This spring's warm, dry conditions likely contributed to striped bass having their worst spawning success on record in Maryland, according to an annual survey by the state's Department of Natural Resources.
Scientists from the Virginia Institute of Marine Science also reported poor spawning results from their surveys in Virginia's waters.
Spawning success for striped bass, which is heavily influenced by weather, is notable for its sharp year-to-year changes. This year's index, the lowest since the Maryland survey started in 1954, followed the survey's fourth best year in 2011.
"While we expect large variation in striped bass reproduction from year to year and do not view this low value as an imminent problem, we will be carefully monitoring the results of future surveys," said DNR Fisheries Director Tom O'Connell. He noted it takes three consecutive years of below-average spawning to trigger mandatory conservation efforts.
This year's striped bass juvenile index came in at 0.9. Last year's index was 34.6. The long-term average is 12.
The Maryland index is the average number of juvenile fish caught in 100-foot seine nets at 22 survey sites that are sampled monthly from July through September in four major spawning systems — the Choptank, Potomac and Nanticoke rivers, and the Upper Bay.
Striped bass are an anadromous species that spawns in freshwater but spends most of its life along the coast. About three quarters of the East Coast striped bass population is spawned in Maryland's portion of the Bay, and historically, the state's survey has been closely watched as a reliable indicator of future stock size.
"Generally, warm winters and dry springs are unfavorable conditions for fish that return to freshwater to spawn," said Eric Durell, who heads the annual survey. Other anadromous species such as white perch, yellow perch and river herring, also experienced low reproductive success this year.
At the same time, the survey showed increased reproduction of fish species that spawn in higher salinities or offshore, such as Atlantic croaker and bay anchovies.
Meanwhile, Virginia scientists said preliminary results from their survey, which has been conducted annually since 1967, also suggest poor striped bass production in Virginia's Bay tributaries. VIMS scientists reported finding fewer than three fish per seine haul this year, significantly lower than the historic average of seven. In 2011, they averaged 27 striped bass per seine haul.
The VIMS Juvenile Striped Bass Seine Survey currently samples 18 stations in the Rappahannock, York and James rivers. Each year, biologists sample each site five times from early July through mid-September, deploying a 100-foot-long seine net from the shore.
"A single poor year of recruitment like we saw this year can be weathered by the previous year's high production," said Mary Fabrizio, who directs the VIMS survey. She said the survey has averaged about one unusually poor year of reproduction per decade since 1990, when a moratorium on striped bass fishing was lifted, with the last one coming in 2002.
Juveniles produced this year will start to be large enough to be caught in three to four years.