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Show populations begin to expand rapidly in numbers during the first of June, and one or two generations of flies reach maturity each year. The flies survive the winter in immature stages. Corixids Corixids are small predatory aquatic insects that live in and around the edges of GSL. Their preferred habitat is water with salinity less than six percent along rocky shorelines ( Belovsky and Mellison, 1998). Their diet includes, but is not limited to, brine shrimp. These insects have the ability to fly and are observed in the main body of the lake. Wurtsbaugh ( 1992), working in Farmington Bay during the 1980s, reported that predation by corixids and copepods on brine shrimp may decrease shrimp population densities. This bay has lower salinity than the main body of the lake due to its being diked and freshwater inputs from the Jordan River. Gliwicz et al., ( 1995) suggested that similar salinity levels to those observed in Farmington Bay might allow corixids to decrease the brine shrimp population in the south arm of the lake during periods of lower salinity. This has led a brine shrimp harvester to argue that decreasing salinities in the south arm of the lake has led to a decline in brine shrimp populations. Belovsky and Mellison ( 1998) have conducted experiments on predation by corixids on brine shrimp. This information, when combined with the corixid densities in the lake reported by Stephens ( 1998), indicated that corixid predation rate was 1- 2 orders of magnitude less than the brine shrimp population growth rate and has negligible impact on the brine shrimp population in the south arm. Research findings from Farmington Bay ( Wurtsbaugh, 1992) are unlikely to apply to the south arm of the lake due to substantially different limnological conditions. If salinity in the south arm remains higher than six percent, conditions for corixids will be poor and their impact on brine shrimp will be negligible. Wurtsbaugh now considers corixid predation unable to decrease brine shrimp populations in the south arm without dramatic declines in salinity. Furthermore, Wurtsbaugh now considers that brine shrimp in Farmington Bay may have been reduced during his study by other factors ( e. g. lack of abundance of high nutrition foods for brine shrimp) that were not examined ( Belovsky, 1998). If corixid numbers were to increase to the point of decreasing the shrimp population, there is no known remedy ( e. g., insecticides) that would be environmentally acceptable. Current knowledge suggests that corixids do not limit the brine shrimp population in the lake and sampling programs will continue to monitor corixid abundance in the lake as salinity varies. Fish The current salinities of the north and south arms of GSL are too saline to support fishes. In the shallow water areas near fresh water inflows, fish are also important- mostly carp ( and pre- carp), but sometimes Utah chub. ( BRMBR, unpub., SRC, 1999c) During high lake elevation cycles, the fishery has been known to persist for several years concurrently. Both of these bays receive substantial freshwater inputs from the 72 |
