**7. Results**

In the adult population were found significant differences (p<0.05) on the average treatment in the daily growth rate, duplication time and mortality. The daily growth rate from T1 to T8 presented the following values: 0.15 ± 0.05b, 0.50 ± 0.05a, 0.33 ± 0.12a,b, 0.23 ± 0.03a,b, 0.31 ± 0.08a,b, 0.33 ± 0.18a,b, 0.40 ± 0.20a,b and 0.19 ± 0.11a cladocerans per day, respectively. The major growth rate occurred on T2 with 0.50 ± 0.05a cladocerans per day, presenting a significant differences p (<0.05) in the treatment T1, that showed a value of 0.15 ± 0.05b cladocerans per day compared with T2 with values of 0.50 ± 0.05a cladocerans per day, as can be seen on table 1.

The duplication time of T1 to T8 had values of 4.96 ± 1.52a, 1.39 ± 0.14 b, 2.31 ± 0.90a,b, 2.99 ± 0.48a,b, 2.27 ± 0.53a,b, 2.80 ± 1.83a,b, 2.10 ± 1.06a,band 4.40 ± 2.43a,b days respectively. This parameter presented significant differences p (<0.05) during the treatment T1, where a duplication time of 4.96 ± 1.52a was observed, in relation to T2 that presented a minor duplication time with 1.39 ± 0.14 b days, as can be seen on table 1.

The mortality rate from T1 to T8 presented the following values: 0.15 ± 0.05 b, 0.49 ± 0.0a, 0.32 ± 0.12a,b, 0.21 ± 0.04a,b, 0.31 ± 0.08a,b, 0.31 ± 0.17a,b, 0.40 ± 0.20a,b, 0.21 ± 0.10a,b, respectively. The highest mortality rate was presented in T2 with 0.49 ± 0.07a cladocerans per day, presenting significant difference p (<0.05) betweenT1 with 0.15 ± 0.05bcladocerans per day with regard to T2 with 0.49 ± 0.07a cladocerans per day (table 2).

Even though there were no significant differences (p>0.05) between the treatment media in the rest of the evaluated parameters, not only in the adult population group, but also the young breeding group, it is important to notice in a general matter, that it was a better population performance in T2 and T6 (tables, 3, 4, 5 and 6). In T2 where growth rate was the highest with 0.37 ± 0.13a cladocerans per day, the minor duplication time with 2.02 ± 0.59a days, and the mayor performance with 1.23 ± 0.46 a cladocerans per period. Likewise T6 presented the highest maximum density and the mayor egg number per female with 15.0 ± 9.76a and 8.25 ± 1.70a cladocerans, and 5.0 ± 0.0 a and 3.83 ± 0.82a eggs per female, respectively. This information can be seen on table 4.

#### **7.1 Population comparisons**

The daily average density (Dmd) of *D. magna* in the adult population was 4.0 individuals per cell and in the population of young breeders were 2.0 individuals. The maximum Doubling Time (Td) in adults was 2.43 days and in the population of young breeders was 12 days. The maximum Performance (r) was, in adults 2.7% and in young breeders 0.58%. The


Dmáx: maximum density; Dmd: Daily media density; k: intrinsic growth rate; Td: Duplicating time; r: Performance. DE= Standard deviation. Different letters indicate statistical difference (p<0.05) between columns, per population.

Table 1. Average ± DE, for population parameters during the evaluated period in two populations of *Daphnia magna,* according to treatment

254 Aquaculture

Additionally, a comparison test with adult population and young breeders was made. To do this, the Mann Whitney test was applied, for the productive variables: daily average density (Dmd), doubling time (Td), specific growth rate (k), performance (r) and biomass productivity (Pw) and for reproductive parameters: egg number/female (HPP), neonates number/female (NPP), litter number (NC), net reproduction rate (Ro) and generation time (Tc). A correlation analysis was completed between the variables. For reproduction net rate and generation time, one way analysis of the variance and the Tukey test took place, in

