280 
BULLETIN OF THE BUREAU OF FISHERIES 
AGE AT MATURITY 
The only data obtained that give much indication of the age at maturity in 
central Alaska were taken from the sample caught with a beach seine in Halibut Cove 
lagoon. In this sample no 2-year-olds were mature; out of twenty-five 3-year-olds, 
13, or 52 per cent, were mature; out of twenty-four 4-year-olds, 20, or 83 per cent, were 
mature; all of the 5-year-olds were mature. 
The sample of mature herring from Homer Spit on May 15 were all 3 and 4 years 
of age. From the scale readings there were twenty-nine 3-year-olds and sixty-one 
4-year-olds, 32 and 68 per cent, respectively. If we take only the mature 3 and 4 
year olds from the Halibut Cove lagoon sample we find that 39 per cent of them were 
3-year-olds and 61 per cent were 4-year-olds, making the proportions between mature 
3-year-olds and mature 4-year-olds in the two samples rather similar. 
In Stephens Passage, southeastern Alaska, all 2-year-olds were immature; out 
of twenty-two 3-year-olds, 19, or 84 per cent, were mature; all of the 4 and 5 year olds 
were mature. 
Comparing Stephens Passage with Halibut Cove, in Stephens Passage 62 per 
cent more spawned at 3 years and 20 per cent more spawned at 4 years than at 
/ 2 3 4 
Figure 27.— Length frequency of herring under 230 millimeters in length taken in the lagoon at Halibut Cove with a 
beach seine, April 22, 1926. The large figures show the position of the age groups as determined from scale readings 
of Halibut Cove samples 
Halibut Cove. This is even more remarkable considering the much faster growth rate 
at Halibut Cove. 
AGE AND GROWTH 
DETERMINATION OF AGE 
A knowledge of the proportions of fish of various sizes in the commercial catch 
is necessary in determining the causes and extent of the fluctuations in abundance. 
But information as to the sizes present is chiefly of value in the light of knowledge as 
to the ages and rates of growth. 
We have determined the age of the Pacific herring by the well-known method 
of making a microscopic examination of the scales and counting the number of annual 
rings (Fig. 26). Our age determinations among the younger age groups are partially 
confirmed by size frequencies. Figure 27 shows the length frequencies of herring 
under 230 millimeters in length, taken in Halibut Cove lagoon, April 22, 1926. The 
large figures are placed at the mean lengths of the younger age groups as taken from 
the curve in Figure 29. Figure 27 shows the 1-year group (in this case almost exactly 
1 year old) quite distinctly, but the other year groups are not very clearly shown, as 
the number of specimens is too small. Figure 28 shows the length frequency of 
463 Cape Elrington herring taken on August 25, 1925. This curve shows well the 
2-year group (in the second summer) between 130 and 160 millimeters. The 2 and 3 
