Lack of Angling-Sized Yellow Perch in a Canadian Boreal Lake: Potential Influences of Growth Rate, Diet, and Predation by Double-Crested Cormorants

Abstract

Fisheries for yellow perch Perca flavescens are economically important in North America, but in many lakes this species does not attain sizes desirable to anglers (total length [TL] > 250 mm). We investigated factors potentially contributing to the lack of angling-sized yellow perch in Dore Lake, Saskatchewan. This large boreal lake has a long history of exploitation and is subject to current controversy regarding the impact of double-crested cormorants Phalacrocorax auritus on its fisheries. We found that yellow perch in Dore Lake attained greater maximum ages (mean ± SD = 7.4 ± 1.0 years) but smaller maximum sizes (215 ± 7 mm TL) than other yellow perch populations. Thus, the lack of angling-sized yellow perch in Dore Lake is probably the result of slow growth rates rather than short life spans. Double-crested cormorants preyed heavily on yellow perch, but predation was highly skewed toward much smaller sizes (<100 mm TL) than those preferred by anglers. Stomach contents and stable nitrogen isotopes confirmed that yellow perch in Dore Lake undergo expected ontogenetic diet shifts and become predominantly piscivorous at around age 3. Analysis with stable isotopes also revealed long-term dietary differences between age-2 and age-3 yellow perch captured in littoral versus offshore habitats, suggesting some degree of intrapopulation variability in resource and habitat use among yellow perch in Dore Lake.