The tiger trout (''Salmo trutta'' × ''Salvelinus fontinalis'') is a sterile,
intergeneric hybrid of the
brown trout (''Salmo trutta'') and the
brook trout (''Salvelinus fontinalis''). Pronounced vermiculations in the fish's patterning gave rise to its name, evoking the stripes of a
tiger
The tiger (''Panthera tigris'') is the largest living cat species and a member of the genus ''Panthera''. It is most recognisable for its dark vertical stripes on orange fur with a white underside. An apex predator, it primarily preys on ...
. Tiger trout are a rare anomaly in the wild, as the parent species are relatively unrelated, being members of different
genera and possessing mismatched numbers of chromosomes.
However, specialized hatchery rearing techniques are able to produce tiger trout reliably enough to meet the demands of stocking programs.
Natural occurrence
Prior to the 19th century, naturally occurring tiger trout were an impossibility, as the native range of brown trout in Eurasia and brook trout in North America do not overlap and the species could therefore never have encountered one another in the wild.
When the widespread stocking of non-native gamefish began in the 1800s, brown trout and brook trout began establishing wild populations alongside each other in some places and the opportunity for hybridization in the wild arose.
Instances of stream-born tiger trout were recorded in the United States at least as early as 1944 and, despite being exceptionally rare, they've been documented numerous times since during the 20th and 21st centuries.
Tiger trout result exclusively from the fertilization of brown trout eggs with brook trout milt, as brook trout eggs are generally too small to be successfully fertilized by brown trout milt.
Tigers are known as intergeneric hybrids as the two parent species share only a relatively distant relationship, belonging to different genera with the
Salmon family. In fact, brook trout and brown trout have non-matching numbers of chromosomes, with the former possessing 84 and the latter 80.
Consequently, even in cases in which brown trout eggs are fertilized by brook trout in the wild, most of these eggs develop improperly and fail to yield any young.
Hatchery rearing
Tiger trout can be produced reliably in
hatcheries
A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish, poultry or even turtles. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled condi ...
and they've been incorporated into stocking programs in the United States at least as early as the 1960s. Hatchery productivity is enhanced by heat shocking the fertilized hybrid eggs, causing the creation of an extra set of chromosomes which increases survival rates from 5% to 85%. Tiger trout have been reported to grow faster than natural species, though this assessment is not universal.
Tiger Trout & Hybrids
Pennsylvania Fish & Boat Commission. Retrieved 11 September 2006 They are also known to be highly piscivorous
A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evoluti ...
and are consequently a useful control against rough fish Rough fish (or the slang trash fish or dirt fish) is a term used by some United States state agencies and anglers to describe fish that are less desirable to sport anglers within a defined region. The term usually refers to larger game fish specie ...
populations.
See also
* Splake
The splake or slake (''Salvelinus namaycush x Salvelinus fontinalis'') is a hybrid of two fish species resulting from the crossing of a male brook trout (''Salvelinus fontinalis'') and a female lake trout (''Salvelinus namaycush''). The name it ...
References
{{reflist
Salmonidae
Fish hybrids
Salmo
Salvelinus
Intergeneric hybrids