64 ' DEPARTMENT OF THE NATAL SERVICE 



6 GEORGE V, A. 1916 



the percentage of chlorine and the amount of total solids in these. His results are 

 given in the last two columns of the table. In certain cases two sets of results are 

 given. Those in italics are from the bottom. 



The temperatures at top and bottom were taken with a Negretti and Zambra 

 reversing thermometer. A few of these temperatures are shown in the table. The tem- 

 peratures rose until about the first of July. The highest temperature recorded, 77°F., 

 was taken on the 10th of July. A temperature of 60° F. was not recorded until June ~ 

 20; after July 1, no temperatures of less than 60° F., except on one occasion, that of 

 August 25. Early in the season there were often great differences between the surface 

 and bottom temperatures. These differences became much smaller towards the end of 

 the summer. A difference of 9-5°F. is recorded for a depth of 30 feet on June 23. 

 On some occasions the bottom temperature was higher than that at the surface, e.g. at 

 station 5 on September 3: top, 65°75; bottom, 67°. Owing to the low temperature of 

 early summer the oysters did not spawn until after the first of August. Spatting 

 began about three weeks later, and thus the season was short for the growth of the 

 young oysters. The lateness of spawning must considerably increase the danger of the 

 fry being destroyed by sudden falls in the temperature. The fry of the Malpeque 

 oyster, however, must be quite resistent to such falls of temperature, since spatting 

 occurred even after the sudden drop to 54° F. on the night of August 24. 



PLANKTON OYSTER FOOD. 



The diatomaceous oyster food collected in various parts of the bay throughout the 

 summer is being worked over by Dr. A. H. MacKay, Superintendent of Education, 

 Halifax, a well-known authority, and his results will be included in a future report. 



INFLOW AND AMOUNT OF FRESH WATER. 



Arrangements were being made to estimate the inflow of fresh water when it was 

 decided that the desired result "was more directly attained by taking the salinities. 

 Fresh water affects the oyster by altering the salinity of the water in which the oyster 

 lives. There are a great number of small streams flowing into Richmond bay. Owing 

 to the fact that the woods are largely cleared away, the water rushes down quickly in 

 the spring, and the volume of many of these streams is greatly augmented at this 

 season while it is inconsiderable during the summer months. Unfortunately, records 

 are not yet available of the densities of the water in the various parts of the bay while 

 these spring floods are on. 



PRESENCE OF OYSTER ENEMIES. 



Starfish {Asterias vulgaris Verrill.) are abundant now in Richmond bay. A few 

 years ago they were a curiosity. They constitute one of the worst enemies of the oyster 

 in this bay. They are found in all parts of it, but are particularly abundant on the 

 oyster grounds around the Curtain islands and in the Big bay. The government 

 oyster steamer, the Ostrea, under Captain Kemp, the Dominion oyster expert, did 

 good work during the summer, cleaning out starfish on the beds to the west of Curtain 

 island and in the Big bay. He was assisted during the month of June by government 

 patrol boats D and E. Some of the oyster companies also did service in this line. Both 

 government and oyster companies should pursue this line of work much more vigour- 

 ously, and the good results attained should be conserved and not lost as they were to a 

 great extent last summer. The starfish fished from the beds are removed from the bay 

 of course, but in the case of the work done by the Ostrea there was an indirect but 

 none the less important result which was not conserved. The bed effectively cleared of 

 starfish was swept by the starfish-mops and left white and clean and in good condition 

 to secure a set of spat had it not been torn to pieces by oyster-planters dredging for 

 shell. Thie shell might have been secured from other beds not cleaned in this way. 



