The application of the Endangered Species Act to the protection of freshwater mussels: a case study.

• Author: Biber, Eric

1. INTRODUCTION

   The Endangered Species Act (ESA or Act) (1) remains one of the most controversial environmental laws in the United States. Supporters depict it as the only legal bulwark against the mass extinction of species in the United States and the destruction of threatened ecosystems essential to the survival of natural biological systems. (2) Opponents depict it as a misguided law that has failed to achieve its objectives of protecting and conserving endangered species, and that has created hostility towards its goals among the private landowners who are crucial to efforts to preserve biodiversity. (3)

   This Comment examines the success or failure of the ESA in protecting a particular group of endangered species: freshwater mussels. Freshwater mussels constitute a substantial portion of the species listed as threatened or endangered under the ESA, and moreover, are the most endangered taxonomic group of species that scientists are aware of in the United States. (4) As such, they represent a group that should be a focus of conservation efforts under the Act, if the goal is the preservation of all species, regardless of economic, aesthetic, or social value. Mussels are also a group that has almost been entirely ignored in the legal literature's analysis of the Act, (5) and therefore represent an understudied area in the analysis of the Act's success or failure.

   This Comment begins with an overview of the biology and status of freshwater mussels (Part II), and then provides a detailed survey of the current human threats to the survival of freshwater mussel species (Part III). Part IV gives a short overview of the ESA and the tools the Act provides that might be used to protect and restore freshwater mussel species. Part V discusses the current legal and regulatory efforts by the United States Fish and Wildlife Service (the Service or FWS), the federal agency responsible for the application of the ESA to protect freshwater mussels, and discusses the current success of those enforcement and recovery efforts. Part VI summarizes the legal, policy, and biological literature analyzing why the ESA may be unsuccessful. Part VII assesses the conclusions of the legal literature, and discusses possible reasons for the success or failure of the ESA in the context of freshwater mussels. (6)

   This case study reveals that, while the ESA has prevented the extinction of most species of freshwater mussels, nonetheless many, if not most, freshwater mussel species remain critically endangered and declining. This Comment concludes that the inability of the ESA to provide for the recovery of freshwater mussel species is due to three factors: 1) the near-impossibility of recovering a species after most of its habitat has been destroyed and its populations eliminated; 2) underlying flaws in the ESA that make it much more difficult to address the threats to endangered freshwater aquatic species; and 3) a persistent and substantial historic bias against funding and enforcement of the ESA to protect freshwater mussel species. To provide for greater protection of freshwater species such as mussels, the ESA may need to adopt provisions similar to that of the Clean Water Act (CWA), (7) or alternatively, the CWA may need to be implemented in a manner that is more protective of endangered species. This case study of freshwater mussels not only reveals some fundamental areas of needed reform for the ESA, but also the broader importance of using environmental laws that have absolute theoretical mandates (such as the ESA's requirement that all species be saved) to ensure that otherwise ignored environmental harms are addressed.

2. BASIC BIOLOGY AND CONSERVATION STATUS OF FRESHWATER MUSSELS

   Freshwater mussels are similar to the saltwater or estuary mussels that are familiar to any lover of seafood--they are mollusks, (8) and are protected by a hardened shell made of calcium and other minerals, with an interior soft body that contains all vital organs. The exterior shells (or "valves") protect the animal against predators, and a muscular foot on the rear underside of the animal can extend between the valves allowing it to move as necessary. On the other side of the animal, two siphons allow the mussel to take in and expel water, and gills to take up oxygen extend on either side of the animal, poking out through the valves except in situations of extreme danger. (9) Mussels are filter feeders, consuming the algae and other organic materials they trap as they siphon water from the water column. (10)

   While mussels can move with their foot, their rate of movement is limited, and they tend to remain in one location for extended periods of time--adults are always partly embedded in the bottom of some body of permanent water. (11) The requirement of remaining embedded in the bottom (substrate) of the water body means that the substrate characteristics (sandy, silty, gravelly, etc.) and the depth of the water can be essential factors in determining where mussels will settle and grow. (12)

