Conservation, like beauty, is clearly in the eye of the beholder. The lack of a clear definition of what is meant by the term conservation, however, may encourage misconceptions about the degree to which biological objectives can be traded off against pressing economic and social objectives. Our purpose is to promote a dialogue about the meaning and practice of conservation, which might lead toward consensus on essential biological objectives. We present a brief history of the philosophical evolution of the term conservation and offer a definition of conservation based on the argument for an ecological ethic. This ethic requires that human benefits be derived in a sustainable manner and recognizes that human uses need to be reconciled with intrinsic and necessary ecosystemic functions and structures. We then present a preliminary set of operating principles applicable to the management of fish stocks that are consistent with an ecological or ecosystemic view of conservation. By proposing a set of conservation principles for fisheries management we hope to initiate a debate about just what those principles ought to be.

Commonest lake types of the 15 combinations of four fish species (walleye, Stizostedion vitreum vitreum; northern pike, Esox lucius; lake trout, Salvelinus namaycush and smallmouth bass, Micropterus dolomieui) were walleye–pike (22%), pike "only" (19%), lake trout "only" (16%) and smallmouth bass "only" (10%). Lake trout–walleye and lake trout–walleye–smallmouth bass types were extremely rare. Lake depth and area were variables of greatest significance in distinguishing lake types by discriminant analysis. Climatic factors explained the general geographic distribution of smallmouth bass. Hypotheses to explain the low frequency of walleye in small lakes include possibilities of (1) low probability of successful coexistence of pike and walleye, (2) lack of wind fetch to clear spawning areas, and (3) "Lebensraum requirement" of the walleye. Key words: limnology, Percidae, methodology, Ontario lake types, Stizostedion vitreum vitreum, Esox lucius, Salvelinus namaycush, Micropterus dolomieui, distribution, associations

We propose that the optimum habitat of the percid fishes Perca flavescens, P. fluviatilis, Stizostedton vitreum vitreum, and S. lucioperca in lakes may be defined by the littoral and sublittoral environmental conditions equivalent to those in large, temperate rivers. Analogous habitat conditions include sand or gravel substrate, low current velocity, reduced light penetration (Stizostedion spp. only), temperatures optimal for growth and reproduction, and well-oxygenated spawning substrates. The species' evolutionary origins and reproductive patterns also reflect their riverine ancestral habitat. Evidence in support of the hypothesis is derived from the diversity of papers contributed to the PERCIS Symposium. Key words: Percidae, habitat, theory, Perca, Stizostedion

No abstract

No 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

No abstract

1987. Evaluation of the effects s f fish community structure o n observed yields s f lake trout (Salvelinus namaycush). Can. 1. Fish. Aquat. Sei. 44(Supp!. 2): 239-248.Crees and lake survey data from 87 Ontario lakes with self-sustaining Bake trout (Salvelinus namaycush) populations were analysed t o determine the effect of intrinsic factors, such as fish community structure, and extrinsic factors, such as angling-effort, on the observed yields s f lake trout. Multiple regression analyses showed that angling-effort and lake area, in order of importance, explained almost 82% of the variation in annual catches. Analyses of covariance were used t o test a variety of hypotheses about how R e p le "lovembre "185