Fish Often ignored in limnology courses Why important 1' Role in freshwater ecosystems A' Trophic B'

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FishOften ignored in limnology coursesWhy
important? 1. Role in freshwater ecosystems A.
Trophic B. Reproductive 2. Commercial
value (2nd) 3. Recreational value
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• Fish
• Taxonomy
• Biology
• A. Migration
• B. Feeding
• C. Reproduction
• Economic importance
• Endangered species
• Problem species

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Taxonomy
Phylum Chordata   7 Classes Chondrichthyes --
sharks Agnatha jawless fish (lampreys) Osteich
thyes bony fish (gt25,000 spp!) Amphibia Reptil
ia Aves Mammalia
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Chondrichthyes sharks Cartilaginous
skeleton One freshwater species in Lake
Nicaragua Agnatha jawless fish
(lampreys) Ancestral Most are marine
parasites One introduced freshwater species,
Sea Lamprey Brook Lamprey -- small, rare, not
parasitic Osteichthyes bony fish 11 orders (7
important in freshwater) 8000 freshwater species
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Important orders of freshwater bony
fish Acipenseriformes -- sturgeons and
paddlefish Anguilliformes -- eels Clupeiformes
herrings, shads (schooling fishes) Salmoniformes
-- salmon, trout, char, grayling Cypriniformes Fa
mily Cyprinidae minnows, carp Family
Catostomidae suckers, benthic stream
fishes Siluriformes Family Ictaluridae catfish
(some endemic to U.S.) Perciformes Family
Centrarchidae -- bass, sunfish, crappie Family
Percidae -- perch, darters, walleye,
sauger Family Cichlidae Tilapia, very diverse
and derived group
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Class Osteichthyes
Order Acipenseriformes Sturgeons and
paddlefish Large Large rivers Rare and endangered
Order Anguilliformes Eels Migration
Order Clupiformes Herrings, Shad Mostly marine
planktivores
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Order Salmoniformes Salmon, trout, char,
greyling Anadromous Sport and commercial
fisheries Mostly coldwater
Order Cypriniformes Minnows large family mostly
small includes carp most eaten fish in the
world Suckers trash fish? important in many
freshwater ecosystems
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Order Siluriformes Includes N.A. catfish
(Ictaluridae) Aquaculture, sports fishery, problem
Order Perciformes Bass, perch, panfish,
darters Warm water sports fishery Endangered
species Tilapia
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Biology

• Migration
• Feeding
• Reproduction

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Migration - Anadromous, Catadromous
Anadromous Live as adults in salt water, breed in
freshwater Salmon steelhead trout (rainbow)
(Salmoniformes) Striped Bass Virginia, eastern
U.S. Shad Virginia Alewife (herring)
(Clupeiformes) Originally anadromous, many
populations now freshwater Abundant in Great
Lakes Lampreys (Agnatha) Couldnt get around
Niagara Falls until Wellington Canal was
built in late 1800s. Have eliminated Lake Trout
from Great Lakes and completely changed fish
communities Control methods chemicals, weirs
to block migration
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Migration
Catadromous Live as adults in freshwater, breed
in saltwater Eels (Anguilliformes) Breed in
Sargasso Sea (how??????) Immatures swim upstream
in rivers and streams of NA and Europe
(males stay in brackish water) Live as long
as 15 y before returning to the ocean to
breed Larva ? grass-eel ?elver ? adult
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Dealing with salt Osmoregulation in bony fishes
Salt/water balance Chloride cells in gills Na
and Cl-, active and passive marine
fishes ingest seawater! kidneys conserve
H2O fw fishes dilute urea kidneys
excrete lots of H2O Migratory fishes can
switch mitigated by hormones and ontogony
(e.g. rainbow -gt steelhead)
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BiologyRole of fish in freshwater
ecosystems 1) Trophic 2) Reproductive
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Role of fish in freshwater ecosystems Trophic I.
Predators A. What they eat 1. Piscivores
2. Insectovores (invertevores) 3.
Zooplanktivores 4. Generalists B. How they
eat 1. Visual hunters size selective 2.
Filter feeders zooplanktivores Alewife, Shad
(Clupeiformes) Paddlefish
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• Herbivores
• Filter feeders ?
• Grazers
• Periphyton e.g., stoneroller (algae scrapers)
• Aquatic plants Grass carp
• Introduced from Asia to control weeds
• 3. Feed on blue-green algal mats (gelatinous
• sheath)
• Tilapia -- stomach acidity of 1.4 pH

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III. Detritivores Especially Cypriniformes
(carp, suckers) and catfish Subterminal mouth
Detritivore
Predator
Most fish are polyphagous/generalists What they
eat may change with life stage What they eat may
be affected by competition Werner and Hall
experiment with sunfish Bluegill Pumpkinsee
d Green sunfish resource
partitioning due to generalism
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• Role of fish in freshwater ecosystems
• Reproductive
• Egg scatterers
• aka pelagic spawners
• e.g. some minnows, shad
• no parental care
• no habitat requirement
• strategy is high fecundity
• Nest Builders
• aka simple lithophils (rock lovers)
• e.g. minnows
• bury or hide eggs, leave nest
• minimal parental care

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Role of fish in freshwater ecosystems Reproductiv
e (cont.) III. Nest Guarders lithophils
require clean rocky substrate e.g. some
minnows, trout, bass, darters bury, hide eggs
and remain to guard nest good parental
care lower fecundity, higher survivorship IV.
Nest Associates e.g. chubs, minnows bury or
hide eggs minimal parental care by parents
but nest guarded by builder, e.g. bluehead chub
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• Role of fish in freshwater ecosystems
• Reproductive (cont.)
• Other
• I. Livebearers
• high parental care
• Chondrichthyes
• swordtails, guppies, Gambusia
• II. Selfing hermaphrodites!!!!
• Rivulus rivulus
• all female populations
• Dr. Bruce Turner, VT Biology
• only known selfing vertebrate

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Role of Fish Summary

• Migratory limited by impoundments
• Trophic relationships complex and diverse
• Reproduction is a trade off between fecundity
• and parental care
• Many species require clean substrates for
  spawning
• Human activities spawning habitat loss

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Economic Importance
Food Natural freshwater fisheries are almost
gone throughout the world (e.g. paddlefish,
sturgeon) U.S. salmon anadromy complicates
management Aquaculture Carp Catfish Rainbow
Trout Tilapia Sport Fish Salmonids Bass Cat
fish
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Endangered Species (some examples) Sturgeon
caviar, smoked sturgeon Overfishing Loss of
habitat -- large, clear rivers Paddlefish Loss
of habitat Planktivores Sport fishery (What
bait do you use for a planktivore?) Many small
percids Snail Darter Loss of habitat TVA
dams Preservation of habitat prevented building
of dam on Tellico River back in 80s
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Problem Fish (some examples) Carp
(Cyprinidae) Asian Introduced to NA and Europe
in 1830s Now everywhere How affected native
fish? Rainbow (western U.S.) and Brown Trout
(European) Introduced all over the world In
Smokys one cause of decline of native Brook
Char Snakeheads (U.S.) Introduced and
threatening native stocks Flathead Catfish
(southeast) Aquarium Fish (Florida)
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Why study fish in FW Ecology?

• Pros
• - much is known about physiology/ecology
• - easy to identify in the field
• - integrate space and time
• Cons
• Spatially explicit move around a lot
• Temporally variable spawning, ontogeny
• Many aspects generalist