Brown trout, Salmo trutta

Brook trout, , Salvelinus fontinalis

Rainbow trout, , Oncorhynchus mykiss

Fingerling, 6 mo Adult 2-3 yr

Hatching Sac fry, alevin, <6 wk

Fry, ~6 wk

Fish

Fish dominate the ______________ in most lakes, streams, rivers and estuaries.

Their large size and _________________ greatly influence the biological structure of aquatic ecosystems.

Fish occupy several different levels of the aquatic food chain and comprise over ____________ of the

earth’s vertebrate species.

Fish are the main ______________ product harvested from inland waters.

_________________ recognize that fish yield is a function of the whole-lake or stream production process.

Fish are almost ____________,except in mountain lakes where it is

_____________ impossible for fish to pass upstream over large waterfalls that guard the lake;

except when ______________ has completely changed the natural balance.

Distribution and ____________ preferences

Fish are masters of the turbulent water environment except for early _____________ life stages.

Fish actively _______ sites for feeding, breeding, and resting.

The chemical and biological features of littoral habitats is directly correlated with the _______ (richness) and ________

of fish species.

Many lake fish show strong preferences for a habitat that includes a diverse collection of __________

and emergent _____________.

Important aspects of the submerged vegetation that attract fish include:

_______________ of the plants density of the animal ____________ species ____________

High plant diversity supports a great diversity of _____________________ that are food for the fish.

Additionally, a rich ____________ layer coating most submerged vegetation feeds small juvenile fish

which use this vegetation as a refuge from ___________________.

Divisions of freshwater fish groups

I. Primary

Groups with little or no ___________ for seawater; lungfish, paddlefishes, pikes, minnows,

catfishes, centrarchids (___________), etc.

II. Secondary

Groups usually ___________________ but with enough salt tolerance so that members can

enter the ocean and sometimes cross ______________________

some gars & pikes, killifishes, live bearers (perch), cichlids.

Paddlefish, Polyodon spathula

Northern pike, Esox lucius

Warmouth (sunfish), Lepomis gulosus

Mummichog (killifish), Fundulus heteroclitus

Yellow perch, Perca flavescens

Blue tilapia, Tilapia aurea

III. _______________ Migratory between freshwater and the sea

for purpose of _____________.

______________: diadromous fishes which spend most of their life in the sea and mature. When fully grown they return to

_____________________.

______________: diadromous fishes which spend most of their life in freshwater and go to sea as adults to breed.

_________________: regularly migrating between freshwater and the sea for purposes other than breeding.

Marine: spawning in marine water, with larvae and juvenile stages briefly in freshwater (______________).

Freshwater: spawning in fresh water with larvae and juvenile stages; ____________________ before returning to freshwater.

_______________

Estuarine fishes that often and freely go between marine and freshwater, differing from above categories which

usually are capable of changing mediums ________________________.

__________________ in freshwater fishes

Freshwater fishes are ________________ to their medium and tend to gain water by diffusion through

any ______________________.

If uncompensated, the inward diffusion would dilute the body fluids to the point that the their necessary ________________

functions could no longer be accomplished.A state referred to as “________________”

How do they compensate? Can’t waterproof (______). A balance must be maintained by driving the

____________.

Osmoregulation

The task of removing water is accomplished by the kidney.

The kidneys of freshwater fish are capable of excreting urine that is more _______________________.

Additional contribution to ion balance by the urinary bladder: ____________________ of Na+ and Cl-

through the wall of the bladder.

Osmoregulation

Although the concentration of salt in urine is low, the _______________ causes a

significant amount of salt to be lost.

Salts are also lost by ____________ from the body.

Losses are balanced by __________ in food and by ________ absorption through the gills.

Distribution and habitat preferences

Temperature and _________________ also regulate fish distribution and habitat preferences.

There is a wide variety of thermal preferences both among species and __________________.

Three thermal categories are: cold-water cool-water _____________ fishes

__________ often prefer temperatures that are several degrees warmer than adults of the same species.

Thermal preferences (cont.)

These different thermal preferences act to

_________________ with different thermal tolerances during summer stratification.

Thereby, the thermal preferences can either enhance or reduce _______________ for other resources

depending on whether they __________similar species in more limited areas

or separate ____________________.Although in winter, many species move to deeper water,

____________________ due to the much lower levels of activity and feeding associated with reduced _____________________.

Wading shorebirds from the west coast of North America

Temperature and oxygen gradients can interact to exclude fish from all or a fraction of a water

body.

________________________ are a common problem in ________ eutrophic warm water reservoirs and some natural

lakes.

The hypolimnion initially becomes _________ in summer

and the ____________________ gradually rises through the season.

Meanwhile, the thermocline is descending (_________________ as surface layer warms).

Oxygen-temperature squeeze (cont.)

Temperatures in the epilimnion and metalimnion can approach or ____________ limits,

while dissolved oxygen falls below usable concentrations (__________) in the hypolimnion.

Habitat preferences (cont.)Fish that are vulnerable to predation use a

combination of ____________________ to minimize their

exposure to _____________ predators. Silversides, Menidia sp., migrate from cover in

littoral areas to feed in the _________________ epilimnion offshore at dawn but return to shorelines in the morning

before they are ___________. They could fill their stomachs if they remained

offshore, but they minimize daylight exposure to

offshore __________________.

