RUDD (Scardinius
erythrophthalmus)
Part
of the family Cyprinidae, which includes the carps, the rudd
is a handsome fish frequently mistaken for a large goldfish.
The back is golden olive-orange and the belly is silvery white
with the fins often being bright orange-red.
| The
rudd is a relative newcomer to New Zealand and was established
through an illegal importation in 1967. |
 |
It is a native of the cool waters of Europe but in New Zealand
it is most abundant in many lakes and ponds in the northern
part of the North Island where on average it reaches 20 cm and
0.5 kg. Males mature at one year of age with most females commencing
spawning at two years. Few rudd live longer than four years.
Did
you know?
Concerns exist about the effects of rudd on trout fishing. There
are also concerns about the environmental impact of rudd, hence
they have been declared a noxious fish in the South Island and
most of the North Island. This makes their possession in any
form, alive or dead, an offence and puts anglers that hook them
in an awkward position. Having hooked a rudd it becomes illegal
for the fish to be taken and kept and illegal for it to be released;
whatever is done with the fish, an offence is committed.
GOLDFISH
(Carassius auratus)
Goldfish
exist in wild populations around New Zealand, not just in decorative
ponds and aquaria where they are most commonly encountered.
They are a very hardy fish and can survive very low oxygen levels
and wide temperature fluctuations.
| They
may reach a length of 400mm and a weight of 1kg but these
fish are almost always obese. Goldfish can be confused with
rudd but if you look at the fin shape and colour, the differences
become obvious. |
 |
They feed on a wide variety of aquatic plants and detritus in
addition to small aquatic invertebrates such a snails and insect
larvae. Goldfish mature at one or two years of age and females
may spawn up to several hundred thousand eggs of about 1-2mm
in size.
Goldfish originally came from eastern Asia and have spread throughout
the world, but unlike their cousin the Koi Carp (Cyprinus carpio)
they do not pose an environmental threat.
Did
you know?
Goldfish can display varying body shapes and colours but generally
in the wild they will revert to that of a bronze coloured, stout
fish with normally proportioned fins.
TENCH
(Tinca tinca)
Variable
in colour from blackish olive to golden tan with bright, brick
orange eyes. Native throughout Europe, and introduced successfully
to New Zealand in 1867. Their range in New Zealand has changed
markedly in the past 10-15 years and today populations exist
in both the North and South Islands. New Zealand tench populations
are regarded as being of international quality by coarse fishermen
and often reach 4 kg in weight.
Tench have a high tolerance of warm and poorly oxygenated waters,
and in very cold weather they may become dormant at the bottoms
of ponds. They live on bottom dwelling animals, such as insect
larvae, pond snails and small crustaceans. Spawning is thought
to occur in spring and summer with the eggs taking roughly a
week to hatch. Tench may be long lived, some reaching an age
of more than 20 years.
Did
you know?
Fecundity (the number of eggs carried by a fish) may be very
high in tench with more than 500 000 eggs per kg of body weight!
