Using stable isotopes to investigate movement of fish in rice paddy fields

• Published in: International aquatic research 2015-09, Vol.7 (3), p.211-220
• Main Authors: Lee, Jaeyong, Kim, Jae-Ok, Owen, Jeffrey S., Kim, Bomchul
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Aquatic insects; Aquatic Pollution; Earth and Environmental Science; Ecotoxicology; Environment; Fields; Fish; Food sources; Freshwater & Marine Ecology; Freshwater fishes; Habitat utilization; Insects; Irrigation; Irrigation systems; Isotopes; Livestock; Marine & Freshwater Sciences; Misgurnus; Organic matter; Organic soils; Original Research; Ponds; Rice fields; Soil organic matter; Stable isotopes; Waste Water Technology; Water; Water Management; Water Pollution Control; Watersheds
• ISSN: 2008-4935; 2008-6970
• DOI: 10.1007/s40071-015-0105-y

We evaluated movement of fish, especially Misgurnus spp. (loach), in paddy fields and irrigation ponds by conducting an inventory of δ 13 C and δ 15 N of fish, potential food sources, and soil organic matter in two irrigation pond–paddy field systems in Korea. The pond–paddy systems differ with respect to the presence or the absence of a ridge between the paddy field and the irrigation pond and also whether or not livestock are present in their watersheds. The ridge prevents the free movement of fish between paddy field and irrigation pond habitats in one of the pond–paddy watersheds, but not in the other watershed. We found differences in loach δ 13 C and δ 15 N inhabiting the paddy fields compared to those in loach δ 13 C and δ 15 N in the irrigation ponds. In irrigation ponds, loach δ 13 C was lower in September (average −27.9 and −27.7 ‰) compared to July (average −26.2 and −26.3 ‰) in the watershed with a ridge (station 1) and without a ridge (station 6), respectively. Loach δ 13 C in irrigation ponds in September was similar to loach δ 13 C in the paddy field in July at both sampling sites, indicating loach might have moved into irrigation pond from paddy field. Loach δ 15 N in the watershed with livestock was significantly higher (average 18.2 ‰) in the irrigation ponds than loach δ 15 N in the watershed with no livestock present (average 11.3 ‰), probably reflecting higher anthropogenic nitrogen inputs from livestock. Differences in δ 13 C and δ 15 N in the loach reflected changes in habitat utilization of loach between paddy fields and irrigation ponds. Aquatic insect δ 13 C differed from loach δ 13 C but were more similar to carp δ 13 C. The stable isotope inventory approach used in this study could be used to augment or replace a more traditional field based mark–recapture approach.