There is no Salmon Stamp in existence, at least not in Connecticut. There is a statute that allows the Commissioner to create one however it was never implemented. Apparently when the legislature increased all the fees last year they increased that one too even though the stamp doesn't exist.

Sec. 26-48a. Management of salmon, pheasant, turkey and migratory game birds. Issuance of permits, tags or stamps.
(a) The commissioner may establish, by regulations adopted in accordance with the provisions of chapter 54, standards for the management of salmon, migratory game birds in accordance with section 26-92, pheasant and turkey which shall include provision for the issuance of permits, tags or stamps. The commissioner may charge a fee for a permit, tag or stamp as follows: Not more than ten dollars for turkey; not more than two dollars for migratory game birds; not more than ten dollars for pheasant and not more than twenty dollars for salmon. No person shall be issued a permit, tag or stamp for migratory birds, pheasant or turkey without first obtaining a license to hunt and no person shall be issued a permit, tag or stamp for salmon without first obtaining a license to fish. Notwithstanding any provision of any regulation to the contrary, the commissioner may charge a fee of ten dollars for the issuance of a permit to hunt wild turkey on state-owned or private land during the fall season.
(b) Such permits, tags or stamps shall be issued to qualified applicants by any town clerk. Application for such permits, tags or stamps shall be on such form and require of the applicant such information as the commissioner may prescribe. The commissioner may adopt regulations in accordance with the provisions of chapter 54 authorizing a town clerk to retain part of any fee
paid for a permit, tag or stamp issued by such town clerk pursuant to this section, provided the amount retained shall not be less than fifty cents.