The T2121 Statement of Fishing Activities form is used to calculate fishing income and expenses for income tax purpose. Your gross income should also be reported in Box 78 of a T4 slip or in Box 79 or 80 if you're a partner in a fishing business or a sharesperson. However, the income must still be reported on form T2121. If you have more than one fishing business, then you must use a separate T2121 form for every business.