You have to report your world income (income from all sources both inside and outside Canada) earned after becoming a resident of Canada for income tax purposes on your Canadian tax return.
In some cases, pension income from outside of Canada may be exempt from tax in Canada due to a tax treaty, but you must still report the income on your tax return. You can deduct the exempt part on line 256 of your tax return.
See full reporting requirements for newcomers to Canada in link below.
https://www.canada.ca/en/revenue-agency/services/tax/international-non-residents/individuals-leaving...