02 Ecology

02 Ecology - Paradigm Shift Fish Ecology the most fun you...

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Fish Ecology the most fun you can have with fish without eating them Paradigm Shift ± From: “Balance of nature” ± To: “The only constant is change” ± The dynamic nature of fish faunas makes more sense under new paradigm ± Once assumed an underlying predictable structure to which systems would return if perturbed. ± Underlying structure of ecological systems is a moving target. ± Scales of change Local to regional climatically influenced ecological to evolutionary temporal frames ± Humans are major drivers of change Ecological Filters ± Presence of a particular population of fish dependent on historical events & ecological filters ± Pleistocene events --10,000 ybp ± Zoogeographic barriers ± Physiological factors Codfishes: < 2 o C inhibits Cl-secreting mech ± Biological Interactions --species excluded by competitors, predators, parasites or lack of suitable prey Ecological Filters . .. ± Natural disturbances ; natural community ± Human disturbances ; observed community,changed due to extinctions, introductions, fishing pressure, water management,habitat modifications, etc. Fish Community ± An assemblage of fishes structured by species interactions = fish community ± Assemblage = co-occurring populations does not imply significant interactions ± Fundamental niche (abiotic; G. E. Hutchinson) ± Realized niche (~abiotic - biotic) ± Niche = resources (energy, materials, sites) used (Hurlbert 1981 Evol. Theory) ± Two views of structuring forces: deterministic vs stochastic equilibrium vs non-equilibrium ± Fish communities of both kinds have been described Tropical coral reef communities stochastic Temperate rocky intertidal communities deterministic ± Researchers do not always agree on characterizations Fish Community . ..
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Deterministic communities ± Structured by species interactions ± Characteristics: Persistent, year to year Resilient, bounce back after a disaster Little overlap in use of space &/or food Spp show high degree of co-evolved morphological differences ± This characterization questioned in complex communities Stochastic communities ± Environment too variable to allow a predictable community to develop ± Species populations rarely reach densities high enough for competition or biotic interactions to regulate community ± Overlaps in use of space & food are common & many spp are morphologically similar ± Rests in part on Intermediate Disturbance Hypothesis Intermediate Disturbance Hypothesis Disturbance Low High S p e c i s d v r t y Few dominant spp Few good colonizers Intermediate Disturbance Hypothesis ± Diversity highest where disturbance is moderate ± Competing species coexist because environment favors neither for very long ± Only dominant competitors survive in undisturbed habitats ± Only a few very hardy or good colonizers survive in highly disturbed habitats ± Damsel fish-Keystone species Predator-prey Relationships ±
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02 Ecology - Paradigm Shift Fish Ecology the most fun you...

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