Marine Fishes

What is a fish?? Classic definition: -Any of numerous cold-blooded aquatic vertebrates of the superclass Pisces, characteristically having fins, gills, and a superclass 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 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 are considerably MORE!! considerably MORE!!

Fish similarities... Vertebrate ( chordate)Vertebrate ( chordate) GillsGills PoikilothermicPoikilothermic FinsFins ScalesScales

Drag Reduction Features in Fish “Fusiform” body shape“Fusiform” body shape Reduction of body wave amplitudeReduction of body wave amplitude Reduction of surface areaReduction of surface area Boundary layer modificationsBoundary layer modifications

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

Ostracoderms –Class Pteraspidomorphi (sp. diplorhina = “two nares”) –they literally had two separate olfactory bulbs in the brain. –those with a different shell, i.e. dermal armor

Placoderms - earliest gnathostomes (jawed vertebrates) True jaws = more food!True jaws = more food! Paired fins = more food!Paired fins = more food!

Hagfish (Agnatha): jawless fish

Lamprey Predatory/parasiticPredatory/parasitic Rasping teethRasping teeth

Parasitism of Great Lakes fishes…

Cartilagenous Fishes (Sharks, Skates and Rays)

Distinguishing Elasmobranch Traits cartilaginous skeleton no swim bladder heterocercal tail placoid denticles - scales and teeth spiracles present with 5-7 gill slits (no operculum) urea retained for osmoregulation spiral valve in intestine males have claspers, internal fertilization oviparous, ovoviviparous, viviparous teeth in rows, are constantly replaced Elasmobranch… plate or strap gill

Sharks exhibit extreme variability in size, shape and abilities.

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

Variations on this theme are common.

Carchariniformes – basking sharks, filter feeder Cetorhinus maximus

Great White, Carcharodon carcharias Mako Great White Isurus oxyrinchus Lamniformes - mackerel, mako, white sharks mako, white sharks-carnivores

Skates and rays spend most of their lives near (on) the ocean floor eating molluscs, squid, and small fish. Yellow stingray, Urolophus jamaicensis

Like sharks, skates and rays come in many shapes and sizes.

Blue spotted ray, Taeniura lymma

Skates (order Rajiformes) pelvic fin divided into two lobes tail relatively stocky, no spine Rays (order Myliobatiformes) each pelvic fin with one lobe tail relatively slender to whip-like spine

Spotted ratfish Hydrolagus colliei Family: chimaeridae Identification: Broad, flat, duckbill shaped snout containing incisor shaped teeth. Prominent, venomous spine at leading edge of dorsal fin. Tapering tail constitutes almost half overall length. Coloration brown or grey with white spots. Skin smooth and scaleless. Can give off an iridescent, silvery sheen. Fins grey or dark.Identification: Broad, flat, duckbill shaped snout containing incisor shaped teeth. Prominent, venomous spine at leading edge of dorsal fin. Tapering tail constitutes almost half overall length. Coloration brown or grey with white spots. Skin smooth and scaleless. Can give off an iridescent, silvery sheen. Fins grey or dark. Size: up to 97cm in length.Size: up to 97cm in length.

Boneless vs. Bony

Found in sharks and rays, and can vary greatly in external appearance. They do not increase in size as the fish grows, instead new scales are added. Placoid scales are often referred to as denticles. Placoid scales consist of a flattened rectangular base plate which is embedded in the fish, and variously developed structures, such as spines, which project posteriorly on the surface. The spines give many species a rough texture. Placoid scales Placoid scales of the Broadnose Sevengill Shark.

Cycloid and Ctenoid Scales Found in bony fishes (the Teleostei). Overlapping = flexibility, over cosmoid or ganoid scales. Cycloid scales—smooth posterior margin, no ctenii. (Greek "cyclo“ or circle.)

Fish form and function show a high degree of variation.

Coloration is also very important in fish. Here a stonefish “disappears” amid the coral background. Chromatophores, specialized pigment cells within its skin provide protective coloration.

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

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

Warning coloration! May indicate poisonous amimal.

Fish Locomotion

Primary forces involved in fish swimming:Primary forces involved in fish swimming: –Thrust - force that propels forward –Drag - friction produced from passing an object through a medium –Gravity – force from earth’s magnetic pull (partially counterbalanced by density of water) –Lift - upward force that counteracts gravity

Skeletal Fish Muscle: Essentially three types of fish muscle: red, white, pink.Essentially three types of fish muscle: red, white, pink. Red muscle (oxidative): Highly vascularized, myoglobin containing tissue used during sustained swimming. Small diameter and high blood volume = rich O 2 supply! Presence leads to strong flavor in some fishes (tuna).Red muscle (oxidative): Highly vascularized, myoglobin containing tissue used during sustained swimming. Small diameter and high blood volume = rich O 2 supply! Presence leads to strong flavor in some fishes (tuna). White muscle (glycolytic): Little vascularization. Used during “sprint” swimming. Large diameter fibers.White muscle (glycolytic): Little vascularization. Used during “sprint” swimming. Large diameter fibers. Pink muscle: This one is sort of in between red and white. Serves in sustained swimming, but not to the extentPink muscle: This one is sort of in between red and white. Serves in sustained swimming, but not to the extent that red muscle is used.

