|Thank you for your interest in warmwater (channel catfish, striped bass, largemouth
bass, etc.) and coolwater (walleye, muskellunge, etc.) fish the Pennsylvania Fish and Boat Commission annually stocks.
Your question focused specifically on survival of fish stocked as fry, fingerlings, and adults. The survival of
fry, fingerlings, or adults is dependent upon the species in question and the characteristics of waters into which
they are stocked.
Before I detail survival specifics or water characteristics let me provide some background. For the most part all
warmwater and coolwater fish (all fish other than trout, which are coldwater fish) are stocked as sub-adults at sub-legal
size. Warmwater fish are stocked into waters where the natural production of young is impaired or adequate spawning
habitats are unavailable such that stocking is necessary to maintain a particular fish population or fishing opportunity.
It usually takes stocked warmwater and coolwater fish several years to grow to legal or desirable size.
After a thorough biological assessment (enumerating sport fish abundance by electrofishing, and trap netting etc.)
and physical assessment (enumeration of water depth, temperature and aquatic plant density etc.) biologists develop
a management plan that describes:
- what warmwater or coolwater species to stock,
- how many of each species to stock, and,
- what "life-stage" to stock.
By life stage I mean fry or fingerlings (fry are fish a few days old typically less than 1 inch long and fingerlings
are fish that are at least several months old, typically two or more inches long, muskellunge fingerlings may be 10
inches long when stocked in fall). As you might guess, for most species, survival is directly related to size with
a greater percentage of larger fish surviving to legal or catchable size. What this means is that biologists stock
more fish of small size relative to fish of large size to produce a given adult density. You might also guess that
large fish cost much more to raise and require more space (pond space) than small fish.
Perhaps the most important question biologists have to answer is: what life stage will survive to produce densities
of fish sufficient for a particular management purpose or sufficient to produce a pre-determined amount of fishing
recreation. Can small fish (fry) produce fishing opportunities equal to that of large fish (fingerlings)? The answer
to the latter question is yes. One example is the walleye fishery at Pymatuning Lake. This lakes walleye population
is maintained by stocking only walleye fry (about 3 days old). Many other lakes in the Commonwealth do not possess
zooplankton densities (walleye food densities) sufficient to support survival of fry and consequently are stocked
with fingerlings. Angler catch rates of walleye at Pymatuning Lake are among the highest in the state a (one walleye
per 2 hours fishing).
As you would expect, when deciding how many warmwater or coolwater fish to stock biologists must consider predator
densities (fish that eat the fish we stock) and availability of various forage organisms (fish and invertebrates that
serve as food for the fish we stock). These elements combine to describe survival of stocked fish of a particular
life-stage. Secondly, biologists must take into account that there is not an "unlimited supply" of warmwater
and coolwater fish for stocking and when earlier life stages produce target angling catch rates then these "less
expensive" life stages should be used. Finally, since most warmwater and coolwater fish are "pond reared" the
vagaries of weather play a role in production which may limit availability of a particular life stage in some years.
To account for production variability biologist request warmwater fish at a "base rate" a minimum number
of fish per surface acre of lake or river section to stock. Biologists also have the option of requesting "supplement
rates" which describe the additional number to stock in years when available. Since we can not predict with high
accuracy the exact number to be produced we don't publish the number we
"intend" stock rather we report the total we actually stocked at the end of the year (after the fish have
Earlier I mentioned that biologists stock more smaller fish (fry) than large fish (fingerlings) to produce a predetermined
amount of fishing recreation. For example walleye fry are stocked at a base rate maximum of 750 per acre of water
and walleye fingerings are stocked at a base rate maximum of 20 per acre to produce similar levels of fishing recreation.
This does not necessarily mean we can substitute fry at 750 per acre for fingerling stocked at 20 per acre, an accounting
of biological and physical conditions at a lake, river, or stream requires consideration before a particular life
stage is chosen. Survival of a particular life stage is a function of the species stocked and the characteristics
of the water into which the species is stocked. Generally we stock at rates that produce a pre-determined angler catch
rate or predetermined assessment catch rate (net or electrofishing catch rate), we have never had the opportunity
to measure the total number of fish that survive to be caught by anglers from a particular life stage stocked.
Of the few studies detailing survival of walleye fry relative to walleye fingerlings, fingerling survival was approximately
35 times greater than that of fry. Anglers must also realize that each water has unique potential to sustain various
quantities of gamefish, with some waters capable of supporting more gamefish than others. The reasons for these differences
are innate, that is geology and land uses within the watershed are different and for the most part cannot be changed
or cannot be changed easily. Those more productive waters, as you would expect, are stocked at greater rates because
they can sustain greater quantities of fish.
Of those waters to be stocked as listed on the web site you can presume most waters will be stocked with fingerling
fish, particularly in the case of lakes. Of all species we stock only walleye are stocked as fry (American shad are
stocked as fry as well) and most fry are released into rivers. I hope this gives you greater insight into warmwater
and coolwater stocking in Pennsylvania and clears up any questions you have. Next year we will try to be more explicit
about the life stage scheduled for release, however it will be impossible to detail an exact number planned for stocking,
numbers actually stocked will be detailed in our annual report.