Northern Prairie Wildlife Research Center
Substantial changes in distribution over time were noted by plotting fish species at sites during each of three different periods (early, middle, and late). The total number and location of sites sampled during each of these periods varied considerably, which makes comparison among them questionable. For example, few sites were sampled on the Red River main stem during the middle sampling period (1962-1977), but during the late sampling period (1978-1994), it was extensively surveyed. Species which have probably always been common in the Red River basin (such as the goldeye, silver redhorse, or spotfin shiner) appear to have increased their range over time. The goldeye was collected at only two sites during 1962-1977, but it occurred at 48 sites during 1978-1994. This is a 10% increase in the number of sites where the goldeye was found. Similarly, the silver redhorse and spotfin shiner showed increases of 12% and 15%, respectively. All of these changes are nothing more than an artifact of sampling intensity.
It is reasonable to assume that the same species should occur at stream sites during repeated sampling over time, even following natural disturbances such as drought. Larimore et al. (1959) noted that most fish species returned to Smiths Branch, Illinois, following virtual destruction of invertebrate and fish populations by drought. Ross et al. (1985) determined that streams in Oklahoma and Arkansas were persistent (presence of species) over a 10-year sampling period, and Matthews et al. (1988) determined the faunal similarity of three streams over 5-17 years. Therefore, by cautiously observing distribution patterns, even with the variability in sampling effort between periods, several notable changes were observed. The chestnut lamprey has not been taken in the Sheyenne River since Woolman's early collection in 1892, but the species has apparently increased its range southward in the eastern basin. Several collections were made in the Wild Rice River, and a single record exists from the Otter Tail River (Figure A1). Records of the silver lamprey are exclusively from the late sampling period, implying that the species has recently expanded its range or earlier collections were misidentified (Figure A2).
Several cyprinids have experienced moderate changes in distribution. Records from the early sampling period indicate that the brassy minnow once occurred in the Wild Rice River and Shotley Brook, a tributary to Upper Red Lake. Later collections have not included the brassy minnow in these or similar locations (Figure A21). The silver chub was once found in the Red River as far south as Breckenridge, Minnesota, but it is found in the system only north of Fargo (Figure A23). The pearl dace, while existing in isolated populations in locations such as the headwaters of the South Branch Buffalo, Park, Thief, Roseau, Snake, Middle, and Tamarac Rivers, has evidently been extirpated from the headwaters of the Otter Tail and Wild Rice Rivers, as it has not been found in these reaches since 1955 (BMNH 1994) (Figure A24). The hornyhead chub once existed in the Sheyenne and Maple Rivers and was collected at the mouth of the Otter Tail River and Daugherty Creek, a tributary to Lake Traverse; but no collections have been made in those locations in recent years, despite its widespread distribution in several eastern basin streams (Figure A25). The pugnose shiner may have been completely eliminated from the Red River basin, as it has not occurred in collections for over 20 years (Figure A27). The river shiner no longer occurs in the Red Lake or Sandhill Rivers, but it has increased its range and occurs throughout the Sheyenne River; NDGF reported it at one site above Baldhill Dam (Figure A29). The blacknose shiner has had its distribution in the Sheyenne River reduced to only the spring fed streams at the Mirror Pool Wildlife Management Area (Figure A32); and even though the overall distribution did not substantially change, it is possible that the blacknose dace is becoming more common in the basin, as a 10% increase in overall occurrence at sites was noticed for this species between the middle and late sampling periods (Figure A43).
Changes in distribution of other species include the brown bullhead, for which a 10% reduction in overall occurrence at sites was noticed between the middle and late sampling periods (Figure A48). The banded killifish has not been collected from the Sheyenne River since 1892 and likely does not occur there (Figure A54). The Iowa darter no longer occurs in the Park and Tamarac Rivers, as the species has not been collected in those streams since the early sampling period (Figure A68); and the current distribution of the river darter appears to be restricted to the Thief, Middle, and Roseau Rivers (Figure A74).
The distributions of many species may have been influenced directly by anthropogenic disturbances such as barriers to migration or agricultural runoff, while others may have been indirectly influenced through increased predation or competition with species which are not affected by disturbance. Determination of optimal flow and water quality conditions for many of these species may provide some insight.