Rainbow trout are freshwater fish known for their colorful appearance and delicious taste. They are native to North America, but have been introduced to many other parts of the world for recreational fishing and aquaculture. Rainbow trout prefer cold, clear, and highly oxygenated water, often found in streams, rivers, and lakes. They are opportunistic feeders, consuming insects, crustaceans, and small fish. With their adaptability and popularity among anglers, rainbow trout play a significant role in recreational fishing and conservation efforts.

1. UNIVERSITY OF CHAKWAL
PAKISTAN

2. RAINBOW TROUT
• Department of Zoology
• Semester 8th
• Presented by : Sidra Rehman
• Roll # UOC-BSZOL-F2020/023
• Session 2020-24
• Instructor : Dr Syeda Nadia Ahmad

3. ICHTHYOLOGY
ZOL-425
RAINBOW TROUT

4. CONTENTS
Introduction
Taxonomy
Distribution
Importance
Interesting facts
Morphology
Behavior
Recent research findings
References

5. INTRODUCTION
• The rainbow trout (Oncorhynchus mykiss) is a species of
trout native to cold-water tributaries of the Pacific Ocean in
Asia and North America.
• Rainbow trout was first introduced in Pakistan (NWFP)
during 1928.
• The three species of trout in Pakistan — the snow trout, the
rainbow trout and the brown trout – are now rarely seen in
the wild outside hatcheries. (Smith & Stearley,1989)
Fig.1:Description
(https://png.pngtree.com/rainbow-trout-floats-
in-water)

6. TAXONOMY
• Kingdom: Animalia
• Phylum: Chordata
• Class: Actinopterygii
• Order: Salmoniformes
• Family: Salmonidae
• Genus: Oncorhynchus
• Species: mykiss

7. DISTRIBUTION
• With native populations found in Amur River in
eastern Asia, the Kamchatka Peninsula, and
northeastern Russia, rainbow trout have a wide range
of distribution.
• Found in North America west of the Rockies and the
North Pacific Ocean.
• With the exception of Antarctica, rainbow trout have
been introduced to nearly every state in the union and
every continent. (Nabi et al., 2022)
Fig.2: Rainbow Trout
(https://www.wildtrout.org/assets/img/rainbow_tr
out.jpg)

8. IMPORTANCE
• They are prized greatly as game fish.
• It is one of the most significant finfish sectors in the United States due to their high
nutritional content and safe ingestion, are essential to aquaculture.
• Vital for preserving biodiversity in aquatic ecosystems, however their introduction
to new habitats can disturb local ecosystems and effect native fish populations
negatively.
• Due to their vast distribution & ability to adapt to different habitats and hatchery
rearing, they are an important species for both commercial aquaculture and
recreational fishing. (D’Agaro, Gibertoni, & Esposito, 2022)

9. INTERESTING FACTS
• Native Habitat: Originally from North America, especially the Pacific Coast region.
• Vibrant Colors: These fish have a pinkish lateral stripe down their sides,
recognized for their rainbow-like colors (olive-green to blueish-gray).
• Agile Swimmers: Because of their sleek bodies and robust tail fins, rainbow trout
are excellent swimmers (achieve up to 20 mph).
• Vibrative Diet: These fish are opportunistic eaters, going after insects, crabs, tiny
fish, and occasionally even falling small mammals or birds. (D’Agaro et al., 2022)

10. INTERESTING FACTS (CONT.)
• Jumping Ability: It exhibit a remarkable behavior called "porpoising," leaping out
of the water, possibly to catch flying insects or evade predators.
• Sense of Smell: Possess an acute sense of smell, aiding in food detection and
locating suitable spawning grounds.
• Multiple Spawning: Rainbow trout can spawn multiple times throughout their
lifetime, typically in gravel beds in spring or fall.
• Lifespan and Size: On average, lifespan of 4-6 years, can live longer in protected
environments, growing up to 30 inches in length and over 20 pounds in weight.

11. INTERESTING FACTS (CONT.)
• Adaptability: successfully adapted to various water bodies, tolerating a wide range
of temperatures and conditions.
• Environmental Indicators: These fish are crucial indicators of water quality due to
their sensitivity to pollution, making them valuable in environmental monitoring
efforts.
• They will always return to the area they were born when it comes time to spawn their
eggs. (D’Agaro et al., 2022)

12. MORPHOLOGY
 Coloration: Adult freshwater forms are typically blue-green or olive green with black spotting and a
reddish lateral stripe, while lake-dwelling and anadromous forms are more silvery with reduced red
stripes.
 Morphological Differences: lake-caught rainbow trout differ morphologically from stream-caught
fish. Lake forms exhibit shorter pectoral and anal fins, while stream forms have longer fins.
 Domestication Effects: Domestication influenced the morphology of rainbow trout, with captive
lines showing deeper body profiles, longer dorsal and anal fins, and shorter, deeper caudal peduncles
compared to wild lines. (Delling et al., 2020)

13. • Fig.3:Morphology
(https://i.pinimg.com/736x/f9/b0/80/f9b080d0d9522143ccbed4556e
f5ca46.jpg)

