Defenses
 
column spacer Defenses
 
 

Fish defenses

hot buttons for defensive "tasks" for fishes hot button for avoid detection part of the section on fish defenses in the Biology of Caribbean Coral Reefs website hot button for take evasive action part of the section on fish defenses in the Biology of Caribbean Coral Reefs website hot button for prevent capture part of the section on fish defenses in the Biology of Caribbean Coral Reefs website hot button for prevent being eaten if captured part of the section on fish defenses in the Biology of Caribbean Coral Reefs website

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 tim,e 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.

 
 

Fish defenses: avoid detection: camouflage

There are many ways for a potential prey fish to avoid detection, but some of the main ones are camouflage, considered in this section, and to HIDE AWAY or otherwise CONFUSE THE PREDATOR, considered in their own sections.
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a roughhead blenny taken from a video

"Camouflage is quite common amongst reef fishes. and can involve combinations of colour, pattern, shape, and behaviour. What may seem obvious to us, like this roughhead blenny, may not be so obvious to the blenny's predators. But, are these blue spots on the coney for camouflaging...or for something else? In many cases we're just not sure." - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize.

NOTE Acanthemblemaria aspera

 
 

photograph of
Camouflage involves several interacting features, including colour, pattern, structure, and behaviour. It can disguise a prey fish from its predators, or hide a predatory fish from both its prey and its own predators.

photograph of
The variegated colours of the
ambush-attacking sand-diver
Synodus intermedius
blend
with those of its weedy resting
place 0.6X. Photo courtesy
Anne Dupont, Florida

 


Another ambush predator, the
peacock flounder Bothus lunatus,
employs blue rings as pattern-
disruptors for camouflaging 0.5X

 
 

photograph of
As for all camouflage artists, strategic selection of resting spot can aid in the camouflaging illusion.

 

 

 

 

 

Spotted scorpionfishes Scorpaena plumieri
often rest on their pectoral fins and sit very
still waiting for prey to happen by 0.5X.

Photograph courtesy Anne Dupont, Florida

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a filefish hiding in a gorgonian taken from a video

"It's not enough to have a good matching colour pattern to be well camouflaged. It also requires the right sort of behaviour. This slender filefish is doing everything right as it mimicks its background of gorgonians." - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize

NOTE Monacanthus tuckeri

NOTE someone else is also taking advantage of this gorgonian in order to camouflage itself. Replay the video and see if you can see it. Answer at bottom of page.

 
 

photograph of a juvenile slender filefish Monacanthus tuckeri courtesy Anne Dupont, Florida
Age and experience also play a role in good camouflage. Unlike the adult slender filefish in the previous video, this juvenile of the same species appears to lack the same experience in matching its reticulated skin pattern to its environment. It's a good effort, but the fish is still obvious. Natural selection would tend to eliminate such "failures" from the gene pool.

 

 

 

 

Juvenile slender filefish Monacanthus tuckeri 1X.
Photograph courtesy Anne Dupont, Florida

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a scorpionfish taken from a video "Camouflage can be doubly beneficial to ambush-type predators like scorpionfishes and trumpetfishes. They can hide from their own predators as well as from their intended prey." - Little Cayman 2002
 
 

photograph of a trumpetfish Aulostomus maculatus with a fan gorgonian photograph of a trumpetfish Aulostomus maculatus with sponges
Trumpetfishes Aulostomus maculatus align themselves against all manner of vertically projecting structures. This serves the dual purpose of camouflaging them from their own predators as well as from their intended prey, which they usually attack from a head-down orientation.


...against a fan gorgonian
Gorgonia ventalina 0.15X

 

...and against 2 sponges 0.1X

 
  photographs of faces of spotted scorpionfishes
In addition to matching colours and patterns, surface adornments may also be involved in the subterfuge. Photographs courtesy Anne Dupont, Florida
 
 

photograph of seahorse Hippocampus erectus courtesy Anne Dupont, Floridfa
This lined seahorse Hippocampus erectus is not only good at matching its body colour to that of the substratum, but its frilly skin surface adds another dimension to the camouflage, leading to an almost perfect matching with the variegated bottom cover on which it is resting. Many other species of seahorses are brightly coloured, perhaps signifying that their flesh is distasteful...but not this one. Photograph courtesy Anne Dupont, Florida.

 

 

If you find it hard to locate the seahorse, first try to distinguish its
head. Its eye is located just below and to the right of centre, and it
is looking towards the 4 o'clock position. The rest is easy 0.8X

 

photograph of a seahorse Hippocampus erectus with its prominent eye digitally removed

 

 

 

 

 

Here's the same photo with the eye digitally removed
to show that it is even harder to discern the fish in
the absence of its eye as a visual reference.

