FAS 2024 Exam A Review

Fish stock:

a collection of populations or subpopulations of fish that is large enough to be self-reproducing and members show similar patterns of growth, migration, and dispersal

Stocks (wild capture) include:

fishes, invertebrates (e.g. crab, shrimp), and algae (e.g. brown kelp)

Habitat characteristics:

water (quality/quantity), plants and their ecology, physical substrate (quality/quantity), weather events

Human dimensions in fisheries:

sociology, economics, politics

How we manage fisheries

humans, organisms, and habitats are interconnected

Types of fisheries:

commercial, recreational, subsistence

Commercial fisheries

fish for food, aquarium trade, fish meals, fish products

Recreational fisheries

fish caught for food, sport, and aesthetics

Subsistence fisheries

fish caught for survival, harder to get statistics on (doesn’t require reporting, small-scale, dispersed, and decentralized)

Aquaculture vs. Capture fisheries

Aquaculture: ~51% production globally, becoming increasingly important to sustain our populations

Capture fisheries: ~49% production globally, maxed out at an unsustainable level since the 1980s

Marine vs Inland capture fisheries

World capture fisheries split between marine ~87% and inland ~13%

Sustainable:

catch/harvest can be continuously taken while still assuring the persistence of the resource

Unsustainable/over-exploited/over-fished:

Resource is not exploited at a sustainable level

Sustainable vs. unsustainable fished stocks

• World’s major fish stocks: ~65% fished at sustainable levels,~35% overfished

• U.S. major fish stocks: 82% fished at sustainable levels, 18% overfished

Overfishing vs. overfished

Overfishing is when the harvest rate is too high —> becomes overfished when the stock size is too low

• stocks can become overfished due to natural events (e.g. El Nino and La Nina)

2 major groups of fishes:

jawless and jawed

Jawless (agnatha) examples

hagfish, lampreys

Hagfish

have mucus pores, horny plates in mouth, barbels, and nostrils

Hagfish slime and skin

Slime

• used for protection from predators and covering up the scent of scavenged prey

• humans use it for its chemical makeup: substance is lighter and stronger than Kevlar, has anti-fouling properties for ship hulls, and can be used medicinally to heal wounds

Skin

• used for faux-eel skin products

Lampreys

have buccal funnel with horny teeth, mouth, and tongue

~50% of species are parasitic

Jawed (gnathostomata) fish examples:

sharks, rays, skates, bony-fishes (95% of all fishes)

Sharks

• largest fish is the whale shark ~55ft

• vertebrate with the longest lifespan is the Greenland shark (~250-500 yrs)

Bony fishes

• lobe-finned fishes

• ray-finned fishes (most fishes)

Sides of fishes

dorsal = back, ventral = belly, lateral = sides

fusiform/torpedo shaped

fast, streamlined simmers

compressed/deep bodied

moderate swimmers, can turn in tight spaces

• flatfishes are the exception- they start out bilaterally symmetrical and upon finding a suitable habitat they metamorphosize to a flat body, laying on their side

depressed body

laying on belly

anguilliform/eel-like body

small body cross section, but long axis

can be round or slightly compressed

globiform body

not “good” swimmers when puffed up

dorsal fin modifications

• remora have a sucking disc that allows them to stick to larger fish

• angler fish and others have fishing lures (illicium)

• some fish can tuck in more flexible dorsal fin to reduce drag

pectoral fin modifications

• gliding: flying fish try to escape predators from below by using their hypocercal tail

• swimming: flying gurnard use winged pectorals to swim along bottom

• leg-like batfish use pectoral and pelvis fins to “walk” on bottom

pelvic fin modifications

• clingfish and spiny lumpsucker: pelvic fins come together to hold/suction onto rocks

