The river flounder is a flat fish with a body that lies on one side. Both eyes are on the upper side, which helps it see prey and danger while hiding on the bottom.
The river flounder differs from marine flounders by its ability to live in fresh water of rivers and estuaries. It is important for nature because it controls the population of bottom-dwelling animals and serves as food for larger fish, birds, and seals.
Immature form that undergoes metamorphosis before adulthood.
Worker
birth time
ambush
bottom
Dogs, dolphins, lynx hang out for 9-25 years and party on their birthday three times a year
m
Map
will celebrate their {n} birthday
g
t
When your next jubilee falls in {name} life years
Human
days
How old you would be if you lived as {name}
Theoretical maximum lifespan estimated from the Dynamic Energy Budget (DEB) mathematical model. This value reflects a biological potential derived from metabolic parameters, not from direct observation — real recorded lifespans are often significantly shorter.
mollusks
adult
Maturity
fish of small size
polychaetes
Coconut
live marine and freshwater shrimps
invertebrates
Fins count
About health
marine coastal
When your next birthday would fall if you lived as {name}
Repro interval
results
Eyes count
Colors
Sex
Upcoming jubilees
Gremllins
mo
all seas and oceans
Trophic type
all living animals without backbone
Filters
small fish
Upcoming birthdays
Truly long lives: 40-100 years. Bowhead whales, albatrosses, giant tortoises recall their birthday at most once a year
Lifespan
Age (juvenile)
Age (from birth to death)
Foraging occurs on the floor of aquatic or terrestrial habitats.
Age (embryo)
most of Europe and Asia, various forests, steppes and tundra
Wanderers
Jubilee = every 10th birthday
marine coastal demersal
Earliest developmental stage inside an egg or womb.
Business sausages
zones of mixing fresh and sea water — river deltas, estuaries
Lifespan average
water is almost always cold, there may be ice in winter, not hot in summer
young after fast growth
Juvenile stage following larval metamorphosis but not yet adult.
What do they look like?
Maturity
emergence (insects)
end of lifespan
How do they live?
fertilization / egg laying
How do they behave?
birth / hatching
metamorphosis / end of larval stage
end of acceleration
Share
swampy freshwater biotopes — peat bogs, marshes, river mangroves
live snails, mussels, oysters
Find a pet...
Mature, fully developed individual capable of reproduction.
Freshwater
Cold sea
Egg count
water is cool or warm, cold in winter, comfortable to swim in summer
from 0.5 to 0.8 kilograms, 0.5 – 1 meter
where the river flows into the sea, slightly salty water, lots of fish and birds
Pets
all rivers and lakes
{name} jubilee
cm
zooplankton feeding, animal plankton — small crustaceans and larvae
Old-timers
Find an animal or breed...
turns
Rascals
Flooded grasslands
after fast growth and adult
Litter size
Map data sources: Ecosystem classification — IUCN Global Ecosystem Typology (Keith et al., 2022), indicative distribution maps Keith et al. (2020), https://doi.org/10.5281/zenodo.3546513; Large Marine Ecosystems — NOAA LME Program; Bathymetry — GEBCO Bathymetric Compilation Group (2026), GEBCO_2026 Grid, https://doi.org/10.5285/4f68d5c7-45eb-f999-e063-7086abc036fa; Climate data — Generated using Copernicus Climate Change Service information; Species occurrence data — GBIF.org, Derived dataset "all animals", https://zveriki.com/dataset/dataset.tsv; Terrestrial ecoregions — RESOLVE Ecoregions 2017 (Dinerstein et al., 2017), CC BY 4.0
How to care for them?
Living from 25 to 40 years. Orangutans, bald eagles, African elephants celebrate their birthday twice a year
°C
Not specified
Egg color
Where are they found?
all seas and oceans
Species lacks any fixed or lasting shelter structure.
all rivers and lakes
estuary and delta
Locomotion through water employed while searching for or capturing prey.
Legendary longevity: over 100 years. Galapagos tortoises, Greenland sharks, ocean quahogs celebrate with family once every 4 years
Offspring
Elders
Bro
freshwater marsh and wetlands
Taxons
carnivore
if born as {name}
age
Predator remains still and concealed before launching a sudden attack.
birth date
Palearctic realm
swimming
no permanent shelter
Close
was
Career from 7 to 15 months. Dwarf hamsters, voles, field crickets celebrate their birthday twice a month
Marine world
The basics
My weight?
demersal biotope of coastal marine waters
Non-stop carnival: they only live a few days. Mayflies, rotifers, midges celebrate their birthday more than twice a day
primary food sources
Temperate sea
Potential Habitat
d
In husbandry
On the go from 1.3 to 3.5 years. Forest mice, anoles, rainbow fish party on their birthday once a month
Feeding occurs in water bodies such as rivers, lakes, or oceans.
Mass
annelid polychaetes of marine habitats
cold winter, lots of coniferous trees: spruce, pine
Mosquitoes, fruit flies, small crustaceans hustle for up to 7 months and throw a birthday party every week
Gestation
Body size
aquatic
{name} birthday
No results found
On the map
small crustaceans
all life stages
Female ♀
Body color
Map data sources: Ecosystem classification — IUCN Global Ecosystem Typology (Keith et al., 2022), indicative distribution maps Keith et al. (2020), https://doi.org/10.5281/zenodo.3546513; Large Marine Ecosystems — NOAA LME Program; Bathymetry — GEBCO Bathymetric Compilation Group (2026), GEBCO_2026 Grid, https://doi.org/10.5285/4f68d5c7-45eb-f999-e063-7086abc036fa; Climate data — Generated using Copernicus Climate Change Service information; Species occurrence data — GBIF.org, Derived dataset "all animals", https://zveriki.com/dataset/dataset.tsv; Terrestrial ecoregions — RESOLVE Ecoregions 2017 (Dinerstein et al., 2017), CC BY 4.0
Potential habitat modelled from GBIF occurrence data. Map © Zveriki.com, licensed under CC BY 4.0.
birth year
Maturity
sq mm
yr
How similar?
Egg size
Male ♂
until the celebration
age as {name}
How do they breed?
On the go from 3.5 to 6 years. Hedgehogs, crows, lizards treat themselves to birthday snacks 6 times a year
What if eaten?
Neither
zoo-plankton
What do they eat?
Where do they live?
Marine world
early young
water often floods the land, lots of grass
River estuary into the sea
Freshwater
Temperate mixed forest
Duration
saline marine habitat
This is me
freshwater
Gamers
How are they built?
marine
shallow near the shore, water rises and falls, crabs live here
mm
Theoretical lifespan
ml
Stars
Link copied
coastal marine zone — shelf, neritic zone
My age?
wk
My size?
Taiga
Asexual
swap
freshwater environment — rivers, lakes, ponds, swamps
Rabbits, falcons, red-eared turtles hang out for 6-9 years and party on their birthday four times a year
Where do they take shelter?
celebrated their {n} birthday
When you would have been born if you lived as {name}
Littoral Zone
Daddies
small crabs, amphipods and other crustaceans
Lifespan maximum
from development to end of fast growth
Hermaphrodite ⚥
shrimp
embryo
summer warm, many oaks, birches, maples
Length
kg
Observations
◉{N} more on tap