SOME ECOLOGICAL PARAMETERS OF ARTEMIA PARTHENOGENETICA GAHAI AND THEIR USED IN RESOURCE EXPLOITATION Author: Sun Jingxian Dalian Fisheries University Dr. Jia Qinxian Research Center for Salt Lakes,Chinese Academy of Geological Sciences Academician. Zheng Mianpin Research Center for Salt Lakes,Chinese Academy of Geological Sciences

SOME ECOLOGICAL PARAMETERS OF ARTEMIA PARTHENOGENETICA GAHAI AND THEIR USED IN RESOURCE EXPLOITATION Theme: Brine shrimp eggs is the indispensable ringent bait for the marine animal breeding.Gahai Salt Lake has an abundant Artemia resource, which should be utilized under reasonable exploitation. Based on the annual water temperature regime of Gahai Saltlake ， forecasting the productivity of the population, estimating the potentiality of the resource exploitation.

MATERIALS Brine shrimp eggs – collected from Gahai Salt Lake. The adults and larvae of Artemia – hatched from dormant eggs. Bait – Dunaliella sp., Phaeodactylum tricornutum and marine Chlorella sp. Salt water – 60‰ salinity.

METHODS AND FORMULAE The setting of the experimental conditions: Except for temperature, the conditions(salinity, bait or etc) were consistent with the nature. – Temperature: Between 16 and 34 ℃ at intervals of 2 ℃,with errors of ±0.3 (the temperature was controlled by ICL-216 temperature controller*, ” * ” see remark). – Salinity: Fixed at 60‰. – Illumination: Natural light. – Breed density: 1000 nauplii were added to each culture chamber filled with 2 liters of salt water (60‰).

Methods and Formulae (con.) Vj = 1/Nj Vi = （ ∑Vj/n ） =1/ （ ∑Nj/n ） = n/∑Nj k = ( m r∑ViTi  ∑Vi∑Ti) /m r∑Vi2  (∑Vi)2 C = (∑Vi2∑Ti  ∑Vi∑ViTi) / m r∑Vi2  (∑Vi)2 R = (∑TiVi  ∑Ti∑Vi/m r) / SQR [(∑Ti2  (∑Ti)2/m r)(∑Vi2  (∑Vi)2/m r)] i = 1,2,…,m  r Degrees of freedom (df) = m  r  r  2 ) = 15  2  2  2 = 26 where: Nj -- development time (d) of the jth sample; Vi -- mean development rate (d -1 ) ; Ti -- experimental temperature ( ℃ ); k -- constant of effective accumulative temperature of a generation (C degree-days); r -- times of repetition at m experimental temperatures; C -- threshold temperature of development ( ℃ ); R -- correlation coefficient; n -- number at each temperature. Based on K=N(T-C),finding the roots by using least square method.The equations are as follows: Threshold temperature of development(C) Constant of effective accumulative temperature(K)

Methods and Formulae (con.) T = (∑l x m x X)/ (∑l x m x ) R o = ∑l x m x r m = log e R o / T = exp(r m ) t = log e 2/ r m where: X -- age (day); l x -- survival rate at X age; m x -- output female offspring number per female adult at X age. Mean generation time (T), population net reproduction rate(R o ),intrinsic rate of natural increase (r m ), infinite rate of increase ( ) and doubling population time (t) were calculated by the following equations (Wu et al.1991) : TEST OF LIFE TABLE

Methods and Formulae (con.) Y = f(X): – The distributing time (X,day) as abscissa,the water temperature (Y, ℃ ) as ordinate, getting the regression equation f(X). – Counting the temperature above the threshold temperature of development for larvae,calculating the range of effective time [0,t] THE DEFINITION FOR GENERATIONS : – Object function (A) – The lower limit (a) – The upper limit (b) Or set a=0, get b; set a=b, get new b; if b>t, the calculation is finished, otherwise repeat calculation. where: X= distributing time (day)

