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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 benthic-invertebrate eaters, that is, with coral-reef organisms, in this case, mainly fishes, that eat benthic (bottom-dwelling) invertebrates. Other topics relating to carnivory on coral reefs can be accessed via the icons.
 
 

Carnivory: eaters of shellfishes

About 40% if all reef fishes feed on benthic invertebrates, excluding those that eat cnidarians. Prey types include shellfishes, and squids & octopuses, considered in this section, and SEA URCHINS & BRITTLE STARS, found in their own section. The selection of invertebrate prey is not meant to be complete, but just to give a sampling of the diets of some of these carnivorous fishes.

NOTE as used here, a loosely defined category of invertebrates that bear a protective outer shell, such as lobsters, crabs, clams, and snails

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of spotted eagle ray taken from a video

"Oh, what a lovely sight, a spotted eagle ray. Sometimes you can find them digging in the sand for bivalves and snails, or see a cloud of disturbed sand as they swim away."- Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize.

NOTE Aetobatus narinari

 
 

About 5% of Caribbean reef fishes, including eagle rays and stingrays subsist primarily on bottom-dwelling shellfishes and other invertebrates. For photograph of southern stingray Dasyatis americana being fed at Stingray City, Grand Cayman example, the normal diet of a southern stingray is sand-inhabiting molluscs, crustaceans, worms, and small fishes that they catch and crush in vise-like jaws. The prey is stirred up from the sand by sustained "puddling" movements of the ray. Sierra et al. 2001 photograph of southern stingray Dasyatis americana foraging in company with a bar jackEcology of the marine fishes of Cuba. Smiths Inst Press, Wash., D.C.

Southern stingrays
Dasyatis americana
mooch for food in
Stingray City, Grand
Cayman Island


Bar jacks Caranx ruber
commonly hang out with
stingrays, and scrounge
for goodies overlooked
by the stingray 0.1X


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

"Wow! A monster! It's a goliathfish. The largest grouper and, indeed, the largest fish species on the reef.They reach such large size by eating lobsters, crabs, fishes, and sometimes even turtles." - Texas State Aquarium, Corpus Christi 2002

NOTE Epinephelus itajara

 
  histogram showing percentage composition of spiny-lobster diets in Florida
So, lobsters are eaten by various groupers, such as goliathfishes, but lobsters themselves forage at night in seagrass beds, and in sand and rubble areas for various bottom-dwelling shellfish prey. Analyses of stomach contents of night-foraging lobsters in Florida indicate that favoured prey types are small molluscs, especially the snail Cerithium lilttoratum, and arthropods. Cox et al. 1997 Mar Freshw Res 48: 671.
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of southern stingray foraging in the sand taken from a video

"Hmmm! Whose making all this dust over here? It's a southern stingray puddling the sand to get at something buried beneath. Look at all the zooplankton! Probably mysid shrimps. They were either stirred up from the digging or perhaps came over to feed on organic particles caught up in suspension. Wow, what a monster excavation!...wonder whose unlucky day it was..." - Cayman Islands, 2006

NOTE Dasyatis americana

 
 

photograph of southern stingray Dasyatis americana in company with a bar jack
Analyses of 18 stingray stomachs in the Bahamas discloses 106 prey categories of which 76% are crustaceans (crabs, shrimps, and stomatopods), 11% teleosts (wrasses, gobies, and parrotfishes), and about 5% combined molluscs (bivalves, cephalopods, and gastropods) and worms. Stomach fullness peaks in late afternoon. Fifty-eight percent of all prey is made up of epibenthic species such as fishes and crustaceans, showing that stingrays are readily able to catch moving prey. One individual was captured with its gut full of sand lancelets Branchiostoma, a primitive sand-inhabiting vertebrate, supporting the notion that a stingray's selection of prey is often "opportunistic". Gilliam & Sullivan 1993 Bull Mar Sci 52: 1007; Stokes & Holland 1992 J Fish Biol 41: 1043.

Southern stingray Dasyatis americana
with ubiquitous bar jack Caranx (Carangoides) ruber

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of southern stingray Dasyatis americana taken from a video of activities at Stingray City, Grand Cayman Island

"You can get quite a nice look at the jaws of a stingray here. Top and bottom are just roughened epidermis, but their crushing potential is immense." - Grand Cayman, 2006

NOTE Dasyatis americana

 
 

photograph of shoal of goatfishes
Other snuffling-type predators of sand-dwelling shellfishes are goatfishes. A goatfish's barbels are covered with tastebuds and function like long, slender tongues. When not sifting in the sand for small crustacean and worm prey, goatfishes form up in loose schools and move about the reef.

