Gutting and gilling the fish leaves the recipient with a clean and ready to cook/smoke/boil frame and head, heres how I do it.

Nice work Coxie my method is very similar.

I'm a touch curious why you don't do this at sea?

Standard practice for me to pull into a sheltered spot on the way home & gut & gill my whole catch.

 As the blade tip goes up towards the head inside and hit the breastplate mic part of the blade. Leaver the tip of the knife against the back bone, and go thru the breast plate.

Quick cut with fish still laying down across the throat.

 this then enables the tip of the knife slice the bottom of the gill away.

 Smaller fish can pull gills and gut out as illustrated but larger fish, the gills can be very abrasive to the hands and the top end of the gills hard to pull away clean.

 So on larger fish, cut the bottom if the gill away then with tip of the knife a good knick, or if lucky slice the top of the gill anchor and pull away.

Gutting thru the breast plate kills the butt to middle of the knife edge very quick.. sSo do this at the end of filleting and skinning, not during.

 And when sharpening the knife (my edges are stroped convex) with the filleting / point about 22 deg and the main blade 30/35 deg.. The 22 deg gives fine 'peel away' but not robust to cutting bones. And the 30/35 deg far more robust to keeping an edge for bpin bones and skinning.

Aski any chef, butcher etc, be it fish lamb , beef , the sweetest most tender meats are next to the bone... ie back strap, chops cheek , wings, fish forehead... 

And another hint.. gutting at sea.. assuming a bait board.. fix a insert into the bait board to raise the floor up. that way you can cut straight into the fish rather than over the edge.

 I leave an 1" or so at the back of the board for sinkers etc.

 I used to have a wooden insert, great, this board have one of those white plastic chopping board trimmed to fit.

 Dont use the plastic chopping boards, they kill the edge on knives very quick... big mistake yet to fix.

I think the flesh is firmer maybe a bit of rigormortis set in?

100% right MacSkipper, the idea is in fact for the whole process of rigor mortis to pass. The energy needs to fully dissipate from the fish. Two key element to this with fish temp & time. The quicker you can get the core temp to 0c the better, hence the beauty of a good slurry. At this point the fish sets (rigor), ideally you want to wait a min of 3-4 hours after this for rigor to pass. At this point the fish has set & relaxed (rigor has passed) the fish is firm & tender.

To my mind this is when fish is at is premium.

The Cook, I don't fillet or gut/scale/prepare fish at sea simply because I prefer the nice stable platform that a concrete floor has to offer. On a calm day, maybe the boat is ok for flashing knives around but when you are as awkward as I am there's nothing like having your feet on mother earth to do a good butchering session. I agree the fish needs time for the flesh to set before filleting.

I'm interested on your thoughts about time before serving too The Cook. I prefer my snapper (especially snapper) to age at least a day in the fridge before eating. Do you agree?

Catch a fish, on the board, gut and fillet straight into a hot pan beside..., allow to rest a few minutes, tender full of taste, excellent.

Catch, yes or nah to gut before bin.. gutting means chilling also from center thu.. home fillet, and in the pan...again very similar if not the same as from hook to pan.

Cook up the following day or days the meat doesnt cook as well , melt in the mouth  texture.. As it is a little more firm, stir fries, butter fish, pies curries etc... anything chicken in particular maybe used in.

Have to agree. I scale my fish at sea if I can because it makes such a bloody mess, but working with sharp tools on a bobbing jet ski is no fun!

Anyway, I also save my heads/frames for donation. Have a big box ready to go, all gutted/gilled and fresh frozen. I believe there is a local charity that takes them, so will try there this time.

BTW, I use a pair of heavy duty shears/scissors to make the cut from the anus to the head. Saves dulling knife edges and a bit safer.