Creasy's Column - By Hugh Creasy April 2017

The river runs low and slow, murky with algae and slime and giving off an odour of decay. In the turbid gloom a crayfish dissects the body of a bully, and with dainty movements of its pincers transfers the softer parts to its mouth. The crayfish is out in the open in daylight, unafraid, bold in the absence of predators.

There is a trout nearby but it is lethargic, its normally bright-eyed watchfulness has been reduced to a dull awareness and its movements are slowed, barely sending a ripple through the thickening slime on its body.

Upstream there is a riffle where the water bubbles over pebbles and into a weedy run where stronger fish maintain a watch, invigorated by the oxygen and jealous of their position. The downstream fish is dying from the heat and the lack of oxygen. It was never strong enough to compete and left a run to the sea too late in the season, and that passage is now cut off by shallows and sand bars and bigger fish, more aggressive, savage in their territorial battles.

The fish pumps thickened water through its gills, but with little effect. It is dying, and the goggle-eyed crayfish senses its distress. There will be a feasting and the lesser creatures of the river will grow fat on the misfortune of some.

A long, black sinuous shape moves into the tail of the pool. An eel reacts to the odour of death, and slides through the algae and weed, mouth gaping white and tasting the drifting slime. The crayfish senses its approach and scuttles to cover under an overhang, still clutching the bully, now a desiccated skeleton.

As the water table lowers, so the insects and animals that live in shallow wetlands avoid drought by migrating to a water source. They can only do this by following rivulets, seeps and puddles with outlets to the river’s edge. Otherwise they must rely on the remaining dampness of mud and tree roots and hibernate until the rains come.

In the shallows of the pool where our unfortunate fish is living out its last days, there are backswimmers and the larvae of damsel flies and dragonflies. There are mosquito and midge larvae, replacing the mayfly and caddis that have moved to more oxygen-rich water upstream and down where small rapids oxygenate the water, if only for a short distance. Duckweed has taken root at the pool’s edge and here the bloodworms proliferate, along with sandfly larvae and snails.

Nitrate levels are concentrated and the water is far from drinkable. In some parts of the river there are underground springs forcing cool, oxygenated water through the gravels and bedrock and it is this water that is giving life to the benthic fauna. Brown and rainbow trout gather at these springs, and in rivers like the Motueka and the Upper Manawatu their numbers are quite astonishing. But they are often under stress and their flesh may be distasteful. They are lethargic feeders and hard to catch.

There is a key imperative though, as winter approaches, that impels the fish to gain condition. By June the hens will be on the redds and the jacks will be fighting for dominance. Now, they need to feed and gain condition, and the first fresh through the river drives them in search of food. Hardships of the drought are replaced by voracious carelessness, and autumn becomes the season of plenty for anglers. It is an idyllic time to be on the river. Cool nights and warm days mean waders are unnecessary, and spates have washed ordure from the water. The air smells fresh and the only odours in the air are from farmers feeding out the last of the silage while waiting for grass to spring back into growth.

 Mayflies, stoneflies and caddis proliferate. They, too, have only a short time to reproduce before the chill winds of winter bring things to a standstill. Damsels, with their jewel-like bodies, flutter in cheerful abundance over still water and the trout rise to them as they would to a mayfly.

Ducks have finished their moult and their young ones have fledged. They patrol the rivers and lakes along with Canada geese and black swans. The young birds must gain condition before winter comes, and their proliferation annoys farmers. They destroy crops, but hunters eye their burgeoning numbers with great expectation.

 Autumn is here and it is time to share in nature’s bounty.      

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