In the adult population were found significant differences (p<0.05) on the average treatment in the daily growth rate, duplication time and mortality. The daily growth rate from T1 to T8 presented the following values: 0.15 ± 0.05b, 0.50 ± 0.05a, 0.33 ± 0.12a,b, 0.23 ± 0.03a,b, 0.31 ± 0.08a,b, 0.33 ± 0.18a,b, 0.40 ± 0.20a,b and 0.19 ± 0.11a cladocerans per day, respectively. The major growth rate occurred on T2 with 0.50 ± 0.05a cladocerans per day, presenting a significant differences p (<0.05) in the treatment T1, that showed a value of 0.15 ± 0.05b cladocerans per day compared with T2 with values of 0.50 ± 0.05a cladocerans per day, as

The duplication time of T1 to T8 had values of 4.96 ± 1.52a, 1.39 ± 0.14 b, 2.31 ± 0.90a,b, 2.99 ± 0.48a,b, 2.27 ± 0.53a,b, 2.80 ± 1.83a,b, 2.10 ± 1.06a,band 4.40 ± 2.43a,b days respectively. This parameter presented significant differences p (<0.05) during the treatment T1, where a duplication time of 4.96 ± 1.52a was observed, in relation to T2 that presented a minor

The mortality rate from T1 to T8 presented the following values: 0.15 ± 0.05 b, 0.49 ± 0.0a, 0.32 ± 0.12a,b, 0.21 ± 0.04a,b, 0.31 ± 0.08a,b, 0.31 ± 0.17a,b, 0.40 ± 0.20a,b, 0.21 ± 0.10a,b, respectively. The highest mortality rate was presented in T2 with 0.49 ± 0.07a cladocerans per day, presenting significant difference p (<0.05) betweenT1 with 0.15 ± 0.05bcladocerans per day

Even though there were no significant differences (p>0.05) between the treatment media in the rest of the evaluated parameters, not only in the adult population group, but also the young breeding group, it is important to notice in a general matter, that it was a better population performance in T2 and T6 (tables, 3, 4, 5 and 6). In T2 where growth rate was the highest with 0.37 ± 0.13a cladocerans per day, the minor duplication time with 2.02 ± 0.59a days, and the mayor performance with 1.23 ± 0.46 a cladocerans per period. Likewise T6 presented the highest maximum density and the mayor egg number per female with 15.0 ± 9.76a and 8.25 ± 1.70a cladocerans, and 5.0 ± 0.0 a and 3.83 ± 0.82a eggs per female,

The daily average density (Dmd) of *D. magna* in the adult population was 4.0 individuals per cell and in the population of young breeders were 2.0 individuals. The maximum Doubling Time (Td) in adults was 2.43 days and in the population of young breeders was 12 days. The maximum Performance (r) was, in adults 2.7% and in young breeders 0.58%. The

order to compare the life history parameters between the different diets.

duplication time with 1.39 ± 0.14 b days, as can be seen on table 1.

with regard to T2 with 0.49 ± 0.07a cladocerans per day (table 2).

respectively. This information can be seen on table 4.

**7.1 Population comparisons** 

**7. Results** 

can be seen on table 1.


Pw: Biomass productivity; B: Biomass; PB: Productivity index, b: birth rate and d: Mortality rate. DE= Standard deviation. Different letters indicate statistical difference (p<0.05) between columns, per population.

Table 2. Average ± DE, for population parameters during the evaluated period in two populations of *Daphnia magna,* according to treatment


NPP: Neonates per female, NCP: Offspring number, EPR: First reproduction age y FR: Reproduction frequency. DE= Standard deviation. Different letters indicate statistical difference (p<0.05) between columns, per population.

Table 3. Average ± DE, for population parameters during the evaluated period in two populations of *Daphnia magna,* according to treatment

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Pw: Biomass productivity; B: Biomass; PB: Productivity index, b: birth rate and d: Mortality rate. DE= Standard deviation. Different letters indicate statistical difference (p<0.05) between columns, per

Table 2. Average ± DE, for population parameters during the evaluated period in two

populations of *Daphnia magna,* according to treatment

population.


HPP: Egg number, D: Development time. DE= Standard deviation. Different letters indicate statistical difference (p<0.05) between columns, per population.

Table 4. Average ± DE, for population parameters during the evaluated period in two populations of *Daphnia magna,* according to treatment


Pf: Final weight, PN: Numeric average, N prom: Number average. DE= Standard deviation. Different letters indicate statistical difference (p<0.05) between columns, per population.

