Brown trout, Salmo trutta. , Brook trout, Salvelinus fontinalis.
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Transcript of Brown trout, Salmo trutta. , Brook trout, Salvelinus fontinalis.
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)