Transcript Schooling, migration

Fish Schooling
“Never let schooling interfere with your education….”
(apologies to Mark Twain)
Schooling
not all fish aggregations are schools
aggregation: group created by the attractiveness of some
feature of the environment.
www.seafriends.org.nz
www.blackchampagne.com
www.blackchampagne.com
Schooling
not all fish aggregations are schools
aggregation: group created by the attractiveness of some
feature of the environment.
shoal: group of fish remaining together for social reasons
www.seafriends.org.nz
www.blackchampagne.com
Schooling
not all fish aggregations are schools
www.seafriends.org.nz
aggregation: group created by the attractiveness of some
feature of the environment.
shoal: group of fish remaining together for social reasons
school: polarized, synchronized shoal of fish that
swim together in the same direction, at
a similar speed, with a similar distance
between one another
school
shoal
Schooling
who?
25% of fish shoal throughout lives
50% shoal at some point in lives
Schooling
shape ( highly variable)
fast-traveling schools = wedge-shaped
feeding schools = circular
minimum size for effectiveness as predation defense
maximum limit for effective coordinated movement
Schooling
how?
primarily visual cues, as schools often break up at night
optomotor reaction - explains prevalence of vertical bars
Schooling
how?
primarily visual cues, as schools often break up at night
optomotor reaction - explains prevalence of vertical bars
Tank exps. with vertical bars….
Schooling
why?
reduced risk of predation
“dilution” effect
- predators only get strays
Schooling
why?
reduced risk of predation
“dilution” effect
- predators only get strays
“confusion” effect
- flash expansion
Schooling
why?
reduced risk of predation
“dilution” effect - predators only get strays
“confusion effect" for predators
“flash expansion”
traveling: increased hydrodynamic efficiency?
usually similar in size
Schooling
why?
reduced risk of predation
“dilution” effect - predators only get strays
“confusion effect" for predators
“flash expansion”
traveling: increased hydrodynamic efficiency?
usually similar in size
increased efficiency of food finding
schooling to round up prey
shoaling to optimize finding food
- fish follow those that are most successful
Schooling
why?
reduced risk of predation
“dilution” effect - predators only get strays
“confusion effect" for predators
“flash expansion”
traveling: increased hydrodynamic efficiency?
usually similar in size
increased efficiency of food finding
increased reproductive success
minimal sexual segregation in schooling species
consensus on where to go for spawning
Schooling
Why not?
group feeding dictated by productivity of environment
when food is scarce, feeding is solitary
when risk of disease/parasite transmission is high
Pitcher 1983