''Bellapiscis medius'', the twister, is a

triplefin Threefin or triplefin blennies are blenny, blenniiforms, small Percomorpha, percomorph marine fish of the family Tripterygiidae. Found in tropical and temperate waters of the Atlantic Ocean, Atlantic, Pacific Ocean, Pacific and Indian Oceans, the ...

fish of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Tripterygiidae, commonly found around the coast of

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. Its length is between 5 and 10 cm.

Habitat

This species is the only triplefin that as an adult lives in

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

habitat. It can be observed in

tidal pools A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. These pools typically range from a few inches to a few feet deep and a few feet across. Many of these pools exist as separate bodies of water only ...

and has adapted to survive the changes in temperature, oxygen saturation and levels of water acidity that accompany living in that habitat. The abundance of this fish in tidal pools decreases during the winter months.

Prey

''B. medius'' feeds on small crustaceans including barnacles, molluscs including snails, and

amphipods Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphip ...

References

medius Endemic marine fish of New Zealand Fish described in 1861 Taxa named by Albert Günther {{Blenniiformes-stub