Pest fish survey nets mixed results for Northland
Archived content: This media release was accurate on the date of publication.
IntroductionA recent pest fish survey done by the DOC and Northland Regional Council has provided useful advice for planning the battle against two Northland pest fish, koi carp and rudd.
Date: 19 July 2019
“The survey covered 12 pest fish sites in Northland and the good news is that we confirmed that two historic koi populations have been successfully eradicated, and no new koi sites were located during the survey. The bad news is that the battle has just begun, with significant pest fish populations in waterways across Northland,” says Amy Macdonald, DOC Freshwater Technical Advisor.
“DOC and Northland Regional Council will use this survey information to develop a pest fish surveillance and eradication programme to help protect Northland waterways. This will enable us to prioritise sites for control and eradication, and to work with communities to prevent the pests spreading to new sites.
"Pest fish upset the balance in our freshwater systems, affecting ecological, cultural and recreational values. Koi carp and rudd are both bad news for water quality so they are also a problem for our agriculture and tourism industries - we’ve all got a reason to work together to stop them spreading and taking over.”
Koi are big and brightly coloured; they breed prolifically and can have devastating impacts on New Zealand waterways. Rudd are smaller but also prolific breeders; they eat the growing tips of native aquatic plants, and can turn lakes into barren algae-filled waterways that nobody wants to swim in. Pest fish expert Helen McCaughan from Wildland Consultants has flown in from Christchurch to support the operation.
The survey was funded from Budget 2018 which allocated DOC $76 m over four years to invest in targeted biodiversity initiatives across land, freshwater and marine ecosystems to address New Zealand’s biodiversity crisis.
This included $4.5 m over four years to contain key aquatic pest species populations and reduce the likelihood of them spreading to sites with high biodiversity values, where it’s more difficult and expensive to control them. The aim is to contain at least four serious freshwater pests (koi, gambusia, rudd, hornwort) which have the potential to expand to other parts of New Zealand.
The new fund will also be used to control invasive aquatic plants with a high risk or impact on freshwater biodiversity values, to reduce their impact on river, lake and wetland ecosystems and reduce the likelihood of dispersal to other indigenous habitats. The aim is to increase reduction of invasive aquatic plants to at least 10 sites per year.
New Zealand’s freshwater ecosystems face a number of threats - pollution, deforestation, loss of habitat, changing land-uses, sedimentation and nutrient enrichment, and the impact of invasive aquatic animals and plants such as koi carp and rudd.
Koi carp superficially resemble goldfish, except they grow much bigger and have two pairs of whisker-like feelers, also called barbels, at the corner of their mouth. They are highly variable in colour, often blotchy shades of black, red, gold, orange or pearly white.
Koi carp can often be observed during summer months in ponds and slow flowing water during the day when they are close to the water surface. When koi carp feed they stir up the bottom of ponds, lakes and rivers, muddying the water and destroying native plant and fish habitat.
They are opportunistic omnivores, which means they eat a wide range of food, including insects, fish eggs, juvenile fish of other species and a diverse range of plants and other organic matter. They feed like a vacuum cleaner, sucking up everything and blowing out what isn’t wanted. Aquatic plants are dislodged in the process and are unlikely to re-establish. Koi carp cause habitat loss for plants, native fish, invertebrates and waterfowl and degrade water quality.
Rudd are stocky fish with distinctive red fins and large, shiny scales that range from silver to pale or burnished orange in colour. Rudd normally grow to about 25 cm, and about 500 g. As they are the only herbivorous freshwater fish they are the 'possums of the waterways', feeding voraciously on native aquatic plants.
They are found in ponds, lakes and slow-flowing streams where they build up to high numbers quickly and destroy the food and habitat for native species.
