G. M. Thomson. — Natural History of Otaijo Ilarhour. 227 



facts — viz., the direction of the wind, the rainfall, and especially the 

 temperature of the air, of the water of the bay, and of the hatching-ponds. 

 These have been regularly recorded at 9 a.m. each day for more than seven 

 years. At the same hour, through the courtesy of the engineers of Mr. 

 F. J. Sullivan's trawling-steamers, the ocean temperature has been fre- 

 quently (but only from time to time) recorded. None of these observations 

 can be treated as strictly accurate, because the station is not provided 

 with suitable instruments ; therefore they can only be looked on as approxi- 

 mately correct. But, making this allowance, it may be affirmed generally 

 that the temperature of the ocean-water at a distance of about two miles 

 outside Taiaroa Head does not fall below 8-8° C. (48° Fahr.) in winter, 

 nor does it rise above 12-2° C. (54° Fahr.) in summer. On the other hand, 

 inside the harbour the variation, both seasonal and diurnal, is much greater, 

 while in the hatchery-ponds it is greater still. In very cold winter weather 

 the temperature of the water in the bay just outside the hatchery-ponds 

 Jias fallen as low as 4-5° C. (40-1° Fahr.), while in the ponds on one occasion 

 it went as low as 0° C. (32° Fahr.). 



The effect of changes of temperature in the water on the animal-life 

 which it contains has not yet been much studied, but it probably accounts 

 for a good deal of the migration of organisms which seems to be such a 

 conspicuous phenomenon in studying the natural history of the sea. It 

 is probable that at the approach of winter many species of fish and other 

 organisms leave shallow bays and estuaries, and move out into deeper 

 water, where the temperature conditions are more uniform. Blue-cod, 

 trumpeter, and some other species which are not uncommon in Otago 

 Harbour in the summer months are conspicuous by their absence during 

 \vinter. 



Notes on Fishes. 



In the " Transactions of the New Zealand Institute," vol. 38, p. 549, I 

 gave a list of the principal fishes which have been recorded from Otago 

 Harbour and the adjacent sea. Since the establishment of the Portobello 

 Hatchery a good deal of valuable information on the subject has been 

 accumulated by Mr. T. Anderton, the Curator, and this is now summarized 

 up to date. In the following notes the numbers refer to the above list. 



1. Polyprion prognathus Forster. 



The hapuka, or groper, is caught in Otago throughout the whole year. 



It appears to spawn about August, for the roes are sold in abundance in 

 the Dunedin shops in July, while all big fish taken in September are " spent." 

 But perfectly ripe fish have never been taken, for they cease to take bait 

 some time before they spawn, and those which are taken in August are 

 usually small and immature fish. The roe is estimated by Mr. Anderton 

 to contain about 1,250,000 eggs. The most mature eggs which have been 

 taken show no signs of oil-globules, and at once sink when placed in sea- 

 water. 



The hapuka is a gross feeder, and is most destructive to fish smaller than 

 itself. Over 150 stomachs have been examined, and among the contents 

 were red-cod, mackerel, warehou, soles, pig-fish, octopus, squid, whale- 

 feed (Munida), swimming-crabs {Nectocarcinus), Nyetiphanes, and tests of 

 Sal'pidae. Evidently all the food they take swimming, and they do not 

 feed on the bottom on any stationary food. 



