Reef Fish Feeding
Odyssey Expeditions – Reef Fish Feeding
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Introduction
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Fishes feed on plants, animals, plankton, and detritus
Feed at night (nocturnally) or during day (diurnally)
Mouth shape and size determines prey type
Diets can change throughout life
Generally all start out as planktivores during larval stage
in water column
• As juveniles settle on reef they change to adult diet
• Diets are not written in stone, most fishes switch prey
when something else is abundant (called optimal
foraging theory)
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Introduction
• Most fishes forage by day
• Low light hours when most feeding occurs
• Vision a key to daytime foraging
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Feeding Categories
• Herbivores – Consume plant material (algae,
seagrass)
• Carnivores – Feed on animals (inverts, plankton,
fishes)
– Invertebrate feeding – primary prey are invertebrates
– Piscivores – fishes are the primary prey
– Planktivores – prey upon planktonic creatures
• Detritivores – Consume decomposing plant and
animal matter
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Feeding Behaviors
• Specialist
– Single food source
– When food source scarce they must change or perish
• Generalist
– Feed on a variety of foods (no preference)
– Generally stay in their feeding category
• Opportunist
– Feed on anything regardless if in feeding category or
not
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Herbivores
• Small number of herbivorous
species
• Large population sizes
• Common families (parrotfish,
damselfish, surgeonfish)
• Mostly found in water < 30’
(more light = more algae)
• Consume large amounts of
algae
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– Healthy populations consume
most of daily algae production
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Herbivores
• Highly maneuverable
– Swim with pectoral fins
– Many have compressed bodies
• May contain organisms in gut
to enable efficient plant
material digestion
• Incisor-like teeth makes
feeding on algae easier (may
be fused to form beak like
structure)
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Herbivorous Feeding Strategies
• Nomadic Feeders
– Scour over large areas of the reef in
search of algae
– Parrotfishes, surgeonfishes
• Sedentary Feeders
– “Farm” mats of algae
– Damselfishes
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Nomadic Feeders
• Parrotfishes
– Use beaklike teeth to
scrape algae off hard
surfaces
– Large amounts of
calcium carbonate is
taken in along with algae
– Can excrete over 1 ton
of sand per year
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Nomadic Feeders
• Surgeonfishes
– Mouths enable them to pluck algae efficiently
– Feed alone or in large number
– Can overwhelm damselfishes and therefore
eat their farm-fresh algae
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Sedentary Feeders
• Damselfishes
– Most abundant
– Aggressively guard mats of algae from other
herbivores
– Can be aggressive towards divers
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Herbivorous Fishes
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Blennies
Damselfish
Gobies
Mullets
Chubs
Surgeonfish
Triggerfish
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Planktivores
• Most larval/juvenile fishes are
planktivores
• Planktivores continue this
feeding type in adulthood
• Water column yields the most
plankton
• Many have protrusible
upturned mouths
• Good eyesight
• Long gill rakers allow them to
strain plankton from water.
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Planktivores
• Quick, schooling, and/or
large fishes feed up in the
water column
– Chromis, creole wrasse,
manta ray
• Generally the smaller fishes
school in large #’s for
protection (silversides)
• Slower fishes feed just
outside their hiding places
– Yellowhead jawfish, garden
eel, fairy basslet, sweepers
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Planktivorous Fishes
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Cardinalfish
Garden eel
Jawfish
Manta ray
Silversides
Sweepers
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Bicolored Damselfish
Blue Chromis
Brown Chromis
Creole Wrasse
Blackbar Soldierfish
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Invertebrate Feeding Carnivores
• Excellent maneuverability
• Good close-up vision (inverts
excellent at camouflage)
• Mouth types designed for
specific prey
• Typically hunt alone, no schooling
(avoids competition for limited
resource but riskier)
• Rely on other defenses
(spines-porcupine fish, body
plates-trunkfish, broad bodiesangelfishes)
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Invertebrate Feeding Carnivores
• Goatfish use chemical
sensing barbels to locate
prey in sand
• Spotted eagle rays use
their dental plates to crush
shells
• Trunkfish shoot a jet of
water at the prey to
uncover it
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Invertebrate Feeding Carnivores
• Angelfishes feed primarily on sponges
– Prefer those will less spicules
– Secrete layer of mucus to protect stomach
from spiclules
– Only a few bites are taken from each sponge
so it does not kill the sponge.
