The ITM Fishing Show host is in no doubt this is because of a ban on bottom trawling in the inner gulf, which has been producing an abundance of snapper and other species.
"Running a trawl net along the bottom destroys the habitat and kills all the juveniles.
"I'm not a marine scientist but you don't have to be to work that one out."
In recent weeks, the coveted snapper have been spawning and feeding on aggregations of bait fish.
"The Rangitoto Channel should be fishing well and even right up under the Harbour Bridge there will be patches of fish.
"The ones that have moved into the channel you will catch using soft baits, but because the water visibility isn't as good in the inner harbour, they won't see your lure as easily, so that's when you might want to anchor up and use a bit of burley."
He says rock fishing is generally a bit trickier at this time of year with the snapper roaming further from shore. But there is a silver lining.
"What makes up for the snapper moving into more open water over summer is that the kingies [kingfish] are coming in chasing bait fish. So if there's a channel nearby and there's bait fish around, having a popper or a surface lure to cast might produce you a thumper of a kingfish in the shallows."
For the inexperienced angler, Watson recommends getting on to the water early - at dawn - to avoid the heavy summer-season boat traffic and allowing you time to get a bait or lure in the water at prime bite-time.
Dusk is also a good time to fish but Watson prefers dawn as the sea breeze generally hasn't come up then; he's usually on his way back to shore by 9am.
"And if anything goes wrong it's going to get light soon and there's going to be lots of boats around, unlike if you're fishing on dusk."
Watson says during summer the fish are constantly on the move so it's important to spend less time on your anchor and more time looking for signs of fish. These could be bird activity, schools of small bait fish or signals from your fish-finder.
"The fish aren't going to be in the same spot that your granddad showed you by lining up the pine tree and old shearing shed," he says. "Those ones have already been caught. Just remember, where you caught fish last summer you're not necessarily going to catch them this summer."
And if you're still not landing enough fish for the barbecue, Watson has an easy way to double your catch: use the whole fish.
"Don't just take the fillets off and throw the rest away - eat the whole fish because the head and the wings are the best meat," he says.
"And if for whatever reason you won't eat fish heads like I do, give them to somebody who will because then they won't go fishing and take more fish."
He has set up the fish-head exchange website - freefishheads.co.nz - which has some 4500 registrations.
And to help ensure the fish population is maintained and improved for future generations of fishos, Watson says it's a good policy to throw your big ones back.
As well as it being "good karma", the big fish are the best breeders, and don't taste as good anyway.
"It's like if we went around and shot everyone who was taller than six foot, the next generation would have no tall people."
Watson doesn't keep snapper that weigh more than 4.5kg, and applies the same principle to other species. It is also imperative anglers don't forget recent changes to recreational fishing rules.
The bag for snapper for the upper North Island's east coast, including the Hauraki Gulf, is seven, down from nine.
Snapper there must now measure at least 30cm from the tips of their noses to the V in their tails, up from the previous 27cm limit.
Casting around for an elusive catch
David Cunliffe, Mandy Kupenga. Photos / Supplied
They are a fisher's prize possession - the location of their best fishing spots.
And in 2012, one Waikato woman got the ultimate revenge on her ex-boyfriend when she auctioned off the details of his secret fishing spots on Trade Me after he suddenly left her and fled to Australia.
The woman raised $3000 from selling the GPS co-ordinates, which featured her ex's favourite spots in the Bay of Plenty and other North Island locations.
But not all Kiwis are as coy. Some have let the Herald on Sunday in on their best fishing spots for free.
Former Labour Party leader and keen fisherman David Cunliffe has three favourite sites that have often brought him a plentiful catch.
"There's a deep hole off the southern tip of Tiri [Tiritiri Matangi] that always yields me snapper," he said.
"There's also a decent hole with john dory in it off Hooks Bay in Waiheke, where my then 4-year-old son caught a 9lb john dory on a sprat line - he had caught a baby snapper that the john dory swallowed whole and couldn't get off the line.
"The biggest snapper I've caught was off the rocks on a point beyond Otama Beach in Coromandel - [a] 22-pound snapper."
His mantra when out fishing was: "Just don't think about what's going on on land."
Mandy Kupenga - host of Maori TV show Get Your Fish On - revealed her favourite fishing spot was off the Mokohinau Islands, 21km northwest of Great Barrier Island.
"There's so much sea life out there, there's so much variety.
"There are the two favourites - big snapper and big kingfish - then you've got everything else in between.
"There are schools of trevally cruising around, there's lots of bait fish and you can go for a dive and get crayfish or scallops or whatever," she said.
"I reckon the key to fishing in a place like that is going with someone who knows where the fish are, who knows the spots and knows how to fish them.
"For me, going out with a guide or on a charter is a great way to find out about new spots where you want to go fishing," Kupenga said, "and then you go back on your own boat
when you've got a bit of background."
