Feeding and Responses to Food Abundance
Marine heterotrophs have evolved a very large variety of feeding mechanisms to obtain their rations, and any given species usually makes use of several feeding mechanisms (Pandian, 1975). Heterotrophs may use organic matter dissolved in water or on larger particles. Dissolved food may be taken up through the body or cell surface, as occurs in microorganisms, many invertebrate parasites, and pogonophorans. Other consumers take up fluids through their mouth, as in the case of some nematodes, trematodes, leeches, parasitic copepods, and young mammals. Dissolved food is also obtained by some heterotrophs from their endosymbionts, as in the case of zooxanthellae in corals and other cnidarians, and sulfur bacteria in some pogonophorans and bivalves.
KeywordsFunctional Response Prey Species Prey Density Food Abundance Fishing Effort
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- *.The kinetics of uptake of dissolved organic compounds can often be described by Michaelis—Menten kinetics (Parsons and Strickland, 1962; Wright and Hobbie, 1965). This implies, as in the case of nutrient uptake reviewed in Chapter 2, that there is a maximum uptake rate at some concentration of substrate, and that perhaps the number of transport sites in each cell sets this rate.Google Scholar
- *.Note that cell size and cell density are not independent; this is the first of many examples where we will see that although we discuss components separately as an expository device, the components may be inextricably related.Google Scholar
- *.There is also the intriguing but largely unstudied possibility of chemotactic mimicry in the case of prey of predators that use chemotactic means of detecting prey.Google Scholar
- *.The maximum yield curve has been a key concept for management strategies and models of commercial fisheries (Cushing, 1975; Ricker, 1975). There are many reservations as to its usefulness in actual management of fish stocks (Larkin, 1977), since (1) the concept is not helpful in dealing with the not infrequent catastrophic declines in stocks or in allocating fishing to different geopolitical areas so that no one local stock is depleted, thus maintaining genetic variability of the species; (2) maximum yield ideas have not been developed to include multispecies stocks, so do not include interactions among various species in one area; and (3) maximum yield may not be practically sustainable and may be economically undesirable, since perhaps only a lower supply of certain species may be marketable.Google Scholar
- *.This response of predators to scarce prey is quite general and applies to a variety of quite different predators. The Athapaskan Indians in the Pacific Northwest of North America lived inland and lacked the abundant food supply of the coastal tribes. When hunting the Athapaskans dispersed into small groups to maximize chances of encountering game.Google Scholar