Trout stocking and its impact on different species
Brook trout (salvelinus fontinalis) were designated as the official New York state fish in 1975. Known as brookies, speckles, square tails or natives, they are emblematic of cold, clean, remote wilderness waters.
“Brook trout are the canary in the coal mine when it comes to water quality,” said Gary Berti, Trout Unlimited’s Eastern Brook Trout Campaign coordinator. “The presence of brook trout in a watershed indicates that water quality is excellent. Declining brook trout populations often provide early warning signs that the health of an entire stream, lake or river is at risk.”
Recently, a piscatorial press release caught my eye, primarily due to its location of origin in Cortland, N.Y. However, it was the first few lines that really captured my interest. It read, “Brown trout introductions could hamper the conservation of declining native brook trout populations, according to a new U.S. Geological Survey study.”
The release explained that “brook and brown trout are valuable sport fish that co-exist in many parts of the world due to stocking introductions.”
However, USGS researchers have recently determined that in New York, the direct interactions between the two species in competition for food have had a minor effect on the diminishing brook trout populations in comparison with human-induced habitat disturbances.
I already knew that from experience. Brookies prefer clean, cold, clear, oxygen-rich mountain waters, whereas browns are more tolerant of warmer, murky waters with diminished oxygen content.
Browns are to be found existing peacefully in water alongside both brook trout and rainbows, but browns are often disproportionately stocked in state waters.
The overstocking of browns is not intended to intentionally edge out the brookies. It is simply a by-product of production. Browns and rainbows are fairly easy to rear in the hatcheries. It is not so easy with brook trout.
The press release continued with an ominous tone as it noted the repeated stocking of brown trout in brook trout habitats could drastically decrease brook trout numbers.
“There is great potential for brown trout stocking to reduce native brook trout populations,” said James McKenna, USGS scientist and lead author of the study. “But brown trout aren’t necessarily causing the current brook trout declines, and managers may be able to develop sustainable scenarios to support both fisheries.”
The USGS study reveals that human-induced degradation of the habitats of both species can affect the populations of either. Examples of stream degradation include unintentional barriers such as dams, culverts and similar obstructions that create barriers that interfere with upstream migration for spawning purposes, or limiting their access to cooler refuge pools.
However, because brook trout prefer forested watersheds, while brown trout can thrive in more agricultural environments, the degraded watersheds and/or elimination of forests may negatively impact brook trout more than browns.
Fisheries managers in New York have been rearing and stocking brown trout for more than a century in many rivers and streams in order to supplement natural reproduction.
Brook trout, on the other hand, have been declining within their native range for decades, due to a variety of factors, including acid deposition, competition with non-native species, diminished water quality and climate change.
Added to the mix are current concerns that the continued stocking of brown trout has exasperated these declines.
The full report was published in the North American Journal of Fisheries Management. The study’s analysis indicates a greater abundance of brook trout in highly forested areas, while brown trout were found to be more abundant in – and tolerant of – areas with relatively high proportions of agriculture.
New York state contains large portions of the brook trout’s native range, where both species are maintained by stocking and other management actions.
The researchers found evidence for the decline of brook trout in the presence of brown trout across many watersheds. Twenty-two percent of sampled reaches where both species were expected to occur contained only brown trout.
Brown trout are primarily a freshwater fish, although they have been known to adapt well to salt water, as have brook trout.
Browns have long been renowned for their fast growth rate, whether in streams, lakes or rivers. They are also voracious feeders that primarily target other fish, as well as insects and even mammals such as mice and lemmings.
Original distribution of the species is well documented in Europe, where the species were commonly known as German browns. They could also be found in of Ireland, Iceland, Sweden, Germany, France and Greece.
However, their global range of distribution was greatly expanded over the years and they have been introduced to Argentina, Bolivia, Chile, Ecuador and Colombia in South America, as well as Madagascar, Malawi and Tanzania in Africa. In Asia, the fish has been introduced in India, Sri Lanka, Papua New Guinea and Nepal.
Aquaculture and fish stocking were the primary means of introducing brown trout to new regions following the development of aquaculture in 18th century Europe.
The advent of aquaculture introduced the practice of what has been termed “ecological imperialism” into European colonial areas. The process of transferring European plants, animals and microorganisms such as earthworms, was intended to make the New World more familiar to the Old World.
Many species native to the European continent were shipped abroad during this era of colonialism. This process was responsible for introducing brown trout into the English colonial areas of India, Australia, Nepal and New Zealand.
In 1864, brown trout were first introduced into New York through the Caledonia Fish Hatchery. Seth Greene, director of the first state fish Hatchery, was a proponent of stocking brown trout, as well as smallmouth bass. He
was responsible for introducing both species into Adirondack waters.
In 1883, the U.S. Fish Commission conducted the introduction of brown trout into the United States in Michigan where fish were released into the Pere Marquette River in the Northern area of the state.
Brown trout are better suited to live and grow in warmer waters than native species such as brook trout. Brown trout are also better able to adapt to changes in water temperature, which may prove to be a challenge in the current era of ongoing climate change.
Browns are a hardy fish that grow quickly and are able to withstand fishing pressure better than brook trout. While studies indicate juvenile brook trout often out-compete young brown trout, there is also evidence that brown trout can displace adult brook trout as competition for food and habitat changes over the lifetime of the fish.
New York has experienced significant declines in the brook trout populations, primarily in the Adirondack region where the scourge of acid rain in the 1970s resulted in numerous “dead” lakes and ponds.
Fortunately, many of these ponds have since been restored with native brook trout populations, and in many cases wild brook trout have returned to the streams.
It is interesting to note that despite the natural competition between brook trout and browns, the two species have been known to crossbreed in the wild. Although the chances of survival for such offspring are slim, the unique crossbreeds known as tiger trout have been discovered in several Adirondack waters, including the Chubb River in Lake Placid and the West Branch of the AuSable.
The handsome mix-breeds are known to be healthy fighters and fast growers. In addition to being naturally spawned, they are also reared in several state hatcheries for stocking purposes.
But when it’s all said and done, they can keep their big browns and have all the tigers as well. I’ve always been perfectly content with just a brookie or two.
And remember, trout season begins in less than three months