Since the 1970s, American
shad and hickory
shad populations have declined drastically in the Chesapeake Bay due
to over-fishing, poor water quality and stream blockages. A 1980 fishing
moratorium, habitat improvements, pollution mitigation and fish passage
construction has not resulted in recovery, primarily due to lack of adult
spawners. In 1994, Maryland DNR Fisheries Service and several partners
began a program to reintroduce shad spawning runs to selected tributaries
through restorative hatchery stocking. Traditional strip spawn culture methods
require access to large numbers of ripe adults. We developed a new technique
to induce spawning in broodfish collected from the Susquehanna River using
synthetic reproductive hormone implants and tank spawning systems (Mylonas
et al. 1995). Fertilized
eggs can be produced from any migratory pre-spawned female. Larvae and juveniles
are marked and stocked in target tributaries. Surveys are conducted to sample
larval, juvenile and adult shad. From 1994 to 2008 the program has stocked 25.9 million american shad and 95.1 million hickory shad in the Choptank River,
Patuxent River, Patapsco River and Nanticoke River.
In 1999 we documented
the first appearance of hatchery-produced adult American shad in the Patuxent
River. The proportion of hatchery fish caught in adult surveys increased
in 2000 and 2001 as fish from the 1994 and 1995 stocking events reached
full recruitment to the migrating spawning stock.
No juvenile American shad were collected in the Patuxent River from 1960 to 1993. From 1994 to 1997 we captured hundreds of hatchery juveniles. The first wild juveniles were captured in 1998 and the wild component of the juvenile population increased from 1% in 1999 to 8% in 2000. Wild fish
represented 11% of the juvenile population in 2001.
adult spawning stocks increase, the wild component of the juvenile population
should exhibit corresponding growth. Restoration goals will be realized
when natural reproduction overwhelms the contribution of hatchery-produced
fish in the juvenile population.