Fish

Success of Fish 50,000 Vertebrates Almost 26,000 are fish 9,100 birds; 7,000 reptiles; 4,900 amphibians;

4,500 mammals

Why are there so many Fish

Location of Fish 58% of bony fish are marine 42% of bony fish are freshwater

158 species are found in Minnesota

Fish Variations Size- from under a centimeter to over 40 feet Mass- from a few ounces to a few tons Life span- from a season to 150+ years Reproduction- you won’t believe some things

fish do

Huge Diversity

Fish Types External Anatomy Internal Anatomy Movement Reproduction Growth and Maturation

Behavior Water Environments

Types of Fish Agnatha- Jawless fish; Lamprey, Hagfish Chondrichthyes- Cartilaginous fish; Sharks,

Skates, Rays Osteichthyes- Bony fish; “fish” bass, pike,

trout

Placoderms- extinct class of jawed fish

Agnatha

Lamprey The sea lamprey is an

aggressive parasite -- equipped with a tooth-filled mouth that flares open at the end of its eel-like body.

Lamprey Fastens onto its prey and rasps out a hole with its

rough tongue Saliva keeps the wound open for hours or weeks,

until the lamprey is satiated or the host fish dies

Lamprey Can destroy up to 40

pounds of fish during 12-18 months as an adult

Lamprey Control Barrier dams Safer and more

effective electrical barriers

Mechanical trapping, and the release of sterile male sea lampreys

Release of sterile male sea lampreys

Chemicals TFM Stream velocity

barriers

Non Parasitic Lamprey as Adults American Brook Lamprey Northern Brook Lamprey Southern Brook Lamprey

Adults do not feed

Chondrichthyes

Osteichthyes Fleshy Finned

Have working lungs Two main groups

Lung Fish Lobed finned Fish

Ray Finned- typical “fish” Spiny Rayed Soft Rayed

Lung Fish- fleshy finned Southern Hemisphere Stagnant ponds and swamps Surface to breathe air Aestivate- burrow into mud during dry season

or drought

Lung Fish

Lobed Finned Fish- fleshy finned

Coelacanth- only extant member of the group (not extinct)

Bottom dwellers “Walk” on the bottom Occasionally waddle on land using large

fleshy fins

Coelacanth

Ray Finned Spiny rayed

Sunfish Perch Bass

Soft Rayed Trout Minnows

Spiny vs. Soft Rayed SPINES- Spiny rayed fish have spines in

Dorsal, Anal, and Pelvic fins; Soft rayed do not

Segmented fins in Spiny Rayed; Unsegmented fins in Soft Rayed

Location of Pelvic fins Type of Scales

Anatomy Directions Anterior- towards the head Posterior- towards the tail Dorsal- back Ventral- underneath, front, belly

External Fish Anatomy Fins Tail Shape Body Shape Mouth Location Lateral Line Scale Type Miscellaneous Identification

FinsLocation, use, and number Dorsal- back, single fin, used for stability, don’t roll

on side Pelvic- ventral, anterior, paired fin, used for steering,

hovering, and stopping Anal- ventral, posterior, single fin, used for stability,

don’t roll on side Pectoral-sides, paired fin, used for steering,

hovering, and stopping Caudal- tail, single fin, used for propulsion Adipose- small and fleshy, posterior on tail, single

fin

Spiny Rayed Fins

Soft Rayed Fins

Caudal Fin Shape

Mouth Different shapes and positions Superior - mouth oriented up fish often a surface feeder Terminal - mouth at anterior end, often a midwater

feeder Inferior - mouth oriented downward, often a bottom

feeder Subterminal- mouth underneath fish, bottom feeder Protrusible - mouth can alter shape to be more useful in

suction feeding, can be seen in any of the above but less common among inferior mouths

Mouth continued

Lateral Line Senses water currents, pressure, and

movement; line of pores along side of fish that are fluid filled with a hair like apparatus; sensory organ

