Biology of fishes FINAL

FINAL FML

Ammocoetes

 larval lampreys, sedentary, blind, freshwater, live in rivers

Redds

gravel pit nests that salmon and trout spawn in

Alevins

yolk-sac larvae that reabsorb the yolk

Fry

the stage after alevins

Parr marks

fry that develop species-typical patterns of vertical bars on their sides, also called parr

Smolts

the stage after parr, silver colored and move downstream

Smoltification

the process of reworking almost all the characteristics of a young salmon, change color, shape, and from freshwater to saltwater, less dense purine crystals- not at a fixed age

Rheotaxis

the response to flowing currents in larvae that tell the fish to get into the currents to go upstream

Precocious

when some males stay back to mature even faster than the ocean males at the age of one and can now spawn with the females that come back the next year, can be between 5- 50 % of the population of male salmon and depends on a lot of factors, such as food availability

Hyperosmotic

the water is salter than the fish

Hypoosmotic

the fish is salter than the water

Bilateral symmetry

having mirrored image structures to the right and left of the midline, not having it when the others in your species do may indicate mutations or adaptations 

“Handedness”

some flatfishes eyes move to the right and some move to the left changing which side they lay on, right is more rare than left

Depressed

most flat, benthic laying organism are depressed, meaning flattened on the dorsal-ventral plane

Compressed

when flatfishes are laterally compressed unlike most other sea creatures but still maintain bilateral symmetry

Sinistral condition

when the right eye migrates to meet the left eye in flatfishes

Dextral- describes that flatfish are usually right eyed

Sex determination

process in which the maleness or femaleness of the fish is decided, usually decided during early ontogeny and can be affected by environmental factors or genetics

Differentiation

the development of recognizable gonad structures even if mature gametes or eggs are not present

Maturation

when viable eggs or gametes are present, the marker of an adult in most fishes

Heterogamic

genetically decided XY or ZW, usually at fertilization 

Environmental sex determination

 when factors like temperature or food availability decide if the organism is male or female

Postmaturational sex change

when species change sex even after maturation (think clownfish)

ESD

environmental sex determination

 prematurational sex change

 they differentiate but not mature, with most fish it’s first as females and then some later change to males

Masculinization

when eggs are reared at higher temperatures with effects increasing as temperature rises, and it causes more fish to be born male. It can happen to govies, silversides, rockfishes, cichlids, flounders, minnows.  

Femininization

can occur at higher temperatures and causes fish to be born female. It happens to lampreys, salmon, stickbacks and seabasses.

protogyny

A female to a male

protandry

A male to a female

Simultaneous hermaphrodites

produce eggs and sperm at the same time

Parthenogenetic

fish that have eliminated males from the reproductive process, such as female bamboo and bonnethead sharks had laid fertile eggs or given birth to live young without ever being near a male

Age at first reproduction

and longevity vary greatly among fishes- age of reproduction is a trade-off between committing energy to growth vs reproduction combined with expected mortality rate and living long enough to reproduce. 

Longevity

patterns are slightly more definable, larger fish generally live longer than smaller fish

Senescence

programmed death or when the body just breaks down through age and dies from that. Usually these fish are healthy in every other way, their physical condition just gives up. (Like humans).

Interenal cells

steroid producing cells associated with the kidneys  and are homologous with the adrenal cortex of mammals. 

hyperadrenocorticism

rapid degenerative changes in the heart, liver, kidney, spleen, the thymus, and coronary arteries- the latter degeneration is similar to coronary artery disease in humans. 

Daily growth increments

on otoliths and they are much harder to see, part of age markers

Osteoblasts

bone forming cells and lay down layer of roughly concentric circles of bone called circuli are close together during periods of slow growth . Scales grow by accretion as more bone is added along their periphery.

annulus or annual mark

The number of annuli on a scale gives a record of fish age in years. Temperate areas create one thick and one thin band for one year.

Spawning checks

dense bands that can be mistaken for annuli but are actually when the fish is reproducing.

False annuli

occurs from wet and dry seasons and look like a ring but too light

Validation

he process of proving the annuli, can use dyes, bomb radio carbon, radioisotopes,  etc. 

Greatest relative return

lowest energy to find most amount of food energy- eating a dead whale is the absolute best for this- fish will eat something smaller if it takes less work to get it

Optimally

when fish choose food types, feeding locales and times, and foraging modes to maximize the productivity of your benefits to costs ratio

Benefits to costs

benefits are calories and nutrients ingested, cost is time used up and time lost to other activities

Pharyngeal mills and gizzards

mechanisms for rupturing cell walls and digesting plant matter

Winnowing

a process that occurs in the orobranchial chambers, when fishes pick up a mouthful of bottom material, sift it and expel the inedible sediments back out the mouth

Detritivores

eat detritus and separate edible fin organic matter from refractory inedible sediments. They have ridges in the mouth and a maze of passageways for gill rakers.

Head-first orientation

prey must be manipulated into this orientation for swallowing if they are small enough to be swallowed and have no special external defenses

Postcapture manipulation

required to subdue prey and make it ingestible and digestible. Fish that feed on hard-bodied prey or on prey with primary external defenses must spend time and energy in handling.

Oddity

a difference in appearance or behavior stimulates an attack because that is easier to target and may be weaker

Group-separating tactics

 chase stragglers or those on the outside and separate them from the group, accounts for 89% of a predators success 

center of mass

where predators usually attack because the escape response for most fish involves a pivoting on the center of mass and removes a lot of possibility of escape after it’s hit

 immobilization

A hard hit to prey done by the predators to knock them unconscious. Done by a few special predators. This attack involves a high degree of energy output for a leisurely capture. Usually involves hitting the prey with an object attached to the body, think swordfish, marlins, sawfishes etc.

Cooperative feeding

involves some form of coordinated herding or driving of prey by circling or advancing predators, often observed in many species of sharks, may do this to animals as large as seals

Disruptive coloration

divides the head into halves through color to disrupt its outline and makes the prey need a moment to recognize the pattern as a whole head

split-head color pattern

a convergent coloration made for slow-stalking predators, and it usually has dark lines and light lines that run from the snout to the dorsal fin and makes it much harder for prey to see them

Death feigning

when the predatory cichlid N. livingstonii pretends to be dead through its coloration and the way it lies on the ground to eat scavengers, stonefish also do something similar

Esca

a lure that resembles a small fish, shrimp, or worm, attached to an elongated dorsal spine

Aggressive mimicry

predators disguise themselves by looking like something they prey may want to eat on the ground or higher up in the column try to fit in with non-threatening “friends” of their prey to lower their target’s guard and eat them

lurking

lie-in-wait predators that swim high in the water, or lurk on the edges of vegetation bends. They rely on fast start performance for hunting. 

Cursorial

chasing predators, capable of high-speed sustained chases of rapidly - lamnid sharks, tunas, billfishes

Size at age

varies enormously in fish, through species, populations, individuals

Von Bertalanffy growth equation

Lt = Lmax (1-e^gt)

L is length, t is point in time, L max is the maximum or asymptotic length attained by the species, e is the base of natural logarithms, and g is the all-important constant and describes the rate at which growth slows

The von Bertalanffy growth coefficient K

 when its smaller= that species is more likely to be overfished because they grow a lot slower