• lumpfish: have a suction at the base of the tail

• sharks: claspers for internal fertilization

anal fin modifications

guppies: males have rod shaped anal fin (gonopodium) for internal fertilization

caudal fin types

• homocercal tail: symmetric lobes drive fish forward through midline

• heterocercal tail: asymmetric tail where upper lobe is elongated

• hypocercal tail: asymmetric tail where lower lobe is elongated

• lunate tail: lobes sickle shaped

silvery color pattern

confuses predators by turning into a mass of silver that’s hard to target

countershading color patter

darker on the top and lighter on the base

• to avoid predators

• to be stealth as a predator

false eyes color pattern

distracts predator by thinking the head is in a diff location

disruptive eye-stripe color pattern

confuses predator by disguising head

poster coloration

meant to show that a fish is protecting its territory

mimicry coloration

• prey mimics a predatory fish to seem dangerous

• predators disguise themself as prey to seem harmless

cryptic coloration

changes to match environment

morphological camouflage

evolved to look like an object

scent camouflage

creates a cocoon to mask scent

herbivores

plant eaters (e.g. phytoplankton, seaweed, algae, sea grasses, weeds)

• more common in tropics

carnivores

feed on animals

• have large mouths with well developed teeth

• well developed sensory systems to detect prey

omnivores

feed on both animals and plants

• many fish are omnivores to some degree

• many undergo an ontogenetic shift

lip structures

• most fish have thin lips to swallow food directly

• some have modified lips for sucking

mouth types

• superior mouth: feeds above itself

• terminal mouth: feeding in front or any direction

• anterior mouth: feeds below itself

Teeth types

• canines: fang-like for holding and piercing

• incisors: sharply edged teeth for cutting

• molariform: flattened, broad surfaces for crushing and grinding

• cardiform: short, fine, pointed teeth on pads for grasping and holding

• villiform: elongated teeth, very long

• pharyngeal: modified gill plates for grinding and crushing

gill filaments vs gill rakers

gill filaments and arch are used for respiration

gill rakers are used for feeding

• longer and denser packed rakers indicate filter feeders

• small and less densely packed rakers indicate carnivore

liver

large for storage of fats for energy and oxidizing toxic chemicals

stomach

stores food until it can be processed by breaking it up and mixing it with acid

pyloric caeca

increases surface area of absorption and is the site of fat digestion

intestine

the site of chemical digestion and absorption

Intestine cut off in:

omnivores and detritivores

determining feeding from intestinal length:

ratio of intestine to body length

• carnivores: 1 or less

• omnivores: >1 - 3

• herbivores >3 - 20

Sexual dimorphism

recognizing features to differentiate the sexes

• gonads

• size

• head modifications

• color

• fin modifications

Sexual maturity

the time when a fish has the ability to reproduce for the first time

• can be based on age or size

• females mature slower bc of the energy expense of eggs

• increasing amounts of energy used for reproduction rather than growth

fecundity (egg production)

the ability to produce eggs

• increases with size non-linearly

semelparous

reproduce once during lifetime

• shorter lived

• need a stable environment

leteroparous

spawn multiple times during life time

• longer-lived

• can handle fluctuating environments

Egg layers (oviparous)

external fertilization where sperm and egg are released into water simultaneously

• eggs typically small

• mostly minimal care

• some guard eggs (usually male)

Live bearers (viviparous or ovoviviparous)

internal fertilization occurs with sperm introduced to the female reproductive tract

• viviparous: no eggs, placenta fed

• ovoviviparous: eggs, yolk fed

tryphonemata

maternal resource in rays where oviduct forms long, nutritive strands that secrete uterine milk

oophagy (egg-eating)

maternal resource in sharks where immature eggs pass through the oviduct for embryos to feed on

embryophagy (embryo-eating)

maternal resource of intrauterine cannibalism (strongest and largest embryo consumes its siblings)

embryotrophy

young are bathed in a sac of embryo nutrients rather than placental connection

egg-laying vs live-bearing

TRADE OFF

fecundity of live-bearers is lower (large sized offspring) but offspring have higher survival rates due to size and development

factors affecting reproductive fitness:

1. age and size at sexual maturity

2. parental care

3. live bearing vs egg laying

4. semelparity vs iteroparity

5. number and size of eggs produced

Hermaphroditic

both sexes in one individual

simultaneous hermaphrodites

ripe ovaries and testes at the same time

serial hermaphrodites

change sex during lifetime

• protandrous: first male then female

• protogynous: first female then male (most common)

causes management issues bc larger, older fish are typically targeted by policy but can cause an imbalance of sexes and decreased reproduction

Indeterminate growth

growth slows but continues over lifetime

measuring growth

can measure with any hard part that carries a growth signature of alternating fast and slow growth zones

Scales

advantages: non-lethal, fast, many samples

disadvantages: incomplete growth history on regenerated scales, no lateral line (holes), only for short-lived fish (annuli compaction)

