480fish

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Brown trout, Salmo trutta
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Brook trout, Salvelinus fontinalis
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Rainbow trout, Oncorhynchus mykiss
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Fry, 6 wk
Sac fry, alevin, lt6 wk
Hatching
Fingerling, 6 mo
Adult 2-3 yr
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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 earths
  vertebrate species.

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• Fish are the main ______________ product
  harvested from inland waters.
• _________________ recognize that fish yield is a
  function of the whole-lake or stream production
  process.

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• 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.

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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.

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• 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 ____________

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• 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
  ___________________.

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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.

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Paddlefish, Polyodon spathula
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Northern pike, Esox lucius
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Warmouth (sunfish), Lepomis gulosus
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Mummichog (killifish), Fundulus heteroclitus
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Yellow perch, Perca flavescens
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Blue tilapia, Tilapia aurea
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• 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.

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• _________________ 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.

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• _______________
• Estuarine fishes that often and freely go between
  marine and freshwater,
• differing from above categories which usually are
  capable of changing mediums ______________________
  __.

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__________________ 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?
• Cant waterproof (______).
• A balance must be maintained by driving the
  ____________.

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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.

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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.

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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.

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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
  _____________________.

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Wading shorebirds from the west coast of North
America
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• 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).

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Oxygen-temperature squeeze (cont.)

• Temperatures in the epilimnion and metalimnion
  can approach or ____________ limits,
• while dissolved oxygen falls below usable
  concentrations (__________) in the hypolimnion.

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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
  __________________.

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Menidia sp., silversides
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• 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.

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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)

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Age category terminology

• 1. 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).

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Age category terminology/Aging

• _________ fishes newly hatched.
• Aging methods
• scale annuli, circuli, focus
• ___________

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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 __________________

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• 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 ___________

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• 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

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Feeding

• In _______________,
• some fish eat _____________________
• some pluck insect larvae and crustaceans from the
  _____________
• some feed on _________ in pools
• some seize ____________ adult insects

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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.

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• 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

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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.

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Mottled sculpin, Cottus bairdi
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___________ 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.

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• Energy ____________ resting on bottom versus
  continuous swimming against current (_________)
• Dace have a swimbladder and continuously swim
• they use _______________ than if they sat on
  bottom
• feed largely on insect larvae taken from the
  bottom

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Dace
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• 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
  fishs success in finding food
• and ___________ the extra metabolic cost of
  swimming.

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• 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.

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Roanoke hog sucker, Hypentelium roanokense
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• Most _____________ fish feed on algae which
  encrust the rocks.
• They collect a large quantity of food from one
  rock before making a ________________ for
  another.

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Stream ecology/fish ___________

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

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Stream ecology/fish zonation

• Stream zones have been named for the
  _______________________ or associations found
  there.
• These zones or associations have mainly _______
  application.

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Measurement ______________________

• Fishery studies involve
• collection ______________ of the species
  present
• _____ determination
• growth ______
• habitat __________
• ___________ structure

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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)

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