Brown bullhead catfish and gambusia are two problem fish species found in the Waikato region. Because of Waikato Regional Council’s role in water quality management and regional biosecurity issues, it is appropriate for these species to be included in this strategy as pests. Waikato Regional Council will advocate for a coordinated approach to their management and control.
Perch, rudd and tench are game fish under the jurisdiction of Fish and Game New Zealand. They are not yet present in all freshwater bodies in the Waikato region, and provision is now made for their eradication, in conjunction with Fish and Game New Zealand and the Department of Conservation, should they ever appear in water bodies where they have not been legally authorised.
6.15.1 Brown bullhead catfish
(A. nebulous)
Description
The brown bullhead catfish is a large headed fish with eight long, whisker-like barbels around the mouth. It can grow to 500 mm long and 3 kg in weight. The fish is native to Northern USA and Canada. It is now widespread throughout the Waikato River system, including Lake Taupo. It is also found in a few other localities in New Zealand, but appears to be absent from some neighbouring regions. It was probably accidentally introduced through a case of mistaken identity.
Reasons for the strategy
Environmental threat
The brown bullhead catfish is a predator and scavenger. It eats many native species of fish and invertebrates. It could also affect trout in New Zealand. It can survive for long periods out of water and so can be transferred to new areas easily, both intentionally and accidentally (on boat trailers, for example). Brown bullhead catfish has not yet been classed as a noxious fish or unwanted organism.
Ministry of Fisheries Regulations introduced on 1 April 2007 state: “recreational fishers will be required to kill catfish on capture. Commercial fishers will be allowed to sell dead catfish, but may return live catfish to the water when retrieving their fishing gear where they do not intend to take them for sale. Licensed commercial fishers are also permitted to retain live catfish to the first point of sale.”
6.15.2 Koi carp (cyprinus carpio)
Description 
Koi carp are an ornamental strain of the common or European carp. Koi commonly grow to over 5 kg and 600 mm in length. Each fish has two pairs of ‘feelers’ at the base of the mouth. Koi are native to Western Europe, the Mediterranean and Western Asia, but are now found in every continent except Antarctica. Koi were introduced to New Zealand as ornamental fish, but they now breed in natural waterways. Koi carp are classified as a noxious fish under the Freshwater Fisheries Regulations 1983 and an unwanted organism under the Act. It is illegal to possess live koi, rear or consign them under Freshwater Fisheries Regulations 1983, or under the Biosecurity Act to release, sell or breed them without written authority. The primary responsibility for koi carp lies with the Department of Conservation.
Reasons for the strategy
Environmental threat
Koi carp pose a significant threat to New Zealand’s freshwater ecosystems by uprooting water plants, lowering water quality and eating insects and other young indigenous fish. There are currently no adequate methods for controlling koi carp in rivers, though their numbers may be controlled in small, closed water bodies.
Koi carp are found only in the Waikato and Auckland regions (and near Nelson). Environment Bay of Plenty has classed koi carp as a surveillance animal pest and put in place monitoring controls, research and public awareness methods to prevent their spread to Bay of Plenty waters. Lake Taupo is currently free of koi carp. Waikato Regional Council wishes to work with neighbouring agencies to reduce the chances of koi carp spreading to previously uninfested areas.
6.15.3 Gambusia (Gambusia affinis)Chad-Thomas-Texas-State-University-San-Marcos-2009.jpg)
Description
Gambusia are small fish introduced to New Zealand in the 1930s to control mosquito larvae. However, they have proved to be ineffective in the control of mosquito and instead have become pests. They can be identified by their greenish silvery sheen. Mature females grow 6 cm and males to 3.5 cm. Gambusia give birth to live young that mature at six weeks. Large populations can develop very quickly and outnumber other species.