Cycloid Scale Soft Rayed Fish Smooth exposed edge

Ctenoid Scales Spiny Rayed Fish Ctenii

Teeth on exposed

edge

More Scales Some fish have NO scales There are a few other types of scales Scales are covered in a mucus to protect fish

from infections Scales can be used to age fish

Miscellaneous External Anatomy

Operculum –Gill cover, protects gills Vent- external opening to digestive and

reproductive systems, usually directly in front of anal fin

Odd External Anatomy Eyes

Some fish have four eyes Some eyes are made to be part above water and

part submerged Smell

Can be used to find mates- pheromones Taste

Some fish have external taste buds all over body Magnetic Reception

Ability to detect magnetic fields

More Odd External Anatomy Electroreception

Ability to detect electricity Found in many fish Sharks & Catfish use to find prey Species and sex recognition, social settings,

attacks, submission, courtship, dominance hierarchies

Identification http://www.wiscfish.org/fishid/ http://www.wiscfish.org/fishid/

Internal Anatomy Spine Spinal Cord Brain Lateral Line Swim Bladder Gills Ears? Kidneys

Stomach and Intestines Pyloric Caeca Vent Liver Heart Gonads Muscle

Spine Primary structural framework Connects to the skull at the front of the fish

and to the tail at the rear Made up of numerous vertebrae, which are

hollow and house and protect the delicate spinal cord

Spinal Cord Connects the brain to the rest of the body Relays sensory information from the body to

the brain Sends instructions from the brain to the rest of

the body (main nerve pathway)

Brain Control center Both automatic functions (such as respiration)

and higher behaviors ("Should I eat that critter with the spinning blades?") occur

All sensory information is processed here

Lateral Line One of the fish’s primary sense organs Detects underwater vibrations Capable of determining the direction of their

source 

Swim (or Air) Bladder Hollow, gas-filled balance organ that allows a fish to

conserve energy by maintaining neutral buoyancy (suspending) in water

Fish caught from very deep water (walleye, lake trout) sometimes need to have air released from their swim bladder before they can be released and return to deep water, due to the difference in atmospheric pressure at the water’s surface

No swim bladder then will sink to the bottom if they stop swimming

Primitive Lung?

Swim Bladder continued Primitive fish used

as working lungs Still connected in

some fish Fish gulps air

Not connected in MOST Bony fish Tissue secrets or

reabsorbs gas

Air Bladder

“Gut”

Swim Bladder continued Buoyancy and Density Increased air More volume Less dense

FLOATS Decreased air Less volume More dense

SINKS Lungs came first and became swim bladder

Gills Site of gas exchange in fish (think lungs) Water comes in through mouth and out past

gills Oxygen in and carbon dioxide out Water has much less O2 than does air Water needs to be MOVING through gills

Gills continued

Gills continued

Counter Current Exchange

O2 concentration

Ears Fish are able to hear Ear bones Semi circular canals Ossicle

Modified vertebrae connecting inner ear to swim bladder increases hearing greatly

Hard to find Not present in all fish

Kidneys Filters liquid waste materials from the blood Wastes are then passed out of the body Extremely important in regulating water and

salt concentrations within the fish’s body Osmoregulation

Allows certain fish species to exist in freshwater or saltwater, and in some cases) both

Osmoregulation

More Osmotic Regulation

Osmotic Regulation Review Freshwater fish

Water is always be absorbed Have to secrete copious amounts of dilute urine

Saltwater fish Water is always leaving fish Drink lots of water Little urine (usually) Gills pump out most salt

Stomach and Intestines Break down (digest) food and absorb nutrients Piscivorous (eat other fish) have fairly short

intestines because such food is easy to chemically break down and digest

Herbivorous (eat plants) require longer intestines because plant matter is usually tough and fibrous and more difficult to break down into usable components

Pyloric Caeca Organ with fingerlike projections located near

the junction of the stomach and the intestines Function is not entirely understood, but it is

known to secrete enzymes that aid in digestion

May function to absorb digested food, or do both

Vent Site of waste elimination from the fish’s body

Liver Assists in digestion by secreting enzymes that

break down fats Also serves as a storage area for fats and

carbohydrates Important in the destruction of old blood cells

and in maintaining proper blood chemistry, as well as playing a role in nitrogen (waste) excretion

Heart Circulates blood, nutrients, and wastes

throughout the body

Gonads (reproductive organs) Adult females, the bright orange (generally)

mass of eggs is unmistakable during the spawning season, but is still usually identifiable at other times of the year The eggs (or roe) of certain fish are considered a

delicacy, as in the case of caviar from sturgeon  Adult male organs, which produce milt for

fertilizing the eggs, are much smaller and white but found in the same general location