Table 5. Average ± DE, for population parameters during the evaluated period in two populations of *Daphnia magna,* according to treatment

1 2.36 ± 0.89 a 3.75 ± 1.0 a 1.8 ± 0.50 a 5.0±2.82 a 2 2.26 ± 1.57 a 3.33 ± 0.28 a 1.79 ± 0.34 a 2.5±0.70 a 3 1.72 ± 0.32 a 4.33 ± 0.0 a 2.24 ± 1.04 a 2.85 ± 1.03 a 4 2.53 ± 0.61 a 4.33 ± 2.51 a 3.46 ± 1.07 a 2.77 ± 1.18 a 5 2.7 ± 1.0 a 4.39 ± 1.66 a 3.05 ± 0.97 a 3.41 ± 0.68 a 6 3.83 ± 0.82 a 3.54 ± 0.76 a 3.55 ± 0.98 a 3.36 ± 2.76 a 7 3.23 ± 1.08 a 4.16 ± 1.25a 2.81 ± 1.19 a 2.69 ± 1.33 a 8 3.63 ± 1.17 a 5.20 ± 2.07 a 3.19 ± 1.60 a 2.49 ± 1.37 a

HPP: Egg number, D: Development time. DE= Standard deviation. Different letters indicate statistical

Table 4. Average ± DE, for population parameters during the evaluated period in two

Treatments Female Adult Population Young Breeder Population

N average (Cladoc.) x ± DE

Pf: Final weight, PN: Numeric average, N prom: Number average. DE= Standard deviation. Different

Table 5. Average ± DE, for population parameters during the evaluated period in two

letters indicate statistical difference (p<0.05) between columns, per population.

populations of *Daphnia magna,* according to treatment

1 1.77± 0.26 a 0.70 ± 0.70 a 2.0 ± 1.32 a 2.03 ± 0.0 a 2.67 ± 2.17 a 3.0 ± 2.5 a 2 1.57 ± 0.30 a 3.59 ± 1.28 a 3.75 ± 1.76 a 1.97± 0.0 a 2.64 ± 1.03 a 4.0 ± 1.0 a 3 1.28 ± 0.49 a 3.75 ± 2.03 a 5.37 ± 1.60 a 2.05 ± 0.25 a 1.11 ± 0.0 a 4.0 ± 0.0 a 4 1.70 ± 0.42 a 1.76 ± 0.96 a 4.37 ± 2.52 a 2.03 ± 0.56 a 1.46 ± 1.22 a 2.33 ± 1.15 a 5 1.90± 0.48 a 3.22 ± 1.67 a 4.87 ± 1.25 a 2.01 ± 0.16 a 2.24 ± 2.98 a 3.0 ± 2.59 a 6 1.69 ± 0.21 a 5.13 ± 5.42 a 7.37± 4.85 a 1.89 ± 0.23 a 2.96 ± 0.17 a 4.12 ± 0.85 a 7 1.91 ± 0.14 a 3.49 ± 2.98 a 4.50 ± 3.67 a 1.98 ± 0.16 a 3.44 ± 2.31a 5.0 ± 1.80 a 8 1.78 ± 0.08 a 3.16 ± 2.57 a 5.87 ± 3.56 a 2.66 ± 0.49 a 2.35 ± 1.82 a 3.62 ± 1.43 a

Pf (mg/mL) x ± DE

PN (Ind\*mL) x ± DE

N average (Cladoc.) x ± DE

HPP (N/female/day) x ± DE

D (days) x ± DE

Treatments Female Adult Population Young Breeder Population

D (days) x ± DE

HPP (N/female/day) x ± DE

difference (p<0.05) between columns, per population.

Pf (mg/mL) x ± DE

populations of *Daphnia magna,* according to treatment

PN (Ind\*mL) x ± DE


Ro: Reproductive net rate; Tc: Regenerating time. DE= Standard deviation. Different letters indicate statistical difference (p<0.05) between columns, per population

Table 6. Reproductive net rate, regenerating time in two populations of *Daphnia magna,*  according to treatment

Specific growth rate (k) was 0.65 cladocerans per day in adults and 0.52 in young breeders. The maximum Biomass (B) was 24.73 mg/cell in adults and 13.22 mg/cell in the population of young breeders.

Adult *D.magna* presented a maximum value of 27 neonates/ adult female per each volume unit during the evaluation period, different from the population of young breeders when their fecundity levels reached 12 neonates/female.

