“Predators, Parasites May Wipe Out Oysters”

Press, Volume CII, Issue 30151, 7 June 1963, Page 12

“Predators, Parasites May Wipe Out Oysters”

(New Zealand Press Association)

INVERCARGILL, June 6.

* Predators and parasites, preying on and infecting Foveaux Strait oysters, might wipe out the oyster beds unless all New Zealand’s scientific manpower, including that of universities, were concentrated on getting rid of the predators and parasites, Dr. E. B. Slack said in Invercargill tonight. Senior lecturer in applied fisheries at Victoria University, Dr- Slack has spent the last three days at Bluff studying oystering both from the shore and at sea where he spent a day inspecting the material dredged up by the oyster boat, Marina, under the fleet’s leading skipper, Mr N. Calder.

It was unfortunate, said Dr. Slack, that the increase in the allocation of oyster dredging licenses had coincided with a decrease in the quantity of oysters dredged. "I am concerned,” he said, “that capital should* be made of this by those who wish to retain the system of res rioted licensing and restrictive practices in general in the fishing industry. “Fortunately,” he said, “the decrease in the landings of oysters took place early enough in the season to show that the entry of the new boats had nothing to do with the decline in catches.” Dr. Slack said he had studied the report of the Marine Department biologist at Bluff, Mr D. Stead, who had suggested that the oyster beds were capable of sustaining a catch of 170.000 sacks a year.

“I was perfectly satisfied,” said Dr. Slack, “the survey and calculation of the number of oysters in the strait had been carried out in a thoroughly objective and scientific manner.” Examined Material

# This, said Dr. Slack, had ’ caused him to look for another explanation for the dramatic decline in the catches of oysters. He said he went out on the Marina and examined the material dredged in 46 tows. He noticed a large number of recently dead oysters, and a great number which were dying.

It was fairly apparent he Said, that if these oysters which had recently died had been included in the catch of saleable oysters, Mr

Stead’s figures would have been attained.

The big question. Dr. Slack said, was what was causing the quite appreciable natural mortality rate In oysters. The first cause, said Dr. Slack, was predators. He had seen that one “five-finger” (brittle starfish) for every takeable oyster had been dredged up by the Marina's tows.

“Everywhere else in the world,” said Dr. Slack, “it is recognised that the starfish is a predator of the oyster, and steps have been taken to destroy them. In the United States they are caught in 'tangles’ of rope and dropped into boiling water on board th? vessel.

"Nothing of this sort has been done here,” said Dr. Slack. “Oystermen throw back the starfish with the other material rejected from dredr? loads. “What we are doing it taking out oysters, and depleting stocks, and throwing back the enemies of the oyster to carry on their destructive work.” Second Cause

The second cause, said Dr. Slack, was that oysters were carrying a lot of parasites. Mr Stead had observed organisms in oysters and had sent details of them to Dr. Millar, of the Milliport Marine Station in Scotland. Dr. Millar had discovered that the New Zealand oyster “was so heavily infested with parasites that countries which might have considered importing New Zealand oysters had been warned of the infection.” Dr. Slack said Professor L R. Richardson, head of the zoology department of Victoria University, had been offering the services of university scientific staff to be applied to fisheries for 15 years without success.

"It is my hope that the industry, the Marine Department and the Government will take advantage of the trained manpower and resources that the universities have available.”

Dr. Slack said only £60,600 a year was voted for research into fisheries—just a fraction of that voted for agricultural research.

He said he was not criticising the biology section of the department but the- administration was obviously aj fault.

A heroic job had been done at Bluff by Mr Stead, and his assistant, Mr G. Crowther, and this massive effort had received little recognition and a lot of criticism, said Dr. Slack.