Passage 3 · Science Quiz 3
Amphiprion percula, a species of clownfish, are kept in many home aquariums. Two experiments were conducted to determine how diet and stocking density (number of fish per liter of seawater, fish/L) affect the specific growth rate (SGR; percent increase in length per day, percent/day) in A. percula.
Experiment 1Each of 12 identical 15 L tanks received 10 L of seawater having a salinity of 33 parts per thousand (ppt), a temperature of 27° degrees C, and a pH of 8.2. Salinity, temperature, and pH were kept constant over the course of the experiment. A. percula of similar lengths were selected, and their lengths were measured, in cm, with a ruler. Then they were equally distributed among the tanks at a stocking density of 1 fish/L. The tanks were then divided equally into 4 groups.
For 4 months, each group was fed a different diet (Diets Q–TQ through T). Each group was fed the same mass of food 3 times daily. At the end of 4 months, the length of each fish was measured, in cm, with a ruler, and the SGR of each fish was calculated. The average SGR was then determined for each group (see Table 1).
Table 1| Diet | Average SGR (percent/day) |
|---|---|
| Q | 0.30 |
| R | 0.40 |
| S | 0.50 |
| T | 0.35 |
The procedures for Experiment 1 were repeated except that each group was kept at a different stocking density, 0.5 fish/L, 1 fish/L, 2 fish/L, or 3 fish/L, and all fish were fed Diet T. At the end of 4 months, the average SGR was determined for each group (see Table 2).
Table 2| Stocking density (fish/L) |
Average SGR (percent/day) |
|---|---|
| 0.5 | 0.50 |
| 1 | 0.35 |
| 2 | 0.25 |
| 3 | 0.20 |
Tables adapted from João Chambel et al., “Effect of Stocking Density and Different Diets on Growth of Percula Clownfish, Amphiprion percula (Lacepede, 1802).” ©2015 by Springer.
Suppose that, in the experiments, 1 g of food were added to each tank at each feeding. A total of how many grams of food would have been placed into an individual tank each day?
Correct answer: G
Explanation
F. Incorrect. As stated in the question, this is the amount of food placed into a tank at each feeding. However, it is not the total amount of food placed into a tank each day because the description of Experiment 1 indicates that each group of fish was fed 3 times daily.
G. Correct. The description of Experiment 1 indicates that each group of fish was fed the same mass of food 3 times daily. Therefore, if 1 g of food had been added to each tank at each feeding, then 3 g of food would have been placed into an individual tank each day.
H. Incorrect. This is the amount of food used for 1 feeding in each experiment (1 g of food placed in each of 12 tanks).
J. Incorrect. This is the amount of food used each day in each experiment (1 g of food placed in each of 12 tanks 3 times each day).
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