Ramblings of a Catskill fly fisher

The feeding behavior of wild vs. hatchery brown trout

By TONY BONAVIST
Posted 10/6/21

While it may not be obvious, it’s important for anglers to be aware that there is a difference between hatchery brown trout and wild brown trout when it comes to the way they feed.

The …

This item is available in full to subscribers.

Please log in to continue

Log in
Ramblings of a Catskill fly fisher

The feeding behavior of wild vs. hatchery brown trout

Posted

While it may not be obvious, it’s important for anglers to be aware that there is a difference between hatchery brown trout and wild brown trout when it comes to the way they feed.

The introduction of brown trout changed the species composition of some waters; it certainly changed fishing opportunities for fishermen, including fly fishers. Now, some 100 years after introduction, brown trout are well established throughout the United States, and wild fisheries have evolved wherever spawning and environmental conditions are suitable. In those waters where natural spawning is not possible, fisheries are maintained through annual stocking. As a result, hatchery browns make an important contribution to America’s trout fisheries.

So how does the feeding behavior of hatchery and wild brown trout differ? The difference is significant, and I called the New York State Fish Hatchery at DeBruce to learn about domestic brown trout culture.

I was told that eggs are taken from broodstock in mid-August, and hatch by mid-September, almost eight months sooner than wild trout. Wild browns spawn in late October into November, and the eggs do not hatch until the following May. As a result, hatchery trout have a significant head start over their wild cousins.

Hatchery trout are fed several times a day with dried food. The size of the food is increased as the fish grow from fry into fingerlings and yearlings. Food is delivered by electrically operated feeders, which are on timers, and spray the food at the surface of hatchery raceways. As a result, hatchery trout grow much faster than wild trout, because food is abundant, water temperature is constant and flow is stable. As a result, survival and growth is much higher than with stream-born trout. For example, 18-month-old hatchery stocks reach eight to nine inches in length before stocking. In comparison, a wild trout may reach six inches after 18 months. Quite a difference! In addition, wild trout must survive floods, turbidity, shifts in stream bottom, erratic water temperatures, and predation from a variety of hungry creatures, including larger trout. Those brown trout eggs that survive winter and spring runoff and hatch into fry must fend for themselves; there are no feeders in the wild.

Having established the differences between hatchery brown trout and wild trout as far as growth and survival are concerned, it is important to take a detailed look at their feeding habits, and how those relate to fishing. As previously explained, hatchery fish are fed automatically, with food delivered at the surface of raceways, several times a day, while stream-bred trout must find their own food once the egg sacs are absorbed.

That is why some of us believe that since cultured trout are fed with food that is delivered at the surface, they are “conditioned to look up” for food, and continue that behavior when surface feeding opportunities arise. Wild fish, on the other hand, begin feeding sub-surface soon after hatching and continue to feed that way throughout their lives, even when large hatches of aquatic insects are on the water. I discussed my theory about hatchery brown trout compared to wild trout feeding behavior with Ed VanPut, a fisheries professional who worked with me at the NYS Department of Environmental Conservation and is considered to be the best fly fisherman in the Catskills. When we spoke, Ed agreed that hatchery fish rise more freely than wild fish, because they are imprinted to feed at the surface from birth.

Here are some of Ed’s thoughts, about hatchery trout feeding: “I remember stocking the Willowemoc Creek, at Buck Eddy, years ago when there were Hendricksons on the water. As I released the trout, I watched them swim into the flowing water, and immediately start taking Hendricksons off the surface.” Conversely, “when fishing the Delaware River, the water would be covered with flies and the number of trout feeding on the surface would be far less than the number of wild trout you knew were in the river.” So there is some consensus, among some fly fishers, that hatchery brown trout are more likely to surface feed than their wild cousins.

While it is reasonable for anglers to draw conclusions about the difference in trout feeding behavior, based on field observation, even if they are fisheries professionals, it is essential to determine whether there is scientific evidence to support those conclusions. So it was good to learn after a literature search found two references that support our observations, that hatchery browns are more likely to feed at the surface than wild trout. A study in northeastern Portugal spanning 2002-2004 determined that hatchery-reared brown trout fed almost exclusively at the surface, while young wild brown trout fed on sub-surface organisms. Another study conducted in Sweden found that sea-reared, hatchery brown trout were more aggressive feeders than stream-bred trout.

What does this difference in feeding behavior mean for fly-fishers? Based on our observation, and the support found in the literature, it appears safe to assume that hatchery brown trout are much more likely to surface feed than wild brown trout. As a result, anglers that fish those waters that depend heavily on annual stocking may find a lot more surface activity and dry fly fishing than in those waters that support predominantly wild fisheries.

Comments

No comments on this item Please log in to comment by clicking here