Fish Biology and Identification

Class Osteichthyes

bony fish, mostly ray finned

Class Chondrichthyes

cartilaginous fish, sharks and rays

Lateral line

series of small holes on top of fish spine, used to sense changes in pressure

Cuadal fin

tail

Dorsal fins

fins on top of fish, help maintain straight line swimming

Pectoral fins

fins connected to “chest”, used for braking, steering, and balancing

Pelvic fins

located on bottom side of fish, used to control vertical movement

Anal fin

on back/underside of fin, used for stability

Homocercal caudal fin

fish tails, different types: forked, lunat, truncate, rounded, eel-like

Heterocercal caudal fin

shark tail, non-symmetrical

White muscle

fast glycolytic, burst of high power (sprint muscle)

Red muscle

slow oxidative, sustained low power

Anguilliform

eel-like swimming style, highly efficient, slow, used by bottom dwellers

Carangiform

jack-like swimming form, high efficiency, slow (or very fast for pursuit hunters), most commonly seen in open water column swimmers where back tail oscilates to create the motion

Aviform

paired fins swimming style, low speed and efficiency, improved control, used by reef dwelling species (ex: parrotfish)

Balistiform

triggerfish-like, undulates dorsal and anal fins, gives precise control and allows fish to be able to reverse, allows for fish to hunt for buried inverts

Ostraciform

boxfish-like swimming style, tail only, no speed, must be armored as protection since there’s no chance of evading predators through speed

Sequential hermaphroditism

when fish change sex depending on the stages of maturation to maximize reproductive success

Protandry

type of sequential hermaphroditism where the male is fist, ex: clownfish

Protogyny

type of sequential hermaphroditism where the female are first (about 75% of fish species that have sequential hermaphroditism), ex: wrasses and parrotfish

Typical fish maturation phases

immature → intermediate → adult

Sequntial hermaphrodites maturation phases

juvenlie → initial (first gender, ex: F) → terminal (final gender, ex: M)

Wrasse harems

only large males mate, no benefit to being small male, group of females and one dominant male

Disc and oval

swim: reefs and rocks, laterally compressed, hide and forage in reefs, feed: sessile inverts, algae, sponges, surgeonfish, angelfish, butterflyfish, damselfish

Surgeonfish

disc/oval shaped, grazer on algae and coral

Angelfish and butterflyfish

disc/oval shaped, feed on inverts and coral

Damselfish

disc/oval shaped, grazer (and farmer)

Pectoral fin swimmers

swim: in water-column, aviform locomotion (fins for propulsion → speed and control), forage: algae, coral, inverts, juvenile → initial → terminal, sex-changes common, parrotfishes, wrasses, mexican hogfish

Parrotfishes

pectoral fin swimmers, aviform locomotion, eat coral and ecrusting algae

Wrasses

pectoral fin swimmers, aviform locomotion, eat inverts

Truncate - boxy

swim: water column, slow and controled, ostraciform locomotion, box/balloon shape, fused teeth, skin with spines or plates, TTX (tetrodotoxin), smooth puffer, spiny puffer, boxfish

Rhomboid

swim: water column, balistiform locomotion with undulating dorsal fin, feed: buried inverts in sandy substrate, corals, strong jaws and crushing teeth, dorsal spine, triggerfish, filefish

Triggerfish

rhomboid body type, balistiform locomotion, eat buried shelfish and crustaceans

Filefish

rhomboid body type, eat inverts and algae

Bottom dwellers

benthic (sandy or rocky, often in holes), lack swim bladder, “walk” on modified pectorals, small bodied, large eyed, feed: water column, substrate herbivores, detritivores

Blennies

bottom dweller, either one or three dorsal fins

Gobies

bottom dweller, one dorsal fin

Long and tubular

attenuate, swim: water column, feed: darting attack, reduced and set back fins, predatory on small fish, trumpetfish, cornetfish, halfbeak

Trumpetfish

long and tubular bodytype, also do shadowstalking

Cornetfish

long and tubular body type, cuadal filament

Halfbeak

long and tubular body type, upturned “superior” mouth

Sloping head - mouth low

swim: water column, overhangs, feed: benthic substrate, crustaceans, small fish, medium sized, form large schools, snapper, drum, goatfish

Bottom flatfish

depressed, benthic and bethopelagic, feed on substrate, “bottom” eye travels to top of head, camouflage and color-change, one gill exit, predators of benthic inverts (through ambush), ex: left-eye flounder (only left-eye flounders found in galapagos), right-eye flounder

Eels

elongate, swim: rocky and sandy substrate, feed: hunt in crevices, no pectoral or ventral fins, predators, long teeth, hinged canines, nocturnal hunters, filter feeders (on zooplankton), anguilliform locomotion, moray eel

Moray eel

elongate body type, anguilligorm locomotion, predator

Front flappers

clade Chondrichthyes, swim: bethopelagic and water column, enlarged pectoral fins (look like they’re flying), tail with or without fin, stinger, broad teeth (for predation on molluscs), planktivores (manta rays)

Spotted eagle ray

front flapper, preys on molluscs and crustaceans

Giant manta ray

front flapper, planktivore