Hi Jaysee,
There aren't too many Spearo's on this website, there are better places to go for that

.
To answer your question, and I am assuming you mean rock hopping from the rocks or beaches.
There is pretty much nowhere you can spearfish from the shoreline of Perth Metro. You can shore dive from the Northern end of the Marmion Marine Park which ends about 600m North of Burns Beach, but there is bugger all to see or spear up there as vis is usually pretty crap and no fish!

.
The southern boundary of Marmion Marine Park is Trigg Point so this takes out all of the good reef. The Marine Park extends 3km offshore but you can spearfish from 1800m from the beach. It's a bit of a swim if you're up for it and maybe expect the rangers to be waiting for you to prove you weren't in the Marine Park.
From Trigg Point south is all sand/surf beaches until Cottesloe so totally crap for spearfishing. Cottesloe Reef system is totally protected from spearfishing as it used to get smashed by rock hopping spearos many moons ago. Once past Cottesloe, there is nothing until Cockburn Sound which is also a marine park, so I guess what I'm saying is there is no shore diving in Perth.

All the reef out further ie 3 Mile reef line is hit pretty bad by lino's, spearos on air and breath hold so don't expect much although you can occassionally surprise yourself in the right conditions. I've seen very flighty Mackeral out there once!
You cannot spearfish from Rotto and cannot even take a gun onto the island, it's totally forbidden and the locals get angry when you even talk about spearfishing on Rotto.
If you are keen for a dive, give me a call and you can come out with us. I'm just back from a days trip to Cervantes today. Awesome days diving, sunny, no swell, light breeze, clear visibility (20m+), warmish water (17 deg). We speared some nice big Balchin Gropers (4), a Yellowtail kingfish, and a Western Blue Groper. A nice days catch. Let a few Dhu's go as they weren't quite size.

Dived with Dolphins, Turtles, seals, big rays and plenty of fish, was a great day.
You really need a boat to dive in WA. There is good diving on the reefs off stragglers and Champion Rock (half way between rotto and Freo.) Usually diving for Dhufish, Baldchin, Harlequin fish, KGW, Queen Snapper and Western Blue Groper. Lots of other fish available too if you want a fight, like Sampson Fish but they taste pretty crap. In summer it's Spanish Mackeral.
Give me a call and I'll hook you up with our club if you're keen, there are always divers looking for crew on their boats both midweek and weekends. We have a meeting on Tuesday night at 7pm if you are interested in coming along and meeting some like minded spearos. Bluewater Freedivers of WA. We meet once a month and meet at the Challenge stadium Pool once a week on Thursday nights for pool training.
Good winds,

0433 982 696