Fishing in the Central South Island Region.

Graeme Hughes, Fish and Game Officer

As the traditional fishing season comes to a close the climate has been quite changeable and temperatures are more variable. Despite this trout anglers still report good catches when conditions are optimum. Several fish killed have well developed ova which is not unusual and although there are always a few early spawners there appears to be more this year. On the Waitaki River during a lower flow than the 400 to 500 cumec flows we have been used to, some anglers took advantage of the situation which resulted in good bags of trout being taken. Most fished with fly or nymph and the didymo was not such a problem using this method. The dry autumn has resulted in the smaller waters becoming smaller. The Hakataramea and Maerewhenua Rivers are holding at 1.0 and 0.5 cumecs respectively. In the high country the Ahuriri River is at an amazing 8 cumecs, about as low as I can remember.

The most topical news and observations refer to Chinook salmon in the Waitaki River. There appears to be more salmon in the river than ever and if the reports are accurate it appears this run may be the best for several years. Aerial counts of salmon and redds in the Waitaki River, including the Hakataramea River, will begin mid month. The demise of the Haka run has left us without a method for recording trends in the salmon fishery . We used to rely on the Haka run as an index of the total Waitaki run.

Fish and Game Officer Hamish Stevens has completed the second aerial count of Rangitata River salmon spawning tributaries, Deep Stream and Deep Creek. The first count was completed on the 30^th March 2007 with 30 salmon counted in Deep Stream and 92 in Deep Creek. On the 16^th April 116 live fish were counted in Deep Stream and 42 in Deep Creek.

The 2007 Sockeye salmon run is over and little evidence remains of their recent migrations. Spent salmon were sent to NIWA to establish some history on the fish and in summary Eric Graynoth was able to tell us the following.

The 25 salmon examined averaged 428 mm fork length. 16 were 4 year old fish, 8 were 3 and one was a 5 year old. Otolith measurements indicate that about half of the fish had grown slowly in their first year of life and probably reared in Lake Ohau or other oligotrophic headwater lakes, the remaining fast growing fish either migrated downstream as fry from these headwater lakes or originated from fish spawning in Lake Benmore tributaries.

On the weekend of 21/22 April 40,000 juvenile salmon will be adipose fin clipped at McKinnons Stream hatchery. Volunteers are required for this huge but important job. If you have a spare day or weekend Mark Webb at the Temuka Office will be pleased to hear from you. You can ring him or contact him at : mwebb@fishandgame.org.nz

To enhance spawning distribution and productivity of Scotts Creek at the top end of Lake Alexandrina Fish and Game Officers Mark Webb and Hamish Stevens sprayed the stream banks and prepared the fish barrier in readiness for this years spawning run. Grooming of the creek bed within the terms of our consent to disturb the bed has also been completed.

Fish and Game provided weigh-in services at the Lake Tekapo second annual fishing tournament on Saturday 17 March. The lake was rough and wind was strong so results were not spectacular. There were however, very nice rainbow trout of about 1.5 kg weighed-in. Twenty fish were caught of which five were brown trout. The competition was well run and the organisers are conscious of their responsibility to return something to the fishery.

During the last month over 200 pupils and their respective minders and tutors from Duntroon, Waitaki Valley, Temuka and Methven schools have been educated by Fish and Game staff during stream studies held at school camps or on field trips. The rivers studied included the Waitaki, Hakataramea Maerewhenua and Opihi Rivers. If not before the students are now aware of the importance of water, water quality, and of the complex life history of the many instream inhabitants and their specific aquatic requirements. Other related environmental concerns regarding water and the world we live were also discussed.

Didymo continues its northwards colonisation and now identified in the North Opuha River, this brings the number of infected waters to 43. The closest known infestation is to the south in the Twizel River. The shortest route would therefore have been just over 60 kilometres in a straight line which rules out birds or fish being the carrier. The latest find points directly to man being the vector. If the latest find was at a picnic or camping location or a popular boating or canoeing water then one could assume that the spread of the algae could have been a result of ignorance. It is neither of these. A live didymo cell was most likely transported there by an angler and this is most disappointing.

In summary the 2007 / 2007 fishing season has been, despite didymo, a rather good one, and, surprising everyone, the salmon season produced more fish than anyone expected. The season was blessed with ample rainfall and optimum river levels existed until about February. The rain ceased and the steady decline in water levels began and they never recovered. The higher flows providing optimum invertebrate production in the early season persuaded trout to stay in smaller tributaries longer and even when levels plummeted many still remained. Seeing fish is always interesting but catching low water trout is challenging and CSI trout were no exception. Conversely the Waitaki River remained high and this was frustrating for bank side anglers. The jet boaters faired better however most Waitaki anglers wanted reduced flows but these were rare.

Still water anglers always do well in the Waitaki lakes and this year was no exception. Lake Ohau also featured and was worth a visit if you could guarantee a lull in the prevailing “norwester”.

With the first release of salmon smolts only weeks away, this is an exciting start to the new salmon plan for the future. The early closing of the salmon fishing season did not have everyone’s blessing but overall most believed it was timely. The appearance of good salmon numbers during the closed month must have been frustrating for those who were not successful during the open season however the results in years to come will make this sacrifice well worth while.

The dampener on the entire fishing scene is of course the fact that didymo is here to stay and it appears that nothing man can invent will eradicate it once it has taken hold. We may have to live with it and hope that the river gods will deal to it sometime soon.