* Difficult to Count: Tracking and counting fish populations is incredibly challenging, especially in vast oceans.
* Varying Definitions: There are different ways to define "most populous," such as:
* Total number of individuals: This would be difficult to track.
* Biomass: The total weight of a species.
* Distribution and Abundance: How widespread a species is and how many individuals live in a particular area.
* Species Diversity: There are thousands of fish species, and their populations fluctuate.
However, some contenders for the most populous fish include:
* Anchovies: They are extremely abundant in certain areas, particularly the Pacific Ocean.
* Sardines: Another small, schooling fish found in large numbers.
* Herring: Like anchovies and sardines, herring form massive schools, making them potentially very populous.
Ultimately, the "most populous" fish is a difficult question to answer with any certainty.