Construction Of Individual Growth Model And Estimation Of Carrying Capacity Of Ruditapes Philippinarum In Jiaozhou Bay

China is the dominant country of shellfish farming.In 2018,the total output of marine shellfish was 14.44 million tons,ranking first in the world.In China,the main target of marine shellfish farming is bivalves,whose output accounts for 97%of the total output of marine shellfish.The total output of Ruditapes philippinarum are more than 3million tons,accounting for 90%of the global output.Jiaozhou Bay is an important large-scale aquaculture bay for R.philippinarum in northern China.The output of clams are325 thousand tons,accounting for 90%of the world.In April 2017,Academician Tang Qisheng and 25 well-known experts in the aquaculture industry formed a proposal of the Chinese Academy of Engineering entitled"Proposal on Promoting Green Development of Aquaculture Industry".The core of the proposal was to call for the establishment of"aquaculture capacity management system".Under such a background,it is of great theoretical and applied significance to carry out the research on the individual physiology and carrying capacity of shellfish.This study explored the temporal and spatial distribution of main environmental factors in Jiaozhou Bay,simulated the combined effects of water temperature and body size on the physiological activities of R.philippinarum,and developed an individual growth model for R.philippinarum.Finally,the static Herman model and the dynamical ecosystem model were used to estimate the carrying capacity of R.philippinarum in Jiaozhou Bay,respectively.The main results are as follows:1.Temporal and spatial distribution of main environmental factors in Jiaozhou Bay.From July 2017 to April 2018,this study set up four large-area observation on the Jiaozhou Bay and its surrounding waters.the temporal and spatial distribution of the main environmental factors in Jiaozhou Bay were analyzed based on the survey data of water temperature,potential of hydrogen,dissolved oxygen,transparency,particulate organic matter,phytoplankton,and nutrients?nitrates,nitrites,ammonium,phosphate?.The results showed that there were significant seasonal differences in water temperature,dissolved oxygen,transparency,particulate organic matter and phytoplankton except for potential of hydrogen in jiaozhou bay.In spatial distribution,the water temperature decreased from the bottom of the bay to the mouth of the Bay in spring and summer,but in autumn and winter.The potential of hydrogen distribution was relatively uniform in all seasons.Except for spring,there are significant temporal and spatial differences in dissolved oxygen in other seasons.On the whole,it has the characteristics of small transparency in the near shore and large in the far shore.The concentrations of particulate organic matter was significantly different in four seasons,and spatial differences in summer were more significant than in the other three seasons.The concentration of phytoplankton was high near shore and low far shore.2.Combined effects of water temperature and body size on the physiological activities of Manila clam Ruditapes philippinarum.By using central composite experimental design and response surface methodology,the joint effects of water temperature?5?25??and body size?0.12?0.52g tissue dry weight?on the clearance rate,oxygen consumption rate and ammonia excretion rate of Manila clam R.philippinarum were studied.The results showed that there were significant interactive effects between water temperature and body size on the clearance rate and oxygen consumption rate of R.philippinarum?P<0.05?,but the effect on the ammonia excretion rate was nonsignificant?P>0.05?.The model equations of clearance rate,oxygen consumption rate and ammonia excretion rate towards the two factors are as follows:CR=1.8096+1.0158T-0.9957DW-0.6412T·DW-0.5347T²+1.2941DW²;OR=0.4693+0.5081T-0.2946DW-0.2586T·DW-0.0686T²+0.2197DW²;NR=1.8938+0.6864T-0.6978DW-0.0367T·DW-0.2562T²+0.5698DW²,with the determination coefficients are 0.8705,0.8702 and 0.9207,respectively.3.Simulation and validation of Manila Clam Ruditapes philippinarum growth with a DEB-based individual growth model in Jiaozhou Bay.An individual growth model for R.philippinarum were developed based on dynamic energy budget?DEB?theory.Seawater chlorophyll a concentration and temperature were considered as forcing variables and data were collected from April 24,2018 to January 9,2019.The DEB parameters for the clam were calculated based on field experiment measurements and previous reported data from literatures.The growth of dry tissue weight and shell length of R.philippinarum were simulated with the model Field observations?dry tissue weight and shell length?were used to testify the validate and sensitivities of the clam-DEB model.The simulated results from the clam-DEB model are well fitted with the observed results.Regression analysis showed that there was a significant?P<0.01?linear correlation between the simulated and observed values of dry tissue weight and shell length?R²=0.9374 and 0.9168,respectively?.The model was relatively sensitive to the variations of T_A and T₁.If T_A and T₁ increased by 10%,the dry tissue weight of the clam would increase by 8.86%.4.Spatial and Temporal Distribution of Chlorophyll a and Estimation of Carrying Capacity of Manila Clam?Ruditapes philippinarum?in Jiaozhou Bay.During July 2017 to April 2019,this study used a combination method of large-area observation,field simulation experiment and growth tracking to estimate the carrying capacity of Manila clam?R.philippinarum?based on Dame Indexes and Herman Model in Jiaozhou Bay.The results showed that the chlorophyll a concentration in Jiaozhou bay was between 2.09 and 4.28,with an average value of 3.07.The average clearance rate was 0.45 per unit and 2.52 per unit weight for Manila clams of different sizes?shell length between 2.29 and 3.59cm?.The average dry weight of Manila clams at 1,2 and 3 ages were 0.18,0.30 and 0.42g,respectively.The water mass residence time was 52 days,the primary production time was 1.58 days,and the bivalve clearance time was 2.09 days in Jiaozhou bay.The carrying capacity of Manila clam at the 1,2 and 3 ages was 637,378and 272 ind./m².,respectively.At present,the cultivation quantity of Manila clams has exceeded the carrying capacity.It is suggested that if clams of 2 years old are taken as the collection object,the suitable seedling density is 582,and if clams of 3 years old are taken as the collection object,the suitable seedling density is 789 ind./m².5.An dynamical ecosystem model for estimating carrying capacity of Manila Clam?Ruditapes philippinarum?in Jiaozhou Bay.In this study,the individual growth model of R.philippinarum and biogeochemical model were coupled to build the NPDZ-B dynamical ecosystem model of Jiaozhou Bay,and the carrying capacity of R.philippinarum was estimated dynamically.The simulated partial results from the dynamical ecosystem model are well fitted with the observed results.Regression analysis showed that there was a significant?P<0.01?linear correlation between the simulated and observed values of clam wet weight and phytoplankton concentration?R²=0.9348 and 0.9264 respectively?.The results of the carrying capacity estimation show that the seeding density should be less than 1000ind./m² if clams are harvested within the expected culture time,.According to the maximum profit,the suitable seeding density is 550-750 ind./m².