SURVEY HISTORY
Annual monitoring of juvenile Alosa is conducted with a pushnet collection system as developed in the late 1970s by Dr. Joseph Loesch and William Kriete, Jr. (see sampling design). Because of the negative phototropic behavior of juvenile Alosa, the pushnet is used at night to determine a maximal mean (arithmetic and geometric) catch-per-unit-of-effort (maximal mean CPUE. The research was conducted in the Mattaponi and Pamunkey rivers for nine years (beginning 1979), and a correlation between the river herring index and CPUE of subsequent recruits to the fishery was about 73%. This activity was not continued in 1988 because of a lack of funding. The NMFS funded the program from 1990 to 1992. In 1991 and 1992 the James and Rappahannock rivers were included in the monitoring program. Internal funds provided by VIMS were used to continue the program on the Pamunkey and Mattaponi rivers in 1993.
History of Alosa in Virginia:
Alosa stocks have historically provided Virginia with a major commercial fishery. In 1880, the tributaries of the Chesapeake Bay yielded more than 2,268 metric tons (MT) of shad. In 1896, Virginia ranked second to New Jersey in shad production with 4,990 MT. Usually Virginia ranked first or second in shad production in the early 1900's. In 1908, Virginia's shad catch of 3,311 MT made it the most important fish caught in Virginia, and the catch comprised about one fourth of all shad taken in the United States. In 1970, nearly 4,000 MT were landed in Virginia (VMRC, 1994). The catch of American shad, however, has critically declined since the mid-1970's. In response to the steady decline in landings, VMRC imposed restrictive harvest regulations from 1991 through 1993 and a total moratorium in 1994.
River herring catches in Virginia have had a pattern very similar to that for the shad. In 1920, river herring in Virginia ranked first in quantity and fourth in value, with a catch of 7,258 MT worth 253 thousand dollars (Atran et al., 1983). As late as 1969, river herring in Virginia ranked third in quantity and fifth in value, with a catch of 13,608 MT worth 608 thousand dollars (NMFS, 1972). Since the early 1970's, however, the fishery has also steadily declined. In 1981, the combined catch of river herring and American shad was the lowest ever recorded and, since that time, there has only been a marginal increase in landings.
Historically, the construction of dams, degradation of the environment, and over-fishing were cited as causes for the decline of fish stocks. To varying degrees, the same explanations are offered as contemporary explanations for further declines in stocks. The decline in Alosa landings since the 1970's may be the joint result of the heavy exploitation in the late 1960's, the decimation of the 1972 year class by Tropical Storm Agnes, and continued poor recruitment in recent years. Although landings have increased since 1981, they are still low.
It is important that the basic biology and population dynamics of the Alosa stocks in the Chesapeake Bay region be studied. Anadromous fishes are a renewable natural resource which have a vital ecological role in addition to their economic importance. Juvenile (young-of-the-year) Alosa are the dominant pelagic species in their extensive freshwater and upper estuarine nursery grounds and thus, are important prey for resident piscivores. After spawning, adults return to the sea and are prey of many predatory marine fishes. Because of the ecologic and economic importance of Alosa, it is in the interest of both the State of Maryland and the Commonwealth of Virginia (and other Atlantic coastal states) to conduct Alosa studies. Current data, as well as historical data, are needed for constructive contributions to the formulation and application of rational management strategies.
Estimates of relative year-class strength (indices), the subject herein, are an important facet in the studies of stock recruitment. Indices are particularly sensitive to large changes in juvenile (young-of-the-year) abundance, thus, an expectation of a strong or weak year class can be established. If a juvenile index can be shown to vary directly with the fishery stock size over a large range in stock sizes, the index can be used as a surrogate for actual year-class recruitment.