Reason for the strategy
Environmental threat
Gambusia are aggressive predators that attack native fish by nipping at their fins and eyes and prey on their eggs. Whitebait and mudfish species are especially vulnerable to gambusia as they share similar habitats. This pest is widespread in the Waikato region in the shallow margins of slow flowing ponds, wetlands and streams, especially around aquatic plants. Gambusia habitat overlaps with several native fish species: inanga (Galaxias maculatus), smelt (Retropinna retropinna) and the common bully (Gobiomorphus cotidianus). Of particular concern is a reduction of inanga populations as this effects whitebait fisheries.
6.15.4 Wild goldfish (Carassius auratus)
Description
Wild goldfish lack the bright colours, bulging eyes and feathery fins of their domestic relatives, but are the same species. This section does not apply to “domestic goldfish” which are in proper confinement (for example fish tanks and garden ponds) nor the trade in domestic goldfish.
Wild goldfish are bronze to gold in colour with large scales and average about 150–200 mm in length. They are very numerous and widespread in natural water bodies in the Waikato region and in many cases much more numerous than koi carp. The fish are omnivorous, feeding on plant material, organic detritus and small insects and crustaceans. Wild goldfish are prolific breeders and are capable of laying several hundred thousand eggs during spawning.
Reason for the strategy
Environmental threat
Wild goldfish have the capacity to out compete native fish species and other aquatic life such as water snails and aquatic plants, leading to highly degraded freshwater environments. Recent research has shown that growth of cyanobacteria (blue-green algae) is stimulated by passage through goldfish intestines, thereby potentially contributing to algal blooms.1
Note: this rule does not apply to “domestic goldfish” which are in proper confinement (for example fish tanks and garden ponds) nor the trade in domestic goldfish.
Long-term objective
Contain, and where practicable, reduce or eradicate koi carp, brown bullhead catfish, gambusia and wild goldfish populations in isolated freshwater systems.
Strategic objectives
- Raise public awareness of the effects of koi carp, brown bullhead catfish, gambusia and wild goldfish.
- Gather information and contribute to research on ways to control koi carp, brown bullhead catfish, gambusia and wild goldfish in the Waikato region, for the duration of the strategy.
| Means of achievement |
| Strategy rule 6.15.1 |
The occupier is required, on direction from an authorised person, to destroy all koi carp in isolated ponds, wetlands and ditches on the land occupied. The authorised person shall determine which methods are realistic, including draining/poisoning or electric fishing.
A breach of this rule will create an offence under section 154(r) of the Act. Enforcement will be in accordance with section 11.3.1 of the strategy. Exemptions to a rule may apply, as outlined in section 11.3.2 of the strategy. |
| 6.15.2 |
No person shall release koi carp, brown bullhead catfish, gambusia and wild goldfish, into any water body within the Waikato region outside the known current range for the species concerned within this region.
Consideration will be given to any relevant licences sought under the Freshwater Fish Farming Regulations 1983 |
| Direct control |
Waikato Regional Council, in conjunction with Fish and Game New Zealand and the Department of Conservation, may undertake direct control of koi carp, brown bullhead catfish, gambusia and wild goldfish in any water body to which they have been newly introduced, in accordance with section 11.4 of the strategy. |
| Monitoring |
Waikato Regional Council (in conjunction with Environment Bay of Plenty and the Department of Conservation), may undertake monitoring and surveillance of koi carp, brown bullhead catfish and gambusia to determine extent of populations in accordance with section 11.2.2 of the strategy. |
| Information and advice |
Waikato Regional Council will provide advice and information on the threat of these pest fish, in accordance with section 11.1 of the strategy. |
| Management partnerships |
Waikato Regional Council is a member of an inter-regional koi carp coordination group comprising technical representatives from the Department of Conservation, Environment Bay of Plenty, Waikato Regional Council, Ministry of Fisheries and NIWA.
Waikato Regional Council, as a key member of the group, will promote the establishment of a post graduate research grant to investigate acceptable, realistic and affordable methods for controlling koi carp, brown bullhead catfish, gambusia and wild goldfish in unrestricted ‘open’ waterways. |
Perch, rudd and tench are game fish under the jurisdiction of Fish and Game New Zealand. They are not yet present in all freshwater bodies in the Waikato region, and provision is now made for their eradication, in conjunction with Fish and Game New Zealand and the Department of Conservation, should they ever appear in water bodies where they have not been legally authorised.
