Conversation so far:
What did Innis do that was so important in the 1930s?
Innis wrote extensively in the 1930s about other staple products
What other staple products did Harold Innis write about?
Innis wrote extensively in the 1930s about other staple products such as minerals

Question: How was he involved in fisheries?
Self-contained rewrite: How was Harold Innis involved in fisheries?