Food web structure and trophic levels in polyculture rice-crab fields

Abstract

Stable carbon and nitrogen isotopes were used to investigate nutrient pathways and trophic relationships from the rice-crab system in Panjin, Liaoning Province, China. Values of δ 13 C ranged from -27.38‰±0.44‰ to -18.34‰±0.26‰ and δ 15 N ranged from 1.10‰±0.88‰ to 9.33‰±0.57‰. Pseudorasbora parva (Stone moroko) had the highest δ 13 C and δ 15 N values. The lowest δ 13 C values were obtained for the macrophytes and the lowest δ 15 N value was found in sediments. Stable carbon and nitrogen isotopes were used to determine the contribution of different food items to the diets of crabs. The δ 13 C results indicated that the Pseudorasbora parva made the greatest contribution to the diet of Eriocheir sinensis (Chinese mitten crab), while the δ 15 N results indicated that most food items contributed more than 10% to the diet of the crab. There were three trophic levels identifi ed in the system (Levels 0-2). The crab Eriocheir sinensis , fi sh Pseudorasbora parva and Misgurnus anguillicaudatus (Oriental weatherfi sh), and the oligochaete Limnodrilus hoffmeisteri (Limnodrilus worm), were at the second level, zooplankton were at the fi rst level and suspended particulate matter and macrophytes were at trophic position 0.

Impact of Dietary Protein Content on Soil Bacterial and Fungal Communities in a Rice–Crab Co-culture System

“…Although a high protein diet can effectively promote the growth performance and digestive physiology level of mitten crab, it can decrease soil pH from the rice-crab coculture system and negatively impact soil bacteria community diversity. Moreover, formulated feed does not make up a larger portion of the diet of E. sinensis , and excess formulated feed added to the rice-crab system sinks to the bottom of field, which may lead to water pollution ( Guo et al, 2015 ). Therefore, a lower dietary protein level such as ca.…”

Thirty years of rice‐crab coculture in China—Research progress and prospects

“…Hu et al 52 determined that the crab‐rice coculture environment significantly reduced the rate of precocious crab development and enhanced their economic value. Guo et al 53 demonstrated that crabs prey on phytoplankton, algae, zooplankton, weeds and benthic invertebrates in paddy fields. Analyzing crab diets with isotopic 13 C and 15 N, Hu et al 52 found that approximately 59.1% of food ingested by crabs originated from these organisms rather than artificial crab feed, indicating that crabs fully utilize food resources present in the rice‐crab coculture system without supplementation.…”

Ecological engineering for rice pest suppression in China. A review

“…It can reduce fertilizer use by over 30% and pesticide use by 50%, and significantly improve rice quality in terms of no herbicide and less pesticide used, and increasing coarse rice rate, head rice rate, gel consistency, and chalkiness rate of grain quality in rice-duck production systems, compared with the conventional farming model (Huang et al 2014). The ongoing exploration of coculture models means new co-culture models in the rice ecosystem regularly appear, like rice-crab (Guo et al 2015), ricecrayfish (Jiang and Cao 2021), rice-soft shelled turtle (Zhang et al 2016b), and rice-frog (Fang et al 2021) (Fig. 3).…”