 

 

 

The diet of yellow goatfishes Mulloidichthys
martinicus
includes molluscs, crabs, shrimps,
worms, and other small invertebrates 0.15X

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

"Talk about great dinner guests. Goatfishes vacuum the sand for annelids, molluscs, shrimps, and other small invertebrates. Their sensory barbels probe into the sand and not much escapes them. Whoah!...this spotted goatfish has the manners of...well, a goat!" - Bonaire, 2003

NOTE Pseudopeneus maculatus

 
 

photograph of juvenile queen conch Strombus gigas
Conchs settle from the plankton as tiny veliger larvae and shortly metamorphose into the shelled form. These early juveniles have thin shells and are preyed upon by numerous benthic-feeding animals including polychaetes, crabs, shrimps, and fishes. By early adulthood their shells thicken enough to resist these early-stage predators, but they now confront a new array of larger predators. These include eagle rays, hogfishes, permits, spiny lobsters, crabs, nurse sharks, and loggerhead turtles. Iversen et al. 1986 Bull Mar Sci 39: 61.

 

 

 

At this stage of life, a juvenile queen conch Strombus
gigas
is protected from most small predators 0.6X

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

"Well, what have we here? A pair of milk conches just sitting out on the sand. Other than their strong shells, conches have no protection, and we all know that their flesh is quite tasty. I wonder if these two are at risk of being eaten?" - Grand Cayman, 2006

NOTE Strombus costatus

 
 

photograph of milk conch Strombus costatus in close view
Thus, by about 10-15cm shell length most conchs have attained "size-refuge" against many predators. Predators such as crabs and lobsters that attack by peeling open the lip of the shell, or those that crush, drill, or simply rip the conch out of its shell, become less of an issue as the conch grows in size. Jory & Iversen 1983 Proc Gulf Carib Fish Instit No. 35: 108.

NOTE for this reason, this is the size recommended for their release from hatcheries

A milk conch Strombus costatus peeks out from within
its massive shell 0.75X. The structure on the left is
the operculum, which functions as a protective plug
after the soft tissues of the snail have fully withdrawn
into the shell, and also as a kind of lever that the
snail uses to lurch itself across the sand . Note
the pair of eyes on the right

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

"Hogfishes have quite strong jaws and like to root in the sediments for snails and other shelled invertebrates." - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize

NOTE Lachnolaimus maximus

 
 

photograph of an intermediate-phase hogfish
Hogfishes consume molluscs and crustaceans that they dig out of loose sediments with their long jaws. Analyses of gut contents of 67 hogfishes in Belize indicate that 17 bivalve and 43 snail species are eaten, with the latter representing the bulk of the diet. Crustaceans, especially crabs and hermit crabs, are much less preferred than molluscs. Wainwright 1987 J Zool Lond 213: 283.

 

 

 

Intermediate-phase hogfish
Lachnolaimus maximus 0.15X

  A hogfish's jaws are large and can crush many types of shellfishes, but certain snails are preferred. Arrayed below are different-sized photos of one of the hogfish's favourite prey, the snail Cerithium litteratum. Only one is in correct scale to the size of the fish in the photograph. Based on the gape of the hogfish's jaws and your estimate of their strength in relation to the crushability of Cerithium's shell, choose the photo that you think is the snail's actual size relative to the hogfish. Wainwright 1987 J Zool Lond 213: 283.
 
photograph of hogfish Lachnolaimus maximus with an array of different-sized prey snail Cerithium litteratum

Terminal-phase hogfish Lachnolaimus
maximus
of about 50cm in length
investigates some rocks for food

If you selected the smallest snail shown (2.5cm), then you are correct. This is much less than the gape of the hogfish's jaws, and probably smaller than you thought. Unless there is something special about the taste or nutrient content of Cerithium, or its abundance in the habitat, it seems that the limitation on size of snail prey is dictated by the force able to be exerted by the hogfish to crush the shell. Larger shells appear simply too strong to be crushed even by a large predatory hogfish

 

If a shelled prey, such as a bivalve, is too tough to crush in the jaws, then why not use a nearby rock as an anvil to do the job? Tool-use by coral-reef fishes is not common, but is done by certain species of wrasses on various world reefs. One of these in the Caribbean is the yellowhead wrasse Halichoeres garnoti, which in Key Largo, Florida is observed using a rock of terrestrial origin against which to smash a scallop (unidentified) into photograph of yellowhead wrasse Halichoeres garnotismaller pieces that are then consumed. In this instance, the prey scallop is approximately 6 times wider than the wrasse’s mouth. Common behaviour in such instances is for the fish to whack the prey against a rock using side-to-side motion of the head, as described here, or for the fish to hold the prey in its jaws and then rush head-on into a rock, as is done for smaller bivalve prey also by wrasses. Coyer 1995 Bull Mar Sci 57 (2): 548.

