Fishes

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• Fishes Biology
• Osmoregulation
• Chondrichthyes Sarcopterygii
• Concentration of solutes in blood similar to
  seawater (isosmotic) or slightly higher
  (hyperosmotic)
• Retain urea and TMAO in blood (toxic to most
  other vertebrates)
• Absorb water through gills and skin
• Salts excreted by glomerular kidneys and rectal
  gland
• Large volumes of hypotonic urine
• Actinopterygii/Osteichthyes
• Concentration of solutes much lower than seawater
  (hypo-osmotic)
• 14 vs. 35
• Drink seawater
• Salts excreted by kidneys (often aglomerular) and
  chloride cells in gills
• Small volumes of isotonic or hypertonic urine

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Fig. 10-24
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• Fishes Biology
• Buoyancy Regulation
• Chondrichthyes
• Large liver squalene (20 less dense than
  seawater)
• Up to 20-25 of body weight
• Continuous swimming
• Lift from broad, flat head
• Sarcopterygii
• Lipid-filled swim bladder
• Actinopterygii/Osteichthyes
• Gas-filled swim bladder
• Physostomes Fill SB by gulping air
• Physoclists Fill SB using gas gland (Root
  effect)
• Some fishes lack a swim bladder
• Active pelagic species (tunas, mackerel)
• Demersal or benthic species (scorpionfishes)

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Fig. 10-15
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• Fishes Biology
• Sensory Systems
• Smell/Taste
• Most fishes have a highly developed sense of
  smell
• Detect food, mates, predators, navigational
  information
• Sensory cells in olfactory sacs on both sides of
  head
• Sacs connected to outside through nares
  (nostrils)
• Sharks especially sensitive to scent of blood (1
  ppm)
• Hammerhead sharks nostrils on ends of hammer
  swing head side to side orient by comparing
  concentrations on left/right
• Salmon locate home stream by scent (imprinting)
• Taste with taste buds in mouth and on lips, fins,
  skin, barbels

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Fig. 10-26
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• Fishes - Biology
• Sensory Systems
• Lateral line
• Clusters of sensory cells (neuromasts) in small
  canals lining head and along sides of body
• Sensitive to vibrations in water
• Used for orientation, detection of prey and
  currents, avoidance of predators and obstacles
• Inner ears
• Calcareous otoliths rest on sensory hairs
  (maculae)
• Detect sound waves changes in fish attitude
• Help to maintain equilibrium and balance
• Can be used to determine age of fish

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Fig. 10-27
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• Fishes Biology
• Sensory Systems
• Lateral line
• Clusters of sensory cells (neuromasts) in small
  canals lining head and along sides of body
• Sensitive to vibrations in water
• Used for orientation, detection of prey and
  currents, avoidance of predators and obstacles
• Inner ears
• Calcareous otoliths rest on sensory hairs
  (maculae)
• Detect sound waves changes in fish attitude
• Help to maintain equilibrium and balance
• Can be used to determine age of fish

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• Fishes Biology
• Sensory Systems
• Electroreception
• Found in Chondrichthyes
• Ampullae of Lorenzini
• Detection of prey, navigation
• Extremely sensitive (may be less than 1 nV/cm)
• Can detect a marine mammals electric field 3 m
  away
• Used in combination with other senses

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Spotted dogfish shark (Scyliorhinus canicula)
A) Flatfish (Pleuronectes platessa) buried in sand
B) Flatfish in box of agar made with seawater
(blocks mechanical vibrations) flow-through
C) Chopped fish in box of agar made with
seawater flow-through
D) Flatfish in electrically insulated box of agar
made with seawater
E) Electrodes buried in sand
F) Electrode buried in sand chopped fish on
surface
Kalmijn (1971)
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• Fishes Biology
• Feeding
• Chondrichthyes
• Bite pieces from large prey
• Tiger shark Diverse stomach contents
• Great white shark Wound and wait
• Cookie cutter shark Cut out chunks
• Ingest smaller prey whole
• Nurse shark Benthic invertebrates
• Filter plankton Gill rakers
• Whale shark Warm
• Basking shark Cold
• Megamouth shark
• Manta ray

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• Fishes Biology
• Feeding
• Actinopterygii/Osteichthyes
• Capture large prey whole
• Large mouth, small teeth
• Ex Barracudas, frogfishes
• Crushers Crush prey
• Teeth usually fused into bony plates
• Ex Pufferfishes, porcupinefish, boxfishes
• Pickers Ingest smaller prey whole
• Small mouth, tiny teeth
• Ex Butterflyfishes
• Grazers
• Small mouth, strong teeth
• Ex Parrotfishes, surgeonfishes
• Filter plankton
• Gill rakers
• Ex Anchovies, sardines, herrings

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• Fishes Biology
• Reproduction
• Modes
• Oviparity
• Ovoviviparity
• Viviparity
• Strategies
• Pelagic
• Often in aggregations
• Many small eggs, high mortality
• Ex Tunas, sardines, parrotfishes
• Benthic
• In pairs or aggregations
• Eggs usually attached or sinking
• Ex Smelt, salmon
• Brood hiders
• Benthic spawners no parental care
• Ex Grunion

Fig. 10-33
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• Fishes Biology
• Reproduction
• Hermaphroditism
• Synchronous
• Ex Hamlets
• Protogyny
• Ex Wrasses
• Protandry
• Ex Anemonefishes
• Larval development
• Planktotrophic
• Lecithotrophic

Fig. 10-34
Fig. 10-35
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• Fishes Biology
• Schooling
• One form of shoaling behavior
• Displayed by 25 of all fish species
• Some fishes school throughout life, others only
  when juveniles, feeding
• School sizes vary
• Atlantic herring 4580 m3
• Pacific herring 15 miles long!
• Positioning in school may involve
• Vision
• Other senses (mechanical vibrations, olfaction,
  hearing)
• Types
• Mobile schools
• Usually consist of single species, size range
• Stationary schools
• May contain multiple species, sizes
• Functions
• Protection against predators

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• Fishes Biology
• Migration
• Generally related to feeding and/or reproduction
• Diel
• Horizontal
• Ex Grunts (day on reef, night feeding in
  seagrass beds)
• Vertical
• Ex Mesopelagic fishes
• Large Scale
• Ex Skipjack tuna feed in Eastern Pacific, spawn
  in Western and Central Pacific

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• Fishes Biology
• Migration
• Anadromous
• Spawn in fresh water
• Spend most of life in ocean
• Ex Salmon (seven species) in Pacific Ocean
• Spawn in shallow areas of rivers/streams
• Semelparous (adults die after spawning)
• Young migrate downstream to ocean after 0-5 years
• Spend 3-7 years in ocean before returning to home
  stream
• Homing behavior enabled by olfactory imprinting
• Important source of nutrition for wildlife,
  forests

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• Fishes Biology
• Migration
• Catadromous
• Spawn in ocean
• Spend most of life in fresh water
• Ex Eels (16 species) in Atlantic Ocean
• Spawn in Sargasso Sea (400-700 m or deeper)
• Semelparous
• Eggs hatch into leptocephalus larvae
• Larvae spend a year or more as plankton then
  undergo metamorphosis into juveniles
• Adults spend 10-15 years in fresh water before
  migrating to Sargasso Sea to spawn

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Fig. 10-37
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