What adaptations do pelagic organisms possess to avoid becoming prey?

Schooling

school = large #s of fish, squid, or shirmp that form well-defined social groupings

# of fish in school can be a few to hundreds of thousands
w/in schools, individuals move in same direction and are evenly spaced
- spacing maintained through visual contact and use of lateral line system that detects vibrations of swimming neighbors
school can turn abruptly

what are the advantages of schooling?

during spawning: schooling ensures there will be males to release sperm to fertilize eggs released into water or deposited on bottom
schools of smalelr fish can invade territory of larger aggressive species and feed there bc “owner” of territory can’t chase away whole school
MOST IMPORTAN = protection from predators

schooling advantages for hiding from predators:

reduce the percentage of ocean volume in which a cruising predator might find one of their kind
when a predator encounters a large school, it’s less likely that every fish in the school is consumed, compared to encounters w/ an individual or even a small school
school may appear as a single large and dangerous opponent to potential predator and prevent attacks
predators may find the continually changing position and direction of movement of fish w/in the school confusing, making attack particularly difficult for predators which can only attack one fish at a time

schooling helps fish swim greater distances bc each fish gets a boost from the vortex created by fish swimming in front of it

new ocean predator developed method to take advantage of schooling behavior: humans developed nets large enough to encircle whole schools of fish

Symbiosis

symbiosis = two or more organisms associate in a way that benegits at least one of them - 3 main types:
(1) commensalism: smaller or less dominant participant benefits w/out harming host, which affords subsistence of protection to other

Ex. remora attaches itself to shark or another fish to obtain food or transportation w/out harming host

(2) mutualism = both participants benefit

Ex. stinging tentacles of sea anemone protecting clownfish and clownfish chases away any fish trying to feed on anemone
- clownfish helps clean anemone and may supply scraps of food

(3) parasitism = parasite benefits at the expense of the host

Ex many fish are hosts to isopods, which attach to the fish and derive their nutrition from the body fluids of the fish, thereby robbing the host of some of its energy supply
- parasite usually won’t rob enough energy to kill the host bc if the host dies, so does the parasite

symbiosis has been discovered to be an important component driving evolution

Other Adaptations

speed
secreting poisons
mimicking other poisonous or distasteful species
transparency
camouflage
countershading

RECAP

many pelagic species school, engage in symbiosis, or have other adaptations to increase chances of survival by avoiding predators

CONCEPT CHECK 14.3

(1) What are several benefits of schooling?

reduces volume in which species is in
predators likely can’t eat the entire school so preserves the species compared to individual encounters
may confuse predators and they can’t focus bc they can only prey on one individual at a time
may appear as one large opponent, scaring off predators

(2) What are the three types of symbiosis, and how do they differ?