1992. Biomass spectra of aquatic ecosystems in relation to fisheries yield Can. j. Fish. Aquat. Sci. 49: 1528-1 538.The biomass density of aquatic ecosystems can be expressed as an allsmetric function of organism body sine. The log-log plot of this relation, termed the biomass spectrum, is used to cornpare aquatic ecosystems in various parts of the world. We develop a standardized presentation for several example environments where detailed data on biomass density by body size in the trophic positions, phytoplankton, zooplankton, benthos, and fish, make it possible to establish overall or primary spectral slopes. The basic methodology is adapted for application to other ecosystems where less detailed data are available, Spectra from all the different environments exhibit a unifc~rrn low slope, but with different intercepts that appear to reflect ecosystem differences in nutrient circulation and availability. Detail on the secondary structuring at various positions in the trophic system appears to provide information useful for distinguishing between long-term changes in productivity and short-term perturbations in biomass or abundance.La densite de la biomasse presente dans un 6cosystGme aquatique peut &re exprimee ssus forme de fonction allom6trique de la taille des srganisrnes. On utilise le graphe log-log de cette relation, appelee spectre de biomasse, pour cornparer les 6cosystemes aquatiques de diverses parties du globe. On dabore aussi une presentation normalisee de plusieurs types d'ersvironnernents pour lesqslels des donnees detaillkes sur la densit6 de la biomasse en fonction de la taille des srganisrnes au niveau trophique, nooplancton, phytoplancton, benthos et pisson, permettent d'etablir la pente globaleou primaire du spectre. On adapte les methodes fondamentales pour qu'elles s'appliquent A d'aartres 6cosyst&rnes pour lesquels des dsnnees dktaill6es ne sont pas disponibles. Les spectres obtenus de tous les differents environnernents rnontrent une faible pente uniforrne, mais les differents interceptes semblent r6fl6ter des difgrences dans le cycle et la disponibilit6 des aliments au rsiveau des 6cosyst6mes. Bes details sur la structure secondaire 2 diverses positions du systerne trophique semblent fournir de B'informatisn utile dans la separation des variations 21 long terme de la prsductivit6 et des perturbations 3 court terme de la biomasse ou de t'absndance.(xuesa redicting biological production in communities from energy flux through its trophic components has been a prime focus of ecology. Attempts to use Lindeman's (1942) original fornulation, specifying predator-prey trophic linkages between species grouped into "levels, ' have demonstrated the difficulties of arriving at models that are both sufficiently realistic and sufficiently general (Lane and Collins 1985). The practical failure of the trophic level calculations (Mmn et al. 1989) in the past is due partly to the complexity of the systems modelled and partly to continued uncertainty about the time and space scales on which it is possibl...

The structure of animal communities and the energy flux through them may be characterized by biomass ratios, ecological efficiencies, and production efficiencies of the component organisms. Here, we interpret these ratios in terms of the elementary processes of food intake, specific production rate, and gross growth efficiency that underlie them. Recent information confirms that the magnitude of all these processes is related to the average body mass of the organisms involved. However, our analysis shows that this well—known dependence reflects the influence of two different basic biological properties. One of these is the metabolism—body—size relation of individual that is familiar from physiology. The other less well—recognized property appears as an ecological population factor reflected in the distribution of particle sizes within animal groups in the community and is probably related to the relative sizes and distributions of predators and their prey. It appears that both the physiological and ecological size relationships have to be recognized as scaling factors in order to transform measures of biological production of various parts of communities into common terms for comparison. Current data on the generality and stability of community structure and production suggest that by using this twofold size scaling, trophic energy flow within the community can be determined from the distribution of body sizes without the necessity of specifying trophic levels of the organisms involved. The ecological size scaling can be seen as an index of the system nature of ecosystems.

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Reciprocal transfers of three blue mussel (Mytilus edulis) stocks among three rearing sites resulted in marked changes in growth, mortality, and maximum biomass. Results indicate that site differences were major determinants of the growth effects, while stock differences were chiefly responsible for the mortality effects. The overall effect on biomass and potential yield was approximately equally attributable to site and stock influences. The results have relevance to aquaculture and environmental assessment using mussels and illustrate genotypic responses that may be significant for fisheries management.