What is the Difference Between Anadromous and Catadromous Fish

The main difference between anadromous and catadromous fish is that anadromous fish is born in freshwater, spends most of its life in seawater and then, returns to freshwater to spawn whereas catadromous fish is born in seawater, spends most of its life in freshwater and then, returns to seawater to spawn.

Anadromous and catadromous fish are two types of fish who live in a separate habitat than the habitat they have spawn. Salmon, smelt, striped bass, shad, and sturgeon are examples of anadromous fish while eels are an example of catadromous fish. 

Key Areas Covered 

1. What are Anadromous Fish
     – Definition, Features, Examples
2. What are Catadromous Fish
     – Definition, Features, Examples
3. What are the Similarities Between Anadromous and Catadromous Fish
     – Outline of Common Features
4. What is the Difference Between Anadromous and Catadromous Fish
     – Comparison of Key Differences

Key Terms 

Anadromous Fish, Catadromous Fish, Eels, Euryhaline, Fish Migration, Salmon

What are Anadromous Fish 

Anadromous fish are a type of fish whose hatching and juvenile period occurs in freshwater. Then, they migrate into the seawater and undergo maturation. The adult fish migrate again into freshwater in the up rivers to spawn. Some species travel more than hundreds of kilometres between their breeding ground and marine habitat. But, some of them just migrate a few distances to the brackish water for spawn. Generally, the term ‘anadromous’ means upward-running. 

Figure 1: Sturgeon

Some examples of anadromous fish are striped bass, salmon, steelhead trout, sturgeon, smelt, shad, and herring.

What are Catadromous Fish 

Catadromous fish are another type of fish whose hatching and juvenile period occurs in seawater. Then, they migrate to freshwater in order to undergo maturation. After that, they spend the majority of their life cycle in the freshwater. Here, the term ‘catadromous’ means downward-running. 

Figure 2: Eel – Life Cycle

The main type of catadromous fish is true eels. Generally, their females spend most of their life cycle in freshwater. But, their males tend to live in brackish water. However, they die the first time they breed. 

Similarities Between Anadromous and Catadromous Fish 

• Anadromous and catadromous fish are two types of fish that spend different stages of their life cycle in different habitats.  
• It is a type of fish migration done either for reproduction or to find food. 
• Both are euryhaline fish that can adapt to a wide range of salinities. 

Difference Between Anadromous and Catadromous Fish 

Definition 

Anadromous fish refers to the migrating fish from saltwater to spawn in freshwater, while catadromous fish refers to the migrating fish from freshwater to spawn in the sea. Hence, this is the main difference between anadromous and catadromous fish is the type of migration.

Adults Live in 

The adults of anadromous fish live in seawater, while the adults of catadromous fish live in freshwater. Thus, this is another difference between anadromous and catadromous fish.

Examples 

Salmon, smelt, striped bass, shad, and sturgeon are examples of anadromous fish while eels are an example of catadromous fish. 

Conclusion 

Anadromous fish are the fish that live in seawater. But, they migrate to the freshwater to spawn. Therefore, their young fish also live in freshwater and migrate back to the seawater. On the other hand, catadromous fish are the fish mainly live in freshwater. But, they migrate to seawater to spawn. Therefore, their young also live in seawater and migrate back to the freshwater. Hence, the main difference between anadromous and catadromous fish is the type of migration. 

References:

1. Cooney, Patrick. “Anadromous, Catadromous, Amphidromous, Oceanodromous, or Potamodromous.” The Fisheries Blog, 14 June 2017, Available Here.

Image Courtesy:

1. “Sturgeon” By User:Cacophony – Own work (CC BY 2.5) via Commons Wikimedia  
2. “Eel-life-circle1” (CC BY-SA 2.5) via Commons Wikimedia