Recovery of fish populations in Lake 223 from experimental acidification

The fish populations of Lake 223, a lake previously acidified to pH 5.1, were monitored during 13 years of gradual pH recovery to preacidification pH 6.7. During acidification, recruitment ceased for all fish species in this lake and two were extirpated. During pH recovery, successful recruitment resumed for all fish species that remained in the lake. One of the extirpated species, fathead minnow (Pimephales promelas), successfully colonized the lake. Lake trout (Salvelinus namaycush) abundance decreased during acidification and remained low during pH recovery due to very low recruitment. Growth curves, condition factor, and annual survival of lake trout decreased during acidification and quickly increased to preacidification values during pH recovery. During the early years of pH recovery, white sucker (Catostomus commersoni) abundance increased to almost 10 times the number at the start of the experiment but decreased during the final years due to decreased annual survival and recruitment. Pearl dace (Margariscus margarita) became abundant during acidification and their abundance decreased during pH recovery as fathead minnow abundance increased. Other fish species that were caught infrequently prior to acidification, brook stickleback (Culaea inconstans), lake chub (Couesius plumbeus), and finescale dace (Phoxinus neogaeus), were caught frequently during pH recovery.