Weekly Fishing Report – Central South Island Region – 26/01/18

We have experienced some hot days this summer. Maybe it’s just me but it feels like the hottest summer in a long time. The weather forecast has some more high temperatures and calm conditions for the weekend and into early next week; what the old saying “slip, slop, slap and wrap”.

Hot weather has an influence on fishing, most notably heating the water and speeding up the reduction of river flows by evaporating surface water and increasing demand for irrigation.

Trout will change their behaviour, migrate to cooler waters and go off the bite at about 19°C or 20°C water temperature.

Rainbow trout are slightly more tolerant to high temperatures than browns.

For many waterways, water temps will reach and exceed 19°C daily during hot spells.

Water temps normally peak mid-afternoon. For lakes, a warm surface layer will form and sit on top of distinctly colder water.

Anyone who has swum in a warm lake and then dived only a metre or two deep and hit a cold patch will know exactly what I’m talking about here.

Summer fishing can be tough, and its often a result of high water temps.

It can pay to keep water temperature in mind to increase your success.

Some anglers go as far as carrying around a thermometer and reviewing the ECan river flows website which lists water temps alongside river flows.

Boat anglers should utilise their fish finders which often have thermometers.

If the surface temperatures are high then target the deep cool water using heavy gear, lead lines, or downriggers.

Anglers committed to fishing lake edges or shallow areas, or streams prone to high temperatures should fish around cooler inflowing tributaries streams and avoid fishing in the afternoon.

This may mean late night fishing or early mornings are on the cards and a siesta for the arvo.

I measured water temps in a West Coast River for a couple of years and the water was always at its coldest at sunrise. Very hard to spot a fish at that time of day though!

In response to warm lake temperatures, trout may prefer to run up cooler tributary streams and reside there until the lake cools down.

Some cold southerly rain and windy conditions are what’s needed to cool the waterways down, mix the warm and cool lake water layers together and recharge the cold ground water springs.

Thunderstorms and heat showers are a possibility in the hot spells too.

They may be happening just up the road and you wouldn’t know.

Last week in the report I mentioned I thought only the Rangitata would be discoloured.

A couple of hours later I drove over the Opihi River bridge and the bloody thing was running dirty! Turns out, unbeknownst to me a thunderstorm and downpour in the headwaters of the Te Ngawai River must have caused a small erosion event.

On a totally different note, we were successful in prosecuting an obstructive angler in court last week.

In September a pair of our honorary rangers encountered an angler fishing at the Ohau B Canal.

On request to produce his licence and identify which rod(s) he was using, the angler became abusive and left the scene without complying with the ranger’s requests.

For his actions, the man appeared in the Alexandra District Court facing charges of fishing without a licence, fishing with more than one rod and obstructing a Fish & Game Ranger.

The angler plead guilty and was convicted on all three charges and was ordered by the judge to pay a total of $1,830 in fines and costs.

Let’s hope his three criminal convictions and hefty fines act as strong deterrents to other would-be offenders out there.

Tight lines

Rhys Adams, Fish & Game Officer, Central South Island