Secondary production and diet of an invasive snail in freshwater wetlands: implications for resource utilization and competition

Abstract

Invasive species can monopolize resources and thus dominate ecosystem production. In this study we estimated secondary production and diet of four populations of Pomacea canaliculata, a freshwater invasive snail, in wetlands (abandoned paddy, oxbow pond, drainage channel, and river meander) in monsoonal Hong Kong (lat. 22°N). Apple snail secondary production (ash-free dry mass [AFDM]) ranged from 165.9 to 233.3 g m -2 year -1 , and varied between seasons. Production was lower during the cool dry northeast monsoon, when water temperatures might have limited growth, but fast growth and recruitment of multiple cohorts were possible throughout much (7-10 months) of the year and especially during the warm, wet southwest monsoon. The diet, as revealed by stomach-content analysis, consisted mainly of detritus and macrophytes, and was broadly consistent among habitats despite considerable variation in the composition and cover of aquatic plants. Apple snail annual production was[10 times greater than production estimates for other benthic macroinvertebrates in Hong Kong (range 0.004-15 g AFDM m -2 year -1 , n = 29). Furthermore, annual production estimates for three apple snail populations (i.e.[230 g AFDM m -2 year -1 ) were greater than published estimates for any other freshwater snails (range 0.002-194 g AFDM m -2 year -1 , n = 33), regardless of climatic regime or habitat type. High production by P. canaliculata in Hong Kong was attributable to the topical climate (annual mean *24°C), permitting rapid growth and repeated reproduction, together with dietary flexibility including an ability to consume a range of macrophytes. If invasive P. canaliculata can monopolize food resources, its high productivity indicates potential for competition with other macroinvertebrate primary consumers. Manipulative experiments will be needed to quantify these impacts on biodiversity and ecosystem function in wetlands, combined with management strategies to prevent further range extension by P. canaliculata.

Dieta de Pomacea canaliculata (Gastropoda: Ampullariidae) en su hábitat natural basada en análisis de contenidos digestivos e isótopos estables

“…The fact that the contribution of each feeding resource analyzed was similar and not higher than 40 % suggests that the species feed on those items indiscriminately, supporting their generalist feeding behavior as proposed in earlier studies (Cazzaniga and Estebenet, 1984;Cowie, 2002;Estebenet and Martín, 2002;Kwong et al, 2010).…”

“…These results are comparable with those reported in wetlands of Hong Kong, where this exotic snail exhibits a secondary production greater than any of the native species. Besides, although detritus and macrophytes constitute its main diet, benthic algae are also very common in the gut and can be an additional food source for this omnivorous snail (Kwong et al, 2010).…”

“…Therefore, although the elevated consumption of macrophytes of P. canaliculata is already known (Cazzaniga and Estebenet, 1984;Kwong et al, 2010), the nutrient enrichment (C and N) and high amounts of detritus and biofilm found in the gut content of this snail in our study suggests that these items may also constitute an important food resource and a source of carbon for this species, such as it has been demonstrated for other aquatic organisms of the Pampean sreams (Rodrigues-Capítulo et al, 2002;Licursi and Gómez, 2003;Gómez et al, 2009). …”

“…Also, field studies dealing with the feeding habits of this snail have been carried out in areas where this species is an invader Kwong et al, 2010;Morrison and Hay, 2011). Some studies referring to different topics of the ecology of these organisms have been carried out in environments of our country more recently (Seuffert and Martín, 2009;Seuffert et al, 2010;Seuffert and Martín, 2013) but local investigations are still needed because fundamental issues of its trophic ecology in natural habitat remain unknown.…”

Ecology of the non-native snail Sinotaia cf quadrata (Caenogastropoda: Viviparidae). A study in a lowland stream of South America with different water qualities

“…2). Moreover, Kwong et al (2009) found that mature individuals of P. canaliculata predate on young individuals of S. quadrata, evidencing an interaction (predation) between these snails. This hypothesis, however, will be tested after the study of gut content in future studies, in which not only it will be elucidated if P. canaliculata is predating on young individuals of S. cf quadrata, but also if there is a competition for other food sources.…”