 
 

photograph of a sargassumfish
Sargassumfishes Histrio histrio are gulping-type predators related to frogfishes. Their surface adornments and colour patterns resemble sargassum weed that they are named after, and which they often inhabit. They are voracious predators that attack prey fishes, some even bigger than themselves, from ambush positions. it is extremely difficult to keep sargassumfishes in aquariums with other fishes, as they tend to eat them all.

 

 

 

Sargassumfish Histrio histrio 1.3X

 

photograph of sargassumfish Histrio histrio in a mangrove habitatAlthough floating Sargassum weed is the usual habitat for sargassum fishes Histrio histrio, in some areas such as St. John, US Virgin Islands, they may be found in algae on the roots of mangrove trees. Rogers et al. 2010 Coral Reefs 29: 577.

 

 

 

Sargassum fish Histrio histrio nicely
camouflaged among red algae Acanthophora
spicifera
on the prop root of a mangrove tree

 

photograph of head of a scorpionfish Scorpaena plumieriPerspective is also important in camouflage. A potential prey fish must learn to recognise its predators from different distances and angles.

 

 

 

 

 

A naive prey fish may have this face of a spotted
scorpionfish Scorpaena plumieri as its last view ever 1X

  Ambush predators attack suddenly from hidden locations. In fact, many species including scorpionfishes and trumpetfishes are "gulpers", and rely on fast opening of their jaws to suck in prey rather than quick body movements. These 4 photos show 4 concealed or partly concealed predators. Suppose that you are a naive fish going about your business and you come across them...would you be able to recognise potential danger fast enough to save your life?
 
photograph of yellow stingray Urolophus jamaiensis photograph of a scorpionfish Scorpaena plumieri
Yellow stingray Urolophus jamaicensis lies buried during the day. Its eyes are stalked and can rotate to provide 360 degree vision of both prey fishes and crustaceans, as well asits own predators 0.6X Scorpionfishes Scorpaena plumieri have highly toxic venom in their spines, and the undersides of their large pectoral fins are warningly coloured. Thus, they can sit out in the open with impunity, waiting for prey fishes and crustaceans to happen by 0.3X
photograph of peacock flounder Bothus lunatus photograph of a pipefish Acentronura dendritica
Peacock flounders Bothus lunatus are masters of camouflage, in this case mainly involving differentially coloured chromatophores or colour-cells in the skin. They prey on small fishes, worms, and crustaceans 0.2X With its frills and waving-about posture, this little pipefish Acentronura dendriticaresembles a piece of seaweed. Like their close relatives, seahorses, they are gulping-type predators, subsisting on zooplankters including larval fishes 1X
 

photograph of a pufferfish wrapped in a protective mucous cocoon, photo courtesy Linda Ianiello, FloridaParrotfishes and a few other types of reef fishes overnight in protective mucous cocoons secreted from their gills. The cocoons are thought to provide a chemical camouflage from night-hunting predators such as morays. Photograph courtesy Linda Ianiello, Florida.

NOTE this means that a predator could approach close enough to touch and still not smell its prey

 

 

A fish, possibly a pufferfish, protected
inside a nighttime mucous blanket 1X

 

photograph of princess parrotfish Scarus taeniopterusphotograph of queen parrotfish Scarus vetulaActually, only 2 of 8 species of Scarus parrotfishes in the Caribbean are known to produce mucous cocoons, the princess parrotfish Scarus taeniopterus and the queen parrotfish S. vetula. Sazima & Ferreira 2006 Coral Reefs 25: 212.

Queen parrotfish
Scarus vetula

 


Princess parrotfish Scarus taeniopterus

 
 
Let's see what the nighttime-preying squirrelfish has to say to the mucus-blanketed parrotfish on the matter: cartoon 1 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket
cartoon 2 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket cartoon 3 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket
cartoon 4 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket cartoon 5 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket
cartoon 6 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket cartoon 7 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket
cartoon 8 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket cartoon 9 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket
cartoon 10 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket cartoon 11 of 11 showing a predatory nighttime-hunting squirrelfish conversing with a herbivorous daytime-feeding parrotfish wrapped in a mucous blanket
 
 

photograph of a trumpetfish camouflaged within a gorgonian along with a filefish

FROM THE VIDEO ABOVE OF A CAMOUFLAGED SLENDER FILEFISH:

Can't spot the other organism in the gorgonian along with the filefish? It's a trumpetfish, standing vertically:

 
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