NANFA-- brown trout, ecology and personal viewpoint

Jay DeLong (
Tue, 29 May 2001 11:12:40 -0700

At 10:58 AM 5/28/01 -0400, you wrote:
>I'm not talking about the
>brown trout anymore, that was just yesterday. I hope I have not made anyone
>angry on this list through my opinions. Thanks.

I don't think you made anyone angry by your comments, Dan, just puzzled!

You said:
>I beleive salmonid species are our most valued fish,
>with the brown trout being at the top.

It's wonderful that you have a personal passion for that fish! But let's
balance our feelings with a responsibility to be as objective and
fact-seeking as possible. Alien species can and have been destructive on
native fishes and ecosystems. Chris Scharpf offered some resources dealing
with brown trout ecological aggression. I just took a look at the
Nonindigenous Species Web Page and found this: "The state of California has
attempted to eradicate brown trout in some areas in order to preserve
native golden trout". Even with their valuable information, these
resources have a decidedly ichthyo-centric quality to them. People and
agencies and fishing organizations that manage the environment usually
manage it for fish, so therefore people who collect data generally collect
data on water quality and fish populations. There is more to a stream than
fish. There are the invertebrates, too.

>Slightly changes in arthropodan
>populations are natural in many systems naturally, and things have a way of
>balancing out.

"Balancing out" at the expense or betterment of what? Bruce Stallsmith's
focus on changing abundances of invertebrate species populations gets at
extremely important and often overlooked biological impacts of non-native
species. That was why he mentioned top-predators (and yes, your brown
trout are top predators; even creek chubs can be top predators!). Native
predator-prey relationships are like a complex evolutionary recipe for
ecosystem stew. You can ruin the stew by changing an important
ingredient. Replacing a system's predators has effects that run through
the system. Besides possibly being a better competitor for food and space
with native predators, selective feeding patterns of a new predator may
eliminate previously healthy prey species, or previously rare components of
the system (vertebrate or invertebrate) may lose their natural biological
controls and become dominant, at the expense (extinction) of poorer
competitors. Any resulting decrease in diversity shouldn't be seen as a
healthy or desirable outcome.

You said:
>I stand by my beleif that brown trout do not upset
>the ecological balance, fit well into the system they are part of, and have a
>vital niche.

Let's be careful how we define and use the term "niche". One might say
these inverts or fishes have found their niche, or that they've occupied a
niche. But that really doesn't make sense. What these organisms do (what
they eat, how they interact, where they live, etc) expresses a niche--
that's all. Niches are an ecological concept that are only expressed by
the organisms and their ecosystems. The environment does not contain a
fixed and identifiable number of niches, nor can we humans adequately
measure or determine them. To presume otherwise is really getting away
from an attempt to understand Nature and falling into the human
domination/management mentality, where we would replace understanding and
coexistence and respect with the belief we can manipulate Nature as we
would tune up our cars for more desirable performance.

This is the North American Native Fishes Association. An underlying
principle of this organization is that our continent is the site of the
evolution of a fascinating and important fish fauna. To state that an
exotic fish should be stocked into streams with other native fishes as a
replacement for native species because it is somehow "better" (better than
brook trout because they're prettier, or more challenging to catch, or
what?), or most valued (to whom?) doesn't make sense from an ecological
viewpoint, or for some of us, an environmentally-ethical viewpoint.

Jay DeLong
Olympia, WA

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