Tuesday, January 31, 2023

Juvenile striped bass maintain average abundance in Virginia waters in 2017

Seining on the Rapphannock River. Photo courtesy of VIMS.
Seining on the Rappahannock River. Photo courtesy of VIMS.

Preliminary results from an ongoing long-term survey conducted by researchers at the Virginia Institute of Marine Science suggest an average year class of young-of-year striped bass was produced in Virginia tributaries of the Chesapeake Bay in 2017. The 2017 year class represents the group of fish hatched this spring that will grow to fishable sizes in 3 to 4 years.

The program, formally known as the Juvenile Striped Bass Seine Survey, recorded a mean value of 8.98 fish per seine haul in the Virginia portion of the Chesapeake Bay, which is similar to the historic average of 7.77 fish per seine haul. The 2017 value—what scientists call a recruitment index—was also similar to indices observed in the past 4 years. Although variation in striped bass recruitment among years can be considerable, the average indices observed in recent years may indicate greater consistency in the production of juvenile fish than what was observed in the past.

Striped bass play an important role as a top predator in the Chesapeake Bay ecosystem and are a valuable resource for commercial and recreational anglers. Professor Mary Fabrizio, who directs the Juvenile Striped Bass Seine Survey at VIMS, notes that the economic and ecological value of striped bass lends significant interest to the year-to-year status of their population.

“By estimating the relative number of young-of-year striped bass,” Fabrizio says, “our survey provides an important measure of annual and long-term trends in the Bay’s striped bass population.”

Various sized Young of the Year (YOY) striped bass (Morone saxatilis). Photo courtesy of Chris Davis.
Various sized Young of the Year (YOY) striped bass (Morone saxatilis). Photo courtesy of Chris Davis.

The VIMS Juvenile Striped Bass Seine Survey currently samples 18 index stations in the Rappahannock, York, and James River watersheds. Biologists sample each site 5 times from mid-June to late August, deploying a 100-foot-long seine net from the shore. Each fish captured in the net is counted, measured, and returned to the water. These young striped bass generally measure between 1.5 and 4 inches. Survey scientists in Virginia measured 1,998 juvenile striped bass at these stations in 2017. VIMS has been conducting the survey annually since 1967 for the Virginia Marine Resources Commission.

The striped bass population in Chesapeake Bay has rebounded from historic lows in the late 1970s and early 1980s, after fishing bans were enacted in Delaware, Maryland, and Virginia in the mid-to-late-1980s. Since then, the population has increased to the point that striped bass in the Bay and elsewhere are now considered recovered. Monitoring of juvenile striped bass recruitment will continue next year to provide managers with crucial information to sustainably manage this important species.

Index (scaled geometric mean) of young-of-the-year striped bass in the primary nursery areas of Virginia by year. Vertical bars are 95% confidence intervals as estimated by +/- 2 standard errors of the mean. Horizontal lines indicate the arithmetic mean (thin solid line) and confidence intervals on the mean (dashed lines) estimated from indices observed in the historic reference period (1980-2009). Significant differences exist when confidence intervals do not overlap.

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