Last week I shared with you the miniature world of the sea slugs, so this week I’ll super-size things and bring you some big fish. Silly-season reports of Great-white sharks often hit the headlines in Cornwall, but I prefer rock-pool giants; they’re not made up, and you can get close to them without having your leg bitten off!

Cornwall is brilliant in all sorts of ways, our network of local, grassroots marine conservation groups being just one of them. The public launch, last week, of the new Three Bays Wildlife Group brought experts and volunteers together and gave me a chance to explore some new beaches in the St Austell area.

Judging by the squeals of excitement from the children and adults alike, the crabs, pipefish, prawns and anemones we found at the main rockpool ramble on Portmellon beach near Mevagissey went down well. By the end of the day, the local group had recruited lots of potential new volunteers.

At the end of an event I’d usually relax and enjoy my sandwiches, but the group was keen to survey another local beach. The walk to Colona was like something out of an Enid Blyton adventure. Cresting the hill out of Portmellon, we passed a disused cattle grid filled with nettles, beyond which the view opened out to sheep-grazed pasture plunging down to the bay. The whitewashed house on Chapel Point, to the east of the beach, perches over azure waters and would be any rockpooler’s dream pad.

Matt Slater from Cornwall Wildlife Trust was straight out on the rocks setting fish traps in the deep pools. Matt, of course, is a fully-licensed professional giant catcher.

After just half an hour of mooching about the pools looking at anemones and some fine lugworms, we clambered across to check the traps. The first looked successful. At the back of the yellow-mesh cage, several creatures wriggled while Matt hoisted them onto the rocks and eased them into an awaiting bucket.

Once the greedy shore crabs that had been feasting on fish-bait had been picked out, there were three fish left. Every one of them was large by goby standards. One in particular was what Junior would describe as “a whopper”. Matt’s face said it all. From the fishes’ fleshy lips that could out-pout Mick Jagger to the beady eyes, it was clear that all three were Giant gobies (Gobius cobitus).

These fish have special protection under the Wildlife and Countryside Act and are at the northernmost point of their range around south west England. They’re not well recorded because they’re elusive and can be mistaken for the much more common Rock goby.

To round off our week of giants, Junior and I took a stroll around a sheltered lagoon in Looe, after a Fox Club event and came across a fish even larger than a Giant goby. In fact, I was so busy examining tiny hydroids on seaweed looking for sea slugs that I practically tripped over the young catshark.

The Greater-spotted catshark goes by many different names (bull huss, nursehound, dogfish, etc.) and is far larger than a Giant goby, growing to around one and a half metres long when mature. The one I nearly stepped on in my neoprene beach shoes was just a baby, but still an impressive fish.

Catsharks tend to lie still for camouflage, so they’re easily approached to take photographs. If you touch one, as Junior did at the first opportunity, you’ll also notice that their skin is like sandpaper. Rough sharkskin is remarkably hydrodynamic, so much so that engineers are looking at ways to copy its structure to make swimmers faster and ships more fuel efficient, among other things.

I think Junior would like it even better if we could stumble across a giant squid circling the pools, but for now, a shark will certainly do. The giants of the Cornish rock pools aren’t as easy to spot as you might imagine, but it’s well worth the effort.