Slender sunfish
Slender sunfish held up, showing how small it is. Length was estimated at about 60 cm.
The tiny mouth which cannot be closed.
All photos Guido Zsilavecz.
The slender sunfish is the smallest of the sunfishes, growing only up to 1 meter in length - much less than the massive ocean sunfish Mola mola which is occasionally seen in Cape Town waters: it can grow to 3m!
The slender sunfish can be found in all oceans. It feeds on planktonic crustaceans. The mouth is round and cannot be closed, and food is hoovered in. As with all sunfishes the body is quite rigid, and the fish moves by waving the dorsal and anal fins from side to side. The profile of the fins shows a rigid leading edge, with a much thinner and flexible trailing edge - as it moves the trailing edge bends, creating what looks like the blade of a propeller. This forces water back, resulting in forward motion.
Compared to other sunfishes, this one has beautiful markings: lines on the head as well as numerous spots; the "tail" sports a column of spots in mother-of-pearl sheen, which can be found on other parts as well.
Smiths' Sea Fishes, MM Smith and PC Heemstra, 1986.
Fishbase.org