao often take a rest. Here they come down from the rock in the distance, in order to investigate the photographer.
blue maomao (Scorpis violaceus) school
f031312: blue maomao and demoiselles at the Kermadec Islands.
blue maomao (Scorpis violaceus) school
f024134: blue maomao in Northern Arch.
blue maomao (Scorpis violaceus) school
f045426: blue maomao in Middle Arch. See if you can spot the sweep amongst them. When young, they look very similar.
blue maomao (Scorpis violaceus) school
f023115: blue maomao in Blue Maomao Arch.

Silver trevally (Pseudocaranx dentex) belong to the family of jacks, fast swimming pelagic fishes. They are all characterised by a narrow tail stock and a deeply forked tail. Others belonging to this family are: kingfish (Seriola lalandi), koheru (Decapterus koheru) and jackmackerel (Trachurus novaezelandiae, T declivis). When young, trevally are found in small groups fossicking over sandy bottoms but later they will swim in the open, hunting fast swimming planktonic shrimps. They often team up with kahawai (Arripis trutta).
Trevally can grow old, up to 30 years, even though they are an important source of food in the food chain. Old trevally have blunt snouts, now rare.
large school surface-feeding
f219005: we often forget what a surface feeding school used to look like. Notice the boat in the distance? This combined school of trevally and kahawai with all the shearwaters above it, is a quarter of a hectare in size (half football field), counting many thousands of fish.
trevally feeding at the surface
f990136: a school of trevally feeding at the surface.
school of trevally (Pseudocaranx dentex)
f041118: close-up of a school of trevally (Pseudocaranx dentex), passing close by.
school of trevally (Pseudocaranx dentex)
f052625: young silver trevally circling around the photographer.
school of trevally (Pseudocaranx dentex)
f052629: a mingle of trevally and blue maomao at Fred's Pinnacle.
3-4 year old trevally (Pseudocaranx dentex)
f001017: a 3-4 year old trevally (Pseudocaranx dentex)  showing vertical bands and a yellow side stripe and tail stock. It can turn these patterns and colours on or off at will.
7-9 year old trevally (Pseudocaranx dentex)
f020829: old trevallies of over 10 years old, with their blunt snouts, have become very rare but here is a group of about 8 years old.
kahawai or sea trout, Arripis trutta
f001823: occasionally schools of kahawai or sea trout (Arripis trutta) visit the Poor Knights, often mixed with trevally.

The two-spot demoiselle (Chromis dispilus) is such a darling little fish. Also called sea swallow because of its forked tail, the name chromis means blue, as in the family of damselfishes, the colour blue is dominant. Here on the Poor Knights one can encounter the much rarer single spot demoiselle (Chromis hypsilepis) and the rarer still, yellow demoiselle (Chromis fumea). The females are always greenish-black, whereas the males become more blue as they grow older, as also their tails grow whiter. Most demoiselles seen these days are no older than 3-4 years.
Demoiselles feed on small zooplankton organisms, reason why their eyes are set so close above their mouths. They swim only with their strong breast fins, which moves their bodies rapidly up and down and sidewards. In addition their lips can extend far out and sideways to catch the bug that almost got away. Although demoiselles feed on zooplankton, they are never far away from the rock face. When food is plentiful, one can see them resting underneath and in amongst seaweeds. They also take a rest when the tide changes, and currents stop running.

The change in tide also spurs them to migrate, often for kilometres, along the rock face to another spot that will give more advantage in the turning tide. Divers may see endless streams of demoiselles migrating, often at around 20-25m depth, along invisible paths, and in densities that never fail to amaze.

When demoiselles leave the depth after a rest, to feed again in shallow water, they have to ascend slowly because the pressure of the water diminishes, which expands their swim bladders. An ascent from 30m to the surface causes their swim bladders to expand four-fold, so they need to 'compensate' by degassing. Because this is a slow process, they often group together in high densities, while ascending slowly.

At night all demoiselles descend onto the rock to their private little hollow in the rock face where they are the most common fish seen during a night dive.

