Growth, mortality, production and feeding of yellow perch fry, Perca fluviatilis flavescens (Mitchill) and their effect on the Daphnia pulicaria Forbes of West Blue Lake
Henderson, Michael A.
Distribution, mortality, growth, production and feeding habits of perch fry and their effect on the Daphnia pulicaria population of West Blue Lake was investigated. Perch hatched in the littoral zone in early June and moved into the pelagic zone 7 to 14 days later when they were 9 - l0 mm in length. Perch fry remained in the pelagic zone until they reached a length of approximately 25 - 30 mm in mid-July, and then returned to the littoral area. Instantaneous daily mortality rates ranged from .017 in areas of low perch fry abundance to .140 in areas of high perch fry abundance. From hatching until mid-August perch fry increased in length and dry weight by a factor of 10 and 2616 respectively. Growth occurred in two distinct stanzas. The first stanza, from hatching until the beginning of the pelagic phase, was characterized by a low level of feeding and a slow growth rate, while the second stanza, lasting for the remainder of the summer, was characterized by a high level of feeding and a fast growth rate. Variation in the energy intake and growth of perch fry in different parts of the lake was directly dependent upon the abundance of Dacphnia pulicaria-...Decreases in the abundance of Daphnia pulicaria in areas of the lake with low numbers of perch fry indicated that these populations may decline independently of fish predation...