I. Stocking
Stocking and Aquaculture
K. Limburg, lecture notes
Fisheries Science & Management
Why stock fish?
Fish stocking, at least as a part of aquaculture, has had a
long history, dating back to the ancients.
In the U.S., stocking has been practiced since at least the mid1800s, when fish culturing techniques were brought over from
Europe and applied to species that were feared to be in trouble.
The American Fisheries Society started out as The American
Fish Culturist’s Association in 1870.
Among the species stocked early on: shad, striped bass,
Atlantic salmon, trout
Stocking today is practiced in the U.S. by state and Federal
agencies, as well as by private landowners.
Photo: Utah DNR
Photo: FAO
Reasons why stocking is carried out are many, but include:
• moving species to suitable, but uncolonized, habitat
• providing more constant access to the fish
• increasing fish availability to more kinds of users
• creating new fishing industries as a result of newly
created habitat
• managing exotic species (e.g., introducing
Oncorhynchus to Great Lakes to deal with alewives)
• overharvested species (restoration stocking)
Transactions Vol.1, Issue 1 (1870)
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Types of stocking
Philosophies of stocking
There are many fishery biologists who advocate stocking
and probably equally many who have serious reservations
about this.
The “pragmatists” contend that waters should be stocked
and managed for the best use of that environment and for
maximizing benefits to fishers.
The “purists” advocate maintaining and/or restoring natural
communities, and are averse to introducing non-native spp.
Many people fall somewhere in between these extremes.
How do YOU feel about this?
2. Enhancement: ancillary stocking of spp. already present
• Maintenance – stocking to maintain a population, sometimes
because of problems with reproduction, sometimes because of
overharvesting
• Supplemental – adding fish, for example, under the harvestable
size for future harvesting
Categorized also as
Although there is no fixed terminology for stocking, there are
various purposes that can be described as:
1. Introduction: putting species into waters where they do
not exist naturally.
Has been practiced widely with some spp in the U.S.,
e.g. LmB, bluegill, carp, channel catfish, salmonids
Most introductions are made with the intent of
establishing reproductive populations (exception: triploid
grass carp)
Often goes hand-in-hand with newly created habitat
(e.g., reservoirs created by hydropower dams, farm
ponds)
3. Restoration – increasingly practiced
to bump up populations of
overexploited/endangered/heritage
species
(examples: American shad in
Chesapeake Bay; lake sturgeon in
Oneida L.; paddlefish in Mississippi
drainage states; Atlantic salmon in
Salmon River (NY) and New England
rivers)
 “Put and take” (many urban fisheries)
Potomac River Restoration
 “Put, grow, and take” (most NYS stockings)
PA Fish & Boat Comm.
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Mode of stocking –
Stocking Considerations
1. Goals and objectives –
Must be clear in the minds of managers,
communicable, and the objectives defined so
that meeting them is measurable.
2. Environment –
Is the environment suited to the stocked fish?
Water quality, prey availability, predator field
need to be assessed
How are the fish to be stocked? Considerations:
transportation (trucks with aerators? how many?),
introduction to minimize stress;
What life stage is to be stocked? Often too expensive to
rear fish to fingerling size, must look at economic tradeoffs of stocking smaller fish/losing them to predation
Day/night considerations (or other ecological
considerations) – stocking small fish at night may reduce
predation (Johnson & Ringler’s work on Susquehanna
American shad)
Other concerns:
• The “clientele” – who is going to use the fish?
• Enhancing threatened/endangered species
• Introduced species issues:
• Deleterious genetics from hatchery inbreeding
(examples: rainbow trout, Pacific salmon in native
range)
• Accidental introductions (example: alewife? ruffe,
rudd, snakehead, even rainbow trout)
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Stocking concerns, continued:
Rainbow
Brook
trout
Cutthroat
Brown
trout
Native vs.
introduced
ranges for
popular
salmonids in
North
America.
Source:
Scalet et al.
1996.
Nile perch are voracious predators and prime game fish – over
the next 25 yr, they ate their way through many of the native
fishes.
Nile perch can obtain a very large size – up to
300 pounds (> 130 kg)
Part of their legacy has been the
depauperated fish fauna and
changes in water quality as well
(cascading trophic effects, due
to removal of algivorous
species of cichlids, but also
land use change…)
Threats to biodiversity, ecological mismanagement
Example: Nile perch (Lates niloticus):
In 1954 the British colonial
government introduced L.
niloticus into Lake Victoria
to create a new fishery
Lake Victoria was a
“megadiversity center” for
cichlid fishes – over 300
spp had evolved there and
occupied many niches;
cichlids are small however
CJFAS Vol 57(3): 570
Closer to home…
Interestingly, a world market has developed for Nile perch,
and now they are considered overharvested. Some of the
cichlids are coming back (had found refugia in side lakes).
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II. Aquaculture
Aquaculture: The controlled raising of organisms in
water for human consumption and other uses.
Includes fish, shellfish, bivalves, macro-algae (such as kelp
or dulse), micro-algae (e.g., Spirulina), microcrustaceans
(Artemia for fish food industry)
Photo sources: WHOI; Odyssey Oysters; Arizona State Univ.
Background
Fish culture has been
practiced for over 2,000
years, going back to
practices in China and
Egypt. Much of the
early practice involved
collecting “seed” or
immature forms of
desired species, and
rearing these in ponds.
This practice continues
today, but is only one of
many techniques.
Knysna Oyster Co., S. Africa
Conwy Archive Service, Wales
Photo: J. Dunn, TourEgypt.net.
