MARINE FISH PROFILE - Rockfishes

Rockfishes

Rockfishes (Acanthoclinus species) are small elongate reef fishes that are found only in New Zealand. There are six species, four of which can be found in rockpools but they are cryptically coloured and secretive so they are rarely seen. The inshore ‘rockpool’ species are mainly olive green, brown, or dark grey while the two deeper water species: the splendid rockfish, A. matti, and the orange rockfish, an undescribed species, have larger eyes and are more colourful (Roberts et al. 2015). Most rockfish species are relatively small (about 12 to 20 cm) but one species, the olive rockfish or taumaka, Acanthoclinus fuscus can grow to about 30 cm (Paulin and Roberts, 1992). Olive rockfish are relatively common in the intertidal zone around mainland NZ, and would be a great choice for a dedicated local marine aquarium. Olive rockfish are found on rocky shores around mainland New Zealand from the upper tide level to about 10 metres depth. They are olive green to grey, mottled with cream and darker blotches, and

Above: Olive rockfish Acanthoclinus fuscus Photo: Ian Skipworth

Above: Splendid rockfish, Acanthoclinus matti Below: orange rockfish, Acanthoclinus. sp Photo: © Peter Marriott, NIWA, Ocean Survey 20/20

have a distinctive cream to white band on the forehead (Roberts et al. 2015). Unlike the other rockfish species, the olive rockfish is relatively well studied. They are adaptable and can cope with a wide range of temperature, oxygen, and salinity including stagnant and freshwater (Paulin and Roberts, 1992). Their skin is covered with a thick protective mucus which helps them to resist drying out and males are often found under rocks at low tide with only enough water to keep them damp (Roberts et al.

2015). They are the only rockfish species that can be found in estuarine areas (Paulin and Roberts, 1992).

Above: Olive rockfish Acanthoclinus fuscus Photo: Simon Nicholas

Below: Olive rockfish Acanthoclinus fuscus Photo: Jon Sullivan

Olive rockfish generally mature at two years of age and 90 to 100 mm in length and can live for at least 9 years (Jillet 1968a, Paulin and Roberts, 1992). They spawn from July to January and about 10,000 eggs (8200–17500) are laid beneath a rock in a dense gelatinous egg mass (Jillet 1968b). The male seals the entrance to the nest with small stones and mud and guards the eggs until they hatch (Paulin and Roberts, 1992). They eat a wide range of prey, in particular small crustaceans such as blue half-crabs (Petrolisthes elongatus), but also molluscs, and the occasional small fish (Jillet 1968a). Prey is stalked cautiously with only the pectoral fins used for movement while they use their whole body for regular swimming and swim in an eel-like manner (Paulin and Roberts, 1992).

Above: Blue half crab Petrolisthes elongatus Photo: Graham Bould Olive rockfish are great aquarium fishes, but they do grow quite large and so should be kept in an established aquarium that is at least 200 litres. They are active predators and will eat smaller fish so tankmates should be chosen with care. They will eat most meaty foods but are particularly fond of crustaceans (Paterson 2013). It is not unusual, once one has been put in your aquarium, for it not to be seen again for many months leading people to think it has died then, one day, they will reappear three times the original size.

Darren Stevens and Mark Paterson

References:

Jillet, J.B. (1968a). The biology of Acanthoclinus quadridactylus (Bloch and Schneider) (Teleostei-Blennioidea). I Age and, growth, and food. Australian Journal of Marine and Freshwater Research 19: 1–8.

Jillet, J.B. (1968b). The biology of Acanthoclinus quadridactylus (Bloch and Schneider) (Teleostei-Blennioidea). II Breeding and development. Australian Journal of Marine and Freshwater Research 19: 9–18.

Paterson, M. (2013). NEW ZEALAND Local Marine Aquarium Set Up Guide. 76p. https:// issuu.com/liveart1/docs/guide_to_keeping_ local_marine_life

Paulin, C.; Roberts, C. (1992). The rockpool fishes of New Zealand. Te ika aaria o Aotearoa. Museum of New Zealand Te Papa Tongarewa. 177 p.