Using the mean effective accumulative temperature of a generation as an object function (A). The growth initiation time of the first generation as the lower limit. The upper limits were calculated with a definite integral equation. Subsequently, using the upper limit as the lower limit of the next generation, we calculated upper limits repeatedly to the time of the borderline of each generation in the range of [0,t]:

RESULTS Temperature adaptability and requirement of the quantity of heat for development – Population Productive Potential – Generations and Water Temperature Population Productive Potential and Water Temperature Ecological Parameters and Water Temperature Life Table on Age Character

Result (con.) Table1: Influence of temperature on the mean development rate of Artemia Temperature ( ℃ ) Hatching(d)The larva(d)Whole life time(d) Mean generation time(d) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± r C( ℃ ) K( ℃ d) 22.91± ± ±57.6 Temperature adaptability and requirement of the quantity of heat for development r -- correlation coefficient C -- Threshold temperature of development K -- Constant of effective accumulative temperature

Temperature adaptability and requirement of the quantity of heat for development We recorded the development rate on each development stage of Artemia at 8 temperatures, as Table 1 shows. The close relationship between the mean development rates and temperature was shown by their correlation coefficient. We can clearly see that the development rates for hatching, nauplius, larvae, and adults were obviously shortened with elevated water temperature and so did the mean generation time. By calculations, the threshold temperature of development (C) and the effective accumulative temperature(K) for hatching were 9.94 ℃ and ℃ ·d, respectively. for the larva were ℃ and ℃ ·d, respectively, and for a whole generation were ℃ and ℃ ·d, respectively.

Result (con.) Temperature( ℃ ) eggs 1000 larvae hypo-adults adults male reproductive rate population reproductive times death rate before adult Table 2: Life table of Artemia on age character Life Table on Age Character 19 ℃ 25 ℃ 34 ℃ mean generation time(d) reproductive rate daily reproductive rate Table 3: Daily reproductive rate of Artemia

Life table on age character Constructing a life table of Artemia at seven temperatures. The amount of eggs, larvae, adults were counted, and the survival rate, reproductive rate were recorded. (As Table2 shows) The death rate before adult marked the adaptability of the population to the environment. The death rate was high at either the higher or lower test temperature,low at the range of ℃. Fitting the death rate with temperature,we got the temperature range for development from larvae to adults.The range is ℃.

The population reproductive times reflected the population potentiality of reproduction. Fitting the population reproductive times with temperature,we got that the population have potentialities of increase at the range of ℃. The maximal potentialities of increase is at ℃. Putting the mean generation time and reproductive rate of each female Artemia together, we get daily reproduction. (As Table3 shows) Because of shorter generation time at higher temperature, daily reproduction was higher, and both total reproductive rate and daily reproduction reached the highest values at the optimum temperature. Life table on age character

Result (con.) Temperature r m (ind. ／♀.d) T(d) Ro(Nt ／ No) λ(/d) t(d) Regression equations Ro ＝ exp( 十 X － X 2 ) F (2.4) =13.99 r m ＝ exp( 十 X － X 2 ) F (2,4) =57.49 λ ＝ exp( － 十 X － X 2 ) F (2.4) =9.20 t ＝ — X 十 X 2 F (2,4) = T ＝ X exp( － X) F (1,5) = Table 4 Main ecological parameters of Artemia in different temperature Some Ecological Parameters of Artemia and Water Temperature

Based on the observation of the process from hatching of eggs to death of adults, the life table of Artemia at seven temperatures were set up. The intrinsic rate of natural increase (r m ), mean generation time (T),the reproduction rate (R o ), finite rate of increase ( ) and the doubling time of population increase (t) of Artemia under different temperature were calculated. The results obtained are as Table4. The regression equations of the 5 parameters with temperature were listed in the table.

