Chapter 8Chapter 8Marine FishesMarine Fishes

Classification of FishesClassification of Fishes

Marine FishMarine Fish

• Marine fish are vertebratesMarine fish are vertebrates• Some have vertebra made of cartilage, while Some have vertebra made of cartilage, while

others have bony vertebraothers have bony vertebra• Of the 24,000 known species of fish, about Of the 24,000 known species of fish, about

15,000 species are marine15,000 species are marine• Fish are the oldest of vertebrates (found Fish are the oldest of vertebrates (found

farther back in the fossil record) (farther back in the fossil record) (Mom) () (Coelocanth 2))

• Fish are by far the largest group of vertebrates Fish are by far the largest group of vertebrates in terms of species and abundancein terms of species and abundance

• About half of all vertebrate species are fishAbout half of all vertebrate species are fish

Types of Marine FishTypes of Marine Fish

1.1. Agnatha (jawless fish)Agnatha (jawless fish)• HagfishHagfish• LampreysLampreys

2.2. Chondrichthyes (cartilaginous fish)Chondrichthyes (cartilaginous fish)• SharksSharks• SkatesSkates• RaysRays• ratfishratfish

3.3. Osteichthyes (bony fish)Osteichthyes (bony fish)• Lobe-finned fishesLobe-finned fishes• Ray-finned fishesRay-finned fishes

Types of Marine FishTypes of Marine Fish

• AgnathaAgnatha– These jawless fish have a muscular, circular These jawless fish have a muscular, circular

mouth with rows of teeth in rings mouth with rows of teeth in rings – Long, cylindrical bodyLong, cylindrical body– Lack paired fins and scales seen in other fishLack paired fins and scales seen in other fish– Two types of jawless fish exist- hagfish and Two types of jawless fish exist- hagfish and

lampreyslampreys– EctothermicEctothermic

Lamprey – www.wikipedia.com

Types of Marine FishTypes of Marine Fish

•Hagfishes– 20 species20 species– Exclusively marineExclusively marine– They feed on dead and dying fish and They feed on dead and dying fish and

marine mammals primarilymarine mammals primarily– Live in burrows in soft sedimentsLive in burrows in soft sediments– Produce large quantities of Produce large quantities of mucus from

glands in the skin to protect them while feeding

www.wikipedia.com

Pacific Hagfish (Eptatretus stoutii)

- 4 pairs of sensory tentacles around mouth- 12 pairs of gill slits- SLIME

Types of Marine FishTypes of Marine Fish• LampreyLamprey

– 30 species30 species– Live in freshwater (Live in freshwater (lakes) and salt water) and salt water– Adults of some species spend a large Adults of some species spend a large

portion of their life in the sea, but return to portion of their life in the sea, but return to freshwater to breed; adults normally die freshwater to breed; adults normally die after breeding.after breeding.

– Parasitic: They feed on living fish by rasping Parasitic: They feed on living fish by rasping into the sides of fish with their sucker-like into the sides of fish with their sucker-like mouth and consuming blood, tissue and mouth and consuming blood, tissue and body fluidsbody fluids•Produce anticlotting agentProduce anticlotting agent

More Advanced Groups of More Advanced Groups of FishFish• Fishes in the Classes Chondrichthyes and Fishes in the Classes Chondrichthyes and

Osteichthyes are considered to be more Osteichthyes are considered to be more advanced. advanced.

• General Characteristics (advancements) General Characteristics (advancements) seen in these groups:seen in these groups:– Highly efficient gillsHighly efficient gills– Scales cover the body Scales cover the body – Paired fins Paired fins – A wide variety of jaw and feeding typesA wide variety of jaw and feeding types– Lateral line and other sensory organsLateral line and other sensory organs– Streamlined bodyStreamlined body

External Anatomy of More External Anatomy of More Advanced Fish GroupsAdvanced Fish Groups

• These These representative fish representative fish show the position show the position of fins in of fins in cartilaginous and cartilaginous and bony fish.bony fish.