NOTE tool-use by animals is more commonly found in birds and primates but, perhaps owing to their more “restrictive” body morphology, is rare in fishes. To date, the behaviour is described in fishes only for wrasses (F. Labridae), with their use of rock anvils, and for archer fish (F. Toxotidae), with their use of mouth-projected water jets to knock down prey insects from overhead perches

Yellowhead wrasse Halichoeres garnoti 0.4X

 
  The graphs below show what different labrid fishes (bluehead wrasses: Thalassoma bifasciatum, hogfishes: Lachnolaimus maximus, slippery dicks: Halichoeres bivittatus) in the Florida Keys and Dry Tortugas are eating in the way of sand- and rubble-inhabiting invertebrates. The values above the bars indicate the percentage composition for each category of prey:
 
histogram showing percentage composition of diet of bluehead wrasses in the Florida Keys/Dry Tortugas histogram showing percentage composition of diet of hogfishes in the Florida Keys/Dry Tortugas histogram showing percentage composition of diet of slippery dicks in the Florida Keys/Dry Tortugas
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a trunkfish taken from a video

"Here's a busy little fellow. Trunkfishes have snoutlike mouths, I guess the better to eat worms, crabs, shrimps, and other invertebrates from the sand and between the rocks." - Little Cayman, 2001

NOTE a honeycomb cowfish Lactophrys polygonia

 
 

photograph of a batfish
In Brazil, batfishes hunt nocturnally and during early-morning hours for a variety of invertebrates including hermit crabs, crabs, shrimps, amphipods, isopods, snails, clams, worms, sea urchins, and brittle stars. The prey are either snapped up or rooted out of hiding with use of the mouth and rostrum. Gabron & Castro 1999 J Fish Biol 55: 588.photograph of batfish Ogcocephalus nasutus showing rostrum

NOTE the bony projection of the head of a batfish that is used as a plow to uproot prey in the soil


Shortnose batfish
Ogcocephalus
nasutus
0.5X

 

Closer view of a portion of
the rostrum and the mouth

  Grunts in Bermuda (bluestriped: Haemulon sciurus, tomtate: Haemulon aurolineatum, French grunt: Haemulon flavolineatum) feed primarily on sand- or mud-inhabiting invertebrates, including many crustaceans and polychaete worms. The histograms show the proportion of each invertebrate type in the fishes' springtime diets. Alheit 1981 Proc 4th Int Coral Reef Sympos 2: 544.
 
histogram showing percentage composition of bluestriped grunt diet in Bermuda in springtime histogram showing percentage composition of tomtate diet in Bermuda in springtime
histogram showing percentage composition of French Grunt diet in Bermuda in springtime

There are two points of interest in these graphs:

1. selection of prey by a carnivore is governed by tastiness and nutritional value, by a prey's relative abundance in the habitat, and by ease of capture, ingestion, and digestion of a prey. By their common-ness in these grunts' diets, polychaetes could be fulfilling some or all of the above.

2. the 3 grunt species have to some extent partitioned the food resources in their habitat such that competition between them is minimised.

 
  Certain species of large Caribbean worms, such as Chloeia viridis shown in the photos below, eat both live prey and scavenge on dead matter. Photographs courtesy Anne Dupont, Florida.
 
photograph of polychaete Chloeia viridis eating Bulla photograph of polychaete Chloeia viridis scavenging on an opisthobranch Bulla occidentalis photograph of head end of worm Chloeia viridis
A polychaete Chloeia viridis investigates what could be a live, withdrawn, snail Bulla occidentalis...or... ...it could be just a dead shell and the worm is scavenging. Note how its head inserts completely into Bulla's shell Head end of worm Chloeia viridis showing ventral mouth, a couple of tiny eyes, and multiple palps & tentacles
 
 

Carnivory: eaters of squids & octopuses

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of two divers with an inking octopus, taken from a video

"Oh, that's not very nice, and poor dive practise. He'd better be careful he doesn't get bitten. Octopuses have toxic saliva and they use it to immobilise their own prey - not usually in their own defense. Lots of fishes, like barracudas, would like to chomp down this little fellow." - Bonaire, 2003

NOTE Octopus sp.

 
  Cephalopods, such as squids and octopuses, are eaten by a variety of fishes, including...
 
photo collage of cephalopod-eating sharks in the Caribbean
 

Cephalopods are eaten by numerous roving reef-fishes such as barracudas, and a few groupers and snappers...

  photo collage of cephalopod-eating predatory reef fishes
 

Cephalopods are also eaten by several lie-in-wait ambushing-type species.

 
photo collage of several cephalopod-eating lie-in-wait fish predators
 
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