News release

From: Calum McNeil, The Cawthron Institute, New Zealand (study author)

"Just three years ago the freshwater gold / Asian clam was first detected in Aotearoa New Zealand.

"This little clam invader is an ‘ecosystem engineer’ changing conditions in rivers and lakes to suit itself. It can build up in huge numbers, to tens of thousands per square meter of river or lakebed and it can filter water at such a rate, that it can alter the food webs, chemical processes, and water clarity of the places it invades.

"All of this will affect fish species, some of which may benefit from this ‘engineering’ but many will suffer. Using evidence from clam invasions overseas, a list of predicted future fish ‘winners’ and ‘losers’ has been made.

"Small native fish who need particular types of river flow, habitat and plankton may lose out as the clam could swamp their habitat and compete for the same food.

"Trout and salmon may benefit from clearer waters for feeding but lose out as spawning grounds are lost.

"Pest fish such as koi and catfish may be overall  ‘winners’, as the clam may be a great new food source for them.

"Only time will tell what will happen, as the clam spreads throughout Aotearoa New Zealand."