Geology topics

D.H. Bennett

Publications and source records attributed to D.H. Bennett.

3 recordsLinked to original sources

USGS2009

Composition and location of simulated lake-shore redds influence incubation success in kokanee, Oncorhynchus nerka

Methods for improving spawning habitat for lakeshore spawning kokanee, Oncorhynchus nerka (Walbaum), were explored by quantifying incubation success of embryos exposed to three substrate treatments in Lake Pend Oreille, Idaho, USA. Substrate treatments included no modification that used existing gravels in the lake (EXISTING), a cleaned substrate treatment where existing gravels were sifted in the water column to remove silt (CLEANED) and the addition of new, silt-free gravel (ADDED). Incubation success was evaluated using Whitlock-Vibert incubation boxes buried within each substrate treatment that contained recently fertilised embryos. Upon retrieval, live and dead sac fry and eyed eggs were enumerated to determine incubation success (sac fry and eyed eggs ?? 100/number of fertilised embryos). Incubation success varied significantly among locations and redd treatments. In general, incubation success among ADDED redds (0.0-13.0%) was significantly lower than that for EXISTING (1.4-61.0%) and CLEANED (0.4-62.5%) redds. Adding new gravel to spawning areas changed the morphometry of the gravel-water interface and probably exposed embryos to disturbance from wave action and reduced embryo survival. Moreover, efforts to improve spawning habitat for lakeshore spawning kokanee should consider water depth and location (e.g. protected shorelines) as important variables. Adding clean gravel to existing spawning areas may provide little benefit if water depth or lake-bottom morphometry are altered. ?? 2009 Blackwell Publishing Ltd.

Fisheries Management and Ecology↗

USGS1998

Detection of PIT-tagged subyearling Chinook salmon at a Snake River dam: Implications for summer flow augmentation

Rearing subyearling chinook salmon Oncorhynchus tshawytscha (≥60 mm in fork length) were captured in the Snake River and tagged with passive integrated transponders to provide an index of their survival to Lower Granite Dam, the first of eight dams encountered by seaward migrants. Water was released from reservoirs upstream of Lower Granite Dam to augment summer flows and thereby increase subyearling chinook salmon survival. Mean summer flow and maximum summer water temperature in Lower Granite Reservoir were highly correlated ( N = 4; r = −0.999). Acknowledging this correlation, we conducted two separate least-squares regressions using detection rate as the dependent variable. Detection rate at Lower Granite Dam was positively related to mean summer flow ( N = 4; r 2 = 0.993; P = 0.003) and negatively related to maximum summer water temperature ( N = 4; r 2 = 0.984; P = 0.008). Summer flow augmentation increased flow and decreased water temperature in Lower Granite Reservoir especially in low-flow years. Our results support summer flow augmentation as a beneficial interim recovery measure for enhancing survival of subyearling chinook salmon in the Snake River. Additional research should include replicate within-year releases of PIT-tagged subyearlings as well as studies of fish guidance efficiency.

Washington↗

USGS1981

Forage species in lakes and reservoirs of the western United States

Fisheries management in the western United States has concentrated on salmonid species, particularly in streams. Forage‐fish management in lakes and reservoirs is not highly developed, and has emphasized introductions of both predators and prey. In coldwater lakes, kokanees Oncorhynchus nerka have been established widely as the principal forage for salmonids and often support a sport fishery themselves. Introductions of other forage organisms in coldwater lakes and reservoirs, notably the opossum shrimp Mysis relicta and redside shiner Richardsonius balteatus have had mixed results due in part to food competition with resident species. A variety of exotic predator and prey species have been introduced in coolwater and warmwater reservoirs. Results have varied greatly, and include establishment of successful sport fisheries, elimination of native fishes, failure of introduced predators or prey, and predation on stocked salmonids. Native forage species generally have been overlooked by management, although there appears to be a large potential for their utilization, particularly with coadapted salmonid species. Better screening procedures for exotic introductions and a concerted investigation of the ecological requirements of both native and introduced predator‐prey combinations are required for intelligent management of western lakes and reservoirs.

western United States↗