114 DEPARTMENT OF THE NATAL SERYICE 



8 GEORGE V, A. 1918 



Catch 17 was taken on the morning of August 3, 1916, when numerous schools 

 of small pollock were seen close inshore just north of Wilson's beach, and the shore 

 seine was set at low water. One haul yielded fifty-seven specimens ranging between 

 30 cm. and 47 cm. in total length. The seine was rapidly hauled in over a rocky 

 bottom and the only other fish caught was one Pseudopleuronectes americanus 35 cm. 

 in length. The scales of these pollock all show two winter rings. The length fre- 

 quencies are given in table 4. The mean total length is 39-6 cm. and the mean stan- 

 dard length is 36-4 cm. 



Catch No. 19 has already been described in a previous section. It included sixteen 

 pollock whose scales showed two winter rings. The total lengths of these fish at the 

 ends of their first and second winters, as calculated from their scales, are given in 

 table No. 5. The lengths given are, in each case, the average of two measurements 

 on different scales. The mean total lengths of two-year old fish of the catch are, at the 

 end of the first winter, 15-4 cm. and at the end of the second winter, 31-8 cm. The 

 mean length of the fish when caught on August 4 was 39-2 cm. The mean increase 

 in total length during the second year, t2, was 16-4 cm. and the mean increase during 

 the third year up to August 4 was 7-4 cm. The length frequencies of the fish in the 

 different years of their growth are shown in table 6. The corresponding figures for 

 the standard lengths are: mean standard length at end of first winter, 14-1 cm.; mean 

 standard length at end of second winter, 31-3 cm; mean standard length when caught 

 on August 4, 35-9 cm. 



VI. — THE FREQUENCY OF THE DIFFERENT YEAR CLASSES IN THE YEARS 1914, 1915 AND 1916. 



From measurements made on 1,250 pollock caught in July, 1914, Mr. Douglas 

 Macallum constructed a length frequency curve, given in the paper already referred 

 to. This curve, as Mr. Macallum noted, shows two modes, one at 63 cm., and one at 

 68 cm., the former being the more prominent one. The mean length of 6-year old fish 

 (67-8 cm.) corresponds closely with the frequency curve at 68 cm., as scale studies 

 show, and the mean length of 5-year old fish (63- cm.) with the mode at 62 

 to 63 cm. The most prominent mode is at 68 cm., i.e., 5-year old fish, or the class of 

 1909. 



The material for the study of the pollock in 1915 consisted of the measurements 

 and scales of 652 fish obtained in five catches from Casco bay, off Campobello island, 

 New Brunswick. The first two of these catches were made on June 22, and included 

 331 fish, the other three catches were made on July 16, and included 321 fish. The 

 length frequencies of these pollock, both the actual numbers caught and the per cent 

 in each centimeter class, are given in table 7. In catches 1 and 2, both the standard 

 and the total lengths were measured while the catches 3 to 5, only the standard lengths 

 were taken. The table gives the standard lengths for all five catches and, in addition, 

 the total lengths for catches 1 and 2. From the column in the table giving the per 

 cent of specimens in each centimeter class for the first two catches and the similar 

 column for the last three catches, it will be seen that they agree in showing the most 

 frequent classes at 65 and 66 cm. Since the distribution of lengths in the catches 

 is similar and since the catches were chosen at random, it would seem fair to assume 

 that they represent correctly the distribution in point of size of fish caught during 

 June and July in the vicinity of Campobello island. The frequency curve for the 

 standard lengths of catches 1 to 5 is shown in the graph where the lengths have been 

 grouped in 2 cm. classes and the frequencies plotted in per cent. This curve has a 

 single mode at 66 cm., corresponding to the most frequent class in the per cent column. 

 An examination of the scales of the fish from a typical catch, catch 2, was made in the 



