Study On The Investigation Of Main Economic Fishery Resource And The Law Of Its Variety In The Dongting Lake

The Dongting Lake closely follows the largest freshwater lake inChina. It is the largest filtrating lake and an important bank of natural fishspecies in the Changjiang River. But many factors, such as ecologicalenvironment of fish destroyed, fishery resource irrational exploited andetc, lead fishery resource to greatly decline in the Dongting Lake. Thispaper really shows the situation of present fishery resource, affectedfactors and variety trend with the accurate data. Many things have beenanalyzed, such as the catching production of main fishes, the constructionof fish species, the composition of fish ages and the investigation relatingto the place of producing eggs and seeking food in 1997-2005. Theresults are followed:The catching production of the Dongting Lake (which was at the peakin 1990s) has trended to decrease, while the fishery resource has beendestroyed since the initial stages of 21 century. 80 percent of the maineconomic fish resource was destroyed. Nowadays, Most of fishes belongto lacustrine fishes in the Dongting Lake, the catching production of threefishes, common carp, crucian carp and parasilurus is 62.38 percent in thetotal catching, whose catching takes up to the first, the second and thethird in the total catching respectively. The lower age fish is the maincomposition in the Dongting Lake's catching. As the main catching, the number of producing eggs place little increases, whichbelongs tocommon carp and crucian carp. The area of their producing eggs placetrends to decrease, so does the area of their food place.The catching production is greatly affected by five main factors in theDongting Lake. It resulted in decreasing 39.66 percent of the DongtingLake's area and 43 percent of its capacity. The first is that sludge andover-reclamation lead the area of the Dongting Lake to great decrease.The place of fish producing eggs and growing reduces fast. The second isthat over-catching leads fishery resource to decline in the Dongting Lake.The third is that the migrating line of fish is cut off by water engineering.Over 80 percent of fry production of "Four Demestic Fish" was decreasedby the Sanxia's dam cutting off water flowing. The place of fishproducing eggs is seriously destroyed. The fourth is that water quality isdeteriorated by polluted water in the Dongting Lake. The fishery resourceis greatly destroyed. The fry growing and developing are affected directly.The fifth is that the fishery resource is also threatened by the immigrationspecies in the Dongting Lake.The current fishery resource situation and its trend were known by thestudy of the Dongting Lake's fishery resource in this paper. Many factorswere known as leading to Dongting Lake's fishery resource declining. Itbecame available that the effects of Sanxia's water engineering acting onthe lake's fishery resource of Changjiang River were correctly evaluated. Based on it, to develop sustably and protect Dongting Lake's fisheryresource, some rational suggestions are followed: Fist, it is an importantway to plant trees in the place along Changjian River and "Four WaterSystem", by which water and soil are prevented from draining whilelessening Dongting Lake's fisher area slowers. Second, the current fisheryresource situation should be known more by investigating the fisheryresource in the Dongting Lake throughly. Third, Enforce protecting andmultipicating fishery resources while the fry are artifically put in lakes.Fouth, Protecting Nature Region should be built around Dongting Lakeby the chance of the government greatl dealing with Dongting Lake. Fifth,develop the general thought of environment conservation bypropagandizing it absolutely in the midia. Sixth, fasten steps in disposingpolluted water in the Dongting Lake. Seventh, in order to reduce thedamage of alien species, it is necessary to monitor the introduction ofalien species.