Muscle Provide movement and locomotion The fillet of the fish White Muscle Red Muscle

White Muscle Short duration Quick fatigue Bursts of power (escape/capture prey) Few Mitochondria Mostly Anaerobic (not enough O2) Takes a long time to recover

Red Muscle Sustained swimming Hard to fatigue at slow cruising speeds Many Mitochondria Usually Aerobically (has O2 to use) Recovers quickly Canned Tuna

Spiny Rayed

Soft Rayed Anatomy

Movement Aquatic movement vs. Terrestrial movement

Terrestrial movement works against gravity and air friction

Aquatic movement works against density of water and drag of water

More Movement Water is 800X more dense than air 50X more viscous

Takes much more energy to move through water

Compensation for Aquatic Environment Body shape

Aspect ratio (A.R.)= height/width relationship High A.R.= reduced drag and high sustained

speed; Marlin, Tuna Low A.R.= broad surface area, high drag,

quick and powerful starts; Bass

Body covering helps reduce drag; Mucus

Body Shape and Swimming Style Anguilliform

Trunk and Tail; only head doesn’t move Body moves in S shape motion Allows for forward motion, braking, and reverse Larval fish, Eels, Lampreys, and Sharks

Body Shape and Swimming Style Subcarangiform

Roughly 2/3’s to 1/2 of fish moves side to side Allows for rapid acceleration Bass, Salmon, trout, minnows

Carangiform Posterior 1/3 moves

Body Shape and Swimming Style Thunniform

Tail hinged to body Caudal Peduncle and Tail move Low drag Sustained high speeds Marlin, Sailfish, and Tuna

Body Shape and Swimming Style Ostraciliform

ONLY tail moves; Body canNOT High Drag

Swimming Style continued

Swimming Style continued

Other Swimming Style Not all fish use Caudal Fin for propulsion Some fish use other fins

Dorsal Fin Anal Fin Pectoral Fins

Generally these are found in Marine environments

Movement Oddities Walk on bottom Walk on land “Fly” through air

Reproduction Oviparous

Lay eggs that hatch OUTSIDE the body Most common

Ovoviviparous Eggs develops inside the oviduct, nourished by

egg yolk, eggs hatch in the uterus Viviparous

Young develop within the uterus, nourished through placenta, Live Birth

Reproduction Fecundity

Number of eggs shed in each spawn Varies from one to hundreds of thousands Number of eggs is related to amount of parental

care involved and the success of each egg reaching maturity

Reproduction continued Fish spawn in shallows Deep over structure Flood plains Capable of spawning multiple times Often spawn at the same place they hatched Dioecious

Separate male and female

This is where and how it always happens, RIGHT?

More Reproduction Anadromous fish

Fish that return to their spawning rivers from the ocean at certain seasons for breeding in fresh water

Born in small streams, mature in the ocean, use smell or magnetic field to return to stream where they hatched- thousands of miles, length of time spent in stream after hatching and length of time in ocean varies

Salmon

Anadromous fish Semelparous

All die after reproducing

Pacific Salmons; King, Silver, Sockeye, Chum, Pink

Anadromous fish Iteroparous

Can spawn multiple times Atlantic Salmon, Steelhead (rainbow trout)

Reproduction continued Catadromous

Fish live in fresh water Breed and spawn in the sea Eel

Reproduction- Starting to get Weird Parthenogenesis

Females produce fertile eggs without fertilization This may occur in multiple species of fish Also can happen in other reptiles, amphibians,

birds, and lower organisms Not common

Could it happen in humans?

Komodo DragonThere have been two reported cases of Komodo dragon "virgin births"

Komodo dragons The largest lizards in the world are capable of "virgin births".

Scientists report of two cases where female Komodo dragons have produced offspring without male contact.

Tests revealed their eggs had developed without being fertilized by sperm - a process called parthenogenesis, the team wrote in the journal Nature.

One of the reptiles, Flora, a resident of Chester Zoo in the UK, is awaiting her clutch of eight eggs to hatch, with a due-date estimated around Christmas.