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Pest samaki utafiti wa wavu mchanganyiko matokeo kwa Northland Archived maudhui: Hii vyombo vya habari kutolewa ilikuwa sahihi juu ya tarehe ya kuchapishwa. Uchunguzi wa hivi karibuni wa samaki wadudu uliofanywa na DOC na Halmashauri ya Mkoa wa Northland umetoa ushauri muhimu kwa ajili ya kupanga vita dhidi ya samaki wadudu wawili wa Northland, koi carp na rudd. "Kuchunguza kwa jumla, tovuti 12 za samaki wa wadudu katika Northland na habari njema ni kwamba tumethibitisha kwamba idadi mbili za kihistoria za koi zimeangamizwa kwa mafanikio, na hakuna maeneo mapya ya koi yaliyopatikana wakati wa uchunguzi. """ "Habari mbaya ni kwamba vita vimeanza tu, na idadi kubwa ya samaki wadudu katika njia za maji katika Northland, ""anasema Amy Macdonald, DOC Freshwater Mshauri wa Ufundi." DOC na Northland Regional Council itatumia habari hii ya uchunguzi kuendeleza programu ya ufuatiliaji wa samaki wa wadudu na kuondoa kusaidia kulinda njia za maji za Northland. Hii itatuwezesha kuweka vipaumbele kwa maeneo ya udhibiti na kuondoa, na kufanya kazi na jamii kuzuia wadudu kuenea kwenye maeneo mapya. "Samaki wadudu huvuruga usawa katika mifumo yetu ya maji baridi, ikiathiri maadili ya ikolojia, kitamaduni na burudani. Koi carp na rudd ni habari mbaya kwa ubora wa maji kwa hivyo pia ni tatizo kwa sekta zetu za kilimo na utalii - sote tuna sababu ya kufanya kazi pamoja ili kuzuia kuenea na kuchukua. Koi ni kubwa na rangi nyangavu; wanazaliana kwa wingi na wanaweza kuwa na athari mbaya kwenye njia za maji za New Zealand. Rudd ni wadogo lakini pia wazalishaji wa uzazi; wanakula ncha zinazokua za mimea ya majini ya asili, na wanaweza kugeuza maziwa kuwa njia za maji zilizojaa mwani ambazo hakuna mtu anayetaka kuogelea. Mtaalamu wa samaki wa wadudu Helen McCaughan kutoka Wildland Consultants amepanda kutoka Christchurch kusaidia operesheni hiyo. Uchunguzi huo ulifadhiliwa na Bajeti ya 2018 ambayo ilitoa DOC $ 76m kwa miaka minne kuwekeza katika mipango ya uumbaji wa mazingira ya ardhi, maji safi na baharini ili kukabiliana na mgogoro wa uumbaji wa New Zealand. Hii ilijumuisha dola milioni 4.5 kwa miaka minne ili kuzuia idadi ya wadudu muhimu wa majini na kupunguza uwezekano wa kuenea kwa maeneo yenye thamani ya bioanuwai, ambapo ni ngumu zaidi na ghali zaidi kudhibiti. Lengo ni kuzuia angalau wadudu wanne wa maji baridi (koi, gambusia, rudd, hornwort) ambao wana uwezo wa kuenea kwa sehemu nyingine za New Zealand. Mfuko mpya pia utatumiwa kudhibiti mimea ya majini ya uvamizi na hatari kubwa au athari kwa maadili ya bioanuwai ya maji baridi, kupunguza athari zao kwa mifumo ya ikolojia ya mto, ziwa na maeneo ya mvua na kupunguza uwezekano wa kuenea kwa mazingira mengine ya asili. Lengo ni kuongeza kupunguza mimea ya majini ya uvamizi kwa angalau maeneo 10 kwa mwaka. Mifumo ya mazingira ya maji baridi ya New Zealand inakabiliwa na vitisho kadhaa - uchafuzi wa mazingira, ukataji misitu, upotezaji wa makazi, mabadiliko ya matumizi ya ardhi, sedimentation na utajiri wa virutubisho, na athari za wanyama wa majini na mimea kama vile koi carp na rudd. Koi ni samaki wa aina ya goldfish, lakini kwa upande mwingine, wao ni kubwa zaidi na wana jozi mbili za viboko vya kuonekana kama nywele, pia huitwa barbel, kwenye kona ya mdomo wao. Wao ni tofauti sana katika rangi, mara nyingi blotty vivuli ya nyeusi, nyekundu, dhahabu, machungwa au pearly nyeupe. Karp Koi mara nyingi inaweza kuonekana wakati wa miezi ya majira ya joto katika vidimbwi na maji ya polepole wakati wa mchana wakati wao ni karibu na uso wa maji. Wakati koi carp hula wao kuchochea chini ya vidimbwi, maziwa na mito, muddying maji na kuharibu mimea ya asili na samaki makazi. Wao ni omnivores opportunistic, ambayo ina maana wao kula mbalimbali ya chakula, ikiwa ni pamoja na wadudu, mayai ya samaki, samaki vijana wa spishi nyingine na aina mbalimbali ya mimea na vitu vingine kikaboni. Wao hula kama vacuum cleaner, sucking up kila kitu na blowing nje nini si alitaka. Mimea ya majini huondolewa mahali pake katika mchakato huo na haiwezekani kuanzishwa tena. Koi carp husababisha upotezaji wa makazi kwa mimea, samaki wa asili, wanyama wasio na uti wa mgongo na ndege wa maji na kudhoofisha ubora wa maji. Rudd ni samaki wenye umbo la mviringo wenye manyoya mekundu na magamba makubwa yenye kung'aa, ambayo huanzia rangi ya fedha hadi rangi ya machungwa. Rudds kawaida kukua kwa karibu 25 cm, na karibu 500 g. Kama wao ni tu herbivorous samaki maji baridi wao ni 'possums ya njia za maji', kulisha voraciously juu ya mimea ya maji ya asili. Wao hupatikana katika vidimbwi, maziwa na vijito vya mtiririko wa polepole ambapo wanajikusanya kwa idadi kubwa haraka na kuharibu chakula na makazi kwa spishi za asili. Kwa maswali ya vyombo vya habari mawasiliano: