Rainbow and brown trout were liberated in Lake Taupo more than 100 years ago. Open for fishing 12 months a year, the lake and its adjoining rivers represent one of the last true wild trout fisheries in the world.
* Lake Taupo is an internationally renowned trout fishery.
* The fishery is of great importance to Ngati Tuwharetoa.
* In 1991, 13% of all anglers (marine and freshwater) who fished in New Zealand fished at Taupo.
* Taupo anglers comprised 42% of all freshwater anglers and spent approximately $70 million using the Taupo fishery.
The history of the fishery
Trout were introduced to the Taupo District to provide a sports fishery. Brown trout were introduced into the lake in 1887 and quickly grew to large size but were difficult to catch. As a consequence rainbow trout were introduced in 1898. Although in the early years the size and condition of the fish fluctuated, over the past 40 years this has stabilised and the Taupo Fishery continues to provide excellent fishing opportunities each year.
A description of the fishery
The Taupo Sports Fishery Management Plan requires the fishery to be managed as a self- sustaining wild trout fishery. No stocking is undertaken.
Trout spawn in the tributaries of the lake and the young that hatch spend the next 18 months or so in the streams before migrating to the lake. Once in the lake the fish grow rapidly by feeding principally on smelt. Most mature at approximately three years of age and 2 kg in weight. As winter approaches these fish run back up the rivers to spawn, 30% surviving the rigours to spawn a second time.
Over summer, anglers fish for trout in the lake and over winter, target the spawning trout in the rivers. Approximately 45,000 anglers use the fishery each year catching in the order of 150,000 to 175,000 legal sized (>45cm) trout. Slightly over half of the total angling effort of approximately 650,000 hours is expended on the lake.
The fishery is managed by the Department of Conservation as a consequence of an agreement between the Crown and Ngati Tuwharetoa enshrined in the Maori Land Amendment and Maori Land Claims Adjustment Act 1926. Management is self- funded from fishing licence revenue which this year will be in the order of $1.5 million.
What limits the fishery?
The relatively pristine nature of the streams and lake provide exceptional spawning and rearing habitat, but the environment can also be very harsh. Only one fish from every thousand or more eggs will survive to maturity. The wide range of stream types and diversity of life history patterns amongst Taupo trout is a major strength of the fishery, making it resilient to adverse climatic and environmental impacts.
The key constraints on the size of the trout population are:
* Spawning success
* Juvenile survival - the first few days after emergence constitute the single largest source of mortality when more than 90% of fry are frequently lost. If dramatic events like floods occur then the mortality will be even higher.
* Size on lake entry - the larger the juvenile trout is on entering the lake, the greater it's chances of survival. The number and quality of large juveniles is initially controlled by the number of fry that survived and subsequently by the quality and quantity of the food and habitat available in the rivers.
Ultimately, the size of the adult trout population in the lake varies widely from year to year in response to the prevailing climate and living conditions during the river growing phase of the fish.
This variation is one of the intricacies of managing a wild trout fishery.
Future threats to the fishery
1. Reduction in quality or extent of spawning and rearing habitat. Taupo streams provide extensive areas of good living conditions, but this environment can be easily damaged.
2. Reduction in trout growth and/or numbers caused by water quality change. Changes in water quality are being caused by increases in nutrient content. This is likely to be detrimental for the fishery.
3. Negative impacts arising from the introduction of new species. The risk of accidental release of an undesirable new species or disease appears low. However if a new species does become established, eradication is unlikely to be an option and the potential impact on the fishery could be significant.
4. Overharvest. Overharvest in Lake Taupo can have a significant impact on the number of fish surviving to maturity and in the worst case the sustainability of the fishery will be threatened. Significant poaching, if left unchecked, could have a similar effect.
5. Releasing of fish - anglers are required to release fish that are undersize and many anglers choose to release fish that are in poor condition and not suitable for the table. Unfortunately rough handling of fish prior to release increases the mortality rate and many fish do not survive. The DOC encourages anglers to land fish quickly, ideally leaving them in the water and unhooking them without touching or handling to help ensure their survival.