The CFR States:
PART 123 -- FISH AND FISHERY PRODUCTS
Subpart A--General Provisions
Sec. 123.10 Training.
At a minimum, the following functions shall be performed by an individual who has successfully completed training in the application of HACCP principles to fish and fishery product processing at least equivalent to that received under standardized curriculum recognized as adequate by the U.S. Food and Drug Administration or who is otherwise qualified through job experience to perform these functions. Job experience will qualify an individual to perform these functions if it has provided knowledge at least equivalent to that provided through the standardized curriculum.
(a) Developing a HACCP plan, which could include adapting a model or generic-type HACCP plan, that is appropriate for a specific processor, in order to meet the requirements of 123.6(b);
(b) Reassessing and modifying the HACCP plan in accordance with the corrective action procedures specified in 123.7©(5), the HACCP plan in accordance with the verification activities specified in 123.8(a)(1), and the hazard analysis in accordance with the verification activities specified in 123.8©; and
© Performing the record review required by 123.8(a)(3); The trained individual need not be an employee of the processor.
So yes, your USDA inspector was correct, your HACCP training needs to include curriculum specific to the seafood haccp regulation. Guidance available here: https://www.fda.gov/...176892.htm#viii