Drift diving season in full swing

JACOB LUCAS

The stable weather period we are currently in means an ideal opportunity to undertake fieldwork for monitoring our freshwater species.  All Fish & Game regions regularly monitor fish and game bird resources, using a range of techniques to gain important species data.  Game bird trend counts, and banding programmes are undertaken over summer, and regional staff are currently actively engaged in a busy schedule of electric fishing and drift diving work for fish species.

Drift diving aims to undertake a count of trout or salmon within historical sites in river systems. Comparisons can be made between years to determine how the fishery is looking, and what factors are likely responsible for increase or decreases.  Most weeks over summer when conditions are suitable, you’ll find Fish & Game staff donning 7mm wetsuits and other assorted underwater gear and floating down a river counting trout, and, at the same time, categorising them into size cohorts and sometimes species.   Smaller rivers often only require 2-4 divers, however larger rivers such as the Wairau, Motueka, or Grey require 8-10 divers to ensure sufficient coverage.

The deal is you only count fish once they have gone past you, and communication between divers is essential to make sure there are no double ups and all parts of the river are surveyed. Most of the time the fish know you’re coming and have retreated to the deepest part of a pool or are already hiding under ledges.  On some occasions they are pushed downstream and group up ahead of the divers, only to bolt through towards the tail of the pool, meaning some pretty swift counting for the diver they flee past!

Regardless of what the trout are up to, drift diving is a great way to see the general health of the river.  Habitat qualities, invertebrate life, substrate, algal levels, native fish observations, and water clarity are all best seen through an underwater lens.  At times this information can aid in some of our advocacy functions, especially as many rivers are dived annually and have records dating back to the 1980’s.

We also see some pretty impressive fish, trout and otherwise.  Some of the eels we see have seen have been on this earth longer than we have and demand nothing but admiration and respect, with the occasional one giving us a good hurry up if we get too close!