Yield Properties and Structure of Boreal Percid Communities in Ontario

Abstract

A synoptic review of yield data for 70 northern Ontario lakes from 1917 to 1973 showed that percids mainly walleye (Stizostedion vitreum vitreum) constituted about one-third, by weight, of the total fish yield. This relationship, which was independent of fishing effort, lake size, and lake productivity, is considered to be an emergent property of this type of fish community and represents a degree of homeostasis within the community under exploitation. The relation of percid yield to theoretical yield (based on the morphoedaphic index — MEI) reflected organizational structure and suggested the existence of a community (percid) component within the MEI, and from this we recommend upper limits of percid harvest for boreal percid lakes.Most (83%) of the 70 lakes had an average total yield of less than 2.5 kg∙ha−1∙yr−1, 53% (37 lakes) yielding less than one-half of the theoretical yield (average 3.4 kg∙ha−1∙yr−1). Long-term average yields exceeded the theoretical maximums in only 11 lakes. Mesotrophic to slightly eutrophic waters appeared as optimum for percid yields.Inferences from the data suggest an unexploited boreal percid community is characterized by high community stability and low net community production with resiliency low because of the low productive capacity of the waters. A yield index (RYI), which was assumed to reflect both effort and vulnerability to exploitation, showed that fishing intensity tended to be higher on the smaller, less productive lakes in this study. Key words: Percidae, Stizostedion, community ecology, yield properties, management implications

A holistic approach to ecosystem health assessment using fish population characteristics

“…Mechanisms regulating population size will play a large role in the formulation of the response pattern, and will vary with both species and location. The loss of community diversity and stability evident in many damaged systems can lead to an inefficient operation of the mechanisms regulating population size, resulting in fluctuations in total population size (Adams & Olver, 1977). The effects of these fluctuations on general indicators of population status have not been well documented, but it is clear that changes become difficult to interpret when density-independent mechanisms are the dominant factors governing population size.…”

Aspects of Common Loon (Gavia immer) feeding biology on its breeding ground

“…These were never presented to small chicks but were eaten by the parent . Percid species, predominantly yellow perch in this study area, constitute about 30% by weight of the fish yield from communities in which they occur (Adams & Olver, 1977) . Scott (pers.…”

Evaluation of the Effects of Fish Community Structure on Observed Yields of Lake Trout (Salvelinus namaycush)

“…The significant correlations observed m o n g catch, effort, and area may be simply that anglers fish a great deal when lake trout are abundant and not so much when CUE'S for lake trout are low. The lakes used in the present study were fished moderately, as the mean relative yield intensity (RYI, the ratio of the estimated yield of all species to the potential yield; Adams and Olver 1977) was 0.56 (k0.44). The ratio of estimated yield s f lake trout to the recommended yield of lake trout (25% of potential yield) was B .63 + 1.44.…”