You’ll not hear these lions roar (Jane in Cape Town says lions don’t roar but merely cough, and she should know – Attenborough and Disney, you lied!), but they can certainly do you an injury if you mess with them.
The spines are venomous as distinct from poisonous, which is something different. The Smithsonian says:
In fact, lionfish are distinctly edible as long as you avoid the spines. Several countries have invasive populations creating environmental havoc in their seas, but have made an industry of catching and serving them in restaurants – a win-win situation in those places.
Those spines are defensive and can give you an extremely painful, but not fatal, prod.
NOAA says:
The lionfish’s sharp, slender spines are located on the dorsal, anal and pelvic fins. The venom is a combination of protein, a neuromuscular toxin, and a neurotransmitter called acetylcholine. The sting causes intense pain, redness and swelling around the wound site. Although the worst of the pain is over after an hour or two, some people report pain and tingling sensations around the wound for several days or weeks. On rare occasions, when the venom spreads to other parts of the body, people may experience headaches, chills, cramps, nausea, and even paralysis and seizures.
Now back to Woody Head, where Peter Scharf took these photos. The first three are of the zebra lionfish, Dendrochirus zebra. Its distribution in Australia is Shark Bay, WA to Sydney, NSW. (Distributions are given in a clockwise direction around the country.)

Zebra lionfish, Dendrochirus zebra; photo Peter Scharf