Culture of mollusks (snails, oysters, other bivalves) was
conducted in France at least as early as the 1200’s. It was
found that by setting out posts or tiles in the intertidal zone,
the spat (settling fry) of mussels and oysters would settle
and grow, and be easily harvested. And this is still
practiced today as well.
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The ancient Romans were also versed in
the art of pond culture, including rearing of
oysters.
“There are two kinds of fish-ponds, the
fresh and the salt. The one is open to
common folk, and not unprofitable, where
the Nymphs furnish the water for our
domestic fish; the ponds of the nobility,
however, filled with sea-water, for which
only Neptune can furnish the fish as well
as the water, appeal to the eye more than
the purse, and exhaust the pouch of the
owner rather than fill it.”
History, continued
By the 1500’s, it was discovered that adding
manure to ponds would stimulate production and
enhance the growth of fish and shellfish. Pond
fertilization is still an integral technique for many
fish culturists.
Suite101.com
- Marcus Terentius Varro (1126-27 BC), from
Rerum Rusticarum (cited in Jennings et al. 2001, p.
311)
Although this is not a
nineteenth-century fish culturist,
many of the basic techniques are
the same – here Bill Ridge is
rearing salmon eggs in trays.
In the early-to-mid 1800s, the French developed
techniques to fertilize and hatch eggs of finfish, and
these techniques were readily and rapidly brought
over to the US. As mentioned above, by the early
1870s, hatcheries were established by the Federal
government to enhance and even start new fisheries
enterprises.
Aquaculture has been growing by leaps and bounds,
particularly over the last 20 years. Worldwide, aquaculture
accounted for 27% of total world fisheries production in 2000,
nearly 32% in 2003, and 41% by 2011.
Photo: Northern Appalachian Research Lab, USGS
Hatchery R&D really
flourished and continues
to, today.
Photo: National Marine Fisheries Service archives
FAO 2012
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(millions)
Mississippi State University Coastal
Research & Extension Center
FAO 2012
Estimated aquaculture production, 2005-06
Source: NMFS 2007. Fisheries of the United States.
Goldberg et al. 2001
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Some examples:
Types of aquaculture
Intensive – high concentrations of fish, heavy
inputs of feed, fossil fuels, antibiotics, capital, etc.
Pen-rearing
salmon in the Bay
of Fundy estuary
Extensive – minimal inputs, rear fish and then
release (note: most stocking programs are actually a
form of extensive aquaculture); supplements both
sport and commercial fisheries
(source: Kreeger
2000)
Polyculture – mixed production, often based on
rotating crops according to season (e.g., shrimp and
milkfish in tropics), or some form of “ecological”
farming (recycling wastes as fertilizer)
Vietnam
Shrimp
culture
Fixed cages in a Philippine
farm
Rotating cages in
Kiel, Germany
source: Beveridge 1997
Photos: K. Limburg, 2013
source: Beveridge 1997
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The ever-impending food crisis, global food security,
and aquaculture
Recall that global fisheries production (capture fisheries
+ aquaculture) is currently around 150 million MT/yr
Global prognosis: further demand for 50 x 106 MT/yr
 where is it going to come from? Aquaculture.
Aquaculture production is increasing worldwide
Currently 35-36% of global fisheries production, and
rising.
Source: Arizona State Univ.
Asia accounts for 90% of world aquaculture production!
(FAO 2008)
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Promises and problems.
Over 250 species were cultured worldwide in 1995 (FAO), and
that number has increased to over 430 (Wikipedia). However,
only a few species contribute over 1 million MT apiece.
Largest single species production (and most rapidly growing
culture industry) in 2010:
the japanese kelp, Laminaria japonica (5.2 x 106 MT)
Clearly, aquaculture is a growth industry today and there
are many, many opportunities in the U.S. and worldwide.
There is a great enthusiasm for developing technologies,
improvements in production efficiencies, etc.
Yet, like all other endeavors, there are many problems too.
Some are the “day-to-day” problems in aquaculture, for
example:
 eutrophication from excess feed and from fish
excretion/defecation
 diseases and parasites (very common)
Images:
www.botany.uwc.ac.za/algae/StudentAssignment
s/natalieprins97/laminaria.htm
Sea lice on salmon fry 
source: New York Times, 12/14/2007
Another concern: GMO fish!
 toxicants (used as antifoulants)
(a.k.a. “Frankenfish”)
 antibiotics
 feed production
 habitat loss (shrimp farms in particular displacing
mangroves)
 habitat degradation
 the hidden costs…
All of these issues
have to be dealt with.
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Literature cited.
Beveridge, M. 1996. Cage Aquaculture (2nd edition). Fishing News Books,
Oxford, UK.
Black, K.D., and A.D. Pickering. 1998. Biology of Farmed Fish. CRC
Press, Boca Raton, FL.
FAO online: www.fao.org
Goldburg, R.J., M.S. Elliott, R.L. Naylor. 2001. Marine Aquaculture in the
United States:Environmental Impacts and Policy Options. Pew Oceans
Commission, Arlington, Virginia.
Heidinger, R.C. 1999. Stocking for sport fisheries enhancement, Chapter 14
In Inland Fisheries Management in North America (C.C. Kohler and W.A.
Hubert, editors). 2nd edition. American Fisheries Society, Bethesda, MD.
Jennings, S., M.J. Kaiser, and J.D. Reynolds. Marine Fisheries Ecology.
Blackwell Science, London.
Kreeger, K. 2000. Down on the fish farm: developing effluent standards for
aquaculture. BioScience 50: 949-953.
Scalet, C.G., L.D. Flake, and D.W. Willis. 1996. Introduction to Wildlife
and Fisheries: an Integrated Approach. W.H. Freeman and Co., New York.
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