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Invertebrate Feeding Carnivores
• Butterflyfishes use their tubular mouths to
pluck feather duster and calcareous tube
worms from their tubes
• Surgeonfish and parrotfish remove coral
polyps in their quest for algae
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Invertebrate Feeding Carnivores
• Night predators
– Most invertebrate activity at night
– Difficult to see
– Rely on touch, taste, smell and
lateral lines
– Large mouths open wide and
create suction to capture prey
– Many have large eyes to help
vision
– Generally red or muted in color
(camouflage for the night)
– Grunts and snappers move to
seagrass beds to feed at night,
during the day they hang on the
reef in schools
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Invertebrate Feeding Carnivores
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Angelfish
Bigeye
Blennies
Cardinalfish
Cowfish
Trunkfish
Drums
Eagle Ray
Filefish
Flounder
Goatfish
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Grunts
Hamlet
Hawkfish
Goliath Grouper
Moray
Porcupinefish
Sand Tilefish
Snapper
Stingray
Triggerfish
Wrasse
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Piscivores
• Foraging strategies
– Pursuit
• Jacks, sharks, barracuda, tarpon
– Stalking
• Trumpetfish,
– Ambush
• Lizardfish, toadfish, grouper, flounder
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Pursuit Predators
• Begin attack from great
distance
• Typically already on the
move
• Use speed to capture prey
• Streamlined body enables
them to swim large distances
around the reef more
efficiently in search of prey
• Large eyes
• Silvery bodies aid in open
water camouflage
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Stalking Predators
• Begin attack from stationary position
• Maneuver close to prey in order to
spring attack
• Caudal fin has large surface area in
order to provide quick burst of speed
for strike
• Many fishes have expandable
circular jaws that enables them to
suck in prey
• Trumpetfishes camouflage with
gorgonians to enhance their stalking
success
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Ambush Predators
• Wait for prey to come to them
• Often well camouflaged
• Groupers and others create a
negative pressure inside
mouth area by expanding gill
covers, then the mouth opens
and brings in prey and water.
• Flounders are the snipers of
the ambush predators
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– They lay camouflaged on the
bottom and quickly capture prey
with their sharp teeth
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Piscivorous Fishes
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Barracuda
Black Hamlet
Coronetfish
Spotted Moray
Frogfish
Graysby
Grouper
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Jack
Lizardfish
Mackerel
Scorpionfish
Snapper
Soapfish
Trumpetfish
Tuna
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Detritivores
• Decomposing plant and animal matter
• Few found on the reef
• Some herbivores take in detritus by
accident when feeding on plant material
• Mullets and some gobies
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Different Foraging Behaviors
• Nuclear Hunting – two or more species
work together in order to capture prey
• Shadowing – one species follows another
in close proximity trying to blend in with
the other
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Nuclear Hunting
• Common for Eels and groupers
• Eels will go into holes in the reef
while the grouper will wait
outside the hole
• The prey has two choices:
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– 1) They can stay in the holes and
take its chances with the eel
– 2) Escape the eel by exiting the
hole and take its chances with the
grouper on the outside
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Shadowing
• Trumpetfish and bar jacks
are seen doing this the
most
• These fish hang just
above the shadowed fish
• This camouflage hopefully
enables it to get closer to
unsuspecting prey
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Resources
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Deloach, Ned and Paul Humann. Reef Fish Behaviour: Florida Caribbean Bahamas.
Florida: New World Publications, Inc., 1999
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Humann, Paul and Ned Deloach. Reef Fish Identification: Florida Caribbean
Bahamas Florida: New World Publications, Inc., 1999
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McGinley, Mark. Caribbean Reef Fish Foraging. 2006
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