Some common southern reef fish and their sexy behaviour

Bluethroated wrasse Notolabrus tetricus

Blue-throated wrasse are found from Sydney to Spencer Gulf (S.A.), on both sheltered and exposed reefs from 0 to 40 m. In Tasmanian waters this species grows to 500 mm, and their diet is predominantly molluscs (shellfish), echinoids (like sea urchins) and particularly small shrimp-like crustaceans. These wrasse are easy to identify as the females are Collingwood supporters and wear a crooked black and white stripe down the side. The males are very big and multi-coloured. Nev noticed that these wrasses seem to spend a lot of the day patrolling their ‘turf’ and socialising with other wrasse. Females swim almost continuously over their territory which usually overlaps with many other females and two or three males. They bump into other fish and might get a bit aggro, especially with other females, but they don’t really fight. The males have a bigger and better defined territory and will chase off any intruding male. During the breeding season (mid-August to January) males continuously court the females within their territory. They show off by a raising a caudal fin as they swim past each female. The females generally pretend not to notice them.

These wrasse are “protogynous hermaphrodites”, meaning that a single fish can change from female to male. You can usually tell whether they are currently males or females based on their size and colour. When a male is removed, say by fishing, another female (one of a few that have already partly changed in preparation) will change sex to take his place. Too much fishing of males and the females that have changed to partmale, could seriously damage the sex ratio on the reef. One day you are fishing lots of blue throat wrasse, the next year there are none. This is important as wrasse are now a target species for a large live export trade.

Purple wrasse/ kelpie Notolabrus fucicola

Can’t tell one wrasse from another? Call it a Purple wrasse (or “kelpie”) and there is probably a better than even chance you are right as they are very common from southern New South Wales to Kangaroo Is. (S.A.), and it is usually found on exposed reefs in 0 to 15 m of water. This species grows to at least 450 mm in Tasmanian waters, and has a diet of little crustaceans and molluscs. I identify them by the little row of yellowy ‘half-diamonds’ they tend to have on the top and bottom of the body as sometimes their stripes aren’t that visible except in this area. The fish varies a lot in colour and tends to darken with age, with males and females looking the same. Studying these fish was a bit easier as Nev could easily recognise a few individuals that were unusually marked. Some fish will wander over up to one hectare of the reef. There was no evidence of territorial behaviour, with males and females occupying overlapping home-ranges. Males constantly followed females during the breeding season, occasionally displaying to them with raised dorsal and anal fins, until being either chased off by another male, or swapping to follow another female (a bit like a drunk at a Zoology faculty barrel). Males were frequently involved in chasing each other off during the breeding season (mid-August to January). Studies indicate that this species may not be hermaphroditic but a “secondary gonochorist”. They start off as hermaphroditic male/female youngsters and then change to one sex later.

Senator wrasse Pictilabrus laticlavius

Its distribution is from Seal Rocks (N.S.W.) to the Houtman Abrolhos Islands (W.A.), and is usually found in 0 to 20 m of water on sheltered to moderately exposed reefs. This species grows to 300 mm in Tasmanian waters, with a diet of molluscs and small crustaceans, particularly amphipods. They are a vivid mix of colours, lots of green, yellow and purple, especially the males. The juveniles are a uniform khaki with small iridescent spots. They love hiding in weed. Observations of males in the breeding season (Late August to January) indicated that they may be territorial and frequent chases were observed. One very highly strung male was observed for 60 min actively patrolled a home-range of 175 m2, chasing off all male intruders and courting any females that came near. Like blue-throated wrasse they can change from females to males.

Rosy wrasse Pseudolabrus psittaculus

This species is found from Sydney (N.S.W.) to King George’s Sound (W.A.), and is found on reefs of all exposures, in 10 to 220 m of water. In Tasmanian waters, this species grows to 250 mm, and has a diet of small invertebrates, which are predominantly tiny crustaceans, echinoderms, and molluscs. Nev also saw them cleaning parasites from other reef species, a bit like a tropical cleaner wrasse. In this species, females actively swam within overlapping home-ranges of approximately 325-375 m2 , which were restricted to the deeper parts of the reef (5-10 m). Males were territorial with estimated ranges of 280- 330 m2, and chased off any male intruders. During the breeding season (Late August to January) males regularly displayed to the females within their territory with a raised caudal fin. According to Nev they may actually be a protogynous hermaphrodites just like Bluethroated wrasse, meaning that they can change sex from female to male if they need to.

Toothbrush leatherjacket Penicipelta vittiger

These leatherjackets are found from Coffs Harbour (N.S.W.) to Jurien Bay (W.A.), on exposed to semi-exposed coastal reefs of 0 to 55 m depth, although it is most commonly found in shallow water from 0 to 10 m. This species has a diet of small invertebrates, particularly amphipods and hydrozoans living and growing on seaweed (they also love biting Phil White’s fingers). Feeding on algal animals means that Page 19 they also bite into the weed and up to 40% of their stomach contents are algae, some of this might also give them nutrition. These guys were more like lazy first year undergrads and didn’t move about much. They could spend an hour in one spot before moving off to a different strand of seaweed. They didn’t seem to have a home patch and would move about all over the reef. During the breeding season (September to January) males constantly followed females until either swapping to another female or being involved in a chase with another male. They were so absorbed in fighting off the opposition that they usually forgot about the prize and would lose contact with the female by the time they ran out of puff.

Brownstriped, or southern leatherjacket Meuschenia australis

The distribution of this species is from Wilsons Promontory (Vic.) to Robe (S.A.) and it is found on coastal reefs of all exposures, from 0 to 30 m. While quite common in Tasmanian waters, it is less common elsewhere. This species grows to 320 mm in Tasmanian waters, and feeds on bottom dwelling invertebrates, including molluscs, echinoids, hydrozoans and sponges. There weren’t so many of these species about, making them hard to follow. There was no evidence of site-attachment or territorial behaviour and males and females shared overlapping home-ranges. During the breeding season (September to January) males basically got into the fishy equivalent of ‘stalking’ and were often seen following females for extended periods.

Wrasse Spawning Spectacle

In inshore reefs it looks like that individual males court individual females and chase off other males, on the open coast it is quite different. At the Nuggets from September to roughly December, you can see large gatherings of purple wrasse that clearly are aggregating for spawning, unusually deep at 30 m. Here large groups of males (up to 20), court females that are giving clear chemical signals that they are ripe to spawn. After a few minutes as the group moves about the reef the female rushes vertically up about 2-4 m, before releasing her eggs and diving sharply down again. The males following closely behind release a great cloud of sperm to fertilise the eggs. It is all carried out on the outer ends of the reef so the eggs are quickly carried off in the currents and not eaten by the reef associated planktivores.

It is well worth watching out for on a dive in the area and is pretty easy to see once. Numbers vary from week to week, presumably depending on time of day, moon phase, current strength etc, but no-one has yet worked out the driver of that. Dr Nev Barratt says, “Would suggest it’s a good Honours project or study for some keen naturalists to sort out?”