1. How to Cold-Read a Fish
I’ve included some notes on points not covered in the text. I purposefully haven’t ID’ed the fishes on the slides since part of the point of learning to cold-read is to get us past the mistaken assumption that you know anything about an animal just because you can identify it. What’s in a name anyway? A fish by any other name would smell as ripe.

2. What is a fish, anyway? Vertebrates Fishes have: Fish vs. Fishes
Backbone
CNS with brain
Bilateral symmetry
Sexual reproduction
Fishes have:
Jaws
Gills
Paired fins
Scales (usually)
Cold-blood (almost always)
Fish vs. Fishes
Use fishes when talking about fish of different species, use fish when talking about a single species. Twenty-seven spiny lumpsuckers are “fish” but if a spiny lumpsucker, a monkeyface prickleback and a sarcastic fringehead swim into a bar, they are “fishes.”

3. How to memorize 25,000 fish… Don’t memorize…read them Take clues from:
Body shape
Fins
Mouth
Senses
Color/patterns
Habitat

4. Fins on the football Fusiform Paired fins Unpaired fins Modified fins
Pectoral fins
Pelvic fins
Unpaired fins
Dorsal
Anal
Caudal
Modified fins

5. Fish sense Eyes Nostrils/nares Other Size Position Shape Barbels
Lateral line
Large eyes means vision is important to the fish. Eyes place high on the fish are common on bottom-dwelling fish (all the action is happening above). Many fish have a stripe running through the eye to hide it (eyes are a common target for predators).
Nostrils have an in and an out. They are used only for smell (except in stargazers and ratfish).
Barbels are like having an external tongue. Typically indicate a bottom-oriented fish that lives in a murky environment.

6. Fish mouths Mouth position Size and shape Inside
Point up – surface food and oxygen
Point down – prey on or near the bottom
Point forward – AKA terminal, chase food
Size and shape
Inside
Teeth – all over
Rakers – filtering

7. Staying out of trouble Armor Spines Skin color Schooling
Countershading
Disruptive coloration
Cryptic coloration
Silver and red
Imitation
Schooling
Some fish have heavy, armor-like (ganoid) scales
Spines are unpleasant to bite down on but also make a fish effectively bigger without added much mass (a fish needs a bigger mouth to fit the fish and the spines). Spines may sometimes be venomous.
Countershading is dark on the top and light on the bottom. In the ocean up is light and down is dark.
Disruptive coloration is spots and stripes. They break up the body shape and make the fish harder to spot—especially at a distance.
Cryptic coloration helps a fish blend into its environment (like the stonefish above).
Silver fish live near the surface. Silver scales reflect light and recreate flickering light seen near the surface—fish hide in the light.
Red fish are found at depth. Red wavelengths are absorbed or scattered by about 30 feet. With no red light, the fish appears almost black.
Imitation includes a lot of things. Some fish (like the angler above) imitate algae or other pieces of the habitat. Others use eyespots near the tail to distract predators.
Schooling helps small fish avoid predators by providing more eyes, ears and lateral lines to detect predators and by making a numbers game. Make no mistake, schooling is not “cooperative.” It is selfish. Fish participate because it benefits them. When threatened by a predator, the fish all head for the center.

8. Eco-shapes Rover predators Lie-in-wait predators Surface-oriented
Fusiform, terminal mouth, forked tail, evenly placed fins
Lie-in-wait predators
Fins far back
Surface-oriented
Upturned mouth, large eyes, dorsal back
Forked tail indicates fish is capable of long, sustained bursts of speed. Rover predators also have evenly-spaced fins.
Fins far back, with similarly sized anal and second dorsal fins, indicates potential for quick acceleration. Many lie-in-wait predators are also “skinny fusiform.”
Dorsal fin is located far back on surface-dwelling fish so it doesn’t stick out at the surface and attract predators.

9. Eco-shapes Bottom fish – flat, camouflaged Deep-bodied Eel-like - eely
Rovers – goatfish
Clingers – sculpins, clingfishes
Flatfishes
Rattails
Deep-bodied
Smooshed, pecs, small mouth, large eyes, spines
Eel-like - eely
Clingfishes have pelvic fins modified into sucker discs. Other clingers have large heads and large pectoral fins that, when held down to the bottom, allow the current to push the fish to the bottom instead of tossing it.
Deep-bodied fish are all about maneuverability. They are often found in complex habitats (grass beds, coral reefs, etc.). Pec fins are active and placed high on the side of the fish. Small mouth for picking small prey off of rocks or grass blades.
Eel-shaped fish are eel shaped because they hunt or hide in crevices.

10. Habitat is context
Individual adaptations may only make sense in the context of a fish’s habitat
Specific challenges
Adaptations develop in response to specific challenges posed by the habitat.
The bay pipefish may have an eely shape but they have nothing to do with crevices—they use their narrow profile to blend into eel grass beds.

11. How to cold-read a fish Body shape Fins Senses Mouth Skin color
Fusiform
Flattened
Eel-like
Deep-bodied
Fins
Tail shape
Pectoral fins
Dorsal/anal fins
Modified fins
Spines?
Senses
Eyes
Nostrils/nares
Barbels
Mouth
Position
Size and shape
Skin color
Silvery/counter-shaded
Cryptic/disruptive
Eyespots, etc.
Don’t forget to also consider habitat and behavior.

