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Over the past few decades, fish resources have declined severely owing to the river-lake 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 river-lake 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 river-lake migratoty species were caught during the study, 80% of these during July-October 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 July-August. 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 river-lake migratory fish conservation in the Yangtze floodplain: prolonging the current fishing ban period of April-June to April-September; and opening sluice gates for as long as possible during April-September in order to maximize the opportunities for fish migration. [ABSTRACT FROM AUTHOR]

The present study was performed to investigate the effects of a commercially available probiotic product (compound probiotic) containing Bacillus subtilis 7.0 × 109 CFU g−1, Bacillus licheniformis 3.0 × 109 CFU g−1, Lactobacillus spp. 5.0 × 108 CFU g−1 and Arthrobacter spp. 1.0 × 108 CFU g−1 on the growth performance, non-specific immunity and protection against Vibrio harveyi infection in cobia ( Rachycentron canadum). Fish were fed diets containing six graded levels of compound probiotic (0.0, 1.0, 2.0, 3.0, 4.0 and 5.0 g kg−1) for 8 weeks. The results showed that the survival rate ranged from 81.1% to 84.4% with no significant difference among dietary treatments ( P > 0.05) after feeding experiment. Dietary compound probiotic significantly increased the specific growth rate (SGR), serum lysozyme, alternative complement pathway (ACP) activity, phagocytosis percentage (PP) and respiratory burst activity of head-kidney macrophages of cobia. Moreover, feeding of supplemented diets containing compound probiotic resulted in significantly lower mortality against the pathogens Vibrio harveyi compared with the control group. To elevate the growth and immune resistance ability of cobia, an optimal dose of dietary compound probiotic administration determined by second-order polynomial regression analysis was 3.3 g kg−1, on the basis of the SGR and mortality after challenge with V. harveyi. [ABSTRACT FROM AUTHOR]