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Bay Blog: rockfish

May
16
2017

Rockfish return to find a changing Chesapeake region

Each spring, as waters warm along the Atlantic coast and in the Chesapeake Bay, striped bass begin to migrate. Otherwise known as rockfish or stripers, striped bass are anadromous: they spend most of their adult lives in the ocean but travel back to the freshwater where they were born to spawn. As the fish make their return to the rivers of Maryland and Virginia, recreational fisherman celebrate with striped bass trophy season, hoping to catch and release the largest fish and spending time on the water with a tradition that spans generations.

Watermen Owen Clark, left, and Ashley Elbourn of Rock Hall, Md., catch striped bass with a roughly 1500-foot gill net for the spawning stock survey led by Maryland Department of Natural Resources in the northern Chesapeake Bay near Aberdeen Proving Ground last month. Surveys help inform fishery management decisions, track population size and measure spawning success. (Photo by Will Parson/Chesapeake Bay Program)

Rockfish have served as one of the most popular commercial and recreational fish in the Chesapeake Bay for hundreds of years. When Captain John Smith traveled the estuary in 1614, he wrote of seeing waters so full of “the Basse”—believed by many to mean striped bass—that a man might walk across their backs without getting his shoes wet.

For years, rockfish served as an iconic, ever-present Chesapeake species for both food and sport. But in the 1970s and 80s, the striped bass fishery collapsed. Between 1973 and 1983, commercial and recreational catches fell from a record-setting 14.7 million pounds to just 1.7 million pounds. By the late 1980s, states across the region had put moratoria in place in an attempt to help the species recover. After responding well to harvest restrictions, the population was considered fully restored in 1995. Today, active management and a Bay-wide quota for recreational and commercial striped bass fisheries have helped the species remain at a sustainable level.

The recovery of striped bass in the Bay is often seen as one of the estuary’s great success stories. But environmental pressures could put strain on habitats used by spawning adults and young striped bass, threatening the long-term health of the species. As the largest striped bass nursery area on the Atlantic coast, experts estimate that up to 90 percent of the Atlantic striped bass population uses the Bay and its tidal tributaries to spawn. Healthy habitats are key to the survival of young striped bass, a sustainable population and a robust commercial and recreational fishery in the Bay.

Researchers measure the length, determine the sex, and assess whether spawning has occurred or not during the annual striped bass spawning stock survey. Some fish also have scales removed for aging and some are fitted with tags.

From year to year, striped bass reproduction sees considerable natural variation. This means that the overall population relies on successful spawning years—which require suitable habitat—to compensate for below-average years. But threats like warming temperatures, for example, could disrupt the timing of migration and spawning and alter what areas are viable habitat for these life processes.

A less-discussed but equally significant threat to rockfish habitat, experts say, is land use—particularly development and urbanization. As the region’s human population grows, more farm and forest land is being converted into buildings, roads, parking lots and other paved surfaces. These impervious surfaces cause a surge in the amount and intensity of polluted runoff, which can erode streambanks, transport toxic contaminants and nutrient and sediment pollution into waterways and significantly alter the temperature of rivers and streams.

As the landscape is altered, these changes can turn previously suitable spawning and nursery areas into less productive habitat. Striped bass are sensitive to habitat changes because, when spawning and as larvae, they become concentrated in relatively small geographic areas. Any disturbances in those areas could potentially impact a large number of striped bass from across all life stages: from eggs to larvae to spawning adults.

Jeff Horne of Maryland Department of Natural Resources tags a striped bass. Fishermen who catch tagged fish can report them to DNR for a reward—sometimes as much as $125.

Horne releases a tagged striped bass. Information from reported tags helps determine striped bass migration rates, migration patterns, growth rates, and mortality rates.

When researchers overlaid a map of the Bay’s striped bass spawning areas with a map of projected development, the results showed all spawning habitat to be under moderate to very high development pressure. The Potomac and James Rivers, for example, are among the largest spawning areas in the Bay, and projections of growth show those areas could develop up to 10 percent impervious surface cover by 2020. Fisheries experts consider impervious surface cover at a level of five percent or below the target for a local region, but levels below 10 percent can still help keep the striped bass population stable.

Slight degradations in habitat can be offset by restoration efforts—although, once lost, there’s no guarantee habitat quality can be restored. By conserving farm fields, forests, wetlands and natural shorelines, land managers can help sustain healthy striped bass habitat. Concentrating the development that does occur in and around already-developed areas—a technique known as “smart growth”—can also help ease the effects of development, as can reducing the amount of runoff through green infrastructure like rain gardens, green roofs and permeable pavement.

Each year, researchers in Maryland and Virginia survey spawning and juvenile striped bass to inform fishery management decisions, track population size and measure spawning success. So far, the results of these surveys don’t have experts alarmed. Although results of Maryland’s 2016 juvenile striped bass survey were well below the long-term average, successful spawning years in 2011 and 2015 are expected to compensate for the below-average year. Meanwhile, experts continue to work to better understand how land use changes and other stressors may impact these numbers in the future, helping to ensure a robust rockfish population for years to come.

