River-lake migration of fishes in the Dongting Lake area of the Yangtze floodplain

Over the past few decades, fish resources have declined severely owing to the riverlake disconnection within the Yangtze River floodplain. Studies on fish migrations between rivers and floodplain waters are imperative for fish resources restoration and lake management. However, few studies have as yet documented the migration rhythms of riverlake migratory fishes. Monthly investigations of the fish assemblage structure were conducted in three regions of the Dongting Lake, which is connected to the Yangtze River. Main results were: (i) Fish catches varied greatly, depending on the water level and area of the lake; (ii) Ten riverlake migratoty species were caught during the study, 80% of these during JulyOctober when the water level was high. Species richness and relative abundance both decreased with increasing distance from the river, and the timing of peak abundance occurred later in the year; (iii) Abundance of grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) peaked in July and August and were mainly composed of 0+fishes. The results revealed that the key time for migration into the lake is JulyAugust. Combining the results from previous studies, a comprehensive view is given of migration patterns of four domestic Chinese carps; (iv) Brass gudgeon (Coreius heterodon), appeared to migrate into the Dongting Lake as two separate shoals, differentiated by body size. They also appeared to remain close to the lake mouth area. Based on the above results, two recommendations can be made for riverlake migratory fish conservation in the Yangtze floodplain: prolonging the current fishing ban period of AprilJune to AprilSeptember; and opening sluice gates for as long as possible during AprilSeptember in order to maximize the opportunities for fish migration.Over the past few decades, fish resources have declined severely owing to the riverlake disconnection within the Yangtze River floodplain. Studies on fish migrations between rivers and floodplain waters are imperative for fish resources restoration and lake management. However, few studies have as yet documented the migration rhythms of riverlake migratory fishes. Monthly investigations of the fish assemblage structure were conducted in three regions of the Dongting Lake, which is connected to the Yangtze River. Main results were: (i) Fish catches varied greatly, depending on the water level and area of the lake; (ii) Ten riverlake migratoty species were caught during the study, 80% of these during JulyOctober when the water level was high. Species richness and relative abundance both decreased with increasing distance from the river, and the timing of peak abundance occurred later in the year; (iii) Abundance of grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) peaked in July and August and were mainly composed of 0+fishes. The results revealed that the key time for migration into the lake is JulyAugust. Combining the results from previous studies, a comprehensive view is given of migration patterns of four domestic Chinese carps; (iv) Brass gudgeon (Coreius heterodon), appeared to migrate into the Dongting Lake as two separate shoals, differentiated by body size. They also appeared to remain close to the lake mouth area. Based on the above results, two recommendations can be made for riverlake migratory fish conservation in the Yangtze floodplain: prolonging the current fishing ban period of AprilJune to AprilSeptember; and opening sluice gates for as long as possible during AprilSeptember in order to maximize the opportunities for fish migration