by Dr Peter Trolove
NZ Federation of Freshwater Anglers
17 January, 2021
NZ Smelt Decline Crisis Mirrored Other Side of World
A drastic decline in an important native fish in New Zealand has been matched by a similar decline in a similar species in the USA.
On the east coast of the South Island Stokell’s smelt is the species of the rivers of the Canterbury coastline, which until relatively recently, occurred in huge numbers from about Canterbury’s Waiau River south to North Otago’s Waitaki River.
However depletion of river flows due to irrigation in rivers such as the Rangitata, Ashburton, and Rakaia Rivers where the smelt was most abundant, has seen a drastic decline in numbers, says Dr Peter Trolove, president NZ Federation of Freshwater Anglers.
Meanwhile in the USA for the third successive year the California Department of Fish and Wildlife found zero Delta smelt in the agency’s 2020 Fall Midwater Trawl Survey throughout the Sacramento-San Joaquin Delta.
The 2- to 3-inch-long Delta smelt is an indicator species that reveals the overall health of the San Francisco Bay-Delta Estuary. Once the most abundant fish in the entire estuary, numbering in the millions, it is on the verge of extinction in the wild.
Dr Trolove says New Zealand’s Stokell’s Smelt is in a similar endangered position. The species is an important element in the food chain web that involves native sea birds, native fish and sea run trout.
“If the Stokell Smelt go extinct, the species that feed on the smelt have the potential to go extinct as well. It’s like a red light – you have to stop or there will be a crash,” he says.
The NZ smelt only live for 1-2 years so a single season of failed breeding success could spell disaster. Spawning adults are 65 mm or more long, and have a distinct cucumber aroma similar to its Northern Hemisphere counterparts.
Dr Trolove’s concern was heightened by the complacent attitude of the Department of Conservation, when he referred the crisis to the Minister of Conservation and staff at DOC’s Canterbury office.
“It would be most accurate to state that the trends in the abundance of Stokell’s is not presently known by New Zealand’s regulatory authorities (Ecan), the Department of Conservation, (DOC is the government department charged with conserving native fish), and NZ scientists, although anecdotal angler reports from locals who reside at the Rangitata and Rakaia river mouths show alarm and despair at the dramatic decline in this cornerstone species,” says Dr Trolove.
Stokell’s smelt (Stokellia anisodon or Retropina anisodon) share many physical and biological similarities with their Norther Hemisphere counterpart the Delta smelt (Hypomesus transpacificus) Both species of smelt are on the endangered species list. While there are sufficient physical differences between these smelt to warrant a different taxonomical classification, the range or ecological niche they occupy, their size, and life cycles are virtually identical;
Download the full paper :- https://coranz.org.nz/download/papers/Canterburys_stokells_smelt.pdf