Study On Early Fish Resources At Huangshi Section In The Middle Reaches Of The Yangtze River

The Huangshi section in the middle reaches of the Yangtze River serves as habitat sites,spawning grounds for many kinds of major economic fishes such as the four Chinese major carps and Parabramis pekinensis,meanwhile is also important passage for migrating fishes.In order to estimate the abundance,the species composition and the spawning grounds distribution and graspe the spatial distribution characteristics of larvae,we monitored the early fish resources at Huangshi section from May to July in 2015 and 2016.Main results are as follows:1?In 2015 and 2016,a total of 597 eggs and 2385 thousand fish larvae were collected,and identified to 34 species,9 families,6 orders.There were an estimated amount of(1655.3×10~8)larvae and(6.7×10~8)eggs drifting through the Huangshi section in 2015,while those were(1620.05×10~8)larvae and(19.02×10~8)eggs in 2016.2?The composition of the larvae species showed itself different temporal dynamics.Culterinae fishes had an absolutely advantage during the investigation.The proportion of Hypophthalmichthys molitrix was lower in May and increased gradually later.Pseudolaubuca sinensis had a greater advantage in May and June.Pelteobagrus fulvidraco and Siniperca chuatsi mainly distributed in June and July.Rhinogobius sp had been captured during the whole sampling period,but mainly occured in May.3?There were an estimated average amount of(2.45×10~8)eggs and(16.53×10~8)larvae of the four Chinese major carps drifting through the Huangshi across section in 2015and 2016.the spawning grounds of the four Chinese major carps were estimated at Lijiazhou section of Tuanfeng couty,Ezhou section,Daijiazhou section of Ezhou city and Daoshifu section of Huangshi city,respectively,and the average spawning sizes were(1.05×10~8)ind?(0.20×10~8)ind?(0.90×10~8)ind?(0.15×10~8)ind.4?There were an estimated average amount of(2.79×10~8)eggs of Parabramis pekinensis drifting through the Huangshi across section in 2015 and 2016.The spawning grounds of Parabramis pekinensis were estimated at five sections,which accumulative mileage was 80 km.Lijiazhou and Daijiazhou sections were the main spawning grounds among the five,and the average spawning sizes were(0.71×10~8)ind?(0.73×10~8)ind.5?A total of 12331 fish larvae were collected among three watercourses with different patterns,the highest density of larvae was observed in the meander watercourse,and then in the bifurcation and the straight.6?The characteristics of the spatial distribution for fish larvae in the three watercourse were similar,which the nearshore had the highest density of larvae whereas the middle had the lowest in horizontal distribution,and the surface water layers had the highest whereas underlying the lowest in vertical distribution.The distributions of larvae with different development stages presented a regular pattern that larvae of the yolk exhausting stage preferred to live around the shallow water in the near shore.