KEOKUK DAM 
133 
important that further surveys should be made. (No improvement, but the reverse, 
is shown by the survey of 1927.) 
It may be thought that more detailed consideration should be given to the 
matter of changes from year to year in the amounts of the several kinds of gear 
in use. Undoubtedly such changes have some effect on the returns, particularly in 
the cases of fishes of minor importance. As regards the fishes of major importance, 
shifts in the use of gear are likely to be the result rather than the cause of variable 
yields of particular fishes. On the whole, after studying that question with some 
care, we doubt if the changes of gear reported could have had such an effect as to 
modify significantly the general aspect of the returns. It must be said, however, 
that for strictly accurate comparisons of the catches of different years it would be 
necessary to consider not only the numbers of each kind of apparatus used in each 
year but also the number of days and hours that each piece of apparatus was 
employed. It must never be forgotten that the “margin of error” in the use of 
such statistics is very broad at the best; we can only say that we do not believe it 
is wide enough to make fish appear abundant when they are scarce or rare when 
they are actually abundant. 
NOTES OF A. S. PEARSE ON CHANGES IN FISH FAUNA IN LAKE PEPIN 
Before leaving the subject of fisheries in Lake Pepin, reference should be made 
to two systematic examinations of fishes in that lake conducted, respectively, by 
Dr. George Wagner, of the University of Wisconsin in 1903 and 1904 (Wagner, 
1908), and by Dr. A. S. Pearse, of the same institution, in 1920 (Pearse, 1921). 
Doctor Pearse makes the following comparison of conditions existing in 1903-4 and 
1920, respectively, as regards the more important species of fish: 
Marked changes have evidently occurred in the fish fauna of the lake since Wagner (1908) 
made his observations in 1903 and 1904. The lamprey eel is no longer common, probably because 
its usual host, the spoonbill, has decreased in numbers. Wagner says (p. 27) “The spoonbill 
(paddlefish) is one of the most abundant forms in Lake Pepin throughout the summer.’’ In 1920 
this species was rather uncommon. Again W’agner says that the rock sturgeon is “not uncommon” 
and that the hackleback is rare. In 1920 (Table 2) the backleback was abundant and the rock 
sturgeon (not seen by the writer) very rare. Wagner took no bullheads except the tadpole cat. 
Three species were common in 1920. The buffalo ( Ictiobus cyprinella) was “very abundant” and 
is now rather uncommon. It has been replaced by the carp, which in 1920 led all other species 
in commercial value. Wagner found the skipjack (river herring) “very common,” and in 1920 it 
was quite rare. He found the rock bass very common, and the young “extraordinarily numerous 
alongshore.” In 1920 no rock bass were caught, although special efforts were made. The local 
fishermen all agreed that it was an exceedingly rare fish. The perch was rare in 1904, and in 1920 
was rather common. Small largemouth black bass are no longer so abundant alongshore as to 
be a “nuisance in fishing with a minnow seine.” 
The spoonbill, rock sturgeon (lake sturgeon), and buffalo have evidently been more or less 
“fished out” during the past 15 years, and the last has been replaced by the carp, which has similar 
habits. Wagner probably took no bullheads because he did not fish with trot-lines. The waiter 
sees no apparent reason for the marked decrease of the skipjack and rock bass. 14 
11 Neither of these last-mentioned fishes plays a part in the commercial fishery. The rock bass, however, is important as a 
game fish and local food fish, and the “skipjack,” or river herring, is of great economic importance as a carrier of the larval stage 
of one of the most valuable commercial mussels. 
