Forestry and Natural Resources
Unit 8: Fisheries Management
Unit 8: Fisheries Management
Lesson 2: California Trout
Duration: Two Hours
Students will be able to:
1. Discuss the major characteristics of trout and the conditions needs to maintain a healthy
population.
2. Identify the major types of trout in California.
3. Discuss trout spawning and the factors affecting successful egg development and hatching.
Suggested Activities:
8.2A Trout Embryo Development: Students collect fertilized fish eggs and observe the
embryonic development under a microscope. They research the habitat requirements that
the developing and adult fish need for survival in the natural habitat. They then analyze
how human activities affect fish populations.
Teaching Outline:
I. Trout (family Salmonidae) (TM p 14)
A. General Habits
1. Typically they inhabit the colder streams and lakes of North America, Europe and
Asia
2. Under suitable conditions many species migrate to the sea, but all spawn in fresh
water
3. A varied diet includes some plant material, but normally trout are carnivorous
(TM p 15)
1. Ideal living temperatures range from 60-65 degrees F.
B. Identifying characteristics
1. The mouth is at the tip of the head and is quite large
2. The maxillary bone projects back to the eye or behind it
3. All members of the Family Salmonidae have an adipose fin
4. The pectoral fins just behind the head are set low, almost down to the belly
5. The pair of ventral fins is located about halfway between the tip of the head and the
tip of the tail; on bass these fins are much farther forward than the trout
6 All trout have scales after they have grown to be a couple of inches long; even the
brook trout has scales, though they are so small they are difficult to see
C. The kinds of trout in California
1. Seven Species of trout in California
a. Brown trout (Salmo trutta); introduced
b. Cutthroat Trout (Salmo clarkii); native
c. Rainbow Trout (Salmo gairdnerii); native
d. Golden Trout (Salmo aguabonita); native
e. Eastern Brook Trout (Salvelinus fontinalis); introduced
f. Dolly Varden Trout (Salvelinus malma); native
g. Lake Trout (Salvelinus namaycush); introduced
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Unit 8: Fisheries Management
2. Rainbow trout
a. Has wide distribution in California; it originally occurred in a large part of the
trout streams of the state and in a few lakes; this is the fish most commonly raised
in the trout hatcheries of California; it has been planted in nearly every lake and
stream that can sustain trout populations
b. In many coastal streams and rivers, this species is represented by the migratory
rainbow steelhead in the lower portions and by resident fish in the head waters
i. Rainbows of one species will hybridize with the other species
ii. Resident rainbows rarely attain a large size in California; steelhead rainbows grow
much larger because they migrate to the ocean; the largest resident on record is
18lbs. from Lake Almanor
3. Steelhead Rainbow Trout
a. Found in most of the streams flowing into the ocean from San Luis Obispo
County north
b. Steelhead spawn in the smaller streams, rather than the main rivers
i. Frequently barriers exist which prevent the adult fish from reaching the
spawning areas, including low water levels, sand bars, dams, and water
pollution (caused by urbanization, agricultural and timber operations,
industrialization, etc.)
iii. After spawning the young fingerlings grow for one or two years in fresh water
until they are from 6"-10" in length; they enter the ocean when they are one or
two years old and spend one to three years in the sea; at spawning time the fish
may weigh from 2-12 lbs. or more; the fish nearly always return to the general
area where they were hatched, but not necessarily to the exact stream
4. Salmon/steelhead confusion
a. Yearling salmon up to five inches look so much like steelhead that they are often
confused; count the rays of the anal fin; the salmon has more than 12, and the
trout has 12 or less
b. Mature steelhead trout and salmon are still difficult to distinguish
i. Grasp the fish around the base of the tail -- if it slips through your hand it is a
steelhead; if it can be held easily it is a salmon
ii. The tail of the salmon is more rigid and more strongly forked, while that of
the steelhead is softer and more square
iv. The inside of the mouth of a steel head is white and the inside of the mouth of
a salmon is gray or blackish
D. Trout Spawning (TM p 16)
1. Generally occurs in the spring (February through June); there are exceptions to this in
hatcheries
2. Trout need clear, cool, swift-running, unpolluted water where the size and depth of
the gravel is satisfactory
3. It is necessary for the water to flow through the gravel so that eggs are well
oxygenated and free of smothering silt
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Forestry and Natural Resources
Unit 8: Fisheries Management
4. The female digs a pocket with her tail that is roughly her shape or longer; she then
excretes part of her ripe eggs and the male ejects a stream of white milt into the
gravel pocket
5. The eggs are covered with gravel, or, in lakes eggs are sometimes dropped into rock
crevices
6. The length of time for hatching depends on water temperature (TM p 17)
a. 80 days when the water temperature averages 40 degrees F.
b. 24 days at 55 degrees F.
c. Eggs laid in fall won't hatch until spring
7. After hatching the young fish (fry) stays in the gravel until the yolk sack has been absorbed
8. After the fry work their way out of gravel they immediately begin eating tiny aquatic
animals; at this stage they are called fingerlings
9. Trout are fingerlings until one year of age, then they are called yearlings.
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Unit 8: Fisheries Management
Trout Family
Steelhead Rainbow Trout
Rainbow Trout
Eastern Brook Trout
Golden Trout
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Unit 8: Fisheries Management
Natural Trout Diet
Water Boatman
Fishfly & Larva
Eelfly & Nymph
Mayfly & Nymph
Green Mayfly
& Nymph
Nymph & Green
Darner
Larva & Pupa Mosquito
Stonefly & Nymph
Water Scavenger Beetle
& Nymph
Anderfly & Larva
(Hellgrammite)
Nymph Blue Darner
Dragonfly
Nymph & Black
Dragonfly
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Caddisfly & Caddis-worm
Dobsonfly & Larva
(Hellgrammite)
Crane Fly
& Larva
Blackswimmer
Damselfly &
Nymph
Midge & Larva
Forestry and Natural Resources
Unit 8: Fisheries Management
Spawning
Current Direction
Stream Bottom
Milt
Spawning Nest
The spawning pocket produces an eddy effect in the current,
which helps the milt in the spawning pocket and covering
the eggs even in swift flowing streams.
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Forestry and Natural Resources
Unit 8: Fisheries Management
Regulating Water Temperature
By drawing water from different depths o
of a reservoir we can control the
temperature of the fish hatchery water
during the summer to maintain the 55 to
58 degree temperature.
Water
temperature
drops with
reservoir
depth.
Cannot warm the water in winter, there is
no effective control.
Runway or
Raceway
DAM
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