The offspring maximum number was 6 offspring/period for the adult population, and 4 offspring/period for the population of young breeders. The maximum age for the first reproduction was 7 days in adults, meanwhile in the population of young breeders was 16 days. The maximum level of reproduction frequency in the adult population was 216 hours and for the population of young breeders was 120 hours.

In the following figures 3 and 4, a µ adjustment or specific growth rate founded experimentally can be observed. The regression coefficient for the treatments on the adult population oscillated between r (0.8966 – 0.9364). The dots in both graphics correspond to the experimental data and the curves correspond to de adjustments. In the graphics the differences in the growth rate for both populations can be observed as well. Note that the adult population it is found in a reproductive process and growth in the beginning of the experiment, meanwhile the population of neonates must conquer its maturity to initiate reproduction and growth.

Figs. 3. and 4. Population growth of *D. magna*. The trajectory shows an exponential growth with µ values common for cladocerans. Correspond to nutritional situation, specific conditions of each treatment, depreciable mortality and water temperature closed to 20°C.

#### **7.2 Interactions**

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**Teoric values of µ per tratament in adults** 

**of** *D.magna*

T1 T2 T3 T4 T5 T6 T7 T8

T1 T2 T3 T4 T5 T6 T7 T8

0 5 10 15 20

**Days**

**Teoric values of µ per tratament in juvenile** 

**reproductive** *D.magna*

1

1

2

3

**Daphnia/cells**

4

5

2

3

**Daphnia/cells**

4

5

Figs. 3. and 4. Population growth of *D. magna*. The trajectory shows an exponential growth with µ values common for cladocerans. Correspond to nutritional situation, specific conditions of each treatment, depreciable mortality and water temperature closed to 20°C.

0 5 10 15 20

**Days**

Even though there was not statistic relation (p>0.05) between the parameters of maximum density, daily media density and final weight on the adult population, there was a nutrient significant correlation (p<0.05): The yeast nutrient was highly significant (p<0.01) on the 30 ppm concentration, on the maximum density with 11.46 ± 6.79 cladocerans per volume, while the treatments with a concentration of 15 ppm of yeast, had 6.7 ±4.43 cladocerans per volume, on a concentration of 30 ppm. Similarly happened with the final weight, that presented values of 1.63 ± 0.35 mg in 15 ppm and 1.82 ± 0.26 in 30 ppm, presenting a mayor value on final weight on the diet with 30 ppm yeast concentration.

A highly significant relation was found (<0.01) between the three nutrients. With yeast and potato, with concentrations of 30 ppm and 15 ppm respectively, the highest value on the variable maximum density was found, with 12.62 ± 7.0 cladocerans per volume. The daily media density presented significance (p<0.05) in the relation between the potato and the enrichment, presenting the highest value for 1.85 ± 0.7 cladocerans per volume per day, in the concentrations of 30 ppm and 15 ppm respectively. The daily media density does not seem influenced by yeast addition.

The mortality rate presented significant differences in relation with yeast and enrichment nutrients. The mayor mortality was shown in the treatment with yeast 30 ppm and enrichment of 15 ppm with 0.31 ± 0.12 cladocerans per day. Also it was a highly significant difference (p<0.01) with 0.37 ± 0.16 using potato and enrichment nutrients in the same concentration of 15 ppm. It seems that enrichment concentrations have an impact in the mortality of adult populations of cladocerans.

About the relation of nutrients found in the growth rate, duplication time and performance, two of the three nutrients presented a highly significant relation, in the adult population. The growth rate presented its highest value with 0.38 ± 0.16 per day, in concentrations of 15 ppm and 30 ppm of potato and enrichment respectively, followed by the concentrations of 30 ppm and 15 ppm of yeast and enrichment respectively, with a maximum value of 0.36 ± 0.15 per day.

In the variable duplicative time highly significant differences were observed p (<0.01) reputedly in two nutrients, as follows: In yeast and enrichment nutrients, with 30 ppm and 15 ppm concentrations respectively, the minor duplicative time was observed with 2.18±0.7 days. Additionally, with potato and enrichment nutrient, with concentrations of 30 ppm and 15 ppm respectively, a duplicative time of 2.21± 0.9 days was presented.
