The construction of migration crab passageways and the carapace length-weight relationships of migratory <i>Eriocheir sinensis</i> H. Milne Edwards, 1853 (Decapoda: Brachyura: Varunidae) in the Yangtze River, China

Abstract The Chinese mitten crab, Eriocheir sinensis H. Milne Edwards, 1853, is a migratory species critical to both aquatic ecosystems and aquaculture in China. We investigated the construction of migration passageways through floodgates and examined the length-weight relationships of E. sinensis in the Yangtze River. In response to declining migratory numbers due to fishing and infrastructural barriers, we developed and implemented two types of crab passageways at the Sanchahe River Gate in Nanjing, China: vertical passageways made of burlap cloth and a horizontal passageway constructed from stainless steel and canvas. We observed that crabs could successfully use these passageways, with increased migration activity at night. We analyzed 490 crabs, comparing individuals from the Yangtze River and aquaculture ponds. Results showed that Yangtze River crabs exhibited isometric growth, whereas pond crabs displayed both isometric and negative allometric growth patterns. Additionally, Yangtze River crabs were generally wider at the same length than their pond counterparts. The findings highlight the effectiveness of the constructed passageways in facilitating crab migration and provide new insights into the growth dynamics of E. sinensis. This research contributes to our understanding of crab migration and offers practical guidance for future conservation and aquaculture efforts.