Roberts, C.D.; Stewart, A.L.; Struthers, C.D. (Eds). (2015). The fishes of New Zealand. In 4 volumes. Te Papa Press, Wellington. 2008 p. [Vol. 1: S1–S256; Vol. 2: 1–576; Vol. 3:577–1152; Vol. 4: 1153–1748].

Incubating reptile eggs

Bearded dragons, water dragons and leopard geckos are the most commonly kept exotic pet reptiles in New Zealand. They’re fairly easy to care for and, in the right conditions, can breed in the home terrarium but remember - if successful, you will need to find responsible homes for the offspring. Before incubating the eggs, you will need to be able to provide enough live food to feed the growing juveniles. I will outline the process I go through to achieve a successful hatch. Firstly, you need to provide your female reptile with a container in which she can safely lay her eggs. The container should be large enough that she can enter and comfortably turn around in. Add at least 15cm of a moistened soil/sand mix to the container for her to dig and lay her eggs in (the substrate should be damp not wet). Once the eggs are laid, they need to be carefully transferred to a container which will fit in the incubator. I use Sistema® plastic containers with tightfitting lids because they are strong and clear and enable me to check the eggs quickly at a glance. I create a few small holes in the lid

Bearded dragon eggs set in substrate for incubation Photo: Mark Paterson

Egg laying container Photo: Mark Paterson

(the size a hot needle would make) for air movement. To each container I add about 5cm of substrate media. I use either a 50:50 soil, sand mix or Vermiculite. The soil needs to be moistened lightly with a little water whereas 100gms of dry vermiculite mixed with 100gms of water seems a perfect ratio. Again, the substrate should be moist, but not wet. If you squeeze the substrate you shouldn’t get any water out of it. I then gently place each egg into the media so it’s halfway buried on its side. Space the eggs at least 2 cm apart to allow for growth of the developing embryos. Make a light dent with a fingertip to hold the egg in place. Don’t rotate the eggs. Some keepers make a pencil mark on the top side of the egg to ensure it

is always the same way up. If there are more than a few water drops on the underside of the container lid, I wipe them away with a paper towel. I then place the container in an incubator. There are many brands of incubator on the market. Some are specifically designed for

Incubation container with lid on and ventilation holes Photo: Mark Paterson Bearded dragon hatching Photo: Mark Paterson

reptile eggs but so long as they will maintain a steady set temperature for 2 to 3 months they will do the job but they may require more attention to detail and humidity. It is worth having a separate thermometer inside the incubator to monitor the temperature. In many reptiles, the temperature the eggs are incubated at determines the sex of the offspring (Temperature-dependant sex determination, TSD). This is the case for leopard gecko eggs. If their eggs are incubated at an average of 26.5° C degrees, then 100 percent of the hatchlings will be female. At temperatures around 30.5° C degrees you basically get an equal number of male and female leopard geckos. At 36.6° C degrees 98 percent of the hatchlings will be male. Temperature conditions below 24° C degrees can be fatal. Leopard gecko eggs take 35 - 89 days to hatch, depending on the incubation temperature. Egg incubation temperature does not have much of a role in determining the sex of bearded dragons and water dragons. If you

Bearded dragon hatchlings still in incubation container Photo: Mark Paterson incubate their eggs at 29°C (84°F), they will take around 60 days to hatch and you will get a mix of males and females. Check the incubator daily and make sure the temperature is remaining constant. Remove any eggs that appear mouldy. If the eggs start to pucker, or sink in, they are too dry. Use a spray bottle of warm water to rehydrate them with a light mist. Wipe away any condensation forming on the underside of the lid as you do not want it to drip on the eggs. At the end of the incubation period for the species you are incubating, you may notice movement or tearing of the egg casing, then little heads starting to emerge. Try to leave them alone and not disturb the hatchings. A healthy leopard gecko or dragon will hatch without any interference from you and if any still have a small yolk sac attached this will absorb naturally over the next few days. It is best to leave newly hatched reptiles in the tray as they will help stimulate the rest of the eggs to hatch.

Above: Bearded dragon young and live food Below: Newly hatched bearded dragon Photos: Mark Paterson And of course, while you are waiting for the eggs to hatch, you have been busy breeding live food to be ready for hungry juveniles that are coming - fingers crossed.

Mark Paterson