The relative abundance of different species was estimated by combining counts of individual fishes taken in 290 seine-hauls, 26 hours and 15 minutes of shocking, and seven samples obtained with rotenone. At some stations all seine-hauls were counted. At other stations the seine-hauls in which complete counts were recorded had been selected randomly in advance; that is to say, prior to collecting at each station. I selected those hauls to be counted from a table of random numbers (Snedecor, 1956:10-13). I did not use the frequency-of-occurrence method as proposed by Starrett (1950:114), in which the species taken and not the total number of individuals are recorded for all seine-hauls. However, the frequency of occurrence of each species is indicated by the number of stations at which it was found, and those stations are listed in the previous accounts. Table 3 shows the percentage of the total number of fish that each species comprised in three kinds of streams: sandy (Big Blue and Little Blue rivers), muddy, and gravelly streams. The habitat preferences of some species affect their abundance in different stream-types. _Notropis lutrensis_ and _P. mirabilis_ seemed almost ubiquitous. _Notropis deliciosus_ also occurred in all kinds of streams (rarely in muddy streams); however, this species was represented by the sand-loving _N. d. missuriensis_ in the Big Blue and Little Blue rivers, and _N. d. deliciosus_ in the clear, gravelly, upland creeks (Nelson, personal communication). Because of its widespread occurrence, and for purposes of later discussion, I refer to this minnow also as an ubiquitous species in the Big Blue River Basin. _Carpiodes carpio_, _Cyprinus carpio_, _I. punctatus_, _I. melas_, and _L. humilis_ were widespread, but each was absent or rare in one of the kinds of streams (Table 3). _Carpiodes carpio_, _Cyprinus carpio_, and _I. punctatus_ occurred most frequently in the sandy streams, whereas _L. humilis_ was most common in muddy streams. The high per cent of _I. melas_ in collections from the Big Blue River is a direct result of one large population that was taken with rotenone in a borrow-pit at Station 6-S. In my opinion, this species actually was most abundant in the muddy streams. TABLE 3. RELATIVE ABUNDANCE OF FISHES IN PER CENT OF THE TOTAL NUMBER TAKEN, BIG BLUE RIVER BASIN, KANSAS. TRACE (TR.) IS USED FOR VALUES LESS THAN .05 PER CENT, AND DASHES SIGNIFY THAT THE SPECIES DID NOT OCCUR IN THE COUNTED COLLECTIONS ALTHOUGH IT MAY HAVE OCCURRED IN UNCOUNTED COLLECTIONS FROM THE SAME STREAM-TYPE. THREE SPECIES, _C. AURATUS_, _N. BUCHANANI_, AND _S. CANADENSE_, WERE NOT TAKEN IN COUNTED COLLECTIONS.