Rainbow Trout – Oncorhynchus mykiss – Identification Guide

These are rainbow trout caught in Canterbury’s Lake Selfe. The top fish is a jack trout in spawning colours. The second is a much less colourful hen fish. Note that these fish have spots on their tails whilst brown trout and quinnat salmon generally do not.

Rainbow Trout

Oncorhynchus mykiss

According to the late Bob McDowall in his book Gamekeepers for the Nation, these early Auckland rainbows probably came from Sonoma Creek, a small stream that flows into San Francisco Bay, in the United States of America. Once these fish were established in various Auckland waterways and at the Auckland hatchery, efforts were made to spread them around the country. Liberations of rainbow trout fry were made soon after in Lake Rotorua in 1892.

The first rainbow trout releases in Lake Taupo possibly occurred by 1897 when 5000 fish were liberated into the lake by the Wellington Society. Further releases were made into Lake Taupo by the Auckland Society in 1899, 1901, and 1902.

Rainbow trout from a Canterbury high country lake.

In 1888 Alec Johnson received 1000 rainbow trout ova from the Auckland Society in exchange for a similar number of brook trout. Johnson owned his own hatchery in Opawa, Christchurch. It was from his Troutdale hatchery that stocks were obtained by other South Island Societies for release.

It is interesting to note that the records of exactly where in the United States the ova came from for liberations in New Zealand, and exactly where and when liberations took place in this country are not as well recorded as one might expect.

Rainbow trout are the dominant species in the very successful, and world famous, central North Island trout fisheries. In the central North Island, the rainbow trout are landlocked. They spawn in lake tributaries, and in some smaller lakes also along beach areas such as at Lake Rotoma, where there are no significant in-flowing or outflowing streams.

Allan Burgess with a typical rainbow hen trout from Canterbury’s Lake Selfe.

In the South Island, rainbows are mostly found in the high country lakes bordering the Southern Alps. The only other area in the South Island were rainbow trout liberations have been successful are Wanaka, Hawea and Wakatipu, and some of the rivers adjacent to them. There are also good numbers of rainbows in Lake Mahinerangi and Manorburn Reservoir. Lake Benmore also has good numbers of rainbow trout. The upper reaches of the big braided rivers like the Waimakariri, Rakaia, and others also offer high-quality rainbow trout fishing, but rainbow trout are generally absent from the lower reaches and are also absent from most other rivers and streams. Rainbow trout in the big braided rivers head downstream during the colder months of the year.

Rainbows are often found in the same lakes and streams as brown trout. However, there are many fishing waters in the South Island that hold brown trout only.

Dan Sweeney with a fat looking rainbow trout taken near Lake Brunner. It seems this well-conditioned rainbow hen fish was taken in one of the rivers flowing into Lake Brunner: the Orangipuku, Hohonu or the Crooked River. Possibly the water might also have been the outflowing Arnold River! Photograph courtesy of Brent Beadle’s Moana Trout Fishing Safaris

Rainbow trout, in New Zealand, do not go to sea. Consequently, unlike brown trout, they have not spread naturally to inhabit waters were they have not otherwise been introduced. Hence, rainbow trout are less widespread than brown trout.

Interestingly despite numerous liberations of rainbow trout into New Zealand rivers, many of these releases have proven unsuccessful. It seems that rainbow trout prefer spawning rivers that flow into lakes. In the central North Island, some of the best rainbow trout fishing occurs over winter when the trout run upstream from Lake Taupo to spawn in tributaries such as the famous Tongariro, Waitahanui, and Tauranga-Taupo Rivers

Rainbow trout grown from ova in New Zealand are the same strain of rainbow trout that are sea-running (and known as “steelhead”) in their native North America.

For some unknown reason, rainbow trout raised in New Zealand do not go to sea. Rainbow trout can tolerate higher water temperatures than brown trout. You must have a fishing license to fish for salmon, brown trout and rainbow trout in New Zealand.

A little bit about rainbow trout on the Fish & Game website.

According to Wikipedia, the longest recorded lifespan of a rainbow trout is 11 years.

This is a rainbow hen fish weighing 4kg. It was caught in the Upper Clutha River, Central Otago.
Rainbow trout. A brood fish held at the Wanaka hatchery, Central Otago.
Warren Kemp caught this huge 8kg (17lb 8oz) rainbow trout in one of the Twizel Canals May 2015. Click picture to enlarge.

Rainbow Trout Coloration

The upper back is darkish green fading gradually to silver under the belly. There is a broad pink/reddish stripe running down the full length of each side. There are many small dark spots on the whole of the upper half of the body including the tail and dorsal fins.

Kelvin Derry with a Lake Coleridge Monster. It is an 11.2-pound rainbow jackfish taken while trolling with a blue Rapala. It was caught at 6.05am on January 2009. Photograph courtesy of Kelvin Derry

There is some variation between the sexes with adult males appearing bright red on the flakes, darker coloured overall, as well as heavier in the head and lower jaw. Rainbow trout in the South Island high country can be dark blue on the upper body, silver on the flanks, and sometimes difficult to distinguish from landlocked quinnat salmon.

Like all salmonids rainbow trout can grow very large in a short time if a plentiful supply of food is available. Conversely, rainbow trout can appear small and thin for their age if food is hard to come by.

Sean Konrad of Saskatoon, Saskatchewan, Canada, landed a 15.65 kg (34 lb 8 oz) rainbow trout (Oncorhynchus mykiss) in 20 minutes while fishing Lake Diefenbaker, Saskatchewan.

Rainbow Trout – A Pending World Record

Using 4 kg (8 lb) class line, Sean Konrad of Saskatoon, Saskatchewan, Canada, landed a 15.65 kg (34 lb 8 oz) rainbow trout Oncorhynchus mykiss in 20 minutes while fishing Lake Diefenbaker, Saskatchewan. The current record is 28 lb 8 oz caught April 20, 2003, from the Zymagotiz River in British Columbia. Several other rainbow trout records have come from Lake Diefenbaker.

This post was last modified on 06/12/2017 12:46 pm

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