BBC News

Reproduction Craziness I’m not making this stuff up Think “Jurassic Park” Things to think about while sitting on the ice

Reproduction Craziness 1 When the dominant male of group dies,

largest female becomes the male

Reproduction Craziness 2 Breeding female is the largest of the group When it dies, the male becomes the breeding

female The largest juvenile becomes the male

Remain member of the group stay in as juveniles

Reproduction Craziness 3 Capable to switch back

and forth from male to female

Bluehead Wrasse

Reproduction Craziness 4 Begin the spawn as females and end the

spawn as males Some Sea Bass species

Reproduction Craziness continued When fish switch sexes

Can occur once or switch back and forth multiple times

Length of time required varies from a few hours to a few days

Reproduction Craziness continued Asexual Fish Some fish species

normally have both male and female reproductive organs

Reproduction Craziness 5 Have two distinct types of

males, one takes longer to mature and grows larger, builds and protects nests, hums to attract females; other is smaller, matures quicker, not involved in any courtship, sneaks into nests to mate

Midshipman

Growth and Maturation General pattern

Egg Larva Juvenile Adult

May go through Metamorphosis Transformation form larval stage to adult Tadpole to Frog

Age and Size at Maturation Older

More eggs May die first

Younger Fewer eggs Reduced growth Weaker state if they reproduce

Fish under heavy pressure reproduce sooner

Metamorphosis Lamprey

Ammocoetes to adult. Flounder

Only as adult are they flat with both eyes on one side

Caused problems early with identification

Fish Age and Growth by Scales Use growth rings Annulus 3 growth rings

on this scale Fish is 3 years

old, going on

4 3 yr old age class

Fish Age and Growth by Otolith Ear bone

Fish Age and Growth Mark Recapture

Catch and tag fish Re-catch later

Many different formulas

Fish Behavior Fish as Prey Fish as Predators

Fish as Prey Anti Predation

Avoid detection Evade pursuit Prevent and deflect attacks Discourage capture Discourage handling

Why can’t fish just hide all day long?

Avoid Detection Camouflage Invisibility Swim with Others Detect predator before it finds you Sound or electrical insulation

Camouflage Look like your

background Body growths

e.g. Seadragons

Camouflage Look like your background

Background matching coloration Light ventral surface, dark dorsal surface e.g. flatfish change color and pattern

Reduced movement

Camouflage Mimic a non-prey item

Plant material Toxic fish

Disruptive coloration Body covered in regions of contrasting colors

(e.g. vertical bars or spots) This breaks up the outline of a fish making it less

recognizable as a potential food item

Disruptive Coloration

Invisibility Countershading

Pattern on the fish opposite to patterns of light in the water

Dark on top, light on bottom When viewed from the top the fish blends into the

dark background of the water When viewed from the bottom the fish blends

into the light background of the sky Works for all viewing angles

CounterShading

Invisibility Silvery Sides

Open water species Covered in small “mirrors”

Transparency Larvae and juvenile fish Clear muscles and bones Brain, eye, gonads can’t be clear

Silver Sides

Transparency

Swim with Others Lower probability of detection for an individual in a

school than an individual on its own Predators go after differences Prey can act as a group aggressively towards

predator (i.e. mobbing behavior) Predator inspection

Single fish go out and evaluate predator (i.e. somebody drew the short straw)

Schooling

Evade Pursuit Discourage Predator Move to Shelter Open Water Escape

Discourage Predators Spines Toxic skin/internal organs Make use of aposematic coloration or

behavior Bright, conspicuous coloration and/or slow

escape response Signal to predator that they are dangerous

Move to Shelter Go where predator cannot Bottom sediments Shallows Rocks

Open Water Escape Outrun, out maneuver, or out fly! Most prey can’t outrun their predators

because they are smaller They may be able to out maneuver Flying fish “fly” (i.e. jump and glide) out of

the water Others jump out of water to confuse and

disorient predators

Prevent and Deflect Attack Prevent with last second evasive move Deflect with structural defenses (i.e. spines,

etc) Prevention of attack by group foragers

Dilution effect = individual probability of being consumed decreases with increasing group size.

