[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Fish reintroduction- Species management
This message came out today on the acn-l mailing list. I hope no one objects
to me posting it here. It is a long message but I think many killifish
breeders/hobbyists will find this quite interesting. Please don't flame me.
Jim Eller - Michigan USA
>> the following from the acn-l list <<
Here's an article I wrote for American Currents on hatcheries and some
related fish genetics issues:
Endangered Species Reintroductions - The Need for Good Science
by Jay DeLong, Olympia, Washington
I'm writing this from within the Olympic rain forest on Washington's Olympic
Peninsula, an area which last year received over 14 feet of rainfall. Winter
is the rainy season here and today was a typical January day: It rained all
day, at times a light mist, at other times a torrential downpour that froze
my body right through my rain gear.
I am a fisheries biologist for the Northwest Indian Fisheries Commission,
and I'm spending this week in the Quinault Indian Nation, working at their
Salmon River Hatchery, helping them coded-wire tag juvenile coho salmon.
Coded-wire tags are tiny, uniquely-coded pieces of stainless steel wire
placed in the snouts of juvenile fish. These fish retain their tags until
they are removed upon capture as an adult. As a result, we gain valuable
information about their survival, migration and population numbers.
It's pouring rain now, but I'm warm and dry in my motel room in the town of
Amanda Park, thinking about how the management of Pacific salmon can teach
us lessons about the aquarium rearing of endangered species for
reintroduction into the wild. I'd like to share my thoughts with you.
A Brief Introduction to Salmon Management
Since the 1890s, Pacific salmon hatcheries have released 5.5 billion fish,
mainly to produce more fish for harvest. It was thought that the ocean had
an unlimited food supply, and that the limiting factor to salmon abundance
was freshwater production capability. Hatcheries have been used to offset
habitat destruction caused by logging, urbanization, dams, and other
factors. Over time, salmon habitat became further degraded. Fewer fish
became available for an ever-increasing number of fishers. The fish that
were available were smaller. Concerns over the effects of hatchery fish on
wild fish became a source of ongoing debate.
Despite such concerns, it is generally accepted that it is deleterious to
cross the genetic traits of a wild fish with one which has been
hatchery-spawned for several generations. Hatchery fish are not subjected to
the same environmental pressures as wild fish, and once released survive
poorly compared to fish in the wild. In other words, they just aren't
trained for life in the wild. For example, hatchery fish don't avoid
predators well; a hungry heron's shadow over the water may be seen as the
shadow of a hatchery worker who fed the fish three times a day for a year.
To compensate for the poor survival of hatchery fish, more fish are
released, which compete for food and space with their wild brethern.
Protecting a single stock is difficult and contentious because salmon stocks
intermingle in salt water (a stock being defined as a genetically distinct
group of fish unique to a particular stream or region). Fishing is sometimes
banned in areas where depressed stocks migrate, which frustrates anglers who
want to fish for other abundant stocks in these areas (called "mixed-stock
fisheries"). Now that the federal government is considering listing more
salmon stocks under the Endangered Species Act, the effects of protecting
stocks will continue to be felt at all levels of salmon management.
Recent Improvements in Salmon Hatchery Culture
Hatchery planners are becoming wiser and more informed. A recent workshop in
my state on alternative hatchery rearing methods was encouraging. People are
recommending changing the standard concrete/asphalt hatchery environment to
one with natural rearing channels, complete with submerged cover, areas of
uneven flow, and natural substrate. There's even talk of introducing natural
predators to hatchery ponds. However, hatchery work is physically demanding,
and many agencies will not want the extra work associated with more complex
hatchery setups. Also, remodeling hatcheries and retraining people would be
a slow process, and will probably never become a reality in some areas.
Some improvements have been adopted at some facilities. New spawning
protocols are in place which avoid selective breeding. And fish and eggs are
not being moved between drainage basins as they had been in the past.
Historically, a single hatchery's fish were often used to compensate for
production shortfalls in other areas, or as founding broodstock for new
hatcheries. The present approach to broodstock management is either to
develop and maintain a local stock in a stream, or to maintain distinct
differences between hatchery broodstock and fish that spawn in the wild.
Wild broodstocks are now regularly used in many hatcheries. Adults to be
spawned are captured from among wild fish returning to the river, and their
progeny are reared in the hatchery. The main benefit of wild broodstocking
is that the genetic variability of the stock is not greatly diminished as
often occurs with hatchery stocks (wherein particular characteristics are
intentionally or accidentally selected over successive generations).
Another improvement is supplementation, or the release of salmon fry into
streams away from the hatchery. These fish return as adults to spawn
naturally in the stream. Supplementation is often done where the spawning
potential of a stream is not being met.
This brings me to where I am as I write this. The Quinault Tribe's coho
tagging program combines wild broodstocking and supplementation. Each fall
the tribe captures wild coho adults from individual tributaries of the
Queets River, spawns them, and rears each tributary's offspring separately.
