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Carnivory hot buttons for carnivory part of Biology of Caribbean Coral Reefs website hot button for zooplanktivore part of BCCR hot button for spongivore part of BCCR hot button for corallivores & other cnidivores part of BCCR hot button for gorgonivores part of BCCR hot button for benthic invertebrate-eaters part of BCCR hot button for piscivores part of BCCR
This part of carnivory deals with piscivores, that is, with coral-reef organisms, including fishes, sharks, squids, and marine mammals, that eat fishes. Other topics relating to carnivory on coral reefs can be accessed via the icons.
 
 

Carnivory: cooperative hunting by fishes

This section deals with cooperative hunting by fishes, ones that hunt in packs, sometimes with the assistance of octopuses. Topics dealing with ROVING PISCIVORES, AMBUSH PISCIVORES, and WOUNDED FISHES can be found in their own sections. The section concludes with consideration of mouth design in fishes in relation to diet.

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a group of fishes engaged in cooperative hunting, taken from a video

"Now here’s a determined group…a bar jack, a hogfish, and two trumpetfishes, making their way in formation across the reef.  Note how the group breaks apart as they search for food…whoops, something doesn’t like them…is it a grouper?…why is it so grumpy?!" - Bonaire 2003

 
 

When carnivorous fishes work together to find food it is known as cooperative hunting, or cooperative feeding. This activity can be in the form of shadow-feeding, where one species hangs around another species that is actively hunting, and scrounges food from it, or in the form of nuclear-hunting, where fishes hunt in a group in a concerted way centred around one specie, the nucleus. Common participants are bar jacks, hogfishes, trumpetfishes, and moray eels. As mentioned above and as improbable as it seems, octopuses are sometimes involved. These topics will be considered in the subsections to follow.

NOTE this comment relates to the general vulnerability and tastiness of octopuses, which makes them favoured prey of other fishes, like groupers, and of sharks and dolphins.

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of bar jack hunting with stingray taken from a video

"Do bar jacks ever hunt for themselves?  We see them shmoozing with several species of reef fishes, but their favourites may be southern stingrays.  Do they get tid-bits, I wonder?  All this time and I’ve not seen a single nibble." - Little Cayman 2001

NOTE Caranx ruber

 
 

Carnivory: cooperative hunting by fishes: shadow-feeding

 

photograph of bar jack shadow-feeding with a stingray
Several types of fishes, most notably bar jacks and hogfishes, will deviate from their normal hunting activities to team up with other fishes in a behaviour known as "shadow-feeding". The shadowing fish seems to do little work for the "team", and behaves more like a food thief or even a parasite as it collects food stirred up by the fish being shadowed. It is not known whether the cooperativity is genetically based, or is it something learned by the shadowing fishes.

 

 

Bar jack Caranx ruber shadow-feeding with a southern
stingray Dasyatis americana 0.12X. The regular diet of
a bar jack is fishes, but it may additionally consume
soft-bodied invertebrate prey stirred up by its "partner"

Let's hear from the stingray and jack on the matter:

 
cartoon 1 of a series illustrating a conversation between a stingray and its shadow-feeding bar jack cartoon 2 of a series illustrating a conversation between a stingray and its shadow-feeding bar jack
cartoon 3 of a series illustrating a conversation between a stingray and its shadow-feeding bar jack cartoon 4 of a series illustrating a conversation between a stingray and its shadow-feeding bar jack
cartoon 5 of a series illustrating a conversation between a stingray and its shadow-feeding bar jack cartoon 6 of a series illustrating a conversation between a stingray and its shadow-feeding bar jack
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a hogfish and bar jack hunting together

"This bar jack  is looking for food items stirred up by a hogfish.  This doesn’t seem like cooperative hunting.  Maybe it’s a type of encounter competition involving theft of food." - Turneffe Island, Belize 2000. Video courtesy Andy Stockbridge, Belize

NOTE Lachnolaimus maximus

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of bar jack shadow-feeding with several goatfishes

"Here’s another bar jack mooching for food, this time from a group of rather busy yellow goatfishes.  Let’s watch if the jack gets lucky…nope, don’t think so.  The goatfishes are getting small worms and crustaceans from the sand." - Little Cayman 2001

NOTE Mulloidichthys martinicus

 
 

Carnivory: cooperative hunting by fishes: nuclear hunting

 

When a cooperative hunting group centres around a species accustomed to working within the interstices of the reef to find its own prey, the partnership becomes a nuclear-hunting group. Often such a group has a moray eel or even octopus as its nucleus, as both photograph of a hogfish, bar jack, and moray eel engaged in nuclear huntingtypes of predator are used to working within the 3-dimensional matrices of the reef. When small fishes and crustaceans are flushed out by the nuclear species they are caught and eaten by the partner fishes.photograph of a Spanish hogfish and moray eel engaged in nuclear hunting

