River Ice Can Shape Watershed Ecology

As river ice cover decreases, the physical and biological changes to river ecosystems vary with the watershed characteristics and river size.

Influence of flow velocity, river size, a dam, and an urbanized area on biodiversity of lowland rivers

Biodiversity of aquatic organisms is formed under the influence of not only natural, but also anthropogenic factors. In this work, the influence of the flow velocity, river size, flow regulation and urbanization on various groups of aquatic organisms was studied in several lowland rivers. The study was conducted in 2013 on six tributaries of the Upper Sukhona River. Five sampling sites were in different parts of the Vologda River and five sites on small rivers, Losta, Lukhta, Komya, Chernyj Shingar, and Belyj Shingar (one site per river). Phytoplankton, zooplankton and zoobenthos were sampled six times, from April to October, and macrophytes were studied in August. In total, 469 species of aquatic organisms were found in the tributaries of the Upper Sukhona River, belonging to the following phyla: Cyanophyta (5 species), Chrysophyta (8), Bacillariophyta (62), Xanthophyta (1), Cryptophyta (10), Dinophyta (4), Euglenophyta (12), Chlorophyta (17), Streptophyta (1), Bryophyta (2), Marchantiophyta (3), Equisetophyta (1), Magnoliophyta (63), Rotifera (22), Cnidaria (1), Platyhelmintes (1), Annelida (29), Mollusca (33), Arthropoda (194). The maximum number of species was found in the Vologda River, the largest of all the tributaries. The number of zoobenthos species was similar at different sites in the Vologda River and in the small rivers. The number of species of other groups of aquatic organisms in the small rivers was lower than those registered in the Vologda River. The greatest number of macrophyte and zoobenthos species was recorded in the Upper Vologda River and Belyj Shingar River, where the flow is strong all the year round. The greatest number of phyto- and zooplankton species was found at the extra-city sites where current is almost absent. In the dam backwater, species richness was higher than that registered downstream of the dam. At the same time, the species richness of macrophytes and zoobenthos in the dam backwater was lower. The smallest number of species was found in the Vologda River, downstream of the city of Vologda. Decreases in the species richness and Shannon’s biodiversity index were witnessed in the Vologda River city site and in the small rivers, as they get closer to the city. Cluster analyses performed for the studied groups of aquatic organisms showed dissimilar results; however, the studied sites on the Vologda River having the highest anthropogenic load formed a cluster. Aquatic organisms of the Upper Sukhona tributaries experience both natural (flow velocity and size of the watercourse) and anthropogenic factors (proximity to the city and flow regulation).

Biology, Management, and Conservation of Lampreys in North America

<em>Abstract</em>.—We evaluated two methods for assessing Pacific lamprey <em>Lampetra tridentata</em> spawning populations (visual counts of spawning adults and redds) and one method for assessing larval production (emergent ammocoete counts from drift nets) in the South Fork Coquille River, Oregon in 2004 and 2005. All three methods generally provided similar portrayals of timing, duration, and magnitude of spawning, including greater abundance in 2004 and seasonally bimodal spawning in 2005. We found a linear relationship between adult and redd counts but a high redd to adult ratio that varied seasonally in both years. The high redd to adult ratio can be attributed to short residence time in spawning areas and temperature or habitat-dependent differences in detection of adults, both of which can undermine adult count data. Redds had relatively longer persistence and larger numbers compared to adults and therefore may be a more practical survey method, but variable redd shape, size, and age, as well as superimposition, presented significant counting errors. Both adult and redd counts had no clear-cut way to quantify errors. Sampling emergent ammocoetes in the drift allowed detection of low density early and late season spawning and would be the preferred survey method when surveys of spawning adults and redds are impractical due to river size, visibility, or access. Even when spawning surveys are practical, emergent ammocoete counts may be better for detecting and monitoring small populations. Disadvantages of ammocoete sampling include nighttime work hours, extra laboratory time, and difficulties with species identification. The general absence of a stock–recruit relationship in lampreys means adult and redd counts are poor predictors of ammocoete production and emergent ammocoete abundance is a poor predictor of spawning abundance. The relationship breaks down because of variability in early survival, which is best detected using data from both spawning surveys and larval drift samples.