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Freshwater Mussel Ecology

Freshwater Mussel Ecology: A Multifactor Approach to Distribution and Abundance

David L. Strayer
Copyright Date: 2008
Edition: 1
Pages: 216
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  • Book Info
    Freshwater Mussel Ecology
    Book Description:

    Pearly mussels (Unionoidea) live in lakes, rivers, and streams around the world. These bivalves play important roles in freshwater ecosystems and were once both culturally and economically valuable as sources of food, pearls, and mother-of-pearl. Today, however, hundreds of species of these mussels are extinct or endangered. David L. Strayer provides a critical synthesis of the factors that control the distribution and abundance of pearly mussels. Using empirical analyses and models, he assesses the effects of dispersal, habitat quality, availability of fish hosts, adequate food, predators, and parasites. He also addresses conservation issues that apply to other inhabitants of fresh waters around the globe and other pressing issues in contemporary ecology.

    eISBN: 978-0-520-94252-3
    Subjects: Zoology

Table of Contents

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  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
    (pp. vii-x)

      (pp. 3-8)

      One of the most enduring popular images of science is that of the cinematic mad scientist, scouring a graveyard for body parts from which to build a monster. Dr. Frankenstein is faced with two formidable tasks. First, he and his hunchbacked assistant must gather all of the pieces needed build a living monster (usually while evading the local constabulary). Even more daunting, he then must find some way to animate the collection unliving body parts—he must make the monster walk.

      Dr. Frankenstein might seem to be a strange role model for scientists, but his method is perhaps a compelling...

      (pp. 9-22)

      Pearly mussels of the superfamily Unionoidea (including the families Unionidae, Margaritiferidae, and Hyriidae) are common and widespread in rivers, streams, lakes, and ponds around the world, living on all continents except Antarctica. They can form locally dense populations of>100 animals/m² (Fig. 42), and often vastly outweigh other animals in benthic communities, reaching biomasses (not including their shells) sometimes exceeding 100 g dry mass/m² (e.g., Hanson et al. 1988, Strayer et al. 1994). Although their roles in freshwater ecosystems have not been fully investigated (Vaughn and Hakenkamp 2001), they can be important suspension-feeders, influencing water chemistry and clarity, and the amount...


      (pp. 25-42)

      In the next five sections of the book I will review the five processes—dispersal, habitat, fish hosts, food, and enemies—that I think have the potential to control the distribution and abundance of unionoids. In each of these sections, I will briefly review the state of knowledge about the process, assess the frequency and severity of limitation of mussel populations by the process, try to identify the conditions under which the process is most likely to be limiting, and highlight what I see as critical informational needs.

      I do not explicitly address interspecific interactions among coexisting unionoid species. Indeed,...

      (pp. 43-64)

      Habitat is probably the first factor to have been thought of as limiting mussel populations. By the time that a scientific literature on unionoid ecology began to develop in the late 19th and early 20th centuries, it was already widely stated that different species of mussels required different habitats (Table 3; e.g., Ortmann 1919, Coker et al. 1921, Baker 1928), and the idea that the amount of suitable habitat limits the size of mussel populations was widely accepted, at least implicitly (e.g., Coker et al. 1921). The notion that the availability of suitable habitat generally limits mussel populations (and corollary...

      (pp. 65-86)

      The larvae of most unionoids are parasitic on fish, so it is reasonable to suspect that the distribution and abundance of host fish might be an important factor in limiting unionoid populations. Before discussing the use of fish by unionoids, though, it is worth briefly considering the exceptions to the basic life cycle, which may be of some use in understanding the nature of limitation by hosts. First, there have been occasional reports that some unionoids can dispense altogether with the fish host, and develop directly from larvae to juveniles. In the early 20th century, it was reported thatObliquaria...

    • SIX FOOD
      (pp. 87-104)

      The quality and quantity of food are often regarded as among the primary factors that regulate the distribution and abundance of organisms in nature. It is thus curious that little attention has been given to the possibility that food might limit the distribution or abundance of unionoid mussels. We do not even have a clear idea what unionoid foodis, and know even less about the severity or extent of food limitation in pearly mussel populations.

      Information on unionoid diets has come from analyses of the gut contents of animals collected from the field, laboratory feeding trials, studies of mussel...

      (pp. 105-112)

      Predation, parasitism, and disease are often thought to limit animal populations but these factors have not been thoroughly investigated for unionoids. We can list some of the predators and parasites that affect unionoids and we know something about the selectivity and feeding rates of a few predators. Nevertheless, we know very little about the geographic extent or ultimate demographic impacts of any enemy.

      Mammalian predators (raccoons, otters, and especially muskrats) have received the most attention. These animals conveniently leave the empty shells of the animals they have eaten in neat piles along the shore, so it is possible to count...

      (pp. 113-118)

      It is worth emphasizing that human activities have had major effects on all five of the classes of factors that control unionoid populations, and thus have had large, varied impacts on unionoid distribution and abundance (Fig. 45). Model and empirical analyses (Figs. 11, 12, 15) suggest that the barriers that humans have spread throughout many river systems may have very large impacts on mussel metapopulations, and that the full long-term effects of these barriers probably have not yet been realized. There are now more than 45,000 large dams, which probably pose absolute barriers to mussel dispersal, as well as perhaps...


      (pp. 121-142)

      It seems clear that unionoid distribution and abundance is controlled by multiple factors, and that we therefore need some sort of plan for building a working theory that includes the effects of these multiple factors. It is not just unionoid ecology that needs a Dr. Frankenstein; many ecological variables are simultaneously controlled by multiple factors. Furthermore, the integration of multiple controls into a working theory is not a trivial problem. Consider the acrimonious, decades-long controversy about bottom-up (i.e., nutrient) “versus” top-down (i.e., food-web) control of phytoplankton biomass and production in lakes. Historically, phytoplankton biomass was thought to be controlled largely...

      (pp. 143-156)

      I do not believe that any of the three popular approaches to integration, as currently practiced by ecologists, is likely to lead to a satisfactory predictive understanding of unionoid distribution and abundance. As I suggested earlier (and will discuss further below), it is likely that a simple Liebigian approach will be satisfactory only when applied over limited domains. Uncritical attempts to apply a single-factor approach over a broad range of conditions may well lead to fruitless arguments about which factor is “the” limiting factor, when in reality multiple factors probably limit different mussel populations. Certainly, ecology has seen many such...

    (pp. 157-198)
  8. INDEX
    (pp. 199-204)
  9. Back Matter
    (pp. 205-206)