Halfbeak

From Freepedia

Hemiramphidae

Freshwater halfbeak in aquarium

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Beloniformes
Family:	Hemiramphidae

Genera

Arrhamphus
Dermogenys
Euleptorhamphus
Hemiramphus
Hyporhamphus
Nomorhamphus
Oxyporhamphus
Rhynchorhamphus
Zenarchopterus

Halfbeaks (family Hemiramphidae) are close relatives of the flyingfishes and members of the same order, the Beloniformes. They are notable for their elongate jaws, the lower of which is usually significantly longer than the upper one, hence their common name.

Most halfbeaks are found in the sea, predominantly at the surface, where the feed on small fish, plankton, algae, and fragments of vegetation such as sea grasses. The freshwater species are more predatory, and eat aquatic insect larvae and insects that have fallen on the surface of the water. Marine halfbeaks are known from the warm temperate and tropical parts of the Atlantic, Indian and Pacific Oceans, while most of the freshwater species are from South East Asia. Halfbeaks range in size from 7 cm (e.g., Dermogenys pusillius) to over 40 cm (e.g., Hemiramphus saltator). The larger species are sometimes used as food but are more important as baitfish for large predatory species including dolphinfish and billfish; some of the smaller freshwater species are also kept as aquarium fish.

Reproduction

Halfbeaks exhibit a variety of reproductive strategies including egg-laying, ovoviparity, and viparity. Males of the ovovivaparous and vivaparous species have modified anal fins used to deliver sperm to the females. If necessary, female halfbeaks can store the sperm in a cavity in the ovary wall until her eggs are fully developed. In ovoviparous halfbeaks, such as Dermogenys spp., there is no uterus and the eggs are retained in the ovary more or less intact until the juvenile fish are ready to be born. In contrast, the eggs of the vivaparous halfbeaks such as Normorhamphus spp. pass from ovaries into paired uteri. The egg membranes break down and nutrients pass from the uterus wall to the embryo. As is typical for live-bearing fish, oviparous halfbeaks produce small broods of relatively large offspring compared with egg-laying halfbeaks.

Image:Halfbeak fry.jpeg

Halfbeaks in aquaria

Species of the genera Dermogenys and Nomorhamphus are quite commonly kept as aquarium fish. They are small and generally peaceful towards other species, although males can be aggressive to one another. Male Dermogenys pusillius in particular fight vigorously and sometimes these battles end in injuries; this fish has therefore become known as the wrestling halfbeak and in some Asian countries fights between males are used for betting purposes in much the same way as the Siamese fighting fish.

To be kept successfully, halfbeaks require an aquarium with plenty of space at the surface. Depth is not critical, so a tank that is wide is better than one that is deep. They are sensitive to low oxygen levels but are otherwise relatively hardy, with one important exception: they do not tolerate sudden changes in salinity, pH, hardness, or temperature well. They must be introduced to a new aquarium gently, and subsequent water changes are best small but frequent so that the water chemistry does not suddenly change.

Some species, most notably Dermogeny pusillius, do best in slightly brackish water.

Halfbeaks are nervous fish and things like switching on lights can cause them to swim around the tank frantically. They may hit themselves on the glass, injuring their beaks, or jump out of the tank completely. Injuries to the beak usually heal within a few weeks. They will eat insect larvae such as bloodworms readily, as well as crustacean eggs, shrimps, fruit flies, and even small pieces of chopped white fish. Halfbeaks sometimes eat flake foods as well. Some aquarists also offer them tiny pieces of algae wafer on the basis that most species are omnivorous in the wild, and so a certain amount of green food probably does them good.

Halfbeaks will breed in captivity, but despite being livebearers they are not particularly fecund and represent a significant challenge. Baby halfbeaks will eat newly hatched brine shrimps and other small, live foods.