Eradication of an invasive cyprinid (Gila bicolor) to achieve water quality goals in Diamond Lake, Oregon (USA)

Abstract

Eilers JM, Truemper HA, Jackson LS, Eilers BJ, Loomis DW. 2011. Eradication of an invasive cyprinid (Gila bicolor) to achieve water quality goals in Diamond Lake, Oregon (USA). Lake Reserv Manage. 27:194-204. We used a case study of whole-lake fish removal to demonstrate the importance of the fish community to nutrient cycling in Diamond Lake, Oregon, USA, to meet regulated water quality standards for pH, dissolved oxygen and nuisance algae. The cyprinid tui chub (Gila bicolor) was removed through a process beginning with netting and ending with a whole-lake and tributary rotenone treatment in September 2006. The lake was stocked with rainbow trout in spring 2007. Between 2007 and 2009, lake transparency increased 250%, accompanied by decreases in epilimnetic pH, total nitrogen, and total organic carbon. Mean concentrations of total phosphorus and ortho-phosphorus remained unchanged in epilimnetic waters. Chlorophyll a, phytoplankton biovolume, Anabaena biovolume, and Anabaena cell density declined. Daphnia pulicaria, a large herbivorous cladoceran virtually absent for 10 years, returned in abundance, and benthic biomass increased more than 12-fold. The project successfully demonstrated that water quality and fishery goals can be met through eradication of the invasive cyprinid. Fish populations need to be considered in some lakes to achieve water quality standards.

Water quality and algal conditions in the North Umpqua River, Oregon, 1995-2007, and their response to Diamond Lake restoration

“…In September 2005, after years of planning, the Oregon Department of Fish and Wildlife (ODFW) initiated a drawdown of Diamond Lake through a drainage canal, ultimately dropping the lake level by ~ 2.5 m (photograph 5), and in September 2006 treated the remaining water with the fish toxicant rotenone to eliminate the Tui chub. During the drawdown in 2006, ODFW harvested more than 30 metric tons of fish biomass from the lake to reduce the eventual load of carbon and nutrients from decomposing fish carcasses (Eilers and others, 2008;Eilers and Truemper, 2010). A timeline of significant events related to the rotenone application is shown in table 2.…”

“…The lake has been in this condition for much of its recreational history because of the large amount of internal nutrient loading (Salinas and Larson, 1995). Following blooms in the early 2000s, fisheries managers hypothesized that Tui chub, an invasive non-native fish sometimes used as bait, caused food-web changes that degraded water quality (Eilers and Truemper, 2010). Nutrient loading from natural and human sources, including phosphorus-rich groundwater, septic systems, and nitrogen fixation by bluegreen algae, contributed to nuisance blooms that continued to occur despite the diversion in 1971 of sewage from public recreation and fish cleaning facilities (Eilers and others, 2003;U.S.…”

“…On November 23, 2005, Diamond Lake water was released into Lake Creek by way of a new canal downstream from the lake's normal outlet elevation. By September 6, 2006, the lake surface was 8 ft below normal summer elevation, and the surface area was 13 percent less than during normal summer conditions, exposing about 400 acres of sediment around the perimeter (U.S. Forest Service, 2004;Eilers and Truemper, 2010). On that date, the canal gates were closed to prevent release of rotenone to Lake Creek ( fig.…”

“…2). Data and findings by others involved in the Diamond Lake restoration project (Eilers and others 2007;2008;Sytsma and others, 2007;Sytsma and Miller, 2008;Eilers and Truemper, 2010;Eilers and others, 2011;ODFW, http://www.dfw.state.or.us It is beyond the scope of this report to evaluate the efficacy of the restoration (the rotenone application and subsequent lake management) relative to fisheries production or water quality in Diamond Lake itself. Observations suggest, however, that although there have been blue-green algae blooms in Diamond Lake since implementation of the restoration project, the blooms have been of shorter duration and less intense in recent years (Eilers and others, 2011;Al Johnson, U.S. Forest Service, written commun., 2013).…”

Fate and behavior of rotenone in Diamond Lake, Oregon, USA following invasive tui chub eradication

“…The lake began experiencing severe blooms of cyanobacteria in 2001 (Anabaena sp. The fish biomass in the lake at the time of the rotenone treatment in 2006 was composed almost exclusively of tui chub (99.9% tui chub), and estimates of chub population in the lake varied from 7.6 million to 23 million fish [9]. The cyanobacteria blooms, which occasionally closed the lake to recreational contact, were likely in response to the stimulatory effects of tui chub waste products rather than concurrent reduction of phytoplankton grazing pressure associated with the loss of the large cladocerans [8].…”