Thursday, September 16, 2021

A Season of Hog Trout and Wet Mice
Mouse Year, Mice Hatch, Mice Plauge
By Mike Kirkpatrick

Call it what you want, but this is and will always be one of the most spectacular phenomenons fly fishermen can take part in. If you don’t know what I’m talking about, let me take you through my 2019/2020 season here in South Island, New Zealand.

Early season in New Zealand can come with a lot of variable weather.

October 2019 was no different. A cold front brought snow to low levels in the backcountry and frigid wind chill conditions at times. I teamed up with good mate and guide, Hans Kreuer for a two day overnight trip into a river system renowned for holding big fish during a ‘mouse year’. 

These mouse years are termed as such by the explosion in their numbers due to the proliferation of beech tree seeds dropped after the trees flower in spring. This is not an annual event, but is gaining more frequency as climate change warms our winters and the trees retain the necessary energy to flower and drop seeds. The mice, in their drive to find more food, cross the rivers and lakes and trout quickly lock onto this new and rewarding food source.

We found this stunning sliver coloured brown trout finning quietly in a deep run,

moving to take food in short, maybe 6-9 inch drifts to his right. He wasn’t going to move much and Hans made numerous drifts of a tiny #18 nymph, as that’s what we’d worked out they we’re willing to feed on. Finally the trout moved, with Hans tightening on seeing the subtle flash of his mouth.

This football shaped brownie was a much more simple chance.

He was in a shallow side branch and moving well. A small weighted nymph was taken on the first cast and the fish put up a serious fight before being subdued. Interestingly, the colour varied greatly from the first fish, being very golden, almost buttery, in comparison. He was one of the best conditioned browns I’ve ever landed.

A careful look along the seam of a fast heavy run, revealed a trout of very obvious girth.

even from our viewing position off a metre high bank and some distance back. I snuck into position and all it took was one cast of a small mayfly nymph. The battle was, at first, intense and powerful, but once I managed to get some serious side strain on the big brown, he came sliding into the bank, his belly hitting the bottom and promptly falling over, allowing me to walk over and grab his prodigious tail. He had the body of a 6-7lb fish but dragged the scales down to 13lb. A true pig with fins that had grown so fast on mice, he lacked the ability to sustain any length of fight. Crazy proportions on this brown.

This lovely 10lb brown was pushed right up into the fast water at the head of a long wide pool.

We almost walked past him, but as we know that even early season they can favour these lies, it was worth a look. Our perseverance was rewarded when we spotted him swaying in a tongue between two fast currents. It was a tricky drift but once the cast hit the spot, he took comfortably. An intense 5 minute battle ensued, until I was able to slip the net under him some 120m downstream.

Mid Season

The mid-season, around December and February, held just wonderful conditions and many anglers chasing them as word got out that this was indeed a very good mouse year.

In late December, I took two clients into a fishy spot I had marked on a prior trip.

The prevailing downstream wind and a week of rain preceding our trip had meant no angling pressure, and pretty relaxed fish. The guys had a day for the ages with this magnificent silvery brown topping the scales at 12.5lb. He was caught on a larger stonefly and moved a metre to eat. The boys caught four more trophy sized fish that day. It truly was a red letter day.

This fish staggered even me when he pulled the digital scales down to 18.1lb!!

It was not only the biggest fish I’d guided a client on to, but bigger than my own personal best. I spotted it moving out from an undercut bank about half an hour before dark and one cast of a caddis nymph saw us attached to the behemoth. A tense battle followed and some time later we stood over him, gasping at his size. It truly was the fish of a lifetime. Ironically, after telling my client that I’d very likely never top that effort, a week later I managed to land an even bigger fish.

Another trip with two clients in January saw us strike it right with trout.

This was after a period of weeks of lethargic fish activity. This superb 13lb brown was almost invisible in fast medium depth water, but patience and the belief that there would be a fish in residence paid off handsomely. It took many, many casts, fly changes, and technique changes s before a subtle telltale movement saw me calling the set.

Amazingly the same client, Mick, smashed it again with this hog very close in weight to his previous fish.

This brown made it a lot easier for us by sitting in front of a rock in shallow edge water. Boom, hooked him. That’s where things got tricky, as the big fish dragged the angler all over the run and around every rock or branch it could find. The tippet gave way just as he hit the net. Sweet relief.

Mick's fishing mate Josh wasn't going to be keep out of the trophy hunt for long.

He banked this simply wonderfully coloured and conditioned 12.5lb brown in the hardest fight I’ve ever seen. The cast and set were fairly standard, if standard is trembling hands and sweaty palms, but the fight this fish put up was next level. 15 minutes of mad scrambling, crossing the river back and forth, falling multiple times and freeing trapped tippet. The fish finally landed and Josh fell over and just laid on the ground, trying to process what had just happened.

Late Season


A trip with two good friends to chase a few bigger fish produced the goods once again.

We expected the big browns to be very cagey,

with the volume of pressure they had experienced, but finding the fish that were harder to see brought us much success. This fish was firmly fixed to the bottom of a fast heavy run and a Czech type setup with serious weight and a small training fly did the trick. Did he ever put up a battle!

A tough day out with Hans in bleak cold weather with fresh footprints everywhere produced two moments of magic.

I bagged a big brown early, but Hans trumped me with this brown nearing 15lbs. It was way up into the head of a run we knew to hold several fish but showing nothing until we found him. Multiple casts saw little reaction until he selected the right fly. The water erupted into a shower of spray as the angry hen fish went nuts, preceding to drag him all over the pool. Luckily the hook held and the day was made.

My fish from the preceding story.

A fairly straightforward shot and simple hook set to buck the trend of fussy fish. The fight however, took on another level as two sets of rapids needed to be negotiated before he could finally be subdued. A wonderful clean and shiny example of Salmo Trutta at his trophy sized best. 11.5lbs of sheer muscle.

In the late season,

longtime client Tony tore his elbow tendons to the point where he could hardly hold a rod. But this wasn’t going to get in the way of him scratching his trophy itch’ and catching this stunning golden hued 12.5lb brown. It was a well deserved reward for tenacity and skill. The water was only 18-inches deep and was fast moving. It almost hid this fish from us, but as luck would have it, I was looking in the right spot at the right time. One cast was all it took and for a few brief wonderful moments, Tony forgot about his pain.


As you can probably tell, the fishing in the South Island of New Zealand over the 2019-2020 season was one for the ages. A combination of our largest Beech tree seeding event in 75 years, the proliferation of mice, and the mild spring, made for the best large trout fishing I’ve ever experienced. Interestingly, a few cold snaps that knocked back the mouse populations during the season helped anglers, as the fish had to resume normal feeding until the mice numbers built up again. The result of this series of events meant sight fishing to enormous brown trout feeding freely at times on small nymphs and even dries. I’m sure I’ll look back in years to come with fondness of ‘the year of the mouse’

Photography by

Mike Kirkpatrick