Confusion effect = Predators become confused by so many prey and switch targets too often to actually catch many prey

Discourage Capture Take advantage of gape limitation

Mouth size Static or dynamic adaptations associated with

body size/shape This makes it difficult to handle prey Elongate spines or fins or very deep body Blow up (e.g. pufferfish) or erect spines (e.g.

bluegill) Chemicals released when attacked

Discourage Handling One way spines (think tire spikes) Mucus excretion

Taste very bad Releasable scales

Fish as Predators Searching Pursuing Attacking Capturing Handling

Searching Active

Make use of all senses Speculation searching

Passive Buried by sediment Projections and color have evolved to match substrates

for “camouflage” Passive water column predators just hang in water

column Most passive predators use vision to detect prey

Active versus Passive Passive = Energy savings, but rely on prey

coming to you May be risky to wait for prey, but don’t spend

energy looking Tradeoff between certainty of prey capture and

energy spent catching prey Two different strategies to solve the same

problem

Pursuit Chasers Deceivers Stalkers

Chasers Sustained Chase

Streamlined Maneuvering

Big tails and fins for complex environments Fast Starts

Lie in wait predators Fins far back on body Fast start but little endurance

Deceivers Lure prey within striking distance Make part or all of their bodies look like food

for prey

Stalkers Many of these fish approach prey head on and

make use of disruptive coloration Split head color pattern Visually breaks up shape of whole head Prey have delayed recognition of predator

Similar to big cats

Attack and Capture Ideally predator attacks by overtaking prey

with simultaneous mouth extension and suction

Fast-start predators overtake prey Lie-in-wait predators have great suction

capacity; Largemouth Bass Some fish swim and passively sieve prey

from water

Large Mouthed Bass

Attack and Capture continued Some immobilize prey during attack and then

“capture” Predators often separate out individual prey

from the prey’s shoal or school Greatly increases success rate of predation Attacks on “stragglers” more likely to be successful

Attack and Capture- Just For You Predators often attack those prey that are

different within the shoal Produces strong selection towards morphological

and behavioral uniformity within schooling prey species

Don’t be different, you will be eaten

Handling Post-capture manipulation

Aids in ingestion and digestion Reducing size of prey (i.e. tearing it apart) Get prey to go in head first- makes it easier to

swallow Teeth vary according to prey

Generalist vs. Specialist Generalists = Predators that make use of

multiple resources and behaviors Perch sit-and-wait and pursue)

Specialists = Predators that exploit only one resource or use only one type of behavior Pike only sit-and-wait

Water Environments Lake Zones Lake Stratification Lake Nutrients Dissolved Oxygen

Lake Zones Littoral Zones

Light reaches bottom Pelagic Zone

Light cannot penetrate to the bottom Photic Zone

Depth that light reaches Profundal Zone

Depths beyond where light can penetrate

Lake Zones

Lake Stratification Water of different temperatures have different

densities Warm water is less dense than cold water, it

RISES Cool water is more dense than warm water, it

SINKS For water above 40 degrees

Water is MOST dense between 38-40 degrees Water is least dense at 32 degrees

Lake Stratification Epilimnion

Upper layer Warmer water

Hypolimnion Lower layer Cooler water

Thermocline Transition between the two layers

Lake Stratification Lakes Turn Over twice a year

Occurs in Spring and Fall Due to warming and cooling temperatures Mixes temperatures and nutrients

Lake Nutrients Oligotrophic

Clear, low plant life, LOW nutrients Mesotrophic

Good clarity and average nutrient level Eutrophic

Enriched with nutrients, high plant growth, algae blooms

Hypertrophic Excessively enriched with nutrients

Oligotrophic

Eutrophic and Hypertrophic

Eutrophic and Hypertrophic

Dissolved Oxygen Oxygen put in water through Photosynthesis

and water movement that traps air bubbles Dissolved Oxygen is needed for fish survival Concentrations may get low in Winter

Winter kill or ‘lake froze out’ Concentrations may get low in Summer

Why?

Dissolved Oxygen in Summer

Dissolved Oxygen continued How might this be applied to where you fish and

the depths at which you fish?

Mn Fish by Families Bowfin Bullhead Catfish Burbot Drum Freshwater Eel Gar Goby Herring Killifish and Topminnow Lamprey Livebearer Minnow Mooneye Mudminnow

Paddlefish Perch Pike Pirateperch Sculpin Silverside Smelt Stickleback Sturgeon Sucker Sunfish Temperate Bass Troutperch Trout