Ecological Significance

As prey

Photographer: osteopteryx (CC BY-SA 2.0)

Crayfishes serve as prey for over 200 animal species, including mammals, birds, reptiles, amphibians, fishes, and insects (DiStefano, 2005). Among aquatic predators, the fish family Centrarchidae, including many popular sport fishes such as smallmouth bass (Micropterus dolomieu) and rock bass (Ambloplites rupestris), are particularly prominent crayfish predators (Probst et al., 1984; Rabeni, 1992). A wide variety of other fish species, ranging from brook trout (Salvelinus fontinalis) to creek chubs (Semotilus atromaculatus) have also been shown to allocate portions of their diet to the consumption of crayfishes (Newsome and Gee, 1978; Gowing and Momot, 1979). Crayfishes also represent a vital food source for other aquatic taxa, such as the federally endangered aquatic salamander known as the hellbender (Cryptobranchus alleganiensis; Wiggs, 1976). Beyond aquatic ecosystems, crayfishes are also frequently consumed by a variety of terrestrial animals, including minks, raccoons, and even some wading birds (Baker et al., 1945; Toweill, 1974; Martin and Hamilton, 1985).

As consumers

Photographer: Clinton & Charles Robertson (CC BY 2.0)

Crayfishes are generally thought to be omnivores and have been shown to consume a wide variety of food items, ranging from phytoplankton to fish. In terms of primary producers, crayfishes consume filamentous algae (Goldman, 1973) and aquatic plants (Creed, 1994). Some crayfishes can consume so much algal and plant material that they can strongly influence the population densities of these organisms (Goldman, 1973). Crayfishes also function as important predators, consuming a variety of vertebrate and invertebrate prey. Crayfishes feed on many different types of invertebrate prey, including snails (Kreps et al., 2012), insects and their larvae (Parkyn et al., 2001), and even other crayfishes (Nakata & Goshima, 2006). Beyond invertebrates, crayfishes can consume vertebrates such as fishes (Rahel and Stein, 1988) and amphibians, particularly their eggs or larvae (Axelsson et al., 1997).

As ecosystem engineers

Photographer: P. Tinerella

Crayfishes live in a variety of habitat types, both aquatic and terrestrial, and they can have remarkable impacts on the ecosystems in which they live. Crayfishes can both directly and indirectly alter habitat quality and resource availability for other organisms, often more so than other co-occurring taxa (Reynolds et al., 2013). One mechanism by which crayfishes can accomplish this is through their burrowing behavior. Crayfishes are generally adept in constructing burrows and other subterranean chambers in aquatic, and sometimes terrestrial, habitats. These burrowing abilities allow them to substantially modify and create interstitial spaces within substrates, creating habitats that can be utilized by other organisms (Creed and Reed, 2004).

The same burrowing behaviors can also significantly alter sediment erosion rates in some ecosystems (Statzner et al., 2000; 2003). In terrestrial habitats, primary burrowing crayfishes (those species that spend most – or all – of their adult lives away from permanent bodies of water) construct complex networks of tunnels and chambers deep into the soil. These often expansive subterranean networks can serve as critical conduits for water or gas exchange, oxygenating and draining otherwise poor soils (Richardson, 1983; 2007). Crayfishes can also consume staggering amounts of detritus, primarily in the form of leaf litter and other decaying plant material (Huryn and Wallace, 1987; Schofield et al., 2001). In fact, detrital processing by crayfishes can strongly alter the abundances of insect larvae, such as heptageniid mayflies (Creed and Reed, 2004), which can be an important food source for fishes and other stream vertebrates (Hoopes, 1960).