"Liberation Of Gambusia In Pond Unjustified”

Press, Volume C, Issue 29508, 9 May 1961, Page 11

"Liberation Of Gambusia In Pond Unjustified”

The liberation of 2000 gambusia fish in the muddy water of the North Shore Drainage Board oxodisation pond at Albany, Auckland, was unjustified according to a letter sent to “The Press” by Mr G. Stokell, of Springston.

Mr Stokell was commenting on a report on April 6 that about 2000 gambusia had been liberated in the pond. The fish were supplied by Mr L. S. Gibbs, who breeds fish at Kaikohe. Mr Gibbs had said: "By next spring they should be well established and should prevent a midge and mosquito nuisance.” Mr Stokell, who is regarded as the chief authority on New Zealand fresh-water fish, said his advice and that

of Dr. George S. Meyers, professor of biology and curator of zoological collections at Stanford University, had been sought on the subject of liberating the gambusia but it had not had much influence. Warning A copy of a letter of March 15 sent by Dr. Myers to Dr. E. K. Bassett, of the science department of Kaitaia College, who has aked for information from Dr. Meyers on gambusia said:

“I would, however, warn you very seriously of two things. Gambusia is a top and mid-water feeder and thus is especially suited to feed on cullicid larvae which spend most of their time at the surface. Chironomoid larvae do not. if I am not mistaken: they spend much more time on the bottom. Your Government entomologist should know more about Chironomus than we do.

“Secondly, gambusia is a small but very prolific viviparous fish and spreads quickly when ponds and streams overflow, as they invariably do sooner or later It cannot then be eradicated if it proves harmful. It is often harmful to the young of other fishes. Its use as a forage fish in California black-bass hatcheries had to be discontinued because it killed too many young bass. New Zealand native fishes would be prone to .attack by gambusia when young. Few persons have ever pointed out the danger of gambusia in print, but it exists. Aquarium

“In view of your desire for knowledge of the breeding and feeding habits and body structure of gambusia and the statement that your Mr Gibbs can supply you with gambusia from local ponds, why don’t you put some in a small aquarium and study them yourself.”

In a letter to Mr Gibbs, who had asked for information on gambusia, Mr Stokell says: “The fish has been used so extensively for mosquito control that it is known as the ‘mosquito fish’ in some countries, but whether it would be effective with midges I cannot say. It seems probable that it would if the water in the oxidisation ponds is sufficiently clean for the fish to exist.

“As regards the damage this fish may cause when generally distributed, it could be very serious from a scientific point of view. Interference with trout would be of secondary importance compared with the effect on native fresh-water fishes There are many species up there, as yet unknown, which might be endangered by the general dispersal of this fish.”