Feeding, social, and symbiotic
behaviors
Diet
The bigger the fish, the more food resources it can consume
the better chance of avoiding predators
‘bigger is better’ (Houde 1987)
or
‘you are what you eat’ (Brillat-Savarin 1826*)
or
‘you are what you CAN eat’ (Marsden, 2012)
– mouth configuration
– teeth
– gape
– speed
*“Dis-moi ce que tu manges, je te dirai ce que tu es.”
Fish food resources
piscivores (fish-eating)
planktivores (mostly zooplankton)
herbivores (rare) – periphyton,
phytoplankton, filamentous
algae, macrophytes, fruit
pickers, scrapers, molluscivores
- insect larvae, snails, etc.
detritivores
Fish feeding modes
Planktivores (Clupeiformes)
– algae
– zooplankton
Fish feeding modes
Planktivores (Clupeiformes)
– algae
– zooplankton
• ‘predators’ - visual prey location
• ‘strainers’ - use gill rakers to sieve food
Basking shark (Cetorhinus maximus)
Fish feeding modes
Detritivores (Cypriniformes, Siluriformes, Acipenseriformes)
• benthic feeders
• sub-terminal mouths
Fish feeding modes
Insectivores
• benthic insect larvae (Cypriniformes, Scorpaeniformes)
• surface feeders on terrestrial insects (Salmoniformes)
Fish feeding modes
Herbivores (Cypriniformes)
• algavores - sieve through gill rakers
• grazers - eat macrophytes with crushing teeth
• scrapers - scrape periphyton and filamentous algae
Fish feeding modes
Frugivores (Carachiformes)
• Pacu – crushing teeth, eats fruit, seeds, nuts
– Important role in seed dispersal
Fish feeding modes
Piscivores
• visual predators
• sharp teeth on multiple bones
• types:
– sit-and-wait, ‘ambush’ predators (Amiiformes, Esociformes)
– pelagic chasers (Salmoniformes)
Fish feeding modes
Molluscivores (Cypriniformes, Acipenseriformes, Perciformes)
• grinding pharyngeal teeth
Fish feeding modes
“Hematophagy” (Petromyzontiformes) - parasites
• rasp hole in prey, suck out fluids
S. Beavais
USFWS
Fish feeding modes
ram
suction
biting
picking
scraping
Gape limitations
Angler (Lophius piscatorirus)
Feeding behaviors
•
•
•
•
prey recognition
pursuit
capture
processing
Feeding behaviors
Optimal foraging (maximize gain, minimize energetic losses)
Feeding behaviors
Optimal foraging (maximize gain, minimize energetic losses)
Feeding behaviors
Optimal foraging (maximize gain, minimize energetic losses)
Low prey density
50
300
75
350
200 prey
Feeding behaviors
Optimal foraging (maximize gain, minimize energetic losses)
• bluegill choose zooplankton sizes based on abundance
• stream foragers pick optimum location where current is low,
visibility of prey high
- sub-dominant individuals tend to have less optimal habitats
Feeding behaviors
Optimal foraging (maximize gain, minimize energetic losses)
• bluegill choose zooplankton sizes based on abundance
• stream foragers pick optimum location where current is low,
visibility of prey high
- sub-dominant individuals tend to have less optimal habitats
• prey switching – use of search image?
Social behaviors
Dominance hierarchies
• use displays and nips rather than full-blown aggression
- round gobies will flare fins and operculae, and spit sand
• leaves dominant fish with optimal access to refuge, food, mates
• usually size-related
Social behaviors
Cooperative behaviors
• schooling to feed, round up prey
• shoaling to optimize finding food
fish follow those that are most successful
• group feeding dictated by productivity of environment:
if low, feeding likely solitary
Predator avoidance behaviors
• schooling (discussed)
• leaping from surface - flying fish, mullet, minnows
• roll-and-flash of minnows - makes fish highly visible,
then it disappears
Robert
Harrington
Interspecific interactions
Types of symbiosis
species 1
species 2
mutualism
+
+
parasitism
+
-
commensalism
+
0
Symbioses: mutualism
reproduction: species that guard juveniles of other species
(mutualism)
- keep them outside own flock as protection from predators
- if they are predators of the parent species’ competitor
larval stream cyprinids most abundant in pools with
smallmouth bass, which eat larval predators
Symbioses: mutualism
feeding:
- cooperative feeding between groupers and morays
Symbioses: commensalism
feeding:
- remoras and sharks or turtles
- cichlid species that ‘guard’ feeding partner
Symbioses
Shelter: commensal or mutual
Symbioses
Damselfish ‘cultivate’ algal gardens (mutualistic?)
conspecifics regarded as competitors and chased away
www.flickr.com
Symbioses: parasitism
Feeding
- lamprey…..
- cichlids that specialize on scales
- juvenile piranhas school w. other species then eat their tail fins
- cutlips minnow eats eyes of other fish
- pearlfish hide in sea cucumbers - then also eat viscera
Symbioses: parasitism
Feeding
- lamprey…..
- cichlids that specialize on scales
- juvenile piranhas school w. other species then eat their tail fins
- cutlips minnow eats eyes of other fish
- pearlfish hide in sea cucumbers - then also eat viscera
- candiru catfish, sub-nose eel are internal, burrowing parasites
Symbioses: mutualism
Cleaning behavior:
How: may be substrate pickers - other fishes' bodies as substrate
development of cleaner's attractiveness
advertising coloration of cleaner
‘tickle’ behavior
movement of cleanee to station and stance
Symbioses: mutualism
Cleaning behavior
What: removal of ectoparasites, scales, mucus, etc. from body
surface, oral cavity and/or gill cavity
Who: juveniles of many species
wrasses (Labridae)
(Batesian mimics)
Why: benefits of being cleaned
predaceous mimics….
(Mullerian mimics)