To view more photos, visit the Chesapeake Bay Program's Flickr page.

Photos by Will Parson

Stephanie Smith's avatar
About Stephanie Smith - Stephanie is the Web Content Manager at the Chesapeake Bay Program. A native of the Midwest, she received her Bachelor’s in Professional Writing from Purdue University and Master of Science degree from the University of Michigan. Stephanie’s lifelong love of nature motivates her to explore solutions to environmental problems and teach others what they can do to help.



Oct
22
2015

Researchers observe ‘robust’ rockfish reproduction, spawning success

Striped bass spawning success has improved in the Chesapeake Bay, according to scientists from both Maryland and Virginia.

Image by Kenneth Summers/Shutterstock

Tracking the number of young-of-the-year striped bass in the Bay, or those rockfish that are less than one year old, helps scientists evaluate the health of the striped bass stock. To determine this number, scientists take a series of seine net samples in select striped bass spawning areas—like the Choptank, Potomac and Nanticoke rivers in Maryland and the Rappahannock, York and James rivers in Virginia—each summer. The resulting “juvenile abundance index” serves as an early indicator of future fish populations, helping managers predict the amount of striped bass that will be available to fishermen in the coming years.

“Striped bass are a… resilient species when given favorable environmental conditions for reproduction and survival,” said Maryland Department of Natural Resources Secretary Mark Belton in a media release. “The robust reproduction should give Maryland anglers hope for a successful striped bass season in a few years’ time.”

In each Maryland sample, researchers caught an average of 24 juvenile striped bass; the state’s abundance index value rose from 4.06 to 10.67 this year, which is the eighth highest on record. In each Virginia sample, researchers caught an average of 12 juvenile striped bass; the Commonwealth’s abundance index value rose from 11.37 to 12, which is about equal to average historic values. There, striped bass spawning success has been average or above average in 12 of the last 13 years, which indicates consistent production in Virginia nurseries.

Striped bass hold great value in the watershed: the fish is a top predator in the food web and a critical catch for commercial and recreational fishermen. Fishing bans set in the late 1980s helped striped bass recover from harvest and pollution pressures, and experts now consider it a recovered species.

Learn more about the juvenile striped bass survey in Maryland and Virginia.



Oct
23
2013

Striped bass reproduction is up in the Chesapeake Bay

Striped bass spawning success has improved in the Chesapeake Bay.

Image courtesy randychiu/Flickr

According to data from the Maryland Department of Natural Resources (DNR) and the Virginia Institute of Marine Science (VIMS), the number of juvenile striped bass in the watershed has rebounded from last year, when it was close to the lowest ever observed.

Known as the “juvenile striped bass index,” the number of young-of-the-year striped bass in the Bay is used to track the species’ reproductive success. To count the number of striped bass that hatched this spring, biologists take a series of seine net samples in noted spawning areas, from the Upper Bay to the James River.

Image courtesy VIMS

This year, the average number of juvenile striped bass caught in each Maryland sample was 5.8, which falls below the 11.7 average but above last year’s index of less than one. In Virginia waters, researchers caught more than 10 striped bass per seine sample, which is close to the historic average of 9. A VIMS media release called the results consistent with historically observed patterns in striped bass populations.

Striped bass, or rockfish, hold great value in the watershed: the fish is a top predator in the food web and a critical catch to commercial and recreational fisheries. Late-1980's fishing bans helped striped bass recover from harvest and pollution pressures, and it is now considered a recovered species.

Learn more about the juvenile striped bass survey in Maryland and Virginia.



Oct
17
2012

Striped bass reproduction down in Chesapeake Bay

Striped bass spawning success is at an all-time low in the Chesapeake Bay.

According to data from the Maryland Department of Natural Resources (DNR), the number of juvenile striped bass in the Maryland portion of the Bay fell 97 percent in the last year.

Image courtesy Eddie Welker/Flickr

To track striped bass reproduction rates, biologists take a series of summer seine net samples at more than 20 sites in four striped bass spawning areas. This year, the average number of juvenile striped bass caught in each sample was 0.9. Last year’s juvenile striped bass index was 34.58; the long-term average is 12.

Biologists have blamed unfavorable weather for the decline.

“Generally, warm winters and dry springs are unfavorable conditions for fish that return to freshwater to spawn,” said DNR Striped Bass Survey Project Leader Eric Durrell. Like the striped bass, white perch, river herring and other anadromous fish also experienced low reproductive success this year.

But biologists “do not view this low value as an imminent problem,” said DNR Fisheries Director Tom O’Connell. “Three consecutive years of poor reproduction would be necessary to trigger mandatory conservation measures.”

According to the 2011 Striped Bass Stock Assessment released by the Atlantic States Marine Fisheries Commission, striped bass along the Atlantic coast are not overfished and overfishing is not occurring.



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