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UA ECOL 482 - Communities, Ecosystems and the Functional Role of Fishes

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1Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• Community –Plant and animal assemblages that live together in a common areaLecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• Ecosystems – biotic and abioticinteractionsLecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• Spatial Scale = Watersheds• Landscapes –interactions and linkages among ecosystems and human influences on linkagesLecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• 1) Community interactions between fish and other taxonomic groups?• Type of interaction– Mutualism +/+ both species benefit from interaction– Commensalism +/0 one species benefits, one unaffected– Competition -/- each species affected negatively – Predation, parasitism, herbivory +/- one species benefits, one is disadvantaged2Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• 1) Community interactions between fish and other taxonomic groups?• Competition - primarily for food and space; complex mix commensalisms – e.g. bluefish and terns that feed for anchovies – bluefish drive fish up - terns drive down. Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• 1) Community interactions between fish and other taxonomic groups?• Predation – many species feed on fish and impacts on fish populations can be substantial; • Au Sable River in MI – brook –brown trout – 70-90% mortality. • Many things kill fish - Birds, Inverts (marine), mammals etc even dinoflagellate blooms (Pfiesteria) – over 1 billion menhaden in Neuse River in 1991. Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• 1) Community interactions between fish and other taxonomic groups?• Parasitism – isopods and snappers and tongue by BruscaLecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes2) Effects of fish on plants• Browsing – removing parts of plants • Grazing – removing plant at the substrate3Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes2) Effects of fish on plants• Latitude greatest correlate with herbivore diversity – above/below 40 degrees N/S rare or lacking (depends definition herbivore – 25-50% of diet). • Tropical Communities – minnows, characins, cichlids and (lesser degree) catfish, livebearers, gouramis. • Significant effects on abundance and diversity macrophytes - Panama streams, Costa Rica, • Seed Dispersal – Pacu – Colossoma sp.• Tropical Lakes – filter feeders, grazers, etc.• Coral Reefs – Caging, zonation, secondary defense, food preferences, Damselfish (cichlids) and algal gardens = keystone species. Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes2) Effects of fish on plants• Temperate Communities – minnows, catfish, suckers and pupfish – few exclusive but can effect biomass, species composition, increase growth rates.• Many omnivores eat large amounts of plants esp. when preferred not available.• Lakes – same as rivers more phytoplanktivory e.g. gizzard shad• Marine – species diversity much lower• Temperate – herbivory by inverts more important than fishLecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• 3) Fish effects on Invertebrate Activity, Distribution and Abundance• Effects on Zooplankton – Size-selective predation - fish like to eat large zooplankton; Herring in CT Lake – small individuals and smaller size. Strong and direct influences; Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes•3) Fish effects on Invertebrate Activity, Distribution and Abundance• Effects on Benthic Invertebrates – much less of an effect4Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• 3) Fish effects on Invertebrate Activity, Distribution and Abundance• Biomass (mass per unit area) vs. Turnover rates (production/standing crop biomass –P/B in g/m2/yr – Biomass tells little.• What happens when fish biomass exceeds standing? Inverts can go through several generations etc. Production usually 3 to 10 times greater than biomass. Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• 3) Fish effects on Invertebrate Activity, Distribution and Abundance• Biomass (mass per unit area) vs. Turnover rates (production/standing crop biomass – P/B in g/m2/yr –Biomass tells little.• What happens when fish biomass exceeds standing? Inverts can go through several generations etc. Production usually 3 to 10 times greater than biomass. Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• Fish in Ecosystems• Indirect Effects and Trophic Cascades• Top Down vs. Bottom Up Effects • Nutrient Cycling and Transport– P excretion for algal growth, Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• Fish in Ecosystems• Indirect Effects and Trophic Cascades• Top Down vs. Bottom Up Effects • Nutrient Cycling and Transport– Benthic fishes increase transport from sediment to water column,– Large amounts of nutrients tied up in fish –released by defecations, through gills and death.5Lecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• Fish in Ecosystems• Indirect Effects and Trophic Cascades• Top Down vs. Bottom Up Effects • Nutrient Cycling and Transport– grind coral etc (parrotfish)– Vertical and horizontal migrations; – Fish in Food Webs –linkages between distinct ecosystems - salmonLecture - Chapt 24 - Communities, Ecosystems and the Functional Role of Fishes• Fish in Ecosystems –• Influence of Physical Factors and Disturbance• Temperature, Oxygen and Water Flow – O2 greatest effect – drought, ice cover reduce O2; Water flow – increased river and stream discharge – Desert fishes??? Temperature and lake turnovers and fish kills, stratification of lakes. • Extreme Weather – hurricanes FOOD CHAINS AND WEBS I. Food chains • A. Conceptual: light --primary producers --primary consumers –secondary consumers, etc. • Associated with trophic levelI. Food chains • B. Ecological efficiency -- energy content of trophiclevel• N = energy income, from N-1 minus losses6I. Food chains • C. Currency – 1.calories– 2.C or N– 3.dry


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