Osteichthyes, The Bony FishOsteichthyes, The Bony Fish– Skeleton composed of boneSkeleton composed of bone– More species that all other vertebrates More species that all other vertebrates

combined- over 23,000 species worldwidecombined- over 23,000 species worldwide– Gills used for respirationGills used for respiration– Hinged jaws allow for a variety of different Hinged jaws allow for a variety of different

feeding strategiesfeeding strategies– Homocercal tail (two lobes of equal size) Homocercal tail (two lobes of equal size)

provides forward thrustprovides forward thrust

www.wikipedia.com

Osteichthyes, The Bony FishOsteichthyes, The Bony Fish– Flat bony scales protect bodyFlat bony scales protect body

•ctenoid (tiny spines) or cycloid (smooth)ctenoid (tiny spines) or cycloid (smooth)

– Bony operculum covers the gills (provides Bony operculum covers the gills (provides better protection against injury compared better protection against injury compared to gill slits)to gill slits)

– Lateral line for sensory and communicationLateral line for sensory and communication– Swim bladder used for buoyancy control Swim bladder used for buoyancy control

(some bottom dwelling fish lack swim (some bottom dwelling fish lack swim bladder)bladder)

– Variable body plans are adapted for Variable body plans are adapted for specific environmentsspecific environments

Osteichthyes, Body ShapeOsteichthyes, Body Shape– Body shapes vary Body shapes vary

greatly greatly •dependent on the nichedependent on the niche

•Ex. flounders and soles Ex. flounders and soles (flat shape) live on the (flat shape) live on the bottom and cover bottom and cover themselves slightly with themselves slightly with sand to camouflage sand to camouflage themselves from potential themselves from potential predators as well as prey predators as well as prey

Osteichthyes – Body Shape Osteichthyes – Body Shape of of FAST fish fish

– Tuna, billfish, and other fast moving Tuna, billfish, and other fast moving predators are long, streamlined and most predators are long, streamlined and most of their fins serve as rudders (very little of their fins serve as rudders (very little flexibility except in caudal fin) - flexibility except in caudal fin) - barracuda

– This body shape allows these predators to This body shape allows these predators to cut through the water quickly cut through the water quickly

– Notice, too, that the area of the body Notice, too, that the area of the body called the caudal peduncle (area just called the caudal peduncle (area just before the tail) is very thin – this allows all before the tail) is very thin – this allows all the muscles to concentrate in this area the muscles to concentrate in this area allowing for greater thrust of the caudal allowing for greater thrust of the caudal (tail) fin (this means FAST swimming (tail) fin (this means FAST swimming capabilities)capabilities)•Sailfish

Osteichthyes – Body Shape Osteichthyes – Body Shape of not so fast fishof not so fast fish

– Angelfish – coral reef fish example – not open Angelfish – coral reef fish example – not open ocean fishocean fish

– Angelfish and the like inhabit coral reefs, Angelfish and the like inhabit coral reefs, oyster reefs and other similar environmentsoyster reefs and other similar environments

– In these fish, the body is not as streamlined In these fish, the body is not as streamlined and the fins are feather-like for lots of flexibilityand the fins are feather-like for lots of flexibility

– This flexibility allows for greater control around This flexibility allows for greater control around the features that would be seen in a coral reef the features that would be seen in a coral reef type environment (crevices, etc)type environment (crevices, etc)– Humphead parrotfishHumphead parrotfish

www.animalphoto.tk

Osteichthyes – Shape of fish Osteichthyes – Shape of fish that donthat don’’t swim fart swim far

– Other fish have a shape that allows for Other fish have a shape that allows for camouflage in their environmentcamouflage in their environment