The fish (some 150,000 of them) are raised in the Salmon River Hatchery,
then released just prior to smoltification back into the exact stream from
which their parents were captured. Since the fish imprint on that stream's
water instead of the hatchery where they were reared, more coho return to
each of the Queets' tributaries.
How About Endangered Nongame Species?
So what does Pacific salmon management have to do with protecting pupfishes
in California or darters in Missouri? Everything. Salmon management drives
fisheries research in our country, and there is a lot of information
available as a result. We need to draw on the work already done, not pluck
our own plans from the air because they seem like a good thing to do for the
fish. We've got to do our research. We've got to call on the experts.
First, I'd like to state the obvious: Endangered species reintroductions
won't be successful unless we first address the causes of their decline.
Habitat destruction and exotic species interactions are probably the two
most serious problems facing America's fishes today. If you return fish into
waters where poor habitat or exotics had decimated them, and those problems
haven't been corrected, the fish won't survive.
Second, without scientific study, reintroductions may be detrimental to the
fish. The idea that a rare fish in an aquarium could be used to restore the
population in the wild is intriguing, but thinking it's as simple as rearing
the fish and turning it loose in a stream is naive in light of experience
and current knowledge.
The Need for Scientific Study
The Fall 1997 American Currents (p. 31) reported that several subspecies of
the orangethroat darter have been elevated to species status. I'm sure
darter expert Lawrence Page had known that new species like the strawberry
darter were not orangethroats. What if a well-meaning aquarist had tried to
boost the Strawberry Creek population of the "orangethroat darter" by
releasing tank-bred orangethroat darters, or specimens transferred from
another drainage? This would not have been good for the strawberry darter.
Darters can hybridize. I have crossed fantail, banded and rainbow darters,
and I've crossed rainbow darters and logperch (Etheostoma x Percina). I did
these by hand and all crosses produced fertilized eggs. I didn't hatch them.
Would the offspring be fertile? I don't know. If fertile, would they spawn
in the wild? Again, I don't know. But hybridization has occurred among some
rare pupfishes and among Gambusia species due solely to unwise releases. And
what if the two darter species had similar habitat requirements? The
aquarist would have succeeded in introducing a competitor as well. The
effects of such a well-meaning reintroduction could never be undone.
My point: Know your species and the science behind them. An aquarist cannot
know about the biology, distribution and status of fishes just by reading
popular aquarium magazines or field guides. Contact people like Dr. Page and
ask if he's aware of pertinent research. Contact your local university's
zoology department and library. Contact your state's fishery agency and get
as much information from them as you can. Discuss your ideas with them.
Also, know your subspecies and don't cross them, either in the stream or the
aquarium (if your intent is to produce fish for release). This isn't just
because a subspecies may one day be elevated to full species status; it's
also because they differ genetically. If you cross two subspecies and
release the progeny among one or both of their populations, you will
decrease the total amount of genetic information present. Often the hybrids
perform more poorly than the parents. This undesirable outcome is called
outbreeding depression. If you see that individuals of the same species
behave or appear differently in different streams or habitats (e.g., pools
vs. riffles), don't cross them and dilute their populations. These
differences may be genetic and may need to be preserved.
Learn About Ecological Relationships and Genetics
Study ecology and genetics. Why ecology? Because complex interrelationships
occur in aquatic ecosystems. Learn about competitive interactions for
resources, and what happens when a species is removed or added from an
ecosystem. Why? Because you've got to develop an ecosystem mentality and get
away from single-species thinking. If you are rearing a rare species which
is now missing from its original stream, you need to consider what has
happened in that stream since the species disappeared. Oftentimes, other
species fill in vacant niches. Previously insignificant competitors may now
be present in significant numbers.
Aquarium science has traditionally been about admiring and rearing fish, and
not about improving their ability to survive in the wild. Aquarists do not
breed fish for release. (No one who buys Amazon River fish thinks about one
day returning the fish to the Amazon.) Instead, aquarists have created
artificial strains of fish specifically for coloration, size, fecundity, and
other characteristics. Some of these characteristics would make the fish a
poor candidate for survival in the wild. This is called artificial
selection, or domestication. Aquarists also often keep and breed generations
of the same parental lineage. This is called inbreeding, which leads to the
increased frequency of normally rare traits in the populations. Often these
traits are detrimental to a fish's survival in the wild.
Why learn about genetics? Because it's the best management tool we have for
insuring the permanent survival of species. If you have a basic
understanding of genetics and natural selection, then you understand why
it's important to have an adequate degree of variation in traits, or genetic
variability, in the entire population. Natural selection acts on different
traits of individuals and manifests itself through differences in survival
and reproduction. For example, I read about a study in which a predator (a
sunfish) was introduced into a tank of threespine sticklebacks. Sticklebacks
with fewer vertebrae survived the longest, for they were able to outswim the
sunfish easier than ones with more vertebrae. Under constant pressure from
the sunfish predator, the fewer-vertebrae sticklebacks would reproduce and
pass on their traits.
