Final answer:
The sentence 'He wondered if the fish were biting this weekend' should end with a period as it is an indirect question.
Step-by-step explanation:
The correct end mark that is needed for the sentence "He wondered if the fish were biting this weekend______." is a period (.). The sentence is structured as an indirect question, where the speaker is stating that he wondered about something, rather than directly asking a question. Therefore, the sentence should end with a period, not a question mark or any other punctuation.