With the weight of over 300 years of family history heaped on his shoulders, things looked grim last year at the start of lockdown, but Stewart was determined not to see his family fishing business fold on his watch.
Stewart recalled that his grandfather was still fishing right up to the year before he died.
Previous generations had chased shoals of herrings in this area, but today "lobster and brown crabs are my target," he explained.
He learned his craft working alongside his father on their boat, called Windward.
Stewart said, "he taught me everything I know about fishing. It was good to spend time with him, which in the past I hadn't really done. I wish I had done it a lot earlier."
He also passed on the family tradition of building and mending creels, he said, "I recycle the old stuff to mend them. All the other boats running out of North Berwick, just buy them so I can tell my own creels a mile away."
He said, "when lockdown happened we couldn't sell our lobsters to the usual merchants so I decided to start my business, The Lobster Man.
"I'm sure my dad and granddad would be very happy with what we are doing now."
He fishes all year round but said, "you don't catch many lobsters in winter because the water is colder and they get lethargic."
They are not the only ones to feel the cold, he joked, "I fitted a heater in my boat this year."
But he said, "it is the best job in the world, in summer."
He describes the feeling of freedom you get on the boat, "you are your own boss, there is nobody round about you and it is the best office in the world. I love it."
"Once a gannet came right up and took the fish out of my hand, and there was a seal that would jump out of the water to feed and few times dolphins have come right up alongside boat, so it is not a normal job", he added.
He was not always going to be a fisherman, he explained, "my mum tried to keep me away from fishing for a long time."
She tried to steer him down a different career path, - "I'm actually a fully qualified hairdresser.
"When I was a hairdresser, I used to have to get my uniform and trousers pressed so I could get to work all clean and tidy. Now I don't need to worry what I look like I can just roll out of my bed, I don't need to shave or do my hair," he said.
He gave up on hairdressing and became a tower crane driver on the new Queensferry crossing before deciding fishing with his dad was a better option.
Stewart said, "it was closer to home and I wanted to keep it going for the sake of my dad. He was getting too old to fish."
He has fond memories of his childhood: "When my brother and I were just lads, I remember asking to go out to sea early in the morning with my dad."
He would go out at about 4 am: "Dad was reluctant saying, 'you'll just get in the way, you'll come out for about an hour and be bored and you'll not be happy.'
"We used to end up curled up together in the prow of the boat, with a couple of jackets over us and we would be asleep until we got back in to harbour."
He also tells us some of his fishing superstitions; "You don't ever whistle on the boat, it is called whistling up the wind and I always chuck a couple handfuls of coins in the harbour to give something back to the sea."
When it comes to being in trouble at sea, Stewart said he's not experienced anything he couldn't handle.
However he said, "I had to get the lifeboat out once to tow the vessel back due to engine failure, and sometimes you can get rope tangled around the propeller.
"Normally I can overcome that, I carry a dry suit on the boat in case you have to get in the water and cut the rope off."
His dad taught him what to do in situations like that.
"First, you tethered yourself to the boat so you don't float away, then you get the anchor down and make sure the boat is holding fast before even getting in the suit. I've done it a few times, it is a bit daunting but no one else is going to help you.
"Last year it happened to me up near Fidra island but luckily there was a paddle boarder nearby, he helped me. He was a trained firefighter so he cut off the rope, and he got lobster and chips as his reward."
He has regular lobster haunts he visits, "I leave markers, and I use triangulation points on the land so I know exactly where I am, even if my electronics are down."
It is a dangerous profession, and his partner Gemma does worry about him being out at sea alone.
He said, "but I always have my life jacket on and I take all the necessary safety precautions. I've been doing it for years now so I know how it works, and how to keep myself safe."
The couple have two young children Ford (3) and Molly (1), but when they were courting, a glamorous date night could be a shift on the boat.
He said, "Gemma would helped get the crabs, lobsters and starfish and everything out of the creels, she enjoyed it. She is missing it now, but it was something we did make a night of."
He said, "I fish in a sustainable way like my dad taught me, so you don't just wipe it out fish. You keep yourself comfortable and your roof above your head but you don't get greedy.
"All these new guys are just hammering it. There are no rules. They can do what they want, so it has turned into a free for all.
"They just don't realise what will happen if they keep on doing what they are doing. It is quite sad."
He uses a lobster gauge that measures every lobster he catches. The main body of the lobster from behind the eye to the end of the body shell, has to be 87 mm or above to make sure the catch is legal.
Stewart said, "you can be fined quite heavily, if you are caught with undersized lobsters on the boat."
In the past he has been hurt a couple of times by pesky crustaceans, he said, "my dad was on the boat at the time and I put my hand in the creel and turned to look at him- sheer stupidity- he found it hilarious."
The other time was when he was banding lobsters and putting them in the tanks with Gemma, the crusher claw got him. Lobsters detach their claws as a self defence mechanism.
He said, "it kept getting tighter and tighter and I was desperately trying to get the claw off. Gemma was in stitches. I didn't find it funny."
"When lockdown hit, overnight we couldn't sell our lobsters, he said "we had lots, but I thought 'what are we going to do? How are we going feed the baby?'"
He explains, "we looked at all the government grants, but we weren't eligible for any of them. We were just left on the tide-line to fend for ourselves."
Even if he had applied for benefits he said, "we would have been absolutely stoney broke."
So we decided to sell direct: "we put an advert on my Facebook page, North Berwick Lobsters, saying 'live lobsters can deliver', "a lot of people took us up on it, but they discovered preparing them it is not as easy as you think, then we got requests asking us to boil them."
"We had to think quick on our feet."
He decided to take the plunge and do a food hygiene course, so they could start selling them cooked.
It was daunting initially to set up the catering trailer at nearby Fenton Barns.
But Gemma had worked in a sandwich shop before so she had an idea of how to run a food establishment. Granny was enlisted to babysit so she could help Stewart out.
Luckily the owner at Fenton Barns is very supportive and thinks the couple has had a brilliant idea. Stewart said, "he is behind us one hundred percent"
Business has surpassed their expectations, he explained, "It is getting bigger week by week and because we are getting more orders, we are expanding.
"Watch this space, we are planning to make a sit in area, restaurant and decking area.
He was also fortunate to have found a chef from Tom Kitchin's Bonnie Badger.
Stewart said, "Peter knows what he is doing and he is helping out a lot with the menu."
They supply cooked Lobster and crab with different sauces, Thermidor, Garlic and Coriander butter, as well as Cajun.
He said, "The lobster is cut in half, cleaned out and all the claw meat and everything is taken out of the claws so you don't have to crack anything or go hunting for any meat. It is all there just ready for you to dig in.
"We even put it into oven ready dishes with instructions on the lid to just reheat at home or you can collect it hot from the trailer.
"Lockdown has made people realise what food is actually on their own doorstep and that Scottish seafood is really the best."