demoiselles huddling under a stalked kelp
f041125: demoiselles huddling under a stalked kelp after a good breakfast. Note the young blue maomao in the foreground, still with a yellow anal fin.
demoiselles amongst the tangle wrack
f043108: demoiselles amongst the tangle wrack (flexible weed). Here they are safe from marauding attacks of shags and gannets.
demoiselles always interested in divers
f051116: wherever a diver goes, there are demoiselles showing real interest.
demoiselles always interested in divers
f051120: a diver surrounded by young demoiselles that show no fear at all.
male demoiselle fanning its brood of a few hundred eggs
f038218: a male demoiselle in the serious business of fanning its brood of a few hundred eggs.
two eyes peering out of each demoiselle egg
f038228: a super macro close-up of demoiselle eggs on top of a bryozoan mat, shows two eyes peering out of each egg.
demoiselles in tight formation before ascending
f049004: demoiselles in their thousands, forming a tight formation. This is not a feeding aggregation but a consensus call for surface-feeding.
demoiselles streaming away
f049000: demoiselles streaming away from the photographer on their slow ascent to shallow plankton-rich waters.
one-spot demoiselle (Chromis hypsilepis) and yellow demoiselle (Chromis fumea)
f052735: the one-spot demoiselle (Chromis hypsilepis) is much rarer than the two-spot demoiselle, and the yellow demoiselle (Chromis fumea) rarer still.

pink maomao
Pink maomao (Caprodon longimanus) are spectacular for their soft pink colours, elegant shapes and almost royal behaviour. Never in a hurry, they move at greater depths between 20 and 50m where zooplankton is less prolific. Not surprisingly, these fish live in the slow lane, expending but little energy, while growing very old (40 years?). The pink maomao is not closely related to the blue maomao, but to perches. In their midst, one may encounter one of the most beautiful fishes in New Zealand, the splendid perch (Callanthias australis), also a deep water fish.
Very little is known about the pink maomao. Our own observations show that it has largely survived a sequence of three mass mortalities (1983, 1992, 2001).
pink maomao (Caprodon longimanus)
f021132: pink and blue, a school of pink maomao, first attracted y the photographer, now moving past.
pink maomao (Caprodon longimanus)
f041806: pink maomao (Caprodon longimanus) are often found resting in cool deep water of 30m or more.
pink maomao (Caprodon longimanus) and diver
f023625: a school of pink maomao showing interest in the diver at Landing Bay Pinnacle.
pink maomao (Caprodon longimanus) sleeping
f048407: a resting pink maomao (Caprodon longimanus) changes colour, showing light blotches. At night they can become orange-red.

female northern splendid perch (Callianthias australis)
f036503: female northern splendid perch (Callianthias australis) is found at the boundary of diving depths, in 40-50m and always near a cave. The male is very beautiful.
female butterfly perch (Caesioperca lepidoptera)
f048408: a female butterfly perch (Caesioperca lepidoptera) at sleep, has turned from salmon-pink to brown-grey.

The butterfly perch (Caesioperca lepidoptera) forms small schools, never further than a few metres away from the rock face, at depths between 15 and 35 metres. Their normal colour is salmon-pink, while males have an iridescent spot above their eyes. At night they become dark brown.

Koheru (Decapterus koheru) is the bait fish of the Poor Knights. This is a truly pelagic fish, and seeing it at the Poor Knights could just be because it was passing by. However, divers have known persistent schools of koheru belonging to certain places at the Poor Knights. When young, they can easily be confused with the more coastal, but also pelagic jackmackerel, distinguished by the Z in its side line.
However, as koheru grow older, it also becomes more yellow on top and bluish on its sides. It is a very beautiful fish, particularly the old ones by night.
koheru (Decapterus koheru)
f021834: 2-year old koheru (Decapterus koheru) in a feeding frenzy at the surface. For a photographer a fast moving nightmare.
young koheru (Decapterus koheru)
f048330: one-year old koheru seeking refuge near tall flexible weeds.
koheru (Decapterus koheru)
f045632: two year old koheru and diver.
koheru (Decapterus koheru) and diver
f024704: a school of koheru staying around the diver for protection.
koheru (Decapterus koheru)
f041827: 3-year old koheru have bright yellow backs and very reflective bluish bellies. They can turn their yellow colour off at will.
koheru (Decapterus koheru)
f045634: 3 year old koheru, still young.

golden snapper
The golden snapper (Centroberyx affinis) is not a schooling fish at diving depths, but deeper down at 50-100m, it forms large groups that migrate nearer to the surface at night. Divers encounter golden snapper in small groups, hiding inside caves by day, while feeding from plankton organisms at night. Their large eyes are very light-sensitive, which enables them to hunt by weak moonlight and even in total darkness, because many nocturnal zooplankton organisms produce light.
Like the related slender roughy (Optivus elongatus) and the common roughy (Paratrachichthys trailli), the golden snapper hangs motionless in the water, moving in a start-stop manner in order to be able to estimate the movement of its prey. Its neural networks have been wired to intercept prey rather than pursuing it - amazing.
mature golden snapper (Centroberyx affinis)
f048728: a mature golden snapper (Centroberyx affinis) in motionless suspension.
golden snapper (Centroberyx affinis) in a cave
f038425: golden snapper patiently waiting for the night, hiding under an overhang by a small cave.