They use a internal pouch which is named swim bladder. 
Explanation; Oxygen will enter a fish’s mouth, and passes through their gills. The oxygen will be taken and gets carried by hemoglobin through their bloodstream. Hemoglobin will take out some of the oxygen into their swim bladder. The amount of oxygen will show if they will sink or rise. Your question is how do they rise. If he goes up too much, the meaning of this is when the gas diffuses into their blood and out the gills. 
Got this from a writing, but rephrased it.
        
                    
             
        
        
        
Answer:
a. Determine the allele frequencies of: 
f(T) = 0.485 ≅ 0.48
f(t) = 0.515 ≅ 0.52
b. Determine the genotype frequencies of the exposed generation
- F (TT) = 0.21
 - F (Tt) = 0.55
 - F (tt) = 0.24
 
the genotype frequencies of the next generation
- F(TT) = 0.23
 - F(Tt) = 0.5
 - F(tt) = 0.27
 
Explanation:
Due to technical problems, you will find the complete answer and explanation in the attached files
 
        
             
        
        
        
Answer:
1. C. Animals on land are very different from those in the sea
2. B. The shrimp could move to a new feeding ground
3. C. 300 feet
4. Unsure, but if I were to guess C. There is a similar environment
5. C. role in the food chain
Explanation: