FWS/OBS-80/14

This report describes an investigation of the effects of stream channelization on fish and macro-invertebrates in low gradient reaches of Blacksmith Fork River and the Logan River in the floodplain of Cache Valley in northern Utah. Channelization adversely affected both fish and macro-invertebrate populations and biomass, with the severity of impact directly related to the amount and duration of disturbance of the physical habitat

Annotated bibliography on the ecology of the Lake Washington drainage

This annotated bibliography contains 392 published and unpublished references that pertain to the natural resources in the Lake Washington watershed, with particular emphasis on the aquatic environment. All references are indexed by keywords

A portable vertical gill-net system

Studies of vertical as well as horizontal distributions of fishes often require the use of gill nets hung vertically from the surface to the bottom. By using gill nets in this fashion it is possible to sample the entire water column as a continuous variable

Fight and air exposure times of caught and released salmonids from the South Fork Snake River

Catch-and-release regulations are among the most common types of fishing regulations. In recent years, concerns have arisen regarding the exposure of fish to air during catch-and-release angling. The purpose of our study was to quantify the length of time angled fish were exposed to air by anglers in a typical catch-and-release fishery and relate it to the lengths of time reported to produce negative effects. In total, 312 individual anglers were observed on the South Fork Snake River, Idaho, from May through August 2016. Fight time varied from 1.1 s to 230.0 s, and average fight time was 40.0 s (SD=36.8). Total air exposure times varied from 0.0 s to 91.8 s and averaged 19.3 s (SD=15.0). Though not statistically significant, a trend in reduced fight times was observed when anglers were guided and increased air exposure times when a net was used and a picture was taken. Results of the current study suggest that anglers expose fish to air for periods that are much less than those reported to cause mortality

Strategies to Control a Common Carp Population by Pulsed Commercial Harvest

Commercial fisheries are commonly used to manage nuisance fishes in freshwater systems, but such efforts are often unsuccessful. Strategies for successfully controlling a nuisance population of common carpCyprinus carpio by pulsed commercial harvest were evaluated with a combination of (1) field sampling, (2) population estimation and CPUE indexing, and (3) simulation using an exponential semidiscrete biomass dynamics model (SDBDM). The range of annual fishing mortalities (F) that resulted in successful control (F= 0.244–0.265) was narrow. Common carp biomass dynamics were sensitive to unintentional underharvest due to high rates of surplus production and a biomass doubling time of 2.7 years. Simulations indicated that biomanipulation never achieved successful control unless supplemental fishing mortality was imposed. Harvest of a majority of annual production was required to achieve successful control, as indicated by the ecotrophic coefficient (EC). Readily available biomass data and tools such as SDBDMs and ECs can be used in an adaptive management framework to successfully control common carp and other nuisance fishes by pulsed commercial fishing

Human-aided dispersal has altered but not erased the phylogeography of the tench

Human-aided dispersal can result in phylogeographic patterns that do not reflect natural historical processes, particularly in species prone to intentional translocations by humans. Here, we use a multiple-gene sequencing approach to assess the effects of human-aided dispersal on phylogeography of the tench Tinca tinca, a widespread Eurasian freshwater fish with a long history in aquaculture. Spatial genetic analysis applied to sequence data from four unlinked loci and 67 geographic localities (38–382 gene copies per locus) defined two groups of populations that were little structured geographically but were significantly differentiated from each other, and it identified locations of major genetic breaks, which were concordant across genes and were driven by distributions of two phylogroups. This pattern most reasonably reflects isolation in two major glacial refugia and subsequent range expansions, with the Eastern and Western phylogroups remaining largely allopatric throughout the tench range. However, this phylogeographic variation was also present in all 17 cultured breeds studied, and some populations at the western edge of the native range contained the Eastern phylogroup. Thus, natural processes have played an important role in structuring tench populations, but human-aided dispersal has also contributed significantly, with the admixed genetic composition of cultured breeds most likely contributing to the introgression