Seafriends - Chimaerids, elephant
fish and ghost sharks
Chimaerids (ghost sharks and elephant fish)
are related to sharks and rays, but they have a skin covering their gills,
with a single opening instead of gill slits. Their skins are smooth and
their dorsal fins are preceded by a single large spine.
In Greek mythology, a Chimera is a fire-breathing female monster with
a lion's head, a goat's body and a serpent's tail. (Gk khimaira= female
goat)
Chimaerids are closely related to sharks, having a similar
cartilaginous skeleton but lacking the flattened body form of skates and
rays. Representatives of this order are found in all the oceans of the
world, but they are generally restricted to cool temperate regions in waters
between 200 and 1200m depth. They can be distinguished from sharks by
their gill slits being covered with a skin (operculum), leaving a single
opening on each side. Chimaerids also have smooth skins without the dermal
denticles of sharks. They also have a single spine in front of their first
dorsal fins, which can be laid flat as in bony fishes. Their heads are
grooved with lateral lines and their upper jaws are fully fused to their
heads, unlike in sharks where the upper jaw is only loosely attached to
the skull. Their teeth are modified to form flattened crushing plates with
sharp cutting margins; two pair in the upper jaw, and a single pair in
the lower jaw.
Male chimaerids have the normal claspers or intromittent
sexual organs that are present in the sharks and rays alongside their pelvic
fins, but they also have a second pair of flat, retractable claspers in
front of the pelvic fins. These are usually armed with hooks and are probably
used only to grip the female during mating. There is also a club-like frontal
clasper on top of the head. All chimaerids are oviparous, laying large
eggs in a horny case which is deposited on the bottom. Like most sharks
and rays, development is slow and the young do not hatch until six months
to a year after the eggs are laid.
Cimaerids live mainly on soft muddy bottoms on the deeper
parts of the continental shelf or on the continental slope. They feed mainly
on shellfish and bottom-living invertebrates, as well as a few small fish.
Callorhinchidae: elephant
fishes Callorhinchus milii:
elephant fish
Four closely related species are now recognised, requiring further revision
of this class.
Hardnosed fishes: (L: callosus= hardened skin; Gk: rhinos=nose;
milii=?)
Maori: reperepe
Elephant fishes are found in the Antarctic
Basin and the South Pacific. The New Zealand species grows to 120 cm long,
and is common along the east coast of the South Island, where it comes
in-shore for breeding. Its curious trunk-like proboscis is used for locating
shellfish.
Fishing: The elephant fish is exploited commercially, particularly
off the Canterbury coast. They are also occasionally netted off the North
Island, south of East Cape and south of Kaipara on the west coast. Outside
the breeding season, elephantfish live on the boundary of the continental
shelf in waters up to 200m deep. The fish are caught commercially during
their inshore migration, either in trawls or in setnets, and the total
annual landings are about 1000 tonnes. The firm white fillets are of good
edible quality, resembling that of hapuku (groper, sea bass), but requiring
prior soaking in fresh water to eliminate a slight ammonia taste. The flesh
is either used locally in the fish and chips trade or is exported to Australia.
Description:
A silvery coloured fish with brown markings, half a metre to over one metre
long. On its snout it has a fleshy skin flap, which it uses for finding
its food in the muddy bottoms of deep water. Its two dorsal fins are high
and triangular, and the upper lobe of its tail is shark-like, with a lower
lobe immediately preceded by a pointed anal fin, appearing to be part of
the tail. Immediately before its first dorsal fin it has a large spine,
which is thought to be poisonous.
Fins/size/weight: size 0.5 to 1.2m.
Life
history: Adults migrate inshore during spring to shallow spawning grounds
in water less than 40m deep. An important spawning ground of this fish
is found off Canterbury, near Sumner Beach. On the sandy or muddy bottom
the females lay large eggs contained in a yellow-brown horny capsule measuring
about 25x10 cm, and which look like pieces of seaweed. In the centre of
the egg case is a cavity in which the embryo develops. From one end of
this cavity a passage, closed by a special valve, leads to the exterior,
and it is through this passage that the young fish in due course, escapes.
