HARBOUR BED

New Zealand Herald, Volume LXXIII, Issue 22516, 5 September 1936, Page 16

HARBOUR BED

SURVEY COMPLETED LONG SCIENTIFIC TASK PLOTTING MARINE LIFE A comprehensive survey of the ecology of the sea bottom of \Vaitemata Harbour, involving the plotting and defining of the animal communities in the sub-stratum, which has been in progress since 1925, was completed this week by Mr. A. W. B Powell conchologist of the Auckland Memorial Museum, and the scientific results will probably bo published within about six months. It is the first occasion work had been undertaken in Isew Zealand in establishing a definite correlation between the animal communities in the sea bottom and the particular sub-stratum in which they live. Several species of shell fish new to science were discovered, but of more general interest was the gaining of information that can be applied in indicating approximately the feeding grounds of the schnapper at various months of the year, and the obtaining of material that suggests the ad\eiso effect on food supplies of the fish caused by the reclamation of various mud flat areas; information which possibly suggests one of the chief reasons why this fish, is not so plentiful as ii was before. Many Aspects of Survey The work by Mr. Powell was undertaken under a committee set up in 1925 to deal with various aspects of a Waitcmata Harbour survey. The results of the hydrographical side have already been published by Mr. W. K. Hounsell. Mr. 11. A. Falla, assistant director of the museum, has dealt with the feeding of sea birds; Miss L. M. Cranwell, botanist at the museum, is at work on the seaweeds, and the late Mr. L. T. Griff en, former assistant director, investigated the question of the fish life, in the course of which he discovered a new species of fish. The arduous operation of investigating the sea bottom was made possible by the use of a motor-launch generously made available by Dr. H. A. Cooper. To obtain the material from the sea bottom a conical dredge, operated by hand, was used. It was of a type, though of course much smaller, similar to that used by the Royal research ship Discovery 11. Four Main Communities The harbour bed is that of a typical harbour estuary, and the material obtained was put through a series of mechanical grading tests in order to gain an idea of the particular grade of material suited to each organism. it was found that the marine life of the area could be classified into four, main animal communities. Of interest was tlie fact that one animal community was restricted to the main channel from off Kauri Point to North Head. Then it was replaced by another community extending out into Rangitoto Channel.