About 23,000 different species Osteichthyes: Bony Fish AKA: Teleosts
Diversity of fishes
Anatomical terminology Dorsal Posterior or caudal Anterior Lateral Lateral Ventral Used for relating different parts.eye is posterior to the mouth Conversely the mouth is anterior to the eye
External Anatomy Fins Mouth Scales Sail fish (Istiophorus platypterus) White sucker (Catostomus commersonii) Longnose gar (Lepisosteus osseus) American eel (Anguilla rostrata) River hatchetfish (Gasteropelecus sternicla ) Great white shark (Carcharodon carcharias)
Spines vs. rays Bluegill (Lepomis macrochirus)
Rigid Spines Often for defense Rays Flexible Often branched Mainly for support Fisheries ecologists use both spines & rays for identification and aging!
Mouth placement superior terminal Inferior (sub-terminal)
Fins Caudal Dorsal Pectoral Anal Pelvic Adipose Anal Pelvic Pectoral
Heterocercal Tip of vertebral column turns upward Epicercal: dorsal lobe larger (sturgeon) Hypocercal: ventral lobe longer (flying fish) Protocercal Extends around vertebral column Embryonic fish; hagfish Homocercal Vertebral column stops short of caudal fin, which is supported by bony rays Symmetrical Diphycercal 3 lobed; lungfish and coelacanth Vertebral column extends to end of caudal fin, dividing into symmetrical parts
Scale types Placoid Ganoid Cycloid Ctenoid
Placoid: sharks and rays decrease drag. Ganoid: bowfin, paddlefish, gar, sturgeon Armor-like plates for protection
Cycloid and Ctenoid: most bony fishes (teleosts) Overlapping = Flexibility, reduced drag Both grow in concentric rings Cycloid: smooth outer edge, soft-rayed fish (e.g., salmon) Ctenoid: toothed outer edge, spiny fish (e.g., bass)
Related to lifestyle Body Shape Fusiform (streamlined body)-helps move through water easy, fast swimmer -Ex: Sharks, Tuna, Marlins
Body Shape Cont d Laterally Compressed- leisurely swimming around coral/kelp -Ex: Angelfish, damselfish, butterfly fish
Elongated body- live in narrow spaces -Ex: moray eels, trumpet fish, pipefish Round- porcupine fish
Flatfish- actually laterally compressed. Adapted to live on bottom Lie on side, both eyes on top (born w/ eyes on each side) HALIBUT SOLE FLOUNDER
Dorsoventrally flattened- demersal fish -Ex: Rays, skates
Trumpet Fish Stonefish Blennies
Coloration COUNTER SHADING DISRUPTIVE CRYPTIC LIONFISH WARNING
Locomotion Rhythmic side to side motion swim bladder for buoyancy and lift -pectoral fins used to hover and swim backwards
Fish Circulation Fish heart has 2 chambers Single loop circulation Blood flows into gills, picks up O 2, goes to the body, returns to the heart.
Gills
Gills are the main site of gas exchange in almost all fishes. The gills consist of bony or stiffened arches (cartilage) that anchor pairs of gill filaments.
Numerous lamellae protrude from both sides of each filament and are the primary sites of gas exchange.
Lots of surface area Oxygen diffuses right into blood stream! Microscopic gill structure: showing gill filament and lamellae (Red blood cells evident.)
Water flows over gills as fish opens mouth. Water flows OPPOSITE direction of blood flow (countercurrent system)
COUNTER-CURRENT Higher conc. of O 2 in water than in blood O 2 diffuses from the water into the blood. WHAT WOULD HAPPEN IF THEY FLOWED IN SAME DIRECTION? (Co-Current)?????
Water Blood Water Blood
So, they efficiently extract oxygen by. Short diffusion distance at gill site Large surface area for diffusion at gill site Counter current exchange of gases at gill site Large volume of water passes over gills
Why school? Protects against predation Causes confusion, encircle a predator Hard to pick out one Maybe swimming efficiency (fish in front reduces water resistance)
Hermaphrodites Some marine hamlet fish are hermaphrodites Although they could fertilize own eggs, they still cross fertilize Found in many deep sea fish when mates are hard to find
Sex Reversal Most prevalent in some sea basses, grouper, parrotfish, wrasses, clown male female (protandry) female male (protogyny) controlled by sex hormones but triggered by social cues i.e.: absence of dominant female in hierarchy
Fishing Methods
REDUCING BYCATCH Dolphins and tuna known to swim together and caught in purse seines Backdown method for dolphin safe tuna Turtles often caught in trawlers Turtle Excluder Devices (TED)
Overfishing Growing world population Large scale fishing methods Improved technology Competition for profit No recovery time Depletion of natural populations
Aquaculture (fish farms) Marine aquaculture refers to the culturing of species that live in the ocean. U.S. marine aquaculture primarily produces oysters, clams, mussels, shrimp, and salmon. Marine aquaculture can take place in the ocean (that is, in cages, on the seafloor, or suspended in the water column) or in on-land, manmade systems such as ponds or tanks. Recirculating aquaculture systems that reduce, reuse, and recycle water and waste can support some marine species. Freshwater aquaculture produces species that are native to rivers, lakes, and streams. U.S. freshwater aquaculture is dominated by catfish but also produces trout, tilapia, and bass. Freshwater aquaculture takes place primarily in ponds and in on-land, manmade systems such as recirculating aquaculture systems. -NOAA