 

 

 

 

0.12X


Different combinations of nuclear-hunting groups
involving moray eels Gymnothorax sp., Spanish hogfishes
Bodianus rufus, and bar jacks Caranx ruber 0.2X

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a Spanish hogfish, moray eel, and bar jack engaged in nuclear hunting

"Well, another group of fishes making its way across the reef…this time it’s a green moray joined by a hogfish and, who else?...oh, a bar jack!" - Bonaire 2003

NOTE Gymnothorax funebris

 
 

photograph of a hogfish in company with a trumpetfish possibly as part of a nuclear hunting group
Trumpetfishes commonly link up with other fishes to cross open areas of the reef. Is this just for safe transit or does it represent a nuclear-hunting group? A trumpetfish will often change its colour to match that of the fish it is accompanying. Aronson 1983 Bull Mar Sci 33: 166; Deloach 1999 Reef fish behavior New World Publ, Florida.

 

 

A trumpetfish Aulostomus maculatus follows a hogfish
Lachnolaimus maximus across the reef, with the trumpetfish
possibly being slightly more blanched than usual 0.15X

 

As well as fishes already seen in these photographs, nuclear-hunting groups may include snappers and groupers. In the photo below, a hogfish, bar jack, and trumpetfish join in what could be a mutually beneficial hunting group. Or is it? Other possible explanations of the behaviour are:

Encounter competition: this refers to theft of food by one fish from another. In other words, rather than cooperating the participants are simply there to steal one another's food.

photograph of a hogfish, trumpetfish, and bar jack in what seems to be a nuclear-hunting groupParasitism: in the case of nuclear-hunting group that includes a moray eel or octopus, are the other fishes parasitically exploiting its time and energy? What do the moray and octopus get out of it?

Transport camouflage: as noted earlier, trumpetfishes like to align themselves with other organisms for camouflage, such as gorgonians. Perhaps the trumpetfish uses the other fishes as a means of disguising itself for safe transport across the reef - an idea supported by the observation that the trumpetfish may change its body coloration to match that of its host(s). Ideas from Deloach 1999 Reef fish behavior. New World Publ, Florida.

A hogfish Lachnolaimus maximus, bar jack
Caranx ruber
, and trumpetfish Aulostomus
maculatus
cross the reef as a group 0.15X

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a Spanish hogfish engaged with a moray eel in nuclear hunting

"This little hogfish seems to want to join the moray, perhaps to hunt across the reef. Oh bummer! Maybe I scared the hogfish away. Let's follow the moray for a bit." - Turks & Caicos 2005

NOTE Bodianus rufus

 
 

Studies in the Red Sea show that groupers commonly form feeding associations with moray eels and sometimes with octopuses. Because of their slippery shapes, the nuclear or primary predator (moray eel or octopus) is able to flush prey such as small damselfishes and shrimps from crevices too small for the grouper to enter. The behaviour is thought to be learned by the grouper, while the nuclear predator seems to be naive. Although a naive octopus would seem to be at risk when hunting with a grouper, it does not seem to be eaten. The relationships photograph of tiger grouper Mycteroperca tigris resting on the reefof the organisms comprising a nuclear-hunting group are not well understood, and many questions remain unanswered. The first is, how do the moray and octopus benefit, other than obtaining prey that they would normally capture? Diamant & Shpigel 1985 Envir Biol Fishes 13: 153.


Caribbean tiger groupers Mycteroperca tigris prefer to
eat fishes, but will also eat other prey if the opportunity
arises. If confronted with a naive octopus who might,
in other circumstances, act as a nuclear partner, what
initially stops the grouper from eating it? So, in a broader
context, how does such a hunting group ever evolve?

0.2X

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs photograph of chestnut moray slithering through the reef, taken from a video

"Morays sure are slithery creatures. This little chestnut moray has no problem slipping through the smallest cracks. I wonder where it's going and what it's finding?" - Aruba 2004

NOTE Enchelycore carychroa

 
 

Mouth design of fishes in relation to diet

Often the structure of a fish's mouth will provide clues as to the type of prey eaten. Features to note are jaw structure, extent of gape, nature of the teeth (straight, fused, fangs, raggedy), location of mouth (at front of head, beneath head, on an extended face), and ancillary structures such as barbels and fishing lures. The lever mechanics of the jaw will tell a lot, but require dissection and measurement. Photographs of 12 different types of fishes are arrayed below. See how you do at matching a fish with its diet and, for some species, with eating habits. The quiz is a bit hit-and-miss, but may be a good review of the general topic of carnivory.

 
quiz on mouth design of fishes in relation to diet
   
  The match-ups shown below are not "hard science", and there are overlaps and generalities, but here they are:
 
answers to quiz on mouth design in relation to diet in reef fishes
 
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