– For example, fish like the toadfish and For example, fish like the toadfish and the stonefish actually look like rocks or the stonefish actually look like rocks or ““sceneryscenery”” and thus can go undetected by and thus can go undetected by predators or preypredators or prey

www.fishimage.blogspot.comwww.njsciba.net

Osteichthyes – Color Osteichthyes – Color PatternsPatterns

•Countershading is seen in virtually all fish Countershading is seen in virtually all fish speciesspecies

• In countershading, the ventral (belly) area of In countershading, the ventral (belly) area of the fish is lighter than the dorsal area of the the fish is lighter than the dorsal area of the fishfish

•This allows the fish to This allows the fish to ““blend inblend in”” with the with the environment environment

• If a fish is seen from above, the darker If a fish is seen from above, the darker coloration of the dorsal area blends in with coloration of the dorsal area blends in with the darker color of the ocean bottomthe darker color of the ocean bottom

• If the fish is seen from below, the lighter If the fish is seen from below, the lighter coloration of the ventral surface blends in with coloration of the ventral surface blends in with the lighter coloration of the ocean surfacethe lighter coloration of the ocean surface

www.nationalgeographic.com

Osteichthyes, The Bony FishOsteichthyes, The Bony Fish– Coloration patterns:Coloration patterns:

•Slower swimming fish often have bars or Slower swimming fish often have bars or stripes that help break up the silhouette of a stripes that help break up the silhouette of a fish (a form of disruptive coloration)fish (a form of disruptive coloration)

•This helps with predator avoidanceThis helps with predator avoidance

•Some also have coloration that helps them Some also have coloration that helps them blend in with environment (known as cryptic blend in with environment (known as cryptic coloration)coloration)

www.sunysb.edu

Osteichthyes ColorationOsteichthyes Coloration

Osteichthyes, The Bony FishOsteichthyes, The Bony FishColoration Patterns:Coloration Patterns:– Circular patterns on or near the caudal finCircular patterns on or near the caudal fin

• Confuses predators who are not sure which end of Confuses predators who are not sure which end of the fish is the headthe fish is the head

• If fish attacked on caudal end where the black dot If fish attacked on caudal end where the black dot looks like an eye, she can probably get away with looks like an eye, she can probably get away with minor damageminor damage

• If attacked on his head region, she may sustain If attacked on his head region, she may sustain serious, life threatening damageserious, life threatening damage

– Warning Coloration – Warning Coloration – • use color to advertise their bad taste or poisonous use color to advertise their bad taste or poisonous

nature – nature –

www.animalworld.comwww.fishwallpaper.net

www.inkart.net

Swimming PatternsSwimming Patterns• Fish exhibit an Fish exhibit an ““s-shapeds-shaped”” swimming swimming

patternpattern

• Bands of muscle along the body Bands of muscle along the body called myomeres drive this called myomeres drive this swimming motionswimming motion

• Depending on the type of fish, Depending on the type of fish, different fins may be used primarily different fins may be used primarily for the forward movementfor the forward movement

Swimming PatternsSwimming Patterns

• A) eels swim by undulating body in lateral waves A) eels swim by undulating body in lateral waves from head to tail from head to tail

• B) fast fishes with shorter bodies – flex caudal tailB) fast fishes with shorter bodies – flex caudal tail

• C) surgeonfishes, parrotfishes – move only the finsC) surgeonfishes, parrotfishes – move only the fins

• D) trunkfishes and porcupine fishes swim slowly by D) trunkfishes and porcupine fishes swim slowly by moving base of tail and rest of body remains moving base of tail and rest of body remains immobileimmobile

Specializations for Specializations for swimmingswimming

• Myomeres – bands of muscles that produce Myomeres – bands of muscles that produce rhythmic contractions for swimming in S-patternrhythmic contractions for swimming in S-pattern

