574 REPORT OF THE COMMISSIONER OF FISHERIES. 
very large, and the reproductive capacity of a carp increases greatly 
for the next year or two after it begins to spawn. According to 
Hessel (1881, p. 871) a female weighing 4 to 5 pounds will contain on 
an average 400,000 to 500,000 ova. Day (1880-1884, p. 161) quotes 
other estimates, thus: A female of 9 pounds had 600,000 eggs (Bloch); 
one of 162 pounds had 101,200, one of 254 pounds 203,109 (Harmer); 
one of 214 pounds had 1,310,750, and one of 16} pounds had 2,059,750 
(Buckland). 
In the case of a female mirror carp from Sandusky Bay, which I 
weighed at Port Clinton June 22, 1903, I found that the ova com- 
prised more than a fourth of the total weight of the fish. The fish 
before being opened weighed 17 pounds; after the removal of the ova 
with as little loss of blood as possible, the weight was 12 pounds 6 
ounces, leaving 4 pounds 10 ounces as the weight of the ova. This is 
27 per cent of the entire weight of the fish and 37 per cent (over a 
third) of the weight of the remainder of the fish after the ova had 
been removed. ? 
This enormous fecundity is undoubtedly an adaptation to compen- 
sate for the dangers of the exposed condition in which the eggs ar 
left after being laid, since they are merely scattered about on the 
vegetation in shailow water and are given no further care or attention 
by either of the parent fish. It may also help to explain the remark- 
able increase in numbers of the carp in our waters in a very short 
time, for if we suppose that the ordinary enemies of the eggs were not 
in the habit of searching for food in the kind of locality utilized by 
the carp for spawning, or at least were not present in large numbers, it 
is easy to see what an advantage this would give the carp, especially 
if the conditions were favorable to its growth in other respects. 
Furthermore, it would not be at all surprising if, as has been known 
to have happened in other cases, the increase in the quantity of food 
furnished by the abundant supply of carp eggs would favor the cor- 
responding increase of some other fish or other animal which finds the 
eges good eating. Or possibly, even, some form which has previously 
lived on other food may adjust its habits to the new conditions, and 
come to prey largely upon the spawn of the carp. It will rather be 
surprising if something of the kind does not happen, for in their 
struggle for sustenance nature’s creatures are no respecters of person 
nor property, and it would be an unusual thing for a rich supply of 
food to be lying around long without some of them appropriating 
it. When this does occur, the phenomenal inerease of the carp will 
undoubtedly be checked and the natural balance will again be approxi- 
mated. One thing that militates against this in the case of the 
aDay (1880-1884, p. 161) says that continued cold weather may prevent carp from spawning, so 
that the process may last over several weeks or months, while some fish may retain the ova, thus 
occasioning disease. Bean (1903, p. 169) mentions that confinement of gravid females in a small 
tank may also cause them to retain the eggs, and he speaks of two fish that died from this cause. 
