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BULLETIN OF THE BUREAU OF FISHERIES 
found that the fish were taking the spindle-shaped lead in the mouth rather then the 
baited hook. The very swiftness of the fish prevented an earlier discovery of the 
trouble. With the leads removed from the lines and the bait kept close at the surface 
the fish were caught in fair numbers. 12 
Notwithstanding its poor qualities as a food fish, the river herring represents a 
very distinct economic asset. The niggerhead fresh-water mussel has been regarded 
as the most valuable of all the pearly mussels of the Mississippi Basin because of its 
abundance in all the larger waters of strong current and because it yields a shell of 
the best quality for buttons. Until quite recently, at least, most of the highest- 
grade pearl buttons of domestic manufacture have been produced from niggerhead 
shells, and these owe their existence to the river herring. The reproduction of the 
niggerhead mussel, so far as all evidence goes, is accomplished only through the par- 
asitism of its young (glochidia) upon river herring; there can be no beds of niggerhead 
mussels except in waters frequented by river herring. It is, then, economically 
desirable to maintain the stock of river herring in all waters to which it is adapted and 
in which the bottoms are suitable for the mussel. As matter of fact, however, it 
was found in 1926, by inquiry of manufacturers and shellers and by examination of 
shell heaps on the river bank, that the niggerhead is a vanishing species in the upper 
river, its place being taken to a considerable extent by other kinds of mussels. 
There have been no published observations concerning the breeding of the river 
herring. Our records throw some fight on the question, although we did not succeed 
in determining the place or the precise time of spawning in the vicinity of Keokuk. 
Fish full of roe were taken by the author on April 29, 1914, at the very beginning 
of the “run ” of river herring. Eggs and milt were exuded when pressure was applied. 
It was supposed that the spawning season was almost at hand, and in the course of 
the next few weeks attempts were made to obtain clearly spawning fish, but without 
success. On May 23 of the same year females full of roe were taken and one that was 
possibly spent. Stringham in 1915 examined, for reproductive condition, 191 fish 
from April 19 to September 22. Testes and roe, developed nearly or quite the full 
length of the abdominal cavity, were found April 29 and 30 and on various dates 
thereafter. Eggs measuring 0.8 millimeter were found as early as May 24, and eggs of 
1.1 millimeters on June 5. Milt issuing on pressure was first noted June 23, and on 
12 Stringham examined the stomach contents of about 160 river herring. Approximately one-third were empty; a little more 
than one-third contained fish, chiefly minnows, with some mooneyes, gizzard shad, and other fish not determinable; and less than 
one-third contained insects and larvae, principally May flies, with some caddis flies and others. 
