Why are hatchery shad apparently helping to restore Atlantic shad populations,
while the reliance upon hatchery salmon along the Pacific Northwest is largely
implicated in the decline of Pacific stocks?
I also sent my question to some shad hatchery managers here on the Atlantic
Coast (where shad restoration is as big as salmon restoration is on the West
Coast). Here's one of the answers I received. Pretty interesting stuff,
considering some of our recent discussion re: Iowa darters and whatnot...
Chris: We foresee few genetic problems with hatchery shad because:
1. Unlike salmon, shad are kept in the hatchery a very short time, 7 to 21
days. Thus, there is less chance that artificial selection will occur which
will favor characteristics which enhance survival in the hatchery, but are
deleterious in the wild.
2. Shad hatchery projects are restoration projects, not enhancement
projects. The rivers that are under restoration have no wild shad or very
few shad, too few to expect timely response to other conservation measures
such as fishery closures or fish passage. Many of the salmon enhancement
projects put hatchery salmon on top of wild salmon simply to increase
commercial and sport harvest. Protection of habitat was ignored because the
"quick fix" of hatchery enhancement was too attractive.
3. Numbers of spawners used for shad is large. Several thousand adults are
used annually for the Susquehanna restoration project. This reduces the
potential for founder effects and increases genetic diversity. Our
assumption is that natural selection will occur on the hatchery fish and the
population will evolve from one which is a genetic combination of the rivers
from which we take our eggs to a new "Susquehanna stock", adapted to survive
the unique environmental conditions of the Susquehanna.
4. Eggs are taken from wild broodstock. There is no attempt to domesticate
shad to provide a source of eggs for the hatchery.
5. Eggs are taken from rivers with abundant populations of wild shad so
there is little potential for back-crossing with hatchery-reared fish.
6. We have maximized genetic diversity by taking eggs from a large number
of source populations including: James River, VA; Pamunkey River, VA;
Delaware River, PA; Hudson River, NY; Connecticut River, MA; and Columbia
River, OR.
Christopher Scharpf
Baltimore
"The secret of life is to have a task....And the most important thing is -- it
must be something you cannot possibly do!"
Henry Moore, sculptor
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