I don't blame ya, I had intended to write a much, much shorter guide...

tl;dr

Set the fishing limits to 235/370/373/585 for regular/regular+perk/rich/rich+perk shoals, respectively. Assign 5 families to fishing huts in March and April. You can lower that number for the rest of the year, if you want to stretch fishing over the year, keeping it from spoiling.

And take the perk!

All shoals of fish in Manor Lords (public beta version 0.7.995) work the same way: They spawn more fish at the beginning of March, April and May each year, based on the current number of fish. They gain +50% each time, as long as this doesn't surpass the ponds capacity.

A regular pond contains up to 352 fish (32 per fishing spot). This can be raised to 705 fish by taking the Advanced Pondkeeping perk.

A rich pond contains up to 715 fish (65 per fishing spot). This too can be doubled with the Advanced Pondkeeping perk to a maximum of 1,430 fish.

All ponds have exactly 11 fishing spots - the places a single peasant can occupy to do their fishing animations and gather the fish. This limits how many fisher can work at the same time, and how many fish can be caught in a month.

The Advanced Pondkeeping perk not only doubles capacity and thereby allows you to keep a greater number of fish, spawning even more fish, it also allows you to slow down fishing outside of spawning season to fish even in winter, when the ponds are frozen over. That comes in handy with distributing fish throughout the year and keeping spoilage low.



Side note concerning map generation: No region can contain both a patch of berry bushes and a pond. These two are intended as easy starting food, so getting both would be overkill. You can of course still build forager huts for the upgrade that produces herbs to more quickly recover your sick peasants! They are planted and harvest akin to vegetables in the burgage gardens, though you need to assign a family to the forager hut.
Berries or dyes will have to come from another region of yours via inter-regional trade or bartering, or can be imported for silver from off-map towns.

Now to the juicy math!

If we were to simply set our fishing limit to 67% of the capacity, at the start of March we would gain +50% of that number of fish to bring us back to 100% capacity. Great! I hear you exclaim most jubilantly.

But after March comes in like a lion, April marches in with the same ferocity! So we would need to reach 67% again by the end of March to not go over capacity at the start of April. And rough winds do shake the darling buds of May, as we will see another jump in fish by +50% of the remaining fish at the end of April.

So the task becomes to fish quickly enough in March and April to not lose out on any spawning fish!

Let's go through the different shoal sizes one by one:


Regular Shoal of Fish (352 fishies)

Set the limit to 235 fish. That's what we want to reach before March kicks the number up to 235 x 1.5 = 352, reaching capacity. We can fish that back down to the limit with about 4 assigned families, with huts close to the pond and a nearby large granary with enough workers to empty the pantries quickly and lower spoilage.

The same will repeat in April and May, after which you could stop fishing until next March. If you wanted to stretch fishing out over the year, reduce the number of families at the start of May to just 1. They will probably still fish more than 17 fish per month, though that would be the ideal number to reach the limit of 235 by the end of November, before the pond freezes over.

Here's a little table to show how the number of fish would develop during each month of the year:



This should yield us 352 fish per year!


Regular Shoal of Fish with Advanced Pondkeeping (704 fishies)

Set the limit to 370 fish. This time, we will not be able to fish fast enough to keep up with the +50% spawns three times in a row. With about 5 or more families assigned, the 11 fishing spots seem to almost always be in use, netting us 145 fish per month - the maximum I managed to achieve.

In May, you can lower the number of assigned families to just one, it will probably reach the limit of 370 fish before March. Probably. Well, thanks to the perk, we can go ice fishing now and use those months too!



This should yield us 624 fish per year!


Rich Shoal of Fish (715 fishies)

Set the limit to 373 fish. This basically identical to a regular pond with the perk. Except no fishing in winter, so better keep 2 families employed from May till snowfall.



This should yield us 632 fish per year!


RichShoal of Fish with Advanced Pondkeeping (1,430 fishies)

The holy grail of pescetarians! Well, everyone really, as the Church demands up to 150 days of no meat, apparently - but hey, fish ain't no animal, their flesh no meat! And throw in some beavers for good measure! Totally counts!

Anywho, set the limit to 585 fish. Again we will need 5+ families to keep all fishing spots occupied and hauling in 145 fish in March and April, at the very least. Come May, we can reduce the number of fishing family businesses again, but I found 3 are needed to reach the limit of 585 fish before next March, despite ice fishing extending the time to catch fast spoiling (soon to be ex-) friends.



This should yield us an incredible 1,135 fish per year! Enough to feed almost 95 families for a whole year - on nothing but fish! (Please don't nerf, Greg!)

Spoiling nice fish, scorching it. Give me fish NOW and keep the nasty berries!

Gollum said it, don't leave you fresh fish in the scorching summer heat to spoil!

It's important to move fish quickly from the pantries of the fishing huts to an upgraded granary. Not just to stop the pantries from overflowing, but because at regular spoilage rate, you will lose 10% of your fish there at the start of every month. That's the highest rate of any food type in the game, and there's no salted fish in the game yet!

Move it to the granary and see the rate of spoilage drop to 7%, at least. And from there to the food stalls, where it won't spoil at all. Or sell it - as of now, we can export even the fastest spoiling goods to off-map cities, for some reason.