14. Scales:
Rainbow trout possess cycloid scales characterized by their smooth texture. These scales are
typically small and overlapping, providing protection and aiding in streamlined movement through
water.
Fig.4&5: Scales
(https://liquidconcepts.com/wpcontent/uploads/2023/04/Fish_Scales_Rainbow.jpg)

15. Fins :
1. Anal Fin: Provides stability during swimming.
2. Adipose Fin: A small, fleshy fin located between dorsal fin & tail.
3. Dorsal Fin: Aids in stabilization and maneuvering.
4. Caudal Fin: The tail fin responsible for propulsion and steering,
crucial for swimming and directional control.
5. Pelvic Fins: Paired fins located on the underside of the fish, assisting
in steering and maintaining balance.
6. Pectoral Fins: Found just behind the operculum, used for hovering,
turning at slow speeds, and braking. Rainbow trout can rotate their
pectoral fins over a 30-degree range, enabling various locomotor
activities. (Delling et al., 2020)
Fig.6: Fins
(https://assets.wired2fish.com/uploads/2023/0
9/rainbow-trout-identification.webp)

16. o Mouth
• The mouth of a rainbow trout is well-adapted for its varied diet, allowing it to
consume a range of prey items such as salmon flesh, baitfish, and even
rodents.
• The mouth typically wide and equipped with sharp teeth designed for
capturing and consuming prey.
• Rainbow trout are known for their insatiable feeding behavior, and their
mouths reflect their predatory nature.
• The mouth is conical and slightly protruding, with a slightly downturned
lower jaw. This shape is well-suited for capturing prey, allowing them to
efficiently feed on a variety of aquatic organisms. (Delling et al., 2020)
Fig.7: Mouth shape
(https://norrik.com/wp-
content/uploads/2022/11/rainbow-
trout-with-black-spots.jpg)

17. BEHAVIOR
Parenting behavior
 After spawning, female rainbow trout dig a nest in gravel called a redd to deposit their eggs which are fertilized by
males, the female covers them with gravel to protect them.
 Rainbow trout parents do not provide any further care for their offspring, as the eggs are left to hatch and the fry to
fend for themselves once they emerge. Female stay near the redd to defend it from predators until she eventually
returns to her usual habitat.
Migratory behavior
 Rainbow trout exhibit both migratory and non-migratory behaviors, depending on habitat conditions, availability of
food, and life stage. Rainbow trout populations may remain resident in freshwater throughout their lives, without
migrating to the ocean, typically inhabit rivers, streams, lakes, and ponds. (McGlade et al., 2022)

18. RECENT RESEARCH FINDINGS
• The identification of a new subspecies called the McCloud River Redband trout (Oncorhynchus
mykiss calisulat), native to Northern California, has been isolated for thousands of years and is the first
newly identified subspecies of Pacific trout in over a decade. The study, led by the University of
California, Davis, highlights the importance of genetic research in understanding the diversity and
conservation of rainbow trout population.
• Future research trends related to rainbow trout are likely to focus on areas such as the substitutability
of steelhead for rainbow trout in key markets, greater attention to food service sales, and the impact of
stress-coping styles of parents on the behavior of offsprings. (D’Agaro, Gibertoni, & Esposito, 2022)

19. REFERENCES
D’Agaro E, Gibertoni P, Esposito S. Recent Trends and Economic Aspects in the Rainbow Trout (Oncorhynchus mykiss) Sector. Applied Sciences.
2022; 12(17):8773.
D’Agaro, Edo & Gibertoni, PierPaolo & Stefano, Esposito. (2022). Recent Trends and Economic Aspects in the Rainbow Trout (Oncorhynchus
mykiss) Sector. Applied Sciences. 12. 8773. 10.3390/app12178773.
Delling, B., Sabatini, A., Muracciole, S., Tougard, C., & Berrebi, P. (2020). Morphologic and genetic characterisation of Corsican and Sardinian
trout with comments on Salmo taxonomy. Knowledge & Management of Aquatic Ecosystems, (421), 21.
McGlade, C.L.O., Dickey, J.W.E., Kennedy, R. et al. Behavioral traits of rainbow trout and brown trout may help explain their differing invasion
success and impacts. Sci Rep 12, 1757 (2022).
Nabi, N., Ahmed, I., & Wani, G. B. (2022). Hematological and serum biochemical reference intervals of rainbow trout, Oncorhynchus mykiss
cultured in Himalayan aquaculture: Morphology, morphometrics and quantification of peripheral blood cells. Saudi journal of biological
sciences, 29(4), 2942-2957.
Smith, G. R., & Stearley, R. F. (1989). The classification and scientific names of rainbow and cutthroat trouts. Fisheries, 14(1), 4-10.
Verdile, N., Pasquariello, R., Scolari, M., Scirè, G., Brevini, T. A., & Gandolfi, F. (2020). A detailed study of rainbow trout (Onchorhynchus
mykiss) intestine revealed that digestive and absorptive functions are not linearly distributed along its length. Animals, 10(4), 745.