Tip for a chartered fishing by trip?

So I’m taking my son and daughter charter salmon fishing this upcoming Friday morning in Astoria, Oregon (buoy 10). The cost is $275/person. I put a $150 deposit so I owe $675 cash when we get there. This is a small business consisting of a father and son. Last March I went with the same company and booked a salmon/sturgeon ( sturgeon catch and release) trip and it was $200 per person. Unfortunately we didn’t catch any salmon that time. I gave the son a $30 tip last time but the dad emailed and said they don’t fillet the fish for us if we catch salmon so I’d have to pay the market to do it for $6-$8 per fish. The limit is 2 salmon per person. I’m thinking that the money I spend on fillets well, that’s his tip. Thoughts?