Name an organism found as secondary carnivore in an aquatic ecosystem.

Explanation

In an aquatic ecosystem, food chain can be drawn as follows
Producer (Phytoplankton) `to` Primary consumer (Zooplankton) `to` Secondary consumer (small fish and water beetle)(Ist to carnivore)`to` Tertiary consumer (Iind carnivore like large fish, water birds like fowl and duck).
So, the large fish and water birds like ducks and water fowls which are the tertiary consumers in an aquatic ecosystem occupy a position of secondary carnivove.