12. Tell me about this fish
Note: skinny fusiform shape; dorsal and anal fish equal in shape, large and placed far back on the body = built for acceleration
Note: large, terminal mouth = predator
Note: large eye = vision is important
Note: stripes/disruptive coloration = stripes help break up form and make less visible to prey, may blend into vertical aquatic plants

13. What about me?
Note: Forked tail, evenly spaced fins, wing-like pectoral, fusiform shape, terminal/downward pointed mouth mouth = rover predator
Note: Silvery color, large eye = live near surface, probably in clear water
Note: Deep-bodied body shape may suggest some maneuverability is important for this fish

14. Me?
Note: Cryptic coloration, eyes high on the head, mouth low on the “face” = bottom fish
Note: Non-fusiform, weak tail, large pectorals, pelvic fins moved forward for support of head = more hops and darts than swimming

15. What about me?
Note: Deep-bodied, pectoral fins high on the body and transparent = very maneuverable
Note: Stripe through the eye, eyespot near the tail, spines in dorsal = prey animal
Note: Small mouth = picks small inverts from the reef

16. And us?
Note: Silver color, large eyes, dorsal fin far back on the body, upturned mouth = surface-oriented fish
Note: Spots = disruptive coloration
Note: Weak fins, round tail = quick darts but no sustained speeds
Note: modified fin on bottom fish = modified for internal fertilization

17. Curveballs
Clockwise from upper right: deep sea anglerfish, ocean sunfish, leafy seadragon, hatchetfish

18. Phantasmagoric Fish Stories
It’s all about resource partitioning
Extreme specialization leads to…
Freaks!
If a fish can carve out a tiny but utterly unique little niche, they have a good chance of surviving and thriving—especially in a crowded, species-rich environment like a coral reef, rain forest, etc.
(Sarcastic fringehead)

19. Freaky feeders Archer fish Arawana Dusky damsel Angler fishes
Gulper eels
Electric fishes
Cichlids
Vege piranhas
Top row, left to right: arawana. Second row: dusky damsel, archerfish. Third row: gulper eel, cichlid, footballfish (a deep sea angler). Bottom row: electric eel, piranha.
Archerfish have a groove in the roof of their mouth. They shoot insects off of branches with jets of water.
Arawanas jump right out of the water and snatch small birds, lizards and even monkeys off the branches. They are also known as water monkeys.
Dusky damsels “farm” a patch of algae. They eat a little off the top then let it grow. They also defend it with remarkable vigor.
Angler fishes have fins modified as lures that they use to attract prey. Deep sea anglers have bioluminescent lures.
Gulper eels have stretchy stomachs and can eat animals several times their size.
Many species of fishes use electricity to stun food, defend themselves or detect predators and prey.
There are several lakes in Africa where there are so many species of cichlids that they have become hyper-specialized. One species (pictured above) lie on the bottom of the lake and pretend to be dead. They even have colors that make them look like they are rotting. They go so far as to let other fish pick at them a little—until they get close enough to the head and, of course, the mouth.
Some piranhas eat nothing but fruit and seeds.

20. Bizarre sex stories The mile-high club Lonely and loving it
Splash tetra
Lonely and loving it
Functional hermaphrodites
Lancets, tripods
Transvestites and transsexuals
Sneaker males
Changing with age, population composition
Omega males
Deep sea anglers
Amazon Molly
Top row: splash tetra. Second row: Lancet. Third row: stoplight parrotfish, moon wrasse. Third row: molly, deep sea angler
Tetra females leap out of the water and spray eggs on overhanging rock ledges. The males jump out and fertilize them then hang around and splash water on them until they hatch. Keeping the eggs out of the water keeps them safe from predators.
Some fish, like the lancet, are functional hermaphrodites. Lancets live in deep water and very seldom see another lancet. Luckily, when they do meet, they are guaranteed to have compatible parts.
Sneaker males adopt the colors of female fishes. When the alpha male is busy with another member of his harem, the sneaker males dart in and mate.
In some populations, the largest fish is the male. When he dies, the next largest becomes male. Other fish become female as they reach a certain age or size.
Deep sea angler males and females are very different in size. The males are much smaller and spend most of their lives searching out females. When they find one, they attach themselves and never leave. Eventually, their lips grow into the female’s skin and she nourishes him through her blood supply. His only job is to provide gametes.
Amazon mollies are all female. They only need a male from a similar species to “jump start” the process.

21. We could go on World’s smallest vertebrate Ice-fishes Rivulines
Anti-freeze in blood
Rivulines
Eggs to adults in 4 weeks, dead in a year
Elephant fishes
Huge brains (3%)
Tarpon can drown
Walking catfish
Swimmer’s surprise
Swamp eels
Can live out of water for up to 6 months
Telescope/tripod
Flying fish
30 sec, 1m high, 200m
Four-eyed fish
Pearlfish
Top row, left to right: Trimmatom nanus, rivuline, walking catfish. Second row: ice-fish, elephant fish, swamp eel. Third row: telescope fish. Fourth row: flying fish. Bottom row: tarpon, four-eyed fish, pearl fish
Ice fishes live in sub-freezing waters.
Tarpon are obligate air-breathers—they can’t get enough oxygen through their gills.
When their pools dry up, walking catfish walk to another.
A tiny catfish in certain parts of the world have been known to lodge their spiny bodies in human urethras.
Four-eyed fish sit at the surface and can see above and below at the same time.
The anus of the pearlfish is located under its chin so that it doesn’t have to leave its host cucumber to relieve itself.