Nelson Marlborough Fish and Game annual drift dive
Nelson Marlborough Fish & Game has recently finished their annual drift dive monitoring programme in 18 rivers across the Nelson Marlborough region, with the Motueka catchment one of the focus areas.
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 trout fishery looks, and what factors are likely responsible for increases 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 Motueka require 8-10 divers to ensure sufficient coverage.
Locally, the Motupiko, Upper Motueka, Riuwaka, Wangapeka and main-stem Motueka rivers were dived this season. The mainstem Motueka is one of our key regional fisheries and is dived over five sites, with annual records dating back to 1985. Generally, the Motueka trout population is very good (which is why it is a nationally significant fishery with multiple commercial trout fishing lodges supporting a large fishing tourism industry), due to its diverse catchment and many quality trout spawning streams.
Drift diving is also 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 Fish & Game’s advocacy functions, which seek to get better environmental outcomes for our waterways.
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!