Answer:
Crustaceans, sea urchins, mollusks and fish.
Step-by-step explanation:
The positive effect occurs on crustaceans, sea urchins, mollusks and fish if the shark feeds on sea otter because sea otter feeds on crustaceans, sea urchins, mollusks and fish. Decrease occur in the population of sea otter due to introduction of shark in the ecosystem which indirectly increases the population of crustaceans, sea urchins, mollusks and fish. So we can say that a positive indirect effect occurs on crustaceans, sea urchins, mollusks and fish due to shark.