• Swim bladders in bony fishSwim bladders in bony fish

Swimming PatternsSwimming Patterns• In bony fish, pectoral fins are not needed for lift (like in sharks) In bony fish, pectoral fins are not needed for lift (like in sharks)

and thus are normally not stiff in construction (exception: fast and thus are normally not stiff in construction (exception: fast swimming species like tuna, billfish, etc)swimming species like tuna, billfish, etc)

• In contrast, the pectoral fins in many bony fins are flexible and In contrast, the pectoral fins in many bony fins are flexible and used for maneuverabilityused for maneuverability

• In some slower-swimming species, forward movement is mainly In some slower-swimming species, forward movement is mainly provided primarily by the pectoral fins (see fish in tanks! – coral provided primarily by the pectoral fins (see fish in tanks! – coral reef fish, lionfish)reef fish, lionfish)

• In other species, all the fins may be flexible and highly modified In other species, all the fins may be flexible and highly modified for camouflage (example: sea horses and leafy sea dragons for camouflage (example: sea horses and leafy sea dragons and weedy sea dragonsand weedy sea dragons

• Fins will not allow for significant forward movement Fins will not allow for significant forward movement

• Flying fish exampleFlying fish example

Fish GillsFish Gills

• The construction of the gill is the same in The construction of the gill is the same in all fish – all fish – Gill arch supports the entire structure Gill arch supports the entire structure – Gill rakers are on the forward surface of the gill Gill rakers are on the forward surface of the gill

arch and arch and – Gill filaments trail behind the gill arch Gill filaments trail behind the gill arch

• Like in the human lung, exchange of Like in the human lung, exchange of oxygen and carbon dioxide takes place on oxygen and carbon dioxide takes place on these surfacesthese surfaces

Figure 8.17 The gills of fishes are very efficient for gas exchange. Bony fishes

have 4 pairs of gills (a), each containing 2 rows of gill

filaments (b). Lamellae in gill filaments (c) increase the

surface area of the gill filaments. (d) Diffusion of

oxygen from seawater into the blood gets a boost b/c the water flows across the lamallae in the opposite direction to that of the

blood. (e) The concentration of oxygen (indicated by

dots) is always higher in the water than in the blood. If

circulation were not reversed, blood to the body

would have less oxygen.

VIDEO

Acquiring and Processing Acquiring and Processing FoodFood

• Mouth structure also reveals the dietary Mouth structure also reveals the dietary preferences of fishpreferences of fish

• As an example, the As an example, the ““beakbeak”” (fused teeth) (fused teeth) seen in parrotfish allows for these fish to seen in parrotfish allows for these fish to scrape algae and other organisms off of scrape algae and other organisms off of hard surfaceshard surfaces

• The butterfly fish uses its long tube-like The butterfly fish uses its long tube-like mouth to feed on coralsmouth to feed on corals

• While the barracuda uses rows of sharp While the barracuda uses rows of sharp teeth and a wide mouth to capture its prey teeth and a wide mouth to capture its prey – other fish– other fish

Acquiring and Processing Acquiring and Processing Food Food

Jaw/Mouth StructureJaw/Mouth Structure

Acquiring and Processing Acquiring and Processing Food:Food:Mouth StructureMouth Structure• The position of the mouth is also The position of the mouth is also

importantimportant• A strongly forward facing mouth is A strongly forward facing mouth is

important in fish who chase down important in fish who chase down their prey (as seen in barracuda)their prey (as seen in barracuda)

• A downward facing mouth would be A downward facing mouth would be seen in fish feeding at/near the seen in fish feeding at/near the bottom (opposite for feeding on bottom (opposite for feeding on surface of water) surface of water)

Acquiring and Processing Acquiring and Processing Food:Food:DigestionDigestion• Organs involved: stomach, intestine Organs involved: stomach, intestine

(with anus), liver, pyloric caeca and (with anus), liver, pyloric caeca and pancreaspancreas

