National Park Service


Date of this Version



Copyright Stasiak et al.


In June 2011, a fish inventory was conducted in the Niobrara River at Agate Fossil Beds National Monument (AGFO). Collecting techniques and locations were similar to those used in previous surveys conducted in 1979 and 1989. Results of the 2011 survey indicated a major change in the fish community had occurred during this time period. Although absent in the 1979 and 1989 surveys, Northern pike (Esox lucius) were the dominant fish species at AGFO in 2011. White sucker (Catostomus commersoni) was the single remaining species from the fish community identified in the 1979 and 1989 inventories, and another new species, Green sunfish (Lepomis cyanellus) was added. Except for the addition of the sunfish, these findings basically confirmed the results of an electrofishing inventory conducted in 2008. Compared to the 1979‐1989 surveys, the number of fish species decreased from 9 to 3 in 2011, and the total numbers of individual specimens declined from over 600 to fewer than 70. Additional fish collections in 2011 at the Nature Conservancy’s Cherry Ranch upstream from the monument indicated that a basically intact fish community comprised of 10 species still exists in good numbers. This is west of a control structure on the Nunn property that presumably restricts the upstream migration of pike.