Threats

There are many things that threaten the trout population in the Taupo Fishery. Some of these threats, like a large volcanic eruption, are natural and little can be done to stop them from happening. Other threats, like polluting freshwater environments, are man-made and can be controlled.

Natural disasters - The Taupo Fishery is located in an active volcanic zone. Therefore, there is a high chance that a volcanic eruption could wipe out much of the fishery if a large quantity of ash was to fall on the waterways. Flooding is another type of disaster that can have severe impacts on the fishery. Large amounts of water can wash away trout redds (nests) or kill off large quantities of juvenile trout.

Introduction of pest weeds and fish - Not every aquatic plant or fish belongs in every waterway. A plant or fish released into a waterway which disrupts or takes control of the prevailing ecosystem is called an unwanted or pest specie. In Lake Taupo, catfish are an unwanted species due to its potential to consume trout eggs and juveniles as a result of its scavenging nature. Fortunately, the water temperature and depth of the lake seem to limit the rate of production of this specie and since their release in the early 1980's, catfish have had little impact on Taupo trout.

There is much concern about the possibility of didymo, a type of aquatic alga native to the northern hemisphere, becoming established in Taupo's freshwater environments. It has been nicknamed 'rock snot' because of its tendency to bloom into massive layers that line the gravely bottoms of riverbeds. These blooms are of great concern for our waterways as they smother the insect life that live in these waters as well as create an inhospitable environment for recreational uses like fishing and swimming. Didymo has continued to spread through the South Island since first being identified in the Wairau catchment in July 2005. Fortunately at this stage didymo does not appear to be in the North Island.

Modification of waterways - As the landscape changes through human modification, effects on the freshwater environment and the organisms that live there are taking place. Presently, one of the biggest threats to freshwater fisheries around the world is from water being diverted from their natural course for the purpose of irrigation, water supply and the production of energy.

Human impacts on water quality - A large threat is also posed by humans altering the landscape through urbanisation or farming. Unless done in a sustainable manner, these activities have the tendency to release chemicals, sediment and extra nutrients into surrounding waterways causing them to become polluted. These extra nutrients can also stimulate the growth of algae which in turn tends to throw the freshwater ecosystem 'out of balance' and leads to the onset of a process known as eutrophication. This process causes outbreaks of algal blooms due to the extra heat and nutrients in the water body.

Overharvest - Overuse or overharvest of trout can also have detrimental impacts to sustaining the population of fish for the long-term. Overharvest can arise due to people intentionally not abiding by regulation set out by the fishery by taking trout that are too small in size or taking more than the specified daily bag limit. Overharvest can also occur if the fishery does not set the adequate regulation measures to safe guard the population.