Feeding Preferences and Food Selection of the Red Swamp Crayfish, Procambarus Clarkii, in Habitats Differing in Food Item Diversity

Abstract

We compared the dietary composition, feeding preferences, and food selection of the introduced crayfish, Procambarus clarkii in a natural and a transformed freshwater marsh (rice field) in the lower Guadalquivir basin (southern Spain). Both habitats differed in hydroperiod and food item diversity.Food item diversity in crayfish stomachs is correlated with prey availability, which is significantly higher in the natural marsh. Herrera's index was low in both areas if compared with the theoretical maximum. P. clarkii behaves like a generalist in this area and individual crayfish have very similar feeding preferences.The most frequent items in the stomach were fresh macrophytes, detritus, and sediment grains. However, especially in the untransformed marsh, insect larvae formed an important part of the crayfish's diet, up to 67% by occurrence, with a marked seasonal pattern: crayfish in this area consumed significantly more animal prey in spring than in winter. P. clarkii positively selects for insect larvae (mayflies, chironomids), snails, and microcrustaceans except ostracodes. Negative selection against oligochaetes is explained by their burrowing behaviour and the difficulty to detect them in the stomachs. Cannibalism is stronger in the rice fields as a consequence of high crayfish densities.Animal food for adult P. clarkii is shown to be more important than previously reported. Overestimation of herbivory and detrivory in this omnivorous species might be due to serious methodological drawbacks associated with stomach content analyses. RESUMENPresentamos una comparación de la composición de la dieta, las preferencias alimenticias y selección de los recursos tróficos utilizados por el cangrejo introducido, Procambarus clarkii, en dos ambientes diferentes de marisma de agua dulce de la cuenca del Bajo Guadalquivir (sur de España), natural y transformado (arrozal). Los dos ecosistemas difieren en su hidroperiodo y en la diversidad de las presas.La diversidad de los recursos tróficos encontrados en los estómagos de las dos áreas, estuvo directamente relacionada con la diversidad de especies presentes en el campo, siendo significativamente 1 ) e-mail: paloma.alcorlo@uam.es © Koninklijke Brill NV, Leiden, 2004 Crustaceana 77 (4): 435-453 Also available online: www.brill.nl 436 P. ALCORLO, W. GEIGER & M. OTERO más alta en la marisma natural. El índice de Herrera fue bajo en ambas zonas cuando se compara con el máximo teórico. P. clarkii se comporta como una especie generalista en esta zona y los cangrejos, individualmente, tienen preferencias alimenticias semejantes.Los elementos más frecuentes encontrados en los estómagos fueron, según su orden de abundancia, macrófitos, detritus y granos de sedimento. Sin embargo, en la marisma natural, las larvas de insectos constituyen una categoría muy importante en la dieta del cangrejo (frecuencia de aparición de más del 67%) que fluctúa con un marcado patrón estacional: consumen más presas animales en primavera que durante el invierno.P. clarkii selecciona positivamente larvas ...

Understanding invasion success: life-history traits and feeding habits of the alien crayfishOrconectes immunis(Decapoda, Astacida, Cambaridae)

“…The main prey taxa were Chironomidae larvae, Cladocera and Ephemeroptera larvae, of which the latter tended to be positively selected. A similar high importance of Chironomidae larvae in the diet of Orconectes luteus and O. punctimanus was reported by Whitledge and Rabeni (1997), and a preference for Chironomidae and Ephemeroptera larvae is also known for P. clarkii (Alcorlo et al, 2004). Orconectes immunis positively selected for slow-moving or immobile prey that could be easily captured, such as Dreissena polymorpha and Trichoptera, whereas sediment-dwelling prey, such as Oligochaeta, were significantly underrepresented in the O. immunis stomachs.…”

“…Orconectes immunis positively selected for slow-moving or immobile prey that could be easily captured, such as Dreissena polymorpha and Trichoptera, whereas sediment-dwelling prey, such as Oligochaeta, were significantly underrepresented in the O. immunis stomachs. A similar under-representation of sediment-dwelling prey was reported in the diet of P. clarkii (Alcorlo et al, 2004), suggesting that crayfish might generally select against sediment-dwelling taxa, probably because sediment dwellers are hard to capture and the handling is not profitable for crayfish. However, sediment-dwelling Ephemera sp.…”

“…No ontogenetic shift in the diet of O. immunis was observed in the present study, perhaps as a result of its rather small size and the sustained high growth rate throughout its life. Both a slower growth rate in adult crayfish and an incremental size difference between larger crayfish and their prey have been previously suggested as explanations for ontogenetic shifts in crayfish diets (Nyström, 2002;Alcorlo et al, 2004). Orconectes immunis was found to prey on a wide spectrum of macroinvertebrates.…”

“…Ontogenetic shifts in diet were reported for several larger species, suggesting interdependencies between growth rate, size and feeding preferences (Momot, 1995;Nyström, 2002;Alcorlo et al, 2004). A relatively small species like O. immunis may therefore exhibit other feeding preferences than larger NICS or ICS.…”

Present distribution and future spread of louisiana red swamp crayfishProcambarus clarkii(Crustacea, Decapoda, Astacida, Cambaridae) in Britain : Implications for conservation of native species and habitats

“…Procambarus clarkii has all of these traits (Huner, 2002) and the species is well known for its ecological plasticity (Gutierrez-Yurrita and Montes, 1999; Alcorlo et al, 2004). Procambarus clarkii can even adapt to extreme environments, including temporary streams and polluted water (Scalici and Gheradi, 2007).…”