Marine FishesMarine Fishes

What is a fish??What is a fish??Classic definition:Classic definition:

-Any of numerous cold-blooded aquatic vertebrates of the-Any of numerous cold-blooded aquatic vertebrates of the

superclass Pisces, characteristically having fins, gills, and asuperclass Pisces, characteristically having fins, gills, and a

streamlined body and including specifically, and...streamlined body and including specifically, and...

-Any of the class Osteichthyes, having a bony skeleton, and...-Any of the class Osteichthyes, having a bony skeleton, and...

-Any of the class Chondrichthyes, having a cartilaginous-Any of the class Chondrichthyes, having a cartilaginous

skeleton and including the sharks, rays, and skates. skeleton and including the sharks, rays, and skates.

Although this is all accurate...we will find that fish areAlthough this is all accurate...we will find that fish are

considerably MORE!!considerably MORE!!

Fish similarities...Fish similarities...

• Vertebrate ( chordate)Vertebrate ( chordate)

• Gills Gills

• FinsFins

• ScalesScales

What is a fusiform body shape?What is a fusiform body shape?

• pointed leading edgepointed leading edge• maximum depth 1/3 body length back from headmaximum depth 1/3 body length back from head• posterior taperposterior taper• caudal fin interrupts ideal fusiform shapecaudal fin interrupts ideal fusiform shape

Hagfish (Agnatha): jawless fishHagfish (Agnatha): jawless fish

LampreyLamprey

• Predatory/parasiticPredatory/parasitic• Rasping teethRasping teeth

Cartilagenous Fishes(Sharks, Skates and Rays)

Distinguishing TraitsDistinguishing Traits

cartilaginous skeletonno swim bladderheterocercal tailscales and teethspiracles present with 5-7 gill slitsmales have claspers, internal fertilizationteeth in rows, are constantly replaced

Sharks exhibit extreme variability in size, shape and abilities.

Nearly 850 spp. of sharks, 350 exhibit typical Nearly 850 spp. of sharks, 350 exhibit typical body morphology.body morphology.

Variations on this theme are common.Variations on this theme are common.

Carchariniformes – basking sharks, filter feeder

Cetorhinus maximus Cetorhinus maximus

Great White, Great White, Carcharodon carchariasCarcharodon carcharias

Mako Great WhiteGreat WhiteIsurus oxyrinchusIsurus oxyrinchus

Lamniformes - mackerel,Lamniformes - mackerel, mako, white sharksmako, white sharks-carnivores-carnivores

Skates and rays Skates and rays spend most of their lives near (on) the spend most of their lives near (on) the

ocean floor eating molluscs, squid, and small fish.ocean floor eating molluscs, squid, and small fish.

Yellow stingray, Urolophus jamaicensis

Like sharks, skates and rays come inLike sharks, skates and rays come in

many shapes and sizes.many shapes and sizes.

Blue spotted ray, Blue spotted ray, Taeniura Taeniura lymmalymma

Boneless Boneless vs.vs.BonyBony

Cycloid and Ctenoid Scales

Found in bony fishes (the Teleostei). Overlapping = flexibility, over cosmoid or ganoid scales.

Cycloid scales—smooth posterior margin. (Greek "cyclo“ or circle.)

Coloration is also veryColoration is also veryimportant in fish.important in fish.

Here a stonefish “disappears”Here a stonefish “disappears”amid the coral background.amid the coral background.

ChromatophoresChromatophores, specialized, specializedpigment cells within itspigment cells within itsskin provide protective skin provide protective coloration.coloration.

• • Disrupt the outline of the fish Disrupt the outline of the fish

• • Being dark on top, light on bottom Being dark on top, light on bottom – Look like substrate from above – Look like substrate from above – Look like water surface from below – Look like water surface from below

Warning coloration! May indicate poisonous Warning coloration! May indicate poisonous amimal.amimal.

Fish LocomotionFish Locomotion

• Primary forces involved in fish swimming:Primary forces involved in fish swimming:– ThrustThrust - force that propels forward - force that propels forward– DragDrag - friction produced from passing an object - friction produced from passing an object

through a mediumthrough a medium– GravityGravity – force from earth’s magnetic pull – force from earth’s magnetic pull

(partially counterbalanced by density of water)(partially counterbalanced by density of water)

– LiftLift - upward force that counteracts gravity - upward force that counteracts gravity

Fish Feeding - functionFish Feeding - function

• HerbivoresHerbivores– < 5% of all bony < 5% of all bony

fishes, no cartilaginous fishes, no cartilaginous fishesfishes

• browsers - selective - browsers - selective - eat only the planteat only the plant

• grazers - less selective - grazers - less selective - include sedimentsinclude sediments

• DetritivoresDetritivores– 5 - 10% of all species5 - 10% of all species– feed on decomposing feed on decomposing

organic matterorganic matter

Fish Feeding - function, Fish Feeding - function, cont.cont.