6.15.5 Perch (Perca fluviatilis)
Description
Perch can be identified by their two dorsal fins, with the first fin having 13-17 firm, sharp spines. There is also a broad, flat spine on the gill cover and they have six or more dark bands along their sides that are most prominent in small fish. The bottom edge of the caudal fin is bright red-orange2.
Reasons for the strategy
Environmental threat
Perch have become well established in Otago and Southland and occur in many other parts of New Zealand. They prefer slow-flowing and still water habitats where they feed on insect larvae and other fish. Perch predate on small native fish species and can contribute to water quality deterioration.
6.15.6 Tench (Tinca tinca)
Description 
Tench are olive green in colour and have bright orange eyes. They have a single small barbel at each corner of the mouth. The fins are thick and fleshy and the body is covered in small scales. A golden variety of tench, which is bright yellow-orange, is thought to be present in some lakes in the Auckland region. This variety of tench was illegally imported in about 19803.
Tench is native to Europe and was first introduced to New Zealand in 1867 as a sports fish. Tench grow to a large size in New Zealand (2-4 kg), and some northern lakes have now gained an international reputation among anglers.
Reasons for the strategy
Environmental threat
The biology of tench is not well known. They generally live in still or slow flowing waters and are carnivorous, feeding on insect larvae, crustaceans and molluscs. They are prolific breeders, producing up to hundreds of thousands of small eggs. Tench occur in the Auckland, Northland, Bay of Plenty, Nelson, Waikato and Otago regions.
6.15.7 Rudd
(Scardinius erythrophthalmus)
Description
Rudd have a single dorsal fin, are darker on the back than the belly and have bronze highlights when the light catches on the scales. Fins are usually bright orange. They are generally 200 -250 mm long4.
Reasons for the strategy
Environmental threat
High densities of rudd impact on trout fisheries. They are also detrimental to native fish species and aquatic plants and have a role in suppressing regeneration of aquatic plants in turbid lakes. As juveniles, rudd are carnivorous and, as adults, their diet consists mainly of aquatic plants. Rudd are prolific breeders, capable of producing hundreds of thousands of eggs.
Long term objective
Prevent the spread of perch, rudd and tench to new areas within the Waikato region.
Strategic objectives
In conjunction with Fish and Game New Zealand and the Department of Conservation, to eradicate all perch, tench and rudd from any areas where they threaten water quality or indigenous fish.
| Means of achievement |
| Strategy rule 6.15.5 |
No person shall release perch, rudd or tench, into any water body within the Waikato region where the introduction has not previously been legally authorised. Consideration will be given to any relevant licences sought under the Freshwater Fish Farming Regulations 1983. |
| 6.15.6 |
The occupier is required, on direction from an authorised person, to destroy all perch, rudd and tench in isolated ponds, lakes, wetlands and ditches on the land occupied. The authorised person shall determine which draining/poisoning methods are realistic.
A breach of these rules will create an offence under section 154(r) of the Act. Enforcement will be in accordance with section 11.3.1 of the strategy. Exemptions to a rule may apply, as outlined in section 11.3.2 of the strategy. |
| Direct control |
Waikato Regional Council, in conjunction with Fish and Game New Zealand and the Department of Conservation, may undertake direct control of perch, rudd or tench in any water body (including ponds and shallow lakes with a depth of less than 8 m) in which they have become established, in accordance with section 11.4 of the strategy. |
| Monitoring |
Waikato Regional Council, in conjunction with Fish and Game New Zealand and the Department of Conservation may undertake monitoring and surveillance of perch, rudd and tench to determine the extent of populations in accordance with section 11.2.2 of the strategy. |
| Information and advice |
Waikato Regional Council will provide advice and information on the threat of perch, rudd and tench in accordance with section 11.1 of the strategy. |