No abstract

Effective stewardship of Florida's coast requires, in part, detailed characterizations of ecological components of the marine system. Characterization of one component, manatees (Trichechus manatus latirostris), involves mapping its distribution and abundance and identifying features of the landscape that are intimately associated with its life history. In this study, we developed a raster-based spatial model that transformed radiotelemetry point data to surfaces illustrating the areas manatees visited frequently for relatively long periods, called ''places,'' and areas visited frequently for short periods, called ''movement corridors.'' This work involved (1) simulating manatee movement paths between sequential telemetry points using a cost surface based on manatee bathymetric preferences that were derived from empirical associations between telemetry locations and water depth, (2) distributing movement time to cells that were crossed by the simulated movement path, and (3) extracting cells from the movement-path map that qualified as places and those that qualified as corridors. Movement characteristics of wild and rehabilitated animals were similar. Movement rates of males were significantly greater than those of either females with calves or females without calves. Mean number of visits per cell and mean time per visit for the three adult classes were not significantly different. Males had the smallest mean patch size for places, and females without calves had the largest but fewest places. Based on qualitative evaluations by field biologists, we concluded that the model performed well in estimating places. The locations of movement corridors were less certain, although reasonable, given that manatee spatial cognition was considered sufficient to permit directed movement between places.

No abstract

1987.A perspective on Great Lakes fish community rehabilitatisn. Can. I. Fish. Aquat. Sci. 4-4 (Suppl. 2): 48f5-499.Review of the ASPY syntheses suggested that destabilization and subsequent fish community recovery in the Great Lakes are compatible with a model in which postglacial succession, and the structure and persistence of the fish communities, were governed by piscivores. Recent advances in the areas of particle size distribution, ontogenetic niche theory, and ecosystem stability contributed t o a broader understanding of fishery management alternatives. Species succession in Great Lakes aquatic communities is characterized as a cyclic repetition of maturation followed by seasonal, annual, or periodic setbacks. These are termed "enjuvenation events" and are attributed t o any cultural or climatic factors which induce flux in energy-matter delivery t o the system. The extent of enjuvenation is dependent upon the magnitude of the perturbation and maturity of the community and is predictable t o some degree by the age and biomass distributions of the species present. The time course of rehabilitation t o any arbitrary prior condition of the community is closely related to the ersjuvenation-maturation cycle and t o the life span and reproductive characteristics of the species present. The principal homeostatic mechanism is perceived to lie with variations in the durations of life history stanzas as affected by fish growth rates. The "biomass storage" function of larger organisms in the system i s thought to be a major determinant of the "biotic inertia" or sensitivity of the community to perturbations. We are convinced that trophic linkages from the piscivores downwards must be maintained as biological feedback pathways t o ensure that moderately excessive fishery yields can be segf-limiting. Without these linkages (vulnerable t o intensive exploitation o r other catastrophic reductions in predators), biomass capture of nutrient inputs by algae will vector t o waste as planktivore density limits secondary production. The extent t o which the fish community can be maintained o r driven to a particular species composition is dependent upon the degree of external control of ail sorts that can be applied to the system. The rehabilitation continuum ranges from a self-sustaining assemblage of native species requiring little external controi to a completely artificially supported community of nsn-native species requiring extensive controls for both water quality and fish comsmunity maintenance.U n examen des syntheses de I'ASPY porte h croire que le d6s6quiIibre de la communaute piscicole des Grands Lacs et son r6tablissement ult4rieur csncsrdent 2 u n mod&le 013 la succession post-glaciale ainsi que la structure et la permanence des comrnunautes piscicoles sont r6gl6es par les piscivsres. Les recents prsgres r6alis6s d a m les domatines de la r6partition de la taille des particules, la theorie d'une niche '~o~laABPeatigsw No. 87-04 of the Oratxis Ministry of Natural Resources, Research Section, Fisheries Branch, Bo...

No abstract