29

H.—ls

MARINE FISHERIES INVESTIGATION STATION. Sir, — I have the honour to submit the following report of the operations of the Board of the Portobello Marine Fisheries Investigation Station for the year ending 31st March, 1930. European Lobsters. On the 31st March, 1929, the stock of lobsters consisted of eighteen males and sixteen females. During the year two males and one female died, leaving the present stock at sixteen males and fifteen females. The deaths in two cases were due to injuries received after casting. In the third ease a cancerous growth developed in one of the females, which, however, was not detected till after she had cast her shell. All but three females developed their eggs during the year and these were hatched out during December, all of them being free of their eggs by the end of the year. It is estimated that about 250,000 larvse were liberated. These, as they hatch out, escape to sea on the ebb tide. The loss of life is no doubt considerable, but our past experience with the Macdonald jars has not been favourable, and the probability of survival for the liberated larvse is greater in the open sea than in the tanks, where it is extremely difficult to overcome the cannibalism which prevails among all crowded crustaeea of all ages. The time of year at which larva 3 are set free is favourable, as the average December temperature of the sea outside Otago Heads is 12-58° C. (54-8° F.). The adult lobsters become lethargic and cease to feed when the temperature falls near or below 5° C., but otherwise they do not appear to suffer from the winter temperatures of the outside ponds. Hydrographic Work. The collection of water samples (for salinity) and recording of ocean-temperatures was carried on throughout the year, but the continuity of the work was broken by the launch being out of commission during July and the greater part of August during alterations and fitting of new engine and apparatus. As long as the United States barque " City of New York " lay at Port Chalmers, Mr. Shropshire, Hydrographer to Admiral Byrd's Antarctic Expedition, went out with the launch regularly. Hitherto all temperatures recorded have been entirely surface records, as the station is not furnished with suitable thermometers for deep-sea work. Mr Shropshire was able with, his thermograph (selfrecording) to take observations down to 50 fathoms. It is a matter of interest that at that depth the temperature of the north-east current flowing up the coast past Otago Heads was the same as at the surface. The following shows the temperature (in degrees centigrade) of the surface-water for the three years ending 31st March, 1930. The records were taken at a station three miles east of Taiaroa, Heads on an average once a fortnight between 10 a.m. and 1 p.m. : January, 13-61°; February, 14-55°; March, 14-21° ; April, 13-27°; May, 10-99° ; June, 10-25° ; July, 9-68°; August, 9-51° ; September, 9-67° ; October, 10-71° ; November, 11-68° ; December, 12-58°. The temperature of the air taken at the same time was as follows : January, 15-73° ; February, 15-72° ; March, 14-07° ; April, 12-05° ; May, 8-s°; June, 7-28°; July, 7-58°; August, 6-75°; September, 8-75°; October, 11-02°; November, 12-53°; December, 13-64°. The highest individual water-temperature recorded was 17-6° C. on the 23rd January, 1928, when the air-temperature was only 17-0° C. Again on the 12th January, 1930, the water-temperature was 17-5° C., and the air 16-5° C. In both cases the weather was very fine and the air still. The lowest water-temperature was 8-5° C. on 12th July, 1928, when that of the air was 7° C. The air-temperatures in the above figures are, of coursc, higher than the average temperature for the coast as recorded by the Meteorological Department, because they are all taken in the warmest part of each day. But it is interesting to note that the temperature of the sea off the east coast of Otago during these three years never fell below 8-5° C. (47-4° F.). In the open tanks at the station the temperature of the water has occasionally fallen to 0° C. (32° F.), and at this temperature such fish as blue cod die, while others become quite lethargic, ceasing to feed. This appears to be the case with all flat fishes. The water in the tank-house is prevented from falling below 5° C. (41° F.), by passing the delivery pipe through a small coke-fired heater. Even at this temperature many species of fish cease to feed and become lethargic. It is not possible from a close examination of the salinity returns for the past three years to deduce any observations of value. The period is too short. An attempt to plot the figures and to compare them with temperature curves for the same period gives no informative results. It was recorded in last annual report that Mr. Scofield, light-keeper at Cape Saunders, had made regular observations of temperatures and collections of water samples, the latter being forwarded to the Government Analyst's Department in Dunedin for estimation of salinity. During the year Mr. Scofield was transferred to Puysegur Point, but he expressed his willingness to carry on similar work there, and accordingly he has been supplied with a stock of bottles, and these are forwarded on the regular trips of the " Tutanekai," by which also the collected samples are brought back. If sufficient equally careful and enthusiastic observers could be secured among the lighthouse men round the coast, similar work to that so well carried out by Mr. Scofield could be done at many other points on the coast of New Zealand.