Friday, 21 October 2016

9) Foxface rabbitfish

S.vulpinus - day
One of the great mysteries of this fish is its name. It has a strong head pattern, but it is vastly more like that of a badger than a fox or rabbit. If anyone can give a reason for this, please leave a note in the comments. The face pattern may be aposematic – it has powerful venom glands associated with the dorsal fin spines and can give a painful sting.Another feature of this species is that it changes colour at night, which helps it blend in with the background and avoid predation.

S.vulpinus - night
In the wild, Siganus vulpinus is found in the western Pacific, from Indonesia as far east as Tonga. They are associated with coral reefs, especially staghorn coral (Acropora) where they graze on algae at the base of coral branches and also feed on polyps and zooplankton. Usually they are found singly or in pairs, but juveniles are sometimes in schools.

Although the Foxface is the most often seen member of its genus in aquaria, there are numerous others with a worldwide distribution in tropical and warm temperate waters. Some of these species distributions are changing as a result of human activity – the Red Sea Rabbitfish Siganus rivulatus has now spread along the Suez Canal along with many other Red Sea species into the eastern Mediterranean and is now a commercial catch off the coast of Turkey. Despite living in cooler waters the only noticeable difference is that the Mediterranean population spawns later in the year than in their native waters. This phenomenon is referred to as Lessepsian migration, in commemoration of the French diplomat who oversaw the construction of the Suez Canal, Ferdinand de Lesseps. As the level of the Mediterranean is below that of the Red Sea, there is a permanent current flowing northwards along the canal, carrying many species with it and potentially threatening many Mediterranean endemics. As of now, well over 100 species of fish, and many times that of molluscs and crustaceans, have been found or established breeding populations in the eastern Mediterranean. This may be aided by global warming and fresh water extraction for human populations raising the salinity and temperature of the sea, making it more like their home waters.

Reproduction in rabbitfishes occurs in a similar fashion to tangs, to which they are related. They spawn after dark or just before dawn, producing eggs that adhere to the substrate before hatching into larvae that disperse in the plankton. Some species of Siganus have been reared in a laboratory setting. Siganus canaliculatus was induced to spawn with hormone injections and the larvae reared using rotifers, with artemia nauplii added from day 8, with metamorphosis at around day 30. From this it appears that it should be within the abilities of hobbyists to breed the Foxface, with the main obstacle the need for an extremely large tank, as they can be quite territorial and grow to 25cm long.

Further reading:
Induced spawning and larval rearing of the rabbitfish:

Next week, the last bony fish in the tank, the Blacktailed Damselfish

Images from Wikipedia

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