   The life cycle and reproduction of North American freshwater mussels is complex and unique. Male mussels will release clouds of sperm into the water column, which fertilize female mussels; the female mussels then release an enormous number of juvenile mussels, called "glochidia." The glochidia will float in the water column, but will perish or be consumed in a very short time unless they encounter a fish. The glochidia then attach themselves to the fish and parasitically live off of the fish (usually causing little or no harm) until they have developed to the juvenile mussel stage. (13) The juvenile mussels then break off of the fish and settle onto the bottom of the river, stream, or lake to begin an independent life. They will then develop into adult mussels. (14)

   The odds against any one individual glochidium surviving are extremely large--thousands or millions of glochidia may be produced, but the vast majority never encounter a fish. (15) Moreover, some species of mussels can only parasitize a particular fish species--the specificity of the mussel/host fish relationship reduces the odds that a glochidium will successfully attach to a fish. (16) And once the juvenile mussel has been released from the host fish, the odds against the juvenile mussel finding appropriate substrate to settle upon are also high. (17)

   However, once a freshwater mussel has successfully colonized suitable habitat, it can live for decades (depending on the species) (18) and will have many years of successful reproduction (although success will often be highly variable). (19) Thus, mussel species tend to have a very low rate of population increase, but very stable populations (assuming there are not major changes in the environment).

   Freshwater mussels are taxonomically identified in large part based on shell characteristics. (20) Most freshwater mussels in the United States are classified as members of the order Unionoidea (called "Unionids"). There are currently 297 species of Unionids historically known from North America, of which nineteen are presumed extinct, (21) sixty-one are listed as endangered by the Service, (22) and eight are listed as threatened. (23) These numbers probably underestimate the true proportion of freshwater mussel species that are in danger of extinction--scientists estimate that seventy percent of all freshwater mussel species are endangered, threatened, or of special concern, and only about twenty-four percent are considered stable. (24)

3. THREATS TO MUSSELS

   Freshwater mussels face an enormous range of threats, from direct overharvesting by humans and predation by other animals, to direct habitat destruction by humans, to indirect habitat degradation by human activities, to impacts from newly introduced exotic species. (25) This Part summarizes those threats, and also provides an assessment of how serious those threats are, an assessment based in part on interviews with biologists.

   1. Direct Overharvesting

      Freshwater mussels have historically been subject to extensive and heavy harvesting pressure from humans. Commercial harvesting first reached major levels in the late nineteenth and early twentieth century, with the development of a major market for the use of freshwater mussel shells for button manufacturing. (26) Harvesting soon reached extremely high levels throughout the early part of the twentieth century, and the federal government began research into the conservation and propagation of the major commercial species because of fears that harvesting pressure might lead to the depletion or extinction of mussel species. (27) Eventually, the button industry declined due to the advent of plastic buttons and zippers in the 1940s, but not until the populations of many mussel species had been substantially depleted. (28) Harvesting pressure increased in the 1950s as Japanese and other Asian pearl culture operations began using North American freshwater mussel shells as bead nuclei. (29) Harvesting again reached relatively high levels, particularly in the rivers and reservoirs of Tennessee and Kentucky. Since the 1950s, harvest levels have fluctuated in response to overseas demand for the shells, with another spike in harvest in the early 1990s. (30) The harvesting pressures have led to concern over the status of the major commercial mussel species (which are not threatened or endangered) and over the status of threatened and endangered noncommercial species that may be accidentally taken in the harvesting process. (31) A number of states now have regulations on the time, place, and manner of mussel harvesting to protect both target and non-target species. (32)

      However, most biologists interviewed for this case study did not feel that overharvesting represented a significant, widespread threat today for freshwater mussels. Overall, biologists cited as reasons for the decrease in the importance of this threat a drop in the price for freshwater mussel...