Preventing a catfish infestation

Introduced into New Zealand in the 1870s, for reasons unknown, catfish have now found their way into Lake Rotoiti. The Bay of Plenty Regional Council needs your help to stop them from spreading further. 

Biosecurity Team Leader, Shane Grayling, greeted me at a lakeside property in Te Weta Bay, on the shores of Lake Rotoiti. Te Weta Bay, according to Shane, is the ground zero of the Rotorua Lakes District catfish issue. The bay is dotted with yellow research buoys, telling the story of the research projects conducted beneath the surface.

How it all started

Catfish were introduced to New Zealand waters in the 1870s from America, although there is little understanding as to why.

For many years, they remained restricted to a few Waikato waterways and Lake Taupo, as well as a few isolated locations in the South Island.

In March 2016, a weed harvester working in Lake Rotoiti hauled up an unexpected guest – a catfish. Biosecurity teams in the Bay of Plenty Regional Council (BOPRC) went into full-on research mode, deploying nets that same week. The problem, unfortunately, was already so advanced that they caught 50 catfish in the one night.

The issue

Catfish are an invasive species that pose a threat to both our trout and native koura (freshwater crayfish). Should the impact of catfish develop further, there is also a risk of economic threats, as fewer trout and less desirable lakes mean potentially fewer people visiting the region to experience them.

In an attempt to take a more proactive approach to this issue, BOPRC and partners Te Arawa Lakes Trust have begun a research programme which involves catching and tagging catfish, to better track their movements.

The team is currently targeting critical areas with fyke nets, baited with tins of salted sardines (a catfish favourite!), however the numbers they are bringing up are still only a small fraction of the population lurking below the surface.

As well as all the work being undertaken by the council, it is up to the recreational users of the lake to pitch in to ensure this species doesn’t do further damage to the surrounding waterways.

Stopping the spread – how you can help

The message to fishers and boaties accessing Lake Rotoiti in the coming months is very clear – if you’re out and about, check, clean and dry your boat before moving to another body of water.

This means:

Check

Flush out your bilges, ballast tanks and trailers before leaving the lake where you’ve been boating. This ensures that if you have any catfish in your boat or trailer, they won’t be transferred elsewhere.

Clean

Thoroughly clean your boat/kayak/jetski with fresh water – this not only prevents the spread of catfish but also invasive weed species. Flush out your bilges and ballast tanks, as well as any open areas in your trailer, as small catfish can hide away in these areas and stay alive for up to 48 hours out of the water.

Dry

Give your boat and trailer time to dry out completely before putting it back into a new body of water.

It only takes one small catfish in a new body of water to start a new population that could be the end of some of our native species, and these simple steps can help you play a part in preventing disaster.