Reference |
Minikkinen, S. P., C. P. Stence, and B. M. Richardson. 1995. The use of hatchery-produced striped bass for stock restoration and validation of stock parameters. American Fisheries Society Symposium 15:555-556. |
Abstract |
Since 1985, a joint restoration program by the Maryland
Department of Natural Resources (MDNR) and U.S. Fish and Wildlife Service
has stocked 6,457,000 striped bass Morone saxatilis into Maryland
tributaries of the Chesapeake Bay. All were tagged with binary-coded wire
tags (Northwest Marine Technology, Shaw Island, Washington). Two different
stocking strategies were used: (1) stock 50-mm phase-I-fish during June and
July and (2) stock 100- and 200-mm phase-II-fish in the fall. Cage holding
experiments were conducted over 2 weeks to determine poststocking tag loss
and mortality. The number of fish available for recapture was adjusted using
these estimates. A survey was conducted to assess the contribution of
hatchery-produced striped bass to the juvenile population. Sampling was
conducted with a 3.1m x 1.2m beach seine and a 4.9m semi balloon trawl. The Patuxent River has received 2,816,000 hatchery fish which constituted 30, 72, 85, 48 and 5% of the juveniles collected from the 1989 to 1993 year-classes, respectively (40% overall). Hatchery and wild fish were collected in the same areas and habitats. Peterson mark-recapture estimates in December each year indicated recruitment of 586,000; 125,000; 39,000; 413,000; and 2,575,000 wild striped bass from 1989 to 1993, respectively. Juvenile recruitment indices, which are collected by MDNR to monitor striped bass reproductive success, also demonstrated two levels of production. During 1993, a dominant year-class was indicated by the survey with an index that was an order of magnitude higher than those recorded previously (1983-1992). These dominant year-classes have historically been the primary contributors to the stock (Rago, P.J., and C.P. Goodyear. 1987. Recruitment mechanisms of striped bass and Atlantic salmon: comparative liabilities of alternative life histories. American Fisheries Symposium 1:402-416). Hatchery fish represented 5.3% of the juvenile striped bass collected in the Choptank River during 1991. Six million wild juvenile striped bass were present after phase-I stocking (July) and 1,000,000 wild fish remained after phase-II stocking (December). In the Nanticoke River hatchery fish constituted 18.1% of the 1992 year-class of striped bass collected in summer and 68% of those collected in winter. During 1993, hatchery striped bass constituted 5.6 and 63.7% of the fish collected in the summer and winter surveys, respectively. Abundance estimates for wild striped bass during 1992 were 227,000 in July and 90,000 in December. In 1993, abundance estimates were 3,540,000 (July) and 250,000 (December). Instantaneous mortality varied tenfold (between 0.002 and 0.02) in all three rivers from 1991 to 1993, influencing eventual recruitment to the adult population. Factors that control these mortality rates are being investigated. Hatchery efforts have contributed significantly to juvenile abundance in these systems. These fish should contribute to the adult spawning stock when mature. The use of mass marking to measure absolute abundance validated juvenile abundance indices that predict recruitment of striped bass along the Atlantic Coast. |
Tag |
Coded Wire Tag (CWT) |
Objective |
Evaluate stocking programs |
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