• CarnivoresCarnivores– zooplanktivoreszooplanktivores

• suction feedingsuction feeding

• ram feedingram feeding

– benthic invertebrate benthic invertebrate feedersfeeders

• graspersgraspers

• pickerspickers

• sorterssorters

• crusherscrushers

Fish Feeding - function, Fish Feeding - function, cont.cont.

• Carnivores, Carnivores, cont.cont.– fish feedersfish feeders

• active pursuitactive pursuit

• stalkingstalking

• ambushingambushing

• luringluring

Fish feeding behaviorFish feeding behavior

• Fish feeding behavior integrates morphology Fish feeding behavior integrates morphology with perception to obtain food:with perception to obtain food:– SearchSearch– --> Detection--> Detection– --> Pursuit--> Pursuit– --> Capture--> Capture– --> Ingestion--> Ingestion

Feeding behaviorFeeding behavior

• Fish show versatility in Fish show versatility in prey choice and ingestionprey choice and ingestion

• Behavior tightly linked to Behavior tightly linked to morphology morphology

(co-evolution)(co-evolution)

Lateral line also aids in navigation in close quarters.Lateral line also aids in navigation in close quarters.

Damselfish, Chromis spp.

Predator avoidancePredator avoidance

Migration for some salmon is a one-way trip!Migration for some salmon is a one-way trip!

Marine Reptiles

• Reptiles are cold-blooded, air-breathing animals with tough, scaly skin

• Marine reptiles include:– Sea turtles (7 species)– Sea snakes (55 species)– Marine crocodiles (1)– Marine lizards (iguanas; 1)

Marine Reptiles

• Like most fish, marine reptiles are ectothermic and poikilothermic; “cold-blooded”

• Marine reptiles breath air; they have internal lungs, not gills

• Marine reptiles are equipped with special salt glands to concentrate and excrete salts

• Leathery shells prevent eggs from drying out

Marine Reptiles: Sea Turtles

• Sea turtles belong to an ancient group of reptiles

• Their body is enclosed by an armor-like shell, or carapace that is fused to their backbone

• All are streamlined and adapted for life in the water– Forelimbs are modified into flippers– Hindlimbs act as rudders– Cannot retract head or limbs

Marine Reptiles: Sea Turtles

Our Local Sea Turtles

Leatherback

http://fwie.fw.vt.edu

Green

scienceblogs.com www.underwater.com.au

http://www.costaricaturtles.com/costa_new_seaturtles.html

Loggerhead

Hawksbill Kemp’s Ridley

www.dnr.state.md.us/fisheriesoxford/research/fwh/seaturtles.html

Marine Reptiles: Sea Turtles• Sea turtles spend their entire lives at sea; only

females come ashore to lay eggs– Homing (return to same beach where they were

born to lay eggs)

http://www.conservation.org/great_turtle_race/Pages/main.aspx

http://www.youtube.com/watch?v=UKkScAel52w

Temperature-dependent Sex Determination

• When female sea turtles come ashore to lay their eggs, the depth of the burrow she digs affects the temperature of the eggs that are laid

• Temperature (not genetics) determines the sex of the offspring– Warmer nests females

© Aqua Image/age fotostock

Got Arribada?• Female sea turtles aggregate on the beach in

mass nestings called arribadas

http://www.youtube.com/watch?v=W4u3GL9SyyM

Save the Sea Turtles!

• Most of the world’s sea turtles are threatened or endangered with extinction

• Dangers include:– Shrimp trawling; Long-line fishing– Beach destruction, hardening of shorelines, vehicles

and dogs on beaches– Bright beach lights– Marine debris; Ghost netting– Global warming

Credit: © James Watt/Visuals Unlimited

…and closer to home

• Every fall and winter, the local sea turtles off Long Island need to return south to the warmer waters of the Caribbean and the Gulf of Mexico

• Sea turtles that remain can become “cold stunned”– <50°F– Call the Riverhead

Foundation: 369-9840

Marine Reptiles: Sea Snakes

• Approximately 55 species of sea snakes are found in the tropical Indian and Pacific oceans

• The tail end of sea snakes is flattened into a paddle-shape for swimming

• A few species return to land to lay eggs, but most give birth to live young underwater– ovovivipous

Marine Reptiles: Sea Snakes

• Sea snakes are closely related to cobras; the most venomous of all snakes

• Sea snake bites can be fatal to humans; extremely venomous– Why?

Marine Reptiles: the Marine Iguana

• The marine iguana is found on the Galapagos Islands, off the coast of South America

• Marine iguanas survive in the cold, upwelled waters off the Galapagos by frequently basking on the rocks to raise their body temperature

• Feed on algae• Efficient swimmers

Marine Reptiles: Saltwater Crocodile• The saltwater crocodile inhabits mangrove

swamps and estuaries in the eastern Indian Ocean, Australia, and some of the western Pacific islands

• Very aggressive; fatal attacks on humans

• Commonly 20ft long • Inhabits coast,

rivers and open sea

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