Result (con.) Water temperature data from Gahai Saltlake,during and Jul-Aug in The total effective accumulate temperature is ℃ ·d Mean accumulate temperature of generation is  57.6 ℃ -- as an object function value(A) The theoretical number of generations is 2.67±0.34 per year. The threshold temperature is 10 ℃. Generations and Water Temperature

17/3 30 / 11 ⅠⅡ Ⅲ’Ⅲ’ 10/7 10/8 25/4 23/10 Fitting time distribution with water temperature and got equation: Y= X  X 2 (F (2,6) =99.94**) (1) Y= X  X 2 (F (2,6) =99.94**) (2) where: Y= temperature( ℃ ) ; X= generation time(d) 26/8 – The beginning time of each generation: Generation Ⅱ,Jul 10; Generation Ⅲ,Aug 26 ; The last whole generation, Aug 10. Generations and Water Temperature Ⅲ Generation time (d) Fig.1 The generations of Artemia and environmental temperature in Gahai Salt Lake Ⅰ ~ Ⅲ = 1st to 3rd generations ; Ⅲ ’= last whole generation e(℃)e(℃) Dividing the generation time:

Generations and Water Temperature In order to determine the time borderlines for each generation, we further fit time distribution with water temperature and got equation 1,when water temperature was above 10 ℃ got equation 2. The definition of the border line of each generation time calculated from the definitive integral equation was shown in Figure 1 When the temperature was over 0 ℃ in equation 1, the range of time was from 0 to 260(or from March 17 to November 30). The 2nd ~3rd generation began on Jul 10, Aug 26, respectively. The last whole generation began on Aug 10.

Generations and Water Temperature 17/3 30/11 – The reproductive peak number is 4.69±0.43 per year. – Peak of nauplii in first generation was on April 20 th ~28 th. – Last reproductive peak on September 12 th ~17 th. – * Reproductive peak in last whole generation on september 1 st. The nauplii hatched after September 1st can not complete the development from nauplii to adult, because of insufficient habitat effective accumulative temperature. (” * ” see remark) Time of Reproductive Peak Fig.2 The reproductive peak time of Artemia in Gahai Salt Lake Ⅰ ~ Ⅴ = 1st to 5th reproductive peak ; Ⅴ ’= reproductive peak in last whole generation Ⅰ ⅡⅢ Ⅳ ’ 20/4 27/10 18/6 17/7 3/8 12/9 1/9 Ⅳ

Result (con.) THE RESULT INDICATE ： July 11 th to September 20 th high productivity t <30d r m >0.02 d -1. July 11 th to September 20 th the best season for commercial exploitation BASED ON The changes of water temperature with time(Eq.1)Eq.1 The relationships between parameters and temperature(Table.4)Table.4 The r m ， R o ， T ， and t were converted into the relation of time distribution. Population Productive Potential

CONCLUSIONS These methods of estimating the potentialities for exploitation are only available to the lake(like Gahai Saltlake) with broad area and deep depth. The generation of Artemia were closely in relation to water temperature. The diapause eggs of the last generation after the middle Sep can only be exploited appropriately. The eggs before the middle of Jul should be banned.

How to establish the strategy of exploitation Banning the exploitation of Artemia eggs -- before the middle of Jul – The first generation in a year comes from the overwintered eggs,and the population size is limit without complementary until sex-mature. In first generation,the peak of nauplii was on April 20 th ~28 th,the sex maturation was during the first twenty days of Jun. In order to keep the quantity of the population for sustainable increase,the eggs before the middle of Jul should be banned. Exploiting the diapause eggs appropriately -- after the middle of Sep – The last reproductive peak was on September 12 th ~17 th. Because the last generation provides the basis of producing first generation of next year,to assure enough eggs for the population of next year, the diapause eggs of the last generation after September 12 th ~17 th can only be exploited appropriately.

We also limit the time for exploitation by the environmental variation model,which reflected the annual variations of water temperature,salinity and baits in Gahai Saltlake.(the model will soon be published)

Thank you