Swimming Styles Body waves Anguilliform (eel-like) Lateral curvature in spine and musculature that moves in a posterior direction Start: lateral displacement of head, and then passage of this displacement along the body axis to the tail Result: backward- facing “wall” of body pushing against the water

Swimming Styles Partial body waves (Sub) Carangiform, Thunniform (tuna-like) Body wave begins posterior to head and increases with amplitude as it moves posteriorly Reduced drag compared to full body wave swimming Wave STARTS at the caudal peducle (deeply forked, lunate)

Swimming Styles Caudal peduncle/fin beats Ostraciform (boxfish- like and puffer-like) Sculling action of caudal fin—like rowing No body waves - body remains rigid - useful for odd- shaped fishes

Swimming Styles Medial fin waves Amiiform - bowfin-like Body rigid, but medial fins generate posterior waves (forward) or anterior (reverse) Good for stalking or moving without disrupting body musculature that serves as electric organ (knifefish) Also used for sculling - triggerfish & others

Swimming Styles Pectoral fin beats Labriform wrasse-like Similar to rowing laterally-positioned pectoral fins- often includes feathering as well Especially useful for fine maneuvering e.g. by deep-bodied fishes

Fish Feeding - function HerbivoresHerbivores –< 5% of all bony fishes, no cartilaginous fishes browsers - selective - eat only the plantbrowsers - selective - eat only the plant grazers - less selective - include sedimentsgrazers - less selective - include sediments DetritivoresDetritivores –5 - 10% of all species –feed on decomposing organic matter

Fish Feeding - function, cont. CarnivoresCarnivores –zooplanktivores suction feedingsuction feeding ram feedingram feeding –benthic invertebrate feeders graspersgraspers pickerspickers sorterssorters crusherscrushers

Fish Feeding - function, cont. Carnivores, cont.Carnivores, cont. –fish feeders active pursuitactive pursuit stalkingstalking ambushingambushing luringluring

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

Feeding behavior Fish show versatility in prey choice and ingestionFish show versatility in prey choice and ingestion Behavior tightly linked to morphologyBehavior tightly linked to morphology(co-evolution)

Similar to Darwin’s finches, different shaped mouths permit specialization on many prey items.

Digestive Systems Cartilagenous vs. Teleost (bony)

Fish circulation is a closed system. Heart pumps blood through a loop of arteries, veins, and capillaries.

Gills: the best way to gain oxygen (O 2 ) from an environment where its concentration is already very low. Counter-current circulation permits O 2 to diffuse from high to low concentration, even across venous tissue after most O 2 has been removed from the water by gills.

Salt Balance Revisited Rem: Freshwater fish [salt] inside fish > [salt] outside Saltwater fish [salt] inside [salt] outside Saltwater fish [salt] inside < [salt] outside fish

Structure of Lateralis Canals Epidermal tunnelEpidermal tunnel Pores open from canal to skin surfacePores open from canal to skin surface Neuromasts distributed within tunnelNeuromasts distributed within tunnel Fluid in tunnel is more viscous than water; therefore, more resistant to flowFluid in tunnel is more viscous than water; therefore, more resistant to flow

Lateral line also aids in navigation in close quarters. Damselfish, Chromis spp.

Predator avoidance

Fish Migrations: food, spawning

Migration for some salmon is a one-way trip!

Freshwater eels, Anguilla rostrata are at the extreme end of migratory patterns, taking an entire life to make the round trip. Adults spend 15 years in fresh water before making the return trip to spawning grounds.

Reproduction in Fishes

Reproductive traits and life-history patterns Mating systems: –Promiscuous - both sexes with multiple partners - most (common) –Polygynous - males with multiple mates (cichlids) –Polyandry - females with multiple mates – few (Anglerfish, males “parasitize” females, clownfish) –Monogamy - mating pair remains together over time, long gestation of young (some cichlids, seahorses, pipefish)

Courtship/ritualistic displays are patterns of behavior observed in many fish.

Some marine fish have specialized reproductive organs. Claspers in elasmobranchs: male reproductive organ

Egg laying (ovipary) in sharks, is a common menthod of fish reproduction. swell shark egg, Cephaloscyllium ventriosum