• The stomach is structured very The stomach is structured very similarly to the human stomach – similarly to the human stomach – stretch receptors in the wall of the stretch receptors in the wall of the stomach indicate when a meal is stomach indicate when a meal is present and needs to be mechanically present and needs to be mechanically digested by the churning motion of the digested by the churning motion of the stomach wallstomach wall

Acquiring and Processing Acquiring and Processing Food:Food:DigestionDigestion• Intestine, pyloric caeca (tubes at end of Intestine, pyloric caeca (tubes at end of

intestine), pancreas and liver (bile breaks intestine), pancreas and liver (bile breaks down fat) all secrete digestive enzymesdown fat) all secrete digestive enzymes

• The intestines of carnivorous fish tend to be The intestines of carnivorous fish tend to be short and straight while the intestines of short and straight while the intestines of herbivorous fish are longer and more coiled herbivorous fish are longer and more coiled (plant and algae material is more difficult to (plant and algae material is more difficult to process, so it needs to stay in the intestines process, so it needs to stay in the intestines longer) longer)

Acquiring and Processing Acquiring and Processing Food:Food:DigestionDigestion

The Circulatory SystemThe Circulatory System

• Two chambered heart that pumps blood Two chambered heart that pumps blood throughout the body (in contrast to the 4 throughout the body (in contrast to the 4 chambered heart seen in mammals)chambered heart seen in mammals)

• System of arteries, veins and capillaries System of arteries, veins and capillaries takes blood to the body tissues and takes blood to the body tissues and returns it for re-oxygenation by the gill returns it for re-oxygenation by the gill filamentsfilaments

• OO22 and CO and CO22 diffuses across thin diffuses across thin membranes of capillaries either in the gills membranes of capillaries either in the gills or at the tissues of the bodyor at the tissues of the body

Figure 8.15. The circulatory system of fishes Figure 8.15. The circulatory system of fishes consists of veins that carry deoxygenated blood (in consists of veins that carry deoxygenated blood (in blue) from the body, a two-chambered heart that blue) from the body, a two-chambered heart that pumps blood into the gills for oxygenation, and pumps blood into the gills for oxygenation, and arteries that carry oxygenated blood (in red) to rest arteries that carry oxygenated blood (in red) to rest of body).of body).

Fluid Balance in FishFluid Balance in Fish

• Remember osmosis and diffusion are Remember osmosis and diffusion are always at work in an organismalways at work in an organism

• Fish need mechanisms to combat the Fish need mechanisms to combat the issue of water loss – OSMOREGULATIONissue of water loss – OSMOREGULATION

• Fish osmoregulate by:Fish osmoregulate by:– Swallowing seawater and expel the solutes in Swallowing seawater and expel the solutes in

the digestive process (this allows them to keep the digestive process (this allows them to keep the water and lose the solutes)the water and lose the solutes)

– Most marine fish pass very little urine that is Most marine fish pass very little urine that is processed by the kidneys, and is highly processed by the kidneys, and is highly concentrated with solutes with very little water concentrated with solutes with very little water contentcontent

Fig. 8.18 Marine fishes - salts excreted by

kidneys and drink water

The Fish Nervous SystemThe Fish Nervous System• The fish have a brain, spinal cord and numerous The fish have a brain, spinal cord and numerous

nerves like other vertebratesnerves like other vertebrates• Smell: Fish possess olfactory sacs (with nostrils/nares)Smell: Fish possess olfactory sacs (with nostrils/nares)• Hearing: Inner ears are set in fluid-filled canals with Hearing: Inner ears are set in fluid-filled canals with

sensory cells similar to the lateral line system.sensory cells similar to the lateral line system.• Taste: Detect chemical stimuli by using taste buds are Taste: Detect chemical stimuli by using taste buds are

located in the mouth, lips, barbels and skinlocated in the mouth, lips, barbels and skin• Sight: The Sight: The positionposition of the lens changes like in a camera of the lens changes like in a camera

– (Note: Different from land animals where the lens changes (Note: Different from land animals where the lens changes shapeshape for focusing on items for focusing on items

