Picture this, you are floating over the middle of the lake, you check the fish finder and see the bottom is 500ft away, it might even be so deep that the sounder can not even get a proper signal.
What actually lives at such depths, and is it worth dropping a jig down several hundred feet in the hopes of hooking a monster trout lurking in the dark depths?
In this article, I will answer these questions and more.
|Trout Species||Maximum depth|
*One very localized specie of brown trout has been reported to live close to 1000ft.
How Deep do Rainbow trout live
According to the Fishbase online database Rainbow trout inhabit water between 0 and 200m (656ft). The source of this maximum depth is from the Catalog of marine and freshwater fishes of the northern part of the Sea of Okhotsk. Vladivostok: Dalnauka, 2003.
I was not able to find that book to judge just how accurate that maximum depth is, the deepest I was able to independently confirm Rainbow trout being caught was 82m (270ft). This is still deeper than what is typically fished by anglers.
In general rainbow trout do prefer to feed in the top 20m (65ft) of the water column. Higher in the water column receives more light, and is generally more biologically active which means more potential food for the trout to feed upon.
The exact depth a rainbow trout holds is mostly determined by water temperature and oxygen level. Rainbow trout prefer water temperatures below 21c, and they need oxygen levels greater than 2.5gm per square meter.
In the summer, water temperature normally determines their minimum depth, while oxygen levels determine their maximum depths. So the range of the rainbow trout is often constricted between the upper layer of warm water, and the lower layers lacking in oxygen.
Do bigger Rainbow trout live deeper?
From time to time I have had people ask, do bigger trout live deeper in the lake?
Well, there is little evidence to suggest that larger trout consistently live deeper. They all tend to coexist within the liveable zone and follow where the food it.
One report, in one lake, did find smaller Rainbows were more common in shallower waters (0-20m) compared with large rainbows (20-50m), but this really depends on the presence or absence of thermoclines.
How deep do brown trout live
Brown trout (Salmo trutta) prefer to stick close to the surface, although some complete dives down to 90ft (28m). In extreme water conditions, they might go deeper following the thermocline.
I found it very hard to find solid information regarding the maximum depth of Brown trout. The 28m figure often quoted comes from a Norwegian study monitoring the movement of sea trout in a fjord. How this relates to trout in lakes I am hesitant to speculate.
The Ferox strain of Brown Trout lives in deep glacier lakes throughout the British Isles. They are known as deep divers. Radio-tracked Ferox Trout have been recorded diving as deep as 30m (100ft) presumingly to hunt Artic Char.
Like other trout species, the maximum depths Brown trout can survive at is heavily influenced by water temperature and oxygen levels.
While brown trout can certainly dive down to 90ft, this is not usually the best depth to find them. When fishing for Brown Trout, it is generally best to stick to shallower water, such as around the margins and shoreline of lakes.
Even In the heat of summer, when they seek out deeper water Brown Trout are typically caught holding around the 30ft mark.
Things do become a bit more extreme when we consider the more diverse and sometimes controversial populations of Brown trout within their species complex.
I know of one outlier species of Brown Trout (Salmo carpio) that lives between 200-300m in Lake Garda in Northern Italy. This brown trout wants to be a Lake Trout. It even spawns around deepwater fissures.
This behavior is so distinctive that the natural population of S. Carpio have remained genetically distinct despite introductions of other Brown trout variants. Unfortunately, due to pollution and overfishing, this unique Brown trout is critically endangered.
Weird Italian species aside, Most Brown trout typically live and feed within the first few feet of the surface.
How deep do Lake Trout live?
The deepest living trout in North America is the Siscowet variation of Lake Trout. In scientific studies they have been caught as deep as 1300ft (405m), although in Lake Superior they seem most abundant between 300 to 600 feet (90-180m).
This is outside the typical depths targeted by recreational anglers.
The deepest population of Lake trout are typically found in Lake Superior and the Great Slave Lake. This is almost entirely to do with the extreme depths of these lakes.
When targeting Lake Trout, fishermen often troll heavy spoons, or use jigs. Down riggers are also commonly used peices of equipment.
Do bigger Lake Trout live deeper?
Large Lake Trout can be caught throughout their depth range and there is evidence to suggest that they move up and down the water column in search of food (temperature and oxygen levels permitting).
Terrestrial insects have been found in the stomachs of Lake Trout caught in even the deepest parts of the lakes. This suggests these deep water fish move towards the surface to feed.
While there are fewer small fish at extreme depths the number of larger Lake Trout does not seem to correspondingly increase.
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