Annual Production And Reproductive Characteristics Of Corbicula Fluminea In Datong Lake In Hunan Province

Corbicula fluminea (Miiller,1774) is a major native component of benthic communities in Datong Lake, Hunan Province, China. The fishing of C. fluminea has been increased gradually for these years in Datong Lake due to the higher economic benefits. At the same time, the C. fluminea individual miniaturization has happened, fishery harvert and distribution area has declined rapidly. In order to achieve effective conservation, resource recovery and sustainable usage of C. fluminea, the present study has investigated the population dynamics, annual secondary production and reproductive biology of C. fluminea in Datong Lake. The main results were as follows:1. The calculated length (SL)-weight (WW) equation was log WW=-3.52+3.08 log SL (R2=0.97, N=4,108, P<0.05), the morphometric relationship between WWISL (b= 3.081) indicated positive allometric growth. The recruitment pattern peaked in March-April and August-October analyzed from monthly length frequency histograms of C. fluminea.2. The annual mean abundance and biomass were 274 ± 95 ind. m-2 and 20.1 ± 5.7 g AFDW (Ash Free Dry Weight) m-2, respectively. Monthly mean abundance and biomass showed lower values in spring and summer months, and higher values in autumn and winter months.3. Population parameters derived from the von Bertalanffy Seasonal Growth Formula (VBSGF) were estimated at L8=31.91 mm,K= 0.45 year-1, C= 0.84, WP=0.09. Growth varied apparently with seasons, the slowest growth period was in January and February. C. fluminea was composed of 4 age classes at least recognized from the seasonal growth curve.4. Total mortality (Z), natural mortality (M), fishing mortality (F) and exploitation rate (E) were estimated at 1.68 year-1,0.89 year-1,0.79 year-1 and 0.47 year-1, respectively. Which indicated overfishing is one of the most important reasons leading to death for C. fluminea in Datong Lake. The potential lifespan was calculated to be 4.44 years.5. Tissue dry weight and ash free dry weight converted from wet weight with shell were more precise (the percentage error being 22.8% and 21.7%, respectively) than the other parameters. In conclusion, wet weight with shell could be directly converted to dry weight for C. fluminea in Datong Lake using y=ax.6. The annual production of C. fluminea calculated by the size-frequency method and Brey’s empirical formula were 19.52 g AFDW m-2 year-1 and 16.20 g AFDm-2 year-1, respectively, and corresponding annual P/B ratio were 1.22 and 0.81, respectively.7. Most of C. fluminea were hermaphrodite, and there existed six development stages of gonad in the reproductive cycle, including proliferating stage, growing stage, maturing stage, spawning stage, restoration stage and resting stage. The two main spawning activity for C. fluminea were one in March-Augest and another in Augest-November, with the major peaks on April-May and September-October, respectively.