The Fish Nervous SystemThe Fish Nervous System• All fish rely heavily on the All fish rely heavily on the lateral line systemlateral line system• The lateral line is a series of pores and canals The lateral line is a series of pores and canals

lined with specialized organs called lined with specialized organs called neuromasts that are specialized to detect neuromasts that are specialized to detect vibrationsvibrations– Lined with hair cells – similar to those in your Lined with hair cells – similar to those in your

cochleacochlea• Orientation, predatory behavior, social Orientation, predatory behavior, social

schoolingschooling

Fish BehaviorFish Behavior• SchoolingSchooling

– Widely used (+4000 species school)Widely used (+4000 species school)– Why school?Why school?

•Predator deterrentPredator deterrent•Spawning aggregationSpawning aggregation•MigrationMigration•Enhanced foragingEnhanced foraging

Fish BehaviorsFish Behaviors• TerritorialityTerritoriality

– Some fish are territorial by nature all the time, Some fish are territorial by nature all the time, others are only territorial during reproductionothers are only territorial during reproduction

– Fish maintain their territories normally by Fish maintain their territories normally by ““posturingposturing”” to show their aggression to show their aggression

– Posturing can include raised fins, open mouth, Posturing can include raised fins, open mouth, darting, etc.darting, etc.

– Fights between individuals are actually rareFights between individuals are actually rare– Damselfish and algaeDamselfish and algae

Reproduction in FishReproduction in Fish• Sex hormones control the development of Sex hormones control the development of

sperm and eggs in fishsperm and eggs in fish• Release of sex hormones cued by water Release of sex hormones cued by water

temperature, day length, specific tide cycles, temperature, day length, specific tide cycles, etc.etc.

• Broadcast spawning most commonBroadcast spawning most common• Some fish have internal fertilization (sperm is Some fish have internal fertilization (sperm is

inserted directly into the female by the male)inserted directly into the female by the male)• Complex mating behaviors are seen in some Complex mating behaviors are seen in some

species (Ex. Banggai cardinals, others)species (Ex. Banggai cardinals, others)• Color or body changes can cue reproductionColor or body changes can cue reproduction

Atlantic cod mating behaviors. 1. Male establishes territory. 2. Male makes displays (grunting,

spreading fins, etc). 3. Female (if the male is lucky) spawns with male.

Fish ReproductionFish Reproduction• Some fish are hermaphroditicSome fish are hermaphroditic

– Simultaneous hermaphrodites – rare (ex. Simultaneous hermaphrodites – rare (ex. salmon, some deep sea fish)salmon, some deep sea fish)

– Sequential hermaphroditesSequential hermaphrodites• Protandry - males then females (ex. anemone fish) Protandry - males then females (ex. anemone fish)

• Protogyny – females males (ex. wrasses, parrotfish)Protogyny – females males (ex. wrasses, parrotfish)

– Cues for changes - changes in social structure Cues for changes - changes in social structure or environment or environment

Fish ReproductionFish Reproduction• Depending on the species, fish can either be:Depending on the species, fish can either be:

– Viviparous – young are born liveViviparous – young are born live– Oviparous - egg layers (most common)Oviparous - egg layers (most common)

• Some parents protect eggs, though most do notSome parents protect eggs, though most do not

– Ovoviviparous – eggs are kept inside and Ovoviviparous – eggs are kept inside and ““hatchhatch”” before being released from female reproductive tractbefore being released from female reproductive tract

– RARE: Parthenogenic species - in this reproductive plan, RARE: Parthenogenic species - in this reproductive plan, young develop directly from the unfertilized eggs of the young develop directly from the unfertilized eggs of the female (no DNA from males) – the young are female (no DNA from males) – the young are ““clonesclones”” of of the femalethe female

Spawning Aggrigation

Most Important Most Important Characteristics of Marine Characteristics of Marine

FishFish