Dive Dry with Dr. Bill

073: Balloonfish

Pardon me if I dwell on my experiences in the Sea of Cortez for one more week rather than writing about our local critters. Given our current cold spell, thoughts of warmer water (and mermaids) are more appealing than standing in my wetsuit shivering in the cold wind. Much as I love kelp forests, there are other worlds to explore and understand, especially during the harsh southern California winter.

When I dive in any region other than our own, the first thing I try to do is observe what is happening in the ecosystem. Unless I have done substantial pre-dive research, I often don't know the new species there. Of course simply knowing the names is of little use anyway unless I am communicating with other scientists. I try to watch the "actors" on this new "stage" and look for interactions: feeding, cleaning, aggressive and other behavior. Gradually I am able to put together the ecological puzzle of how the system functions. This is a rewarding mental challenge for me. Afterwards I can research each species to further enhance my understanding of what I've seen... and what I haven't.

One of my favorite fish in the Sea of Cortez is the balloonfish. Many people call it the puffer fish because dead specimens are often found inflated on beaches. However, it is actually a member of the porcupine fish family rather than the true puffers to which they are related. Porcupine fish have sharp spines on their bodies while puffers are smooth skinned and lack the spines. When I lecture on board the Lindblad cruise ships, I call this fish the "E.T." fish. Although normally shy and retreating, I often have them come up from the bottom or turn around while swimming to look at me with their large, sad eyes.

The balloonfish is found throughout the world in tropical seas. I first encountered them diving in Asia and Australia. On our coast there have been reports as far north as San Mateo County, but they are common from the central and lower Gulf of California to Ecuador. Balloonfish are found in shallow waters over sand, in mangrove areas and around nearshore reefs. Large specimens may reach 20" although most I have seen are less than a foot. Their bodies are covered with large brown blotches and smaller dark spots as well as sharp spines.

Although I saw them frequently, I never observed balloonfish feeding during my dives. Most were swimming in the open or hidden in crevices. Apparently balloonfish feed at night on sea urchins, crabs, hermit crabs and molluscs. Looking at beached skeletons, the beak-like jaws are very powerful and can easily crush hard-shelled food. There are few animals other than sharks which feed on the adults for obvious reasons! Juvenile balloonfish may be eaten by tuna, dolphins and other pelagic fish. Some Asian cultures use them for medicinal purposes.

Their common name comes from the fact that they inflate themselves with water and extend their spines when threatened by a predator. Sadly, these fish are often sold inflated as souvenirs in some countries. I have observed many balloonfish in the Sea of Cortez. However, I have only encountered one that was inflated and that was last month at Isla Santa Catalina between La Paz and Loreto. It appeared as I rounded a rocky reef. Apparently some animal had disturbed it. As my camera rolled, it slowly deflated and swam away. In the sea, balloonfish inflate with water and can easily deflate. When beached, they may inflate with air and cannot reverse the condition.

As if the spines and inflation weren't a sufficient defense, balloonfish secrete a toxic substance on their skin and some internal organs are poisonous like their puffer relatives. Fortunately the toxin in these fish is weak compared to that of the puffers which specially trained Japanese chefs prepare as fugu. Despite that specialized training, more than 10,000 people have died from eating fugu.

While diving, I only observed adult balloonfish and wondered if the juveniles lived in another habitat or were just very secretive. Later research answered this question. When they mate, the male pushes the female to the water surface. Eggs fertilized and released there drift for several days as plankton before hatching into larvae. After about three weeks in this stage, the larvae metamorphose into juveniles. This stage is also pelagic (open water), answering my question. Here they often seek shelter from predators in drifting seaweeds and other material. Finally they transform into adults and enter the nearshore habitats where I see them.

Since we about to celebrate the passing of yet another spin around the Sun, I want to wish all my readers a Happy New Year. Much as I appreciate the new 7mm wetsuit that Don from Island Body and Soul gave me recently, my first resolution is to return to warmer waters as soon as possible! Fortunately Lindblad is sending me to Belize and the Honduran Bay Islands for six weeks starting later this month. Should be some interesting new observations to report from that part of the world since the diving is outstanding.

© 2003 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Balloonfish showing characteristic blotches, spots and spines; swimming in mid-water;
turning to look at me; defensive posture with spines extended and inflated with water.

This document maintained by Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia