Geology topics

Research about Juniata River

Source-linked reports with geographic coverage including Juniata River.

2 recordsLinked to original sources

USGS2011

Diel feeding chronology of six fish species in the Juniata River, Pennsylvania

We examined diel feeding chronology of six fish species in the Juniata River, Pennsylvania. Ephemeropteran nymphs were the major prey of redbreast sunfish ( Lepomis auritus ; 70.5%) and smallmouth bass ( Micropterus dolomieu ; 59.7%) during each of six 4-h intervals over a 24-h period. The main dietary component of mimic shiner ( Notropis volucellus ) was chironomids (42.3%), whereas spotfin shiner ( Cyprinella spiloptera ) mainly ate terrestrial invertebrates (50.2%). Juvenile white sucker ( Catostomus commersoni ) exhibited substantial diel variation in diet composition with some prey taxa composing the entire diet during some 4-h intervals and being completely absent from the diet during other periods. Bluntnose minnow ( Pimephales notatus ) contained mostly detritus (75.5%). Interspecific diel diet overlap (Cγ) was low among the six species except for smallmouth bass-redbreast sunfish (0.735). Mimic shiner ([xbar] = 0.302) had the highest diet overlap with other species and bluntnose minnow ([xbar] = 0.134) had the least similar. Smallmouth bass, redbreast sunfish, white sucker, and spotfin shiner all had diurnal feeding peaks. Peak food consumption of mimic shiner and bluntnose minnow occurred at midnight. Our results indicate that because of diel variation in diet composition and feeding periodicity for these six species, dietary analysis conducted at only one interval would not provide an accurate representation of the diet of these species.

Pennsylvania↗

USGS1995

Estimating losses to predation of recently released American shad larvae in the Juniata River, Pennsylvania

Predation on recently released larval American shad Alosa sapidissima was quantified in the Juniata River, Pennsylvania, on 10 occasions during 1991 and 1992. Of the four sites examined (the stocking site and 100, 200, and 350 m downstream) predation on shad larvae was highest at the stocking site; 44% of the total estimated losses occurred within this 30-m zone. Percentage predation mortality was weakly and inversely related to the number of shad larvae released, and it ranged from 0 to 2.2% among sites. Overall percent mortality of larvae within the first 2 h of release was about 5% (range, 2–10%). Major predators included juvenile smallmouth bass Micropterus dolomieu , the spotfin shiner Cyprinella spiloptera , and the mimic shiner Notropis volucellus . Predation by these species varied among sites. Percent mortality of American shad larvae after nocturnal releases (0.17%) was significantly lower than after diurnal releases (1.18%). For most predators, the length of shad eaten increased with predator length. However, among predators of similar size, there were significant differences in the length of shad consumed. Estimated losses to predation were about equally divided among small (<50 mm, 30%) medium (50–99 mm, 37%), and large (>99 mm, 33%) predators. Because 30% of the estimated number of shad larvae lost to predation were eaten by predators less than 50 mm long, releasing slightly larger shad might reduce predation.

Pennsylvania↗