[Spatiotemporal variations of fish feeding guilds in Yellow River basin]. / 黄河流域鱼类食性同资源种团的时空变化.

Conservation of fish resources is the key to ecological protection and high-quality development of Yellow River basin. From 1960 to 2019, Yellow River basin distributed 201 fish species, belonging to 16 orders, 35 families. The species number of Cypriniformes was the largest (accounting for 60.7%), followed by Perciformes (accounting for 10.0%). From 1960 to 1980, there were 182 fish species belonging to 15 orders, 28 families. During 1980-2019, there were 112 species, belonging to 10 orders, 23 families. The total number of fish species in source area, midstream and downstream decreased significantly, while that in the upper reaches increased slightly. Jaccard's similarity index of source area, upstream, midstream and downstream between two periods were 34.2%, 46.0%, 42.4% and 35.7%, respectively. Based on feeding preference characteristic, fish species could be divided into eight feeding guilds: phytobenthivores, herbivores, phytoplanktivores, zooplanktivores, omnivorous, insectivores, zoobenthivores, and piscivores. Compared with the period from 1960 to 1980, the proportion of insectivores decreased significantly in the Yellow River basin during 1980-2019, while that of phytobenthivores, herbivores, phytoplanktivores, omnivorous and piscivores increased significantly. From 1960 to 1980, the proportion of insectivores was higher than other reaches at source area and upstream, then began to decrease along the river continuum from reaches with elevation of 2000-3000 m; while the proportion of piscivores was lower than other reaches at source area and upstream, then began to increase along the river continuum from reaches with elevation of 2000-3000 m. From 1980 to 2019, the proportion of insectivores decreased along river continuum from source area, and that of piscivores increased from source area to midstream but decreased in downstream. Development of cascade hydropower, water pollution, insufficient water flow, overfishing and invasion of alien fish were important factors causing the spatiotemporal variations of fish feeding guilds in Yellow River basin.

[Physiological response of Neocaridina denticulate to the toxicity of Cu2+ and chlorpyrifos].

In order to study the physiological response to heavy metals and organic-phosphorus pesticide toxicity of aquatic organisms, Neocaridina denticulate was used as a test organism to investigate the impact of physiological indices of N. denticulate muscle tissues when they were exposed to Cu2+ and chlorpyrifos for 5 days respectively with the test methods of semi-static toxicity. The results showed that: when exposed to different concentrations of Cu2+ and chlorpyrifos solutions, the protein concentrations in muscle tissues were significantly lower with the extension of time to varying degrees. In the lower concentration groups of Cu2+ (0.086 mg x L(-1) and 0.172 mg-L-') and the higher concentration groups of chlorpyrifos (0. 006 0 [g-L-' and 0.012 0 µg x L(-1)), the total SOD activity showed inhibitory effect; the trend of the higher concentration group of Cu2+ (0.344 mg x L(-1) and 0.688 mg x L(-1)) showed " inhibition-promotion-inhibition", however, the lower concentration groups of chlorpyrifos (0.001 5 µg x L(-1) and 0.003 0 µg x L(-1)) showed the" inhibition-promotion" changes in trends; MDA contents changed similarly, and within a certain range of concentrations, MDA contents presented a gradually rising trend with increasing Cu2+ and chlorpyrifos concentration, which indicated that Cu2+ and chlorpyrifos accelerated lipid, peroxidation in muscle tissues of N. denticulate. In addition, AChE activity in Cu2+ and chlorpyrifos solutions showed inhibitory effect, and in the solutions with higher concentration of Cu2+ and chlorpyrifos, the activity was gradually decreased with the increase of concentration, indicating that Cu2+ and chlorpyrifoscs impacted the normal physiological functions of N. denticulate, and the higher the concentration, the greater the damage effect. Based on the analysis results, we confirmed that the total SOD, MDA and AChE played significant roles as physiological indicators in evaluating toxic effect of heavy metals and organic-phosphorus pesticide on N. denticulate.