No abstract

Since at least the beginning of the last century, sport anglers and commercial fishers have often held cormorants responsible for declining catches. The recovery of double-crested cormorant Phalacrocorax auritus populations throughout the Great Lakes region since the late 1970s has rekindled efforts to assess their impact on sport fish populations. In this paper we compare the species and age composition of fish consumed by double-crested cormorants (diet study) and harvested by anglers (creel survey) with abundance estimates of walleyes Stizostedion vitreum and yellow perch Perca flavescens (mark-recapture and catch per unit effort). The numbers of walleyes consumed by cormorants were similar to those harvested by anglers; however, cormorants consumed only subadults, whereas anglers harvested only age-4 and older adults. Cormorants and anglers combined harvested 7% of age 1-3 walleyes and 14% of the adult walleye population. Cormorant consumption of adult yellow perch was similar to angler harvest, but cormorants consumed almost 10 times more age-2 yellow perch and only cormorants harvested age-1 yellow perch. Cormorants and anglers combined harvested 40% of age-1 and age-2 yellow perch and 25% of the adult yellow perch population. Total annual mortality of adult percids has not changed since cormorant colonization. Although cormorant consumption of adult percids has little effect on harvest by anglers, consumption of subadults will reduce future angler harvest of yellow perch and, to a lesser extent, walleyes.

No abstract

Understanding the relationship between anglers and fish is important to the management of angling fisheries. We compared angler catch rates estimated from creel surveys with (1) population density estimates of age-3 and older walleyes Sander vitreus based on mark-recapture and (2) mean growth of walleyes aged 4-6 in Oneida Lake during 1957-1959, 1997, and 2002-2003. We also compared walleye catchability to walleye population density. Angler catch rates were not related to walleye population density; however, by combining population density and walleye growth, we were able to explain 97% of the variability in angler catch rates, perhaps because growth rates were related to prey abundance. Catchability of walleyes decreased as population density increased. Consideration of these effects should improve our understanding of angler-fish dynamics and allow fishery managers to better predict the effects of management actions.