column spacer Defenses

Defenses of fishes can be categorised into an heirarchical "cascade" beginning with:

1) avoid detection
2) take evasive action if spotted
3) prevent capture
4) prevent being eaten if captured
5) escape

Of these, the last is obviously the most important, but success in any of the others will aid in achieving it. Note that costs and risks to the prey escalate from first to fourth. The fifth and ultimate category, that of escape, can come at any time and won't be considered further here. The first task of any potential prey fish is to avoid detection. Helfman et al. 1997 The diversity of fishes. Blackwell Sci Publ.


hot buttons for defensive "tasks" for fishes

Fish defenses: prevent capture: hard-to-capture body shape

  If spotted by a potential predatory fish, the next "task" of the intended prey fish is to prevent capture. This may include having a hard-to-capture body shape or being able to associate with a superior defense, both topics dealt with here.
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a cowfish taken from a video

"Here's a bony-looking fellow. No kidding! A honeycomb cowfish must be ranked as the number-one-hard-to-get-your-mouth-around-body-shape by its predators!" - Turks & Caicos 2005

NOTE Lactophrys polygonia


photograph of a scrawled cowfish Lactophrys quadricornis
The rectangular-shaped boney bodies of cowfishes and trunkfishes are not only hard to eat, but might leave the predator with part of the prey hanging out of its mouth. This could hamper the predator's ability to escape from its own photograph of a smooth trunkfishpredators.


Scrawled cowfish Lactophrys quadricornis 0.25X


trunkfish Lactophrys triqueter 0.25X

seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a porcupinefish taken from a video

"Oh, who's this shy-looking fellow? When porcupinefishes get mad, they puff themselves up and become what must be an impossible-to-eat hors d'oeuvre for a predator!!" - Turks & Caicos 2005

NOTE Diodon hystrix


photograph of a balloonfish photograph of a porcupinefish Diodon hystrix
During normal daily activity, the spines of balloonfishes and porcupinefishes face backwards and lie tucked away. The spines are modified scales with locking structures at their bases that keep them erect when the fishes inflate.

Balloonfish Diodon


Diodon hystrix


photograph of an inflated balloonfish Diodon holocanthus, courtesy Anne Dupont, Floridaphotograph of a balloonfish Diodon holocanthus inflated
When attacked or otherwise irritated, balloonfishes rapidly inflate their bodies to 3-fold normal size with water. This raises the spines into a prickly barrier, protecting eyes, mouth and, to some extent, fins. The water is taken into the stomach, which expands 100-fold in size and comes under considerable pressure. The spines are pokey, but not venomous. It takes about 20sec and numerous puffs for full inflation.

When a balloonfish Diodon holocanthus is fully inflated, its motility is severely restricted. Note in the close-up view how the spines form a protective barrier in front of the mouth. When uninflated, these spines lie flat between the eyes facing backwards . Close photo courtesy Anne Dupont, Florida.


Prevent capture: associate with a superior defense

seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of wrasses in a sea anemone, taken from a video "Do you see the little wrasses ducking into the anemone for protection as we approach? This is a low-cost method of defense. When bullies come, just hang out with someone bigger and tougher. I wonder how they avoid being stung. Maybe their skin mucus helps, or perhaps they're just extra-careful in amongst the tentacles." - Aruba 2006.

photograph of blue chromises Chromis cyanea in a coral photograph of  flamefish Apogon maculatus in amongst Diadema spines
When danger threatens, many small reef fishes find sanctuary within the interstices of coral, amongst the protective spines of sea urchins, and within the tentacles of sea anemones.


Blue chromis Chromis cyanea and other
planktivorous species prefer to feed
above protective coral heads, then duck
into them for cover 0.2X


Flamefishes Apogon maculatus hide
within the spine canopy of a black
sea urchin Diadema antillarum 0.25X

Several fishes, possibly bigtooth cardinalfishes
Apogon affinis,
shelter within the spines of a
black sea urchin Diadema antillarum 0.5X
phtograph of bigtooth cardinalfishes Apogon affinis in a sea urchin  

photograph of a sea anemone Condyactis gigantea on a reefAt least 10 species of reef fishes live facultatively in or near sea anemones Condylactis gigantea. Some shelter in touch with the tentacles, while others live inbetween the tentacles without appearing to touch them. Hanlon & Kaufman 1976 Bull Mar Sci 26: 225.

NOTE a relationship of 2 organisms in which either or both members opt to be together, as opposed to being required to be together (thus, obligatory). All fish-anemone associations in the Caribbean appear to be facultative


photograph of several sharknose gobies Elacatinus evelynae in the tentacles of a giant anemonephotograph of several cleaning gobies Elacatinus sp. in the tentacles of a giant anemone
Between cleaning sessions, different species of cleaner gobies may shelter within the protective tentacle canopies of giant sea-anemones Condylactis gigantea.


Sharknose gobies


Cleaning gobies Elacatinus sp.
swim through the tentacles
of a giant anemone 0.5X

photograph of an anemonefish in its host
Although not found in the Caribbean region, Indo-Pacific anemonefishes shelter within the nematocyst-bearing tentacles of sea anemones. Apparently, the anemonefishes are initially stung by the host anemone but, after a period as short as a few minutes, the fish in some way modifies the chemical composition of its mucous coating to attain complete protection.





Dusky anemonefish Amphiprion melanopus 0.7X

hot button for take evasive action if spotted part of fish defenses hot button for prevent capture part of fish defenses hot button for prevent being eaten if captured part of fish defenses