Jay Hatch

Larval fish as indicators of reproductive success in unchannelized and channelized tributaries of the red river basin, minnesota

ABSTRACT During 1998 and 1999, larval fish phenology, abundance, and diversity were characterized at 13 reaches in the Buffalo River and Sand Hill River, tributaries of the Red River of the North. Channelized reaches were less stable than unchannelized reaches, showing more overall variation and greater daily fluctuation in temperature and dissolved oxygen (DO), and a higher level of intermittent flow. These reaches also exhibited significantly lower larval diversity. Principal component analysis explained > 84% of the variance for the first two axes for larval catch, with axis 1 associated with channelization and axis 2 associated with temperature and DO. Fathead minnow (Pimephales promelas) was associated with channelized reaches, whereas spotfin shiner (Cyprinella spiloptera), common shiner (Luxilis cornutus), redhorse (Moxostoma spp.), and darters (Etheostoma spp.) were associated with unchannelized reaches in both years. Clear associations of reproductive guilds with channel type were not detected, but species of intermediate pollution tolerance were associated with unchannelized reaches and tolerant species were associated with channelized reaches.

Food use in Minnesota populations of the topeka shiner (Notropis topeka)

ABSTRACT We examined gut contents of 65 Topeka shiners (Notropis topeka) collected from the Rock River drainage of southwestern Minnesota in 1997. Anecdotal and unpublished information regarding food habits have suggested that the Topeka shiner is largely a benthic or nektonic insectivore. Our results show that it is an omnivore that feeds opportunistically on immature aquatic insects, several kinds of microcrustaceans and other invertebrates, larval fish, algae, vascular plant matter, and detritus. The Topeka shiner functions both as a benthic and nektonic feeder and shows strong trophic similarities to its sister species, the sand shiner (N. ludibundis).

Ovarian Cycling, Clutch Characteristics, and Oocyte Size of the River Shiner Notropis blennius (Girard) in the Upper Mississippi River

ABSTRACT Specimens of the river shiner were collected from three locations in Pool 4 of the upper Mississippi River in Wisconsin and Minnesota during June, July, and August 1995. All individuals from the first collection (21 June) displayed early maturing, late maturing or mature ovaries, indicating that spawning commenced prior to this date. Ovarian cycling continued over the next seven weeks but ended by 18 August, when 100% of the individuals were atretic. Clutch sizes varied from 436 to 2754 ova in mature females that ranged from 48.3 to 87.9 mm standard length (SL). Clutch size was significantly dependent on SL, but slopes and intercepts declined significantly over time. Mean clutch size declined significantly from 1600 on 30 June to 1056 and 1010 on 8 July and 11 August, respectively. This decline remained significant after means were adjusted for fish size. Mean mature oocyte size remained constant (0.89 mm) during the same period and was not dependent on standard length. Ovulated ripe oocytes in two fish ranged from 1.06 to 1.22 mm. The overall ovarian cycling schedule supported the hypothesis that the river shiner is a multiple clutch spawner in the upper Mississippi River.