PROGRESS IN BIOLOGICAL INQUIRIES, 1926 665 
For a long time I was puzzled by the peculiar growth history of the Saginaw 
Bay herring. Both actual and calculated measurements of length showed that 
these herring were becoming progressively larger at corresponding ages each 
successive year. Analyzing the growth data, I found that this increased growth 
rate began suddenly in 1919 and involved fish 3 years of age, or younger, only. 
This accelerated growth rate continued in the years 1920, 1921, and 1922. Dur- 
ing this period, 1919-1922 the second and third year fish did not increase their 
growth rate but simply maintained the rate attained in 1919. The first-year fish, 
however, grew more rapidly each successive year. There was a progressive 
increase in the size of the first-year fish each successive year in the period 1919— 
1922. The data show further that in each of the years 1915 to 1918, inclusive, 
the rate of growth was relatively low for herring 3 years of age and younger, 
and that higher rates prevailed before 1915. The growth rates prevailing among 
the herring of Saginaw Bay before 1915, were in some way inhibited during the 
period 1915-1918, and vestored or partly restored in 1919. It is shown that the 
alteration in the rates of growth was due primarily to some local changes in 
the environment of Saginaw Bay. 
That the third year and younger fish only were affected is explained on the 
basis that only these age groups grow while in Saginaw Bay. The first year fish 
spawned in the bay presumably spend most of the first year in the bay, while 
the older fish spend only the early part of the growing season there; but if all 
fish older than 1 year were subject to the same environment, why, then, did the 
second and third year fish show an alteration in growth rate, while the fourth- 
year and older fish did not? This is explained on the basis that (1) the younger 
herring commence the new year’s growth earlier in the spring than the older 
fish, and (2) that, as the annual growth becomes progressively less with age, 
slight alterations in growth rate can not be detected as readily in the average 
measurements of the older fish as in those of the younger. 
The question then presented itself: What controlling factors operated in 
Saginaw Bay during the period 1915-1918 that were absent in the open lake? 
Did these factors exist, also, before the period 1915-1918, and were they absent 
or reduced subsequent to it? The following natural factors were considered: 
Temperature, sunshine, and fishing intensity. It was concluded that these 
factors did not control the unusual growth rates of the Saginaw Bay herring. 
A fourth factor proved to be, in all probability, the effective one, viz, the 
temporary chemical pollution of Saginaw Bay during the World War. In 
the spring of 1915 the Dow Chemical Co., of Midland, began to pour large 
amounts of paradichlorbenzol (a useless by-product) into the Saginaw River. 
This pollution became so severe that many of the fish in the Bay became tainted 
to such an extent that they could not be sold or used for food. This chemical 
pollution continued to taint the fish until the spring of 1918. So far as we 
know, 1919 was the first after 1915 in which the waters of the bay were 
entirely free from the Dow chemical pollution. It is seen, then, that the period 
1915-1918, during which dichlorbenzol wastes polluted the bay, is precisely 
that during which the growth rate of the herring was retarded. Further, it 
was shown that the presence of this pollution explained all the facts in the 
growth history of the herring, and no known fact was inconsistent with this 
explanation. 
The loss to the fisheries during 1915-1918 must have been considerable. 
Not only did the fishermen lose through the nonsalability of part of their 
products, but also through the deleterious effect of the pollution upon the 
growth rate of the fishes. The indirect loss occasioned by the latter factor is 
commonly disregarded as of little consequence, not only by the general public 
but by the fishermen themselves. This attitude can be accounted for by the 
fact that in most cases the magnitude of these indirect losses must be left to 
the imagination or be stated in terms of description instead of dollars and 
cents. In order to stress as emphatically as possible the importance of the 
indirect effect of pollution upon fish life and industry, I have computed roughly, 
from my growth data and herring statistics, the indirect financial losses suffered 
by the herring industry of Saginaw Bay during the affected period, 1917-1923: 







Year Pounds | Value Year | Pounds Value 
ear A 
ead a ee Re 869, 124 | Pale Ge ee | 113,648 | $3, 409 
CC a Cee Ce eer eee oe di, S32 10005| eS aAOS Tal 1023) Ae osi) 0 El ss | 3, 191 96 
UTES. ee takeing OE 1,317,995 | 39, 540 || See ET Se 
LOD LAT RAEN: 2 BT OE rg 628,907 | 20, 754 | TROGale. we peat. 4 eee | 4,450,224] 186, 685 
Hl 
Lisp okie Me Oe Te eee 184, 450 6, 825 | 