Our native fishes are the products of millions of years of selective
environmental and biological pressures. If you destroy all but a few
individuals of a species, you decrease the variability of traits from the
population to what is present in the survivors. No individual normally
contains all the variability present within its species, so the ability of
the species to adapt and survive is dependent on the variability contained
in the genes of the remaining individuals.
Think of the term "variability" as "flexibility" or "insurance". Investors
usually don't put their money in a single account; instead, they prefer
investing in a combination of stocks, mutual funds, bonds, etc. They are
protecting their money in case one investment fails. By sustaining as much
genetic information as possible within a species' population, we are
insuring the survival of that species should a natural or artificial
disaster befall it.
The most important factor in sustaining a high level of genetic variation is
the size of its genetically effective population, which geneticists call
"Ne". There are several factors which reduce Ne. Sex ratios of breeding
individuals other than 1:1 reduce Ne by giving the least abundant sex a
greater chance to pass on its genes. Individuals that are more fecund reduce
Ne by contributing a disproportionate amount of genetic material to the next
generation. And when a population declines, the only genetic information
available is that contained in the surviving individuals. In this case,
genetic information is permanently lost.
What Happens With Small Population Sizes?
Losing some of their genetic variability makes small population sizes more
vulnerable to environmental changes. In addition, they are susceptible to
three closely related effects: genetic drift, bottlenecks and inbreeding.
Genetic drift is the random loss of genetic information present in the
gametes (eggs and sperm). This loss occurs at a rate that is inversely
proportional to the population size. If genetic information is distributed
randomly among the gametes, and the population size is too small for an
adequate number of gametes to result in fertilized eggs containing all
genetic information for the population, some genetic information will be
A bottleneck is a dramatic decline in population size, and, hence, a
permanent loss of rare genetic information. The South African cheetah
experienced a severe bottleneck during its evolution and presently has
seriously limited genetic variation. This is a major cause of its fight for
Inbreeding depression is caused by breeding related fish, and is possibly
the most serious consequence of small population sizes. Expression of a
trait is determined at the gene level by information contributed by each
parent, and predictable percentages of offspring display these traits. If
one parent's gene is recessive, then the trait it codes for will be
expressed by a predictably small number of the offspring. Others will
possess the gene, but won't express it. The population is said to be
The problem with breeding related individuals is that over time you remove
the heterozygosity from the population and create a population homozygous at
all genes (i.e., both genes code for the same trait expression). This can
increase the occurrence of traits which are detrimental to a species'
fecundity, disease resistance, fertility, and growth. The cheetah, for
example, has difficulty breeding, has a high juvenile mortality rate, and is
susceptible to a particular virus. Inbreeding depression is well-documented
in fishes, too. There are cases of reproductive failure, growth reduction,
bodily deformities, and behavioral changes in convict cichlids, carp, zebra
fish, brook trout, and rainbow trout.
People who maintain aquarium populations of extinct-in-the-wild fishes are
performing a truly noble act. By keeping a species from becoming extinct
they are preserving something unique while helping to maintain biodiversity.
However, even though the goodeids, pupfishes and other rare fishes now
living only in aquaria or refugia are the same species which once swam in
the wild, they aren't the same fish anymore. Fish need to be defined by
populations, not by museum specimens or survivors in aquaria. The longer
these fish are inbred the less able they are to survive in the wild. A
single environmental disaster, even a minor one, and the animal is gone
forever. Relying on aquarium-bred populations of endangered fish as the sole
method of restoring a wild population is not the best solution to the
problem of endangered species management.
So what do we do? A crucial step is to identify the goals of endangered fish
management. Is a goal to prevent the immediate extinction of a species? To
insure the survival of the species into the future? To insure that the
species has the ability to adapt to changing environments? Of course, first
and foremost we've got to do what we can to avoid extinction, and aquarium
rearing can accomplish this. But our ultimate goal must be to insure
healthy, genetically safe populations which can survive in the wild forever.
This is why we can't wait until populations are reduced to a few
Earlier, I described lessons we learned with Pacific salmon management. I
also described how we developed scientifically based hatchery techniques and
spawning protocols. Such techniques are also used in Atlantic salmon
management. Nongame endangered species management should be no different.
The Dexter National Fish Hatchery and Technology Center in New Mexico
(described in the Fall 1997 American Currents) is an effective program.
Let us not repeat the unwise and uninformed mistakes of the past. It is
short-sighted and unethical to tamper with nature through poorly designed
releases of fishes. We need to behave responsibly and use good science.
We've got to fight for fish rights and quit complaining about our rights.
Wild fish will stay wild only if they are allowed to retain that which makes
them wild. The real culprit is the high value our society places on land and