Fig. 8.17

I.I. Fishes - BiologyFishes - Biology

F.F. Regulation of Internal EnvironmentRegulation of Internal Environment1.1. ChondrichthyesChondrichthyes

• Concentration of Concentration of solutessolutes in blood similar to in blood similar to seawaterseawater

• Retain Retain ureaurea in blood (toxic to most other in blood (toxic to most other vertebrates)vertebrates)

• Absorb water through gills and skinAbsorb water through gills and skin• Salts excreted by kidneys and Salts excreted by kidneys and rectal glandrectal gland

2.2. OsteichthyesOsteichthyes• Concentration of solutes much lower than seawaterConcentration of solutes much lower than seawater

• ~14 ‰ vs. ~35 ‰~14 ‰ vs. ~35 ‰• Drink seawaterDrink seawater

• Salts excreted by kidneys and Salts excreted by kidneys and chloride cellschloride cells in in gillsgills

• Kidneys produce small amounts of urineKidneys produce small amounts of urine

Fig. 8.18

I.I. Fishes - BiologyFishes - Biology

G.G. Sensory SystemsSensory Systems1.1. Smell/TasteSmell/Taste

• Most fishes have a highly developed sense of smellMost fishes have a highly developed sense of smell• Detect food, mates, predators, navigational Detect food, mates, predators, navigational

informationinformation• Sensory cells in Sensory cells in olfactory sacsolfactory sacs on both sides of head on both sides of head

• Sacs connected to outside through Sacs connected to outside through naresnares (nostrils) (nostrils)• Sharks especially sensitive to scent of blood (1 ppm)Sharks especially sensitive to scent of blood (1 ppm)• Salmon locate home stream by scent (Salmon locate home stream by scent (imprintingimprinting))• Taste with Taste with taste budstaste buds in mouth and on lips, fins, skin, in mouth and on lips, fins, skin,

barbelsbarbels

2.2. Lateral lineLateral line• Clusters of sensory cells (Clusters of sensory cells (neuromastsneuromasts) in small canals ) in small canals

lining head and along sides of bodylining head and along sides of body• Sensitive to vibrations in waterSensitive to vibrations in water

• Used for orientation, detection of prey and currents, Used for orientation, detection of prey and currents, avoidance of predators and obstaclesavoidance of predators and obstacles

Fig. 8.19

I.I. Fishes - BiologyFishes - Biology

G.G. Sensory SystemsSensory Systems3.3. ElectroreceptionElectroreception

• Found in ChondrichthyesFound in Chondrichthyes• Ampullae of LorenziniAmpullae of Lorenzini• Detection of prey, navigationDetection of prey, navigation• Extremely sensitive (may be less than 1 nV/cm)Extremely sensitive (may be less than 1 nV/cm)

• Can detect a marine mammal’s electric field Can detect a marine mammal’s electric field 3 m away3 m away

• Used in combination with other sensesUsed in combination with other senses

4.4. Inner earsInner ears• Calcareous Calcareous otolithsotoliths rest on sensory hairs rest on sensory hairs

• Detect sound waves + changes in fish Detect sound waves + changes in fish attitudeattitude

• Help to maintain equilibrium and balanceHelp to maintain equilibrium and balance• Can be used to determine age of fishCan be used to determine age of fish

II.II. Fishes - BehaviorFishes - Behavior

A.A. SchoolingSchooling• Displayed by ~4000 speciesDisplayed by ~4000 species• Some fishes school throughout life, others only when Some fishes school throughout life, others only when

juveniles, feedingjuveniles, feeding• School sizes varySchool sizes vary

• Atlantic herring – 4580 mAtlantic herring – 4580 m33

• Pacific herring – 15 miles long!Pacific herring – 15 miles long!• Positioning in school may involvePositioning in school may involve

• VisionVision• Other senses (mechanical vibrations, olfaction, hearing)Other senses (mechanical vibrations, olfaction, hearing)

1.1. TypesTypesa.a. Mobile schoolsMobile schools

• Usually consist of single species, size rangeUsually consist of single species, size rangeb.b. Stationary schoolsStationary schools

• May contain multiple species, sizesMay contain multiple species, sizes2.2. FunctionsFunctions

a.a. Protection against predatorsProtection against predatorsb.b. Increased swimming efficiencyIncreased swimming efficiencyc.c. Beneficial when feedingBeneficial when feedingd.d. Beneficial when matingBeneficial when mating

Fig. 8.21

Swimming Feeding Predator Avoidance

II.II. Fishes - BehaviorFishes - Behavior

B.B. MigrationMigration• Generally related to feeding and/or Generally related to feeding and/or

reproductionreproduction• DielDiel

• HorizontalHorizontal• VerticalVertical

• Large ScaleLarge Scale• ExEx – Skipjack tuna feed in Eastern Pacific, – Skipjack tuna feed in Eastern Pacific,

spawn in Western and Central Pacificspawn in Western and Central Pacific

Fig. 8.22