• cycloid scales: smooth, concentric rings

• ctenoid scales: rough, visible teeth

fin rays or spines

advantages: non-lethal, non-destructive, moderately-aged fish

disadvantages: species specific, expensive, needs prep, no longer-lived fish (compaction of annuli)

otoliths

advantages: very accurate (formed during embryonic stages), reliable for all fish

disadvantages: lethal

using age and growth data:

• management of sustainable fisheries (quotas, min size limits, slot size limits)

• investigating human impacts (fishing, environmental, pollution)

buccal ventilation

take water in through mouth, pump it over gills and out the operculum

ram ventilation

swim rapidly and continuously with open mouth and operculum for water to flow over gills

• suffocate if stop swimming

Gas exchange

lamellae of the gill filaments are the site of gas exchange

• increased SA —> increased blood/water contact

• lamellae very thin to reduce barrier between blood and water —> more efficient exchange

• fish suffocate out of water bc lamellae collapses and there’s not enough gas exchange

Counter-current exchange

water and blood flow in opposite directions keeping constant concentration gradient for diffusion to occur

• blood encounters water with higher O2 concentration

breathing air

adaptation to low O2 concentration in water

• modified vascularized gasbladders allow breathing

• surface gulping forces air into swimbladder —> blood supply uptake

• vascularized mouth and gills

excretion

getting rid of waste products

• ammonia is the main form of toxic nitrogenous waste in fish —> passively diffuses out the gills

osmoregulation

maintaining internal balance of ions (salts) and water

freshwater fish osmoregulation

have greater concentration of ions in tissue than surrounding water

• gain water via osmosis through gills and skin (semipermeable)

• osmotic flooding must be checked to stop internal drowning

• kidney excretes excess water through dilute urine (and soluble salts replaced by food and absorption through chloride cells in gills)

marine fish osmoregulation

concentration of ions in the tissues is lower than that of surrounding water

• lose water through osmosis in gills and skin

• water loss compensated by drinking seawater

• remove excess salts using chloride cells in gills and by feces and urine

osmoconformers (sharks)

maintain an internal environment isotonic (equal osmotic pressure) to surrounding water

• keep waste chemicals in body at high concentration

• don’t drink seawater

migratory fish

• costs energy in both osmoregulation and muscle movement

• have to consume more food during of before migration to alleviate physiological stress

Acoustico-lateralis system

composed of inner ear, lateral line complex, and electro-sensitive cells

• fish ear used for balance and hearing

Inner ear

canals are filled with fluid that moves as the fish moves and tilts

• otoliths (ear stones) and fine hairs detect the tilt for balance and vibrations for hearing

• sensory hair cells convert sound from mechanical to electrical signals

hearing range

most fish can only hear at narrow range of frequencies and sound must be relatively loud

• some have specialized hearing structures: shad, carp, goldfish

Lateral line

scales in lateral line have a hole open to surrounding water, forms a lateral line canal beneath skin connected to nervous system via neuromast organs

• cupula of neuromast organ bent by flowing water —> sensory hairs bend —> nerve impulse into body

• responds to displacement of water

• provides info on: swimming speed, direction and speed of water, movement and direction of objects around the fish

electric sense organs

evolved from neuromast organs, very sensitive to electrical currents

• found in most fish ex. ampullae of lorenzini

Olfaction (smell)

sense of smell in fish

• nares lead to a blind-ending pouch with olfactory rosette (highly folded to increase surface area —> more sensitive smell)

• important for migratory fish

Gustation (taste)

sense of taste

• taste buds inside body, on tongue, and outside of body (most concentrated on barbels)

• salinity/saltiness important cue for migratory fish

Vision

• has variable importance in fish ( importance depends on water clarity and color)

• turbid species usually have poor vision and rely on other senses

  • diurnal feeders usually have moderate eyes

  • deep water fish have very small or very large eyes

photoreceptor cells

vision mediated by photoreceptor cells

• rods (night or dim vision)

• cones (daylight and color vision)

Light transmission

light attenuates in red portion of the spectrum first (lure color dependent)

• light transmits well through most of visible spectrum

muscle use

allow fish to move and act as important storage organ for fats and protein

• plus locomotion, protection, communication and detection of habitat, predators, prey,