Oil slick causes mass-scale death of fishes due to

Options

A. Clogging of gills
B. Disruption of food chain
C. Non-availability of food
D. All of these

Answer

### Step-by-Step Solution:

1. **Understanding Oil Slick**: An oil slick is a layer of oil that floats on the surface of water bodies, often resulting from oil spills due to accidents involving ships or drilling activities.

2. **Impact on Aquatic Life**: When an oil slick forms, it creates a barrier on the water surface. This barrier prevents the normal exchange of gases, particularly oxygen, which is essential for aquatic life, including fish.

3. **Fish Respiration**: Fish breathe through gills, which are specialized structures that extract oxygen from water. Water flows over the gills, allowing oxygen to diffuse into the fish's bloodstream.

4. **Clogging of Gills**: When fish attempt to breathe in water that is contaminated with oil, the oil can clog their gills. This clogging prevents the gills from functioning properly, inhibiting the fish's ability to extract oxygen.

5. **Suffocation of Fish**: Due to the inability to extract oxygen from the water because of the clogged gills, fish become suffocated. Without oxygen, their internal organs cannot function, leading to mass-scale death among fish populations.

6. **Conclusion**: Therefore, the mass-scale death of fish due to an oil slick is primarily caused by the clogging of their gills, which prevents them from obtaining the necessary oxygen for survival.

### Final Answer:
Oil slick causes mass-scale death of fishes due to the clogging of the gills.

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