NZ’s Rarest Fish

Successful Breeding of NZ’s Rarest Fish

Even though Santa was a week late Paul Decker (Director of the Mahurangi Technical Institute, Warkworth) said he is totally forgiven as the late Christmas present came in a successful hatching of 20,000 baby Silver Carp on the 30th December.

Several of the Institutes Aquaculture students gave up time with their families during the Christmas holidays to assist in the final stages of a breeding programme which started 5 years ago.

Silver Carp were originally imported into New Zealand in the early 1960’s by the Auckland University and subsequently in the late 1960’s by the Hawke’s Bay Acclimatisation Society. These fish are freshwater filter feeders consuming algae and are capable of growing in excess of 20kg’s. As their reproduction eluded the original importers the Ministry of Agriculture and Fisheries (as it was known then) became involved and achieved limited breeding success. By 1989 there were 9 fish left in New Zealand and they were all given to a private freshwater environmental restoration company.

Silver Carp have huge potential as one of the tools in water quality management as being filter feeders they consume suspended algae from the water column and are biologically incapable of breeding in the wild in New Zealand. One of the prime areas for their introduction was for their use in algae control of the Rotorua Lakes. Indeed the Ministry’s hatchery was even located for many years on the shores of Lake Rotorua.

After hearing of the 15 years of failed breeding attempts in 2004 the staff at the Mahurangi Technical Institute Aquaculture Hatchery (located within Warkworth) came up with a long term breeding plan. As luck would have it in 2005/6 the last two remaining fish (one male and one female) known to exist within New Zealand produced a batch of eggs from which 36 fish made it through to adults which are capable of breeding. Adulthood is reached at 5 years and the fish can live for up to 20 years.
”With all the care and attention bestowed onto these few surviving fish as if they were children, they have become our family”, Mr. Decker says. “It’s now all paid off; with the very last pair successfully reproducing 20,000 babies. We are now absolutely confident that it is now possible to hatchery reproduce these fish by the hundreds of thousands and at the same time be extremely cost effective, we have made it”.

After 50 years as New Zealanders the next step for these fish is to continue the work of the crown in evaluating the use of the species as a biological water management tool. Given the species is incapable of wild reproduction, it is definitely a better alternative then chemicals being used in our waterways.