The young hatch 6-8 months later (April), and as with most sharks, are
slow in growing, taking about 5 years to reach maturity. Large numbers
of the discarded egg cases are frequently washed ashore on Sumner Beach.
Growth:
Distribution:
Chimaeridae:
ghost sharks
Several species of ghost shark are found in
the deep water around New Zealand. Two of these are shown here. The giant
ghost shark (Chimaera phantasma) is rarely seen, is much larger than the
other two and the males have distinctive three-lobed claspers.
The
dark ghost shark is a relative of the elephant fish but lacks its trunk-like
snout. It has a long, tapering tail. It is also smaller, averaging 50-60cm.
This dark, mottled fish, occurs over the outer continental shelf in 350-1000m
deep water, where it is caught in trawl nets.
This fish has a conical snout and an elongate, tapering body. On its
back it has a triangular first dorsal fin (and spine) and a long, low second
dorsal fin. The dark ghost shark is dark grey above with a mottled pattern
of distinct silver-white markings, and pale silver-grey underneath. The
mouth is small, and located well back and beneath the snout.
Hydrolagus
sp: pale ghost shark The pale ghost shark is found in deeper water than the dark ghost shark,
and it is also larger, averaging 60-70cm. Its snout is more rounded than
that of the dark ghost shark, and its colour is paler. Its skin is pale
brown above, with a few distinct darker bands, and it is white below. Pale
ghost sharks occur further south than the dark ghost sharks, being common
on the Campbell Plateau and on the Snares Shelf south of Stewart Island.
Rhinochimaeridae:
long-nosed chimaeras
Long-nosed chimaeras are rare, deepwater fishes
of temperate and tropical seas, living to depths of 2000m. They are larger
than the other chimaeras. Their snouts are elongated into cylindrical or
flattened points, and they have long tails.
Hariotta raleighana: long-nosed chimaera
(hariotta=?; raleighana= named after Raleigh)
Including
its long, tapering snout and fins, this species is usually between 1 and
1.5m long. Its body is more elongate than the other chimaerids. Its snout
is hard and resilient, and rich in sensory organs, being used to dig in
soft muddy bottoms in search of shellfish and crustaceans that make
up the bulk of its diet. Its skin is orange-brown in colour, paler beneath,
and it has some irregular darker markings. It is commonly found in waters
between 350 and 700m depth.
Description:
A silvery coloured fish with brown markings, half a metre to over one metre
long. On its snout it has a fleshy skin flap, which it uses for finding
its food in the muddy bottoms of deep water. Its two dorsal fins are high
and triangular, and the upper lobe of its tail is shark-like, with a lower
lobe immediately preceded by a pointed anal fin, appearing to be part of
the tail. Immediately before its first dorsal fin it has a large spine,
which is thought to be poisonous.
Life
history: Adults migrate inshore during spring to shallow spawning grounds
in water less than 40m deep. An important spawning ground of this fish
is found off Canterbury, near Sumner Beach. On the sandy or muddy bottom
the females lay large eggs contained in a yellow-brown horny capsule measuring
about 25x10 cm, and which look like pieces of seaweed. In the centre of
the egg case is a cavity in which the embryo develops. From one end of
this cavity a passage, closed by a special valve, leads to the exterior,
and it is through this passage that the young fish in due course, escapes.
The young hatch 6-8 months later (April), and as with most sharks, are
slow in growing, taking about 5 years to reach maturity. Large numbers
of the discarded egg cases are frequently washed ashore on Sumner Beach.
The
dark ghost shark is a relative of the elephant fish but lacks its trunk-like
snout. It has a long, tapering tail. It is also smaller, averaging 50-60cm.
This dark, mottled fish, occurs over the outer continental shelf in 350-1000m
deep water, where it is caught in trawl nets.
Hydrolagus
sp: pale ghost shark
Including
its long, tapering snout and fins, this species is usually between 1 and
1.5m long. Its body is more elongate than the other chimaerids. Its snout
is hard and resilient, and rich in sensory organs, being used to dig in
soft muddy bottoms in search of shellfish and crustaceans that make
up the bulk of its diet. Its skin is orange-brown in colour, paler beneath,
and it has some irregular darker markings. It is commonly found in waters
between 350 and 700m depth.