The concentration of polychlorinated biphenyls (PCB, an organochloride contaminant) in many fish population has been declining, since a ban on their production was instituted in the late 1970s. PCBs remain a potential problem, however, because they are lipophilic and are know to biomagnify. Based on this knowledge, what type of fish is expected to be safest for human consumption ?

Options

A. Piscivorous fish species (i.e., which eat other fish)
B. Benthivorous fish species (i.e., which eat invertebrates on the lake bottom )
C. Small (young ) fish
D. Fish species with high fat content

Explanation

To determine the safest type of fish for human consumption in relation to polychlorinated biphenyls (PCBs) and their biomagnification in aquatic food chains, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Biomagnification**:
- Biomagnification refers to the process where the concentration of a substance, such as PCBs, increases in organisms at each successive trophic level of the food chain. This means that organisms higher up in the food chain accumulate more toxins than those lower down.

**Hint**: Remember that biomagnification leads to higher concentrations of pollutants in organisms as you move up the food chain.

2. **Identify Trophic Levels**:
- Fish can be categorized based on their feeding habits into different trophic levels. Generally, the lower the trophic level, the less exposure to accumulated toxins. For example, primary producers (like phytoplankton) are at the base, followed by herbivorous fish, then carnivorous fish.

**Hint**: Think about how fish are categorized based on what they eat – this will help you identify their trophic levels.

3. **Evaluate Fish Types**:
- Consider the types of fish mentioned:
- **Piscivorous fish**: These are fish that eat other fish and are typically higher up in the food chain (higher trophic level).
- **Bentivorous fish**: These fish feed on invertebrates at the bottom of the lake, which may also be at a higher trophic level.
- **Small, young fish**: These fish are usually at the lowest trophic level and consume primary producers or small invertebrates.
- **Fish with high fat content**: These are often larger, older fish that are also higher in the food chain.

**Hint**: Focus on which fish are at the lowest trophic levels, as they will have the least accumulation of toxins.

4. **Determine the Safest Option**:
- Given the understanding of biomagnification and the evaluation of fish types, small, young fish are expected to be the safest for human consumption. They are at the lowest trophic level and therefore have the least accumulation of PCBs.

**Hint**: The safest fish for consumption will be those that are lower in the food chain, not those that eat other fish or have high fat content.

5. **Conclusion**:
- The type of fish expected to be safest for human consumption, based on the information about PCBs and biomagnification, is small, young fish.

**Final Answer**: Small, young fish (Option 3).