@killknerf
Sturgeons are available just fine, simply go to the Roucistre Blockade in Cent and the small and I believe regular ones are all over the river there. Big ones spawn in the Isle of Wit which is that detached island at the bottom-left of the map. Go to the south-east portion of the isle and you'll see a bandit fishing off of a pier. Kill him and then begin meditating in that area until the fish spawn off the coast. There's typically one or two big breams and big sturgeons there. I believe if the regular sturgeons don't spawn in Cent they're also at that pier with the bandit.

The only unavailable fish are big flatfish and big mackerels when it comes to the challenges, I believe the Swordfish request also requires big eels but I'm not 100% sure on that and if that's also only on the coast I believe that's unattainable too. You can get everything else through a bunch of time wasted meditating in area where the fish are supposed to be or near river mouths as some of the coastal fish spawn near river mouths.

I have just spent all day collecting all of the fish needed to get the Swordfish and since this is seemingly the only thread about this with Ubisoft responses please for the love of all that is holy get someone on this issue of fish not spawning at all around the coast.

• You sometimes have to sit at a port for over eight minutes to get one chance at fishing up a single fish if the fish you're trying to get doesn't instantly go after the bobber or two if you do.
• Sometimes the coast fish stay spawned at the coast for a whopping two minutes before vanishing.
• Other times they all instantly disappear after one catch.
• Then other times they instantly disappear as soon as you cast out your line or just use a single Odin Sight.
• Sometimes literally everything but one fish floats away to sea so you can't catch them at all or lure them over when they're coast spawned fish, this doesn't really happen with regularly spawned fish in rivers as far as I can tell.
• Big fish shot by an arrow clip through the ground and fall through the world making it impossible to collect their body at all which makes getting big coastal fish even harder when they do spawn once a fortnight.
• Big flatfish and big mackerels may as well not exist, I've been running around the south of the Isle of Wit which someone said the big flatfish spawns at for about two or three hours and haven't seen a single one let alone any fish spawning there at all. The pier with the bandit fishing off of it occasionally has the big sturgeons spawn and some breams but it's like once every six minutes and multiple meditations.
• Fish are ridiculously skittish to the point that you can't even get close to them while naked and moving slowly without them zipping away.
• Fish also constantly clip into walls instead of bouncing on the terrain meaning chasing one down is effectively impossible a lot of the time.

The fact you want us to get so many fish with all these issues present is ridiculous.

This issue still isn't really fixed. You can mitigate it to a degree by going to the coast, casting out your line, and then waiting. After about one to two minutes of sitting there with your line out it will spawn some fish but they're on some sort of timer because within a minute or two they will all instantly disappear even if you've killed any of them with an arrow. I just had a Flatfish (Large) disappear on me after I shot it and then when I used Odin Sight the small fish I saw less than five seconds ago littering the sea were now all entirely gone and they weren't even close to the flatfish nor off in the distance.

Unless you are very patient it's rough to get any of these things to spawn and those missions where you have to turn in tons of fish are effectively impossible to finish, especially with some of the ones that require four large fish. You pretty much can only catch one fish every two to three minutes if that and you have to catch your first one within like ten seconds of it latching on if you want a chance at maybe getting a second one.

Update: Turns out not only are they on a timer but if they bite your line they will disappear while on it. Just had it happen to me with a halibut (Large). So even if you wait for them to spawn and they bite your line with you hooking them you're not guaranteed a reel in. It also doesn't look like they respawn if you wait, you may need to move away or meditate before they spawn again a single time.

I've had my armor duplicate even after the patches on an Xbone One X. I immediately obtained a second Hunstman Armor after talking to the tattoo guy and submitting my tattoos but I'm not sure how I got a second Galloglach Armor, I think it might have either been looted or happened after I messed with my ship. They're also not removed from my inventory even though they're supposed to be as far as I understand? I'm worried about upgrading either of them or attaching runes to them just because of them eating my materials or duplicating the runes themselves.