Menidia sp., silversides

Similarly, the pelagic juvenile _______________, Oncorhynchus nerka,

stay in ______________ water during the day, and ascend to feed for a short period in the

zooplankton-rich epilimnion at _____ and dawn.

They ascend when light levels are just sufficient to __________________ but dark enough to minimize the probability

of detection by _____________. In contrast, the older, less vulnerable kokanee

feed _________ in the lighted epilimnion.

Reproduction

Reproductive strategies consist of reproductive traits that enable fish to leave some ________.

Reproductive traits reflect responses to environmental fluctuations.

Traits that vary, include: ___________ according to size and age reproductive _____ size of ________ (large eggs---larger larvae---

mouth size, swimming capacity, sensory abilities increase with size

reproductive behavior, __________ timing,___________, the number of times spawning

occurs in the life of the female (parity)

Age category terminology1. Age groups represent the number of years a

fish ____________ age group 0 = fish in ___________ of life age group 1 = fish in second year of life.2. ____________: fish born in 1997 are members

of the 1997 year class.Fry and fingerling; variously defined, often with

different meanings to different people, should not be used unless specifically defined.

____: the time between hatching and the time at which they reach 25 mm in length

____________: fishes between 25 mm and the length at age 1 (Piper et al., 1982).

Age category terminology/Aging

_________ fishes: newly hatched. Aging methods:

scale annuli, circuli, focus ___________

Feeding

Fish are often the only important large aquatic predators

and results of their __________________ Example: one small fish can eat hundreds

more zooplankton than the largest predatory zooplankter.

Effect of fish on zooplankton __________________

Feeding may be divided among

1. pelagic fish, which feed in open water

_______________ (shad, herring, whitefish, minnows) or piscivorous (mosquito fish, white bass), may also eat ________________ some feed at surface (trout,

sunfish)

2. littoral, feed at ___________

3. benthic, feed on the bottom of lakes and streams.

Benthic and littoral feeding is more generalized and can include:

grazing on aquatic plants (___________) ingestion of bottom debris (_____________),

covered with ______________, protozoans, small insect larvae, and worms

ingestion of benthic invertebrates

Feeding

In _______________, some fish eat _____________________ some pluck insect larvae and crustaceans

from the _____________ some feed on _________ in pools some seize ____________ adult insects

Resource _______________

Some fish are ____________,

while others are very specialized in their selection of food.

This resource partitioning means that the fish eat only ______________ of the available food

and thus avoid too much _________________ with others.

Example:

Two species of trout: _______ trout (Salvelus fontinalis) and _________ trout (Oncorhynchus mykiss)

brook feed mainly on bottom, taking chironomid and _________________

rainbow, feed near the surface on ____________ organisms in summer

Resource partitioning

Another example: In streams, the largest, most aggressive carnivores

(such as trout) pick off the ________________

above and below __________, or near banks of submerged vegetation.

smaller fish, (such as sculpin and dace) catch benthic invertebrates in the

_______________ of the riffles suckers ________________ at the

bottom of the pools.

Mottled sculpin, Cottus bairdi

___________ in flowing waters

____________ or negative, (positive) _____________ (yes or no) negative buoyancy is advantageous for

fish that ________________ as _________ tends to hold it in place.

many stream and river fish that live and feed on the bottom, _______ or have reduced swimbladders.

A fish with neutral buoyancy has no __________ in water.

Energy ____________: resting on bottom versus continuous swimming against current (_________)

Dace have a swimbladder and continuously swim they use _______________ than if they sat

on bottomfeed largely on insect larvae taken from

the bottom

Dace

Perhaps they catch more ________ by swimming above the bottom than they could if they crept about on the

bottom. In this case ___________ swimming increases a

fish’s success in finding food and ___________ the extra metabolic cost of

swimming.

Many fish that live in fast ________________ are negatively bouyant and they possess _________.

____ may be expanded to form a relatively small sucker around the mouth (Gyrinocheilus)

The entire ______________ of the body acts as a sucker (Gastromyzon) both are members of Cyprinidae

A fish attached by a sucker depends on friction to ____________________, an extra _________ force is applied by the

sucker, increasing the friction.

Roanoke hog sucker, Hypentelium roanokense

Most _____________ fish feed on algae which encrust the rocks.

They collect a large quantity of food from one rock before making a ________________ for another.

Stream ecology/fish ___________

Distribution of fish is impacted by water temperature ____________________ and discharge level of _______________ substrate type, sediment load depth, food _____________/abundance etc....later

Stream ecology/fish zonation

Stream zones have been named for the _______________________ or associations found there.

These zones or associations have mainly _______ application.

Measurement: ______________________

Fishery studies involve: collection & ______________ of the species

present _____ determination growth ______ habitat __________ ___________ structure

Collecting/Sampling ______________

Nylon nets: __________, gill nets, _______ nets or _____ nets (for collection of

live migrating fish in streams and small rivers) fixed-trap nets with __________ throats which

the fish enter but have difficulty exiting. __________ trawls _______________ (streams and shallow regions

of lakes) Rotenone (blocks ____________________) _______________ assessment (estimates

population abundance, temporal and spatial distribution)