On 'hunter-gatherer' mode: the most sustainable approach?

I am not sure what is happening to me lately, perhaps the sun is giving me some heat-stroke, or perhaps is the many hours spent in the water looking at marine life, but I cannot stop thinking about the things around me as 'good dinners'. 
Yes, I am on hunter-gatherer mode. 

In a previous post, I mentioned how eating seafood isn't really sustainable when bought from commercial sources who fish intensively. But what if you catch it yourself? What if you catch just enough for you and your family to eat? In that case, it seems to me to be a pretty sustainable way of life.
Think of scallops, for example, hand caught by divers - no damage to the environment by trawls and dredges, no by-catch, no excessive catch. And you can use a ruler to check the sizes so you can live the undersized ones in exactly the same spot they were in - sounds great no? 
Same goes for other seafoods and for fish, catching one with a speargun will allow you to catch just the one you wanted, of the right size, and no more lost fishing nets (see previous post on ghost fishing). Just be careful of protected species, especially with regards to molluscs, and inform yourself on the right sizes. In France they have posters on most beaches dedicated to the 'pêcheurs à pied' where they indicate sizes and quantities allowed for each species. Needless to say, follow the rules of the country you are in and inform yourself of any licence needed. 

I find that this 'hunting-gathering' mode also helps you gain appreciation for what you are eating - if you spent some time searching and collecting your dinner you will have more respect for it than if it just came out of a package from the refrigerator section in your local supermarket. If you fatigued, at least just a little, or like me ended up covered in spines (just for one bite of succulent sea urchin eggs), then you will better realise that you are eating something which was just alive. 

Should I mention the health benefit of eating fresh food who hasn't seen pesticides and preservatives?
I think I am heading out to fish soon...