Species on the Brink: Latest Challenges for River Herring Research

 

Once upon a time, river herring multiplied by the millions in North Carolina’s waters. During spring spawning runs in the Chowan and other rivers, fishermen were literally knee-deep in the easy-to-preserve protein source.

River herring — the common name used for both alewife and blueback herring — were so plentiful in the 19th century that prominent scientist Thomas H. Huxley believed stocks could never be exhausted.

The abundance of the past is now long gone. By 1996, landings of river herring in Albemarle Sound were 253,000 kilograms (556,600 pounds) — only 5 percent of average 1880 to 1970 landings — according to a 1996 analysis of historical abundance by Joe Hightower of the N.C. Cooperative Fish and Wildlife Research Unit at North Carolina State University.

Since 2001, N.C. herring landings continued to decline despite agreements to reduce quotas, says Warren Mitchell, a researcher on staff at NC State’s Center for Marine Science and Technology (CMAST). “Commercial fishermen didn’t even catch the quota they’d been allotted.”

Now, with populations dangerously low, Mitchell is working along with a number of other researchers, fishermen and fishery managers to find out how many river herring remain and what to do about the species’ alarming decline.

Mitchell is working with commercial fisherman Terry Pratt and Chris Taylor, a research ecologist at the National Oceanic and Atmospheric Administration’s (NOAA) Center for Coastal Fisheries and Habitat Research in Beaufort, on a two-year river herring N.C. Fishery Resource Grant (FRG).

Their goal is to determine the feasibility of using fisheries sonar to estimate the number of spawning river herring in Albemarle Sound. The FRG program is funded by the N.C. General Assembly and administered by North Carolina Sea Grant.

“Estimates previously came from commercial landings,” Mitchell says, stressing the importance of research to fill the gap left by the fishery’s closure in 2007. Mitchell is a former Marine Fisheries Fellow through the joint Sea Grant and N.C. Division of Marine Fisheries (DMF) fellowship program.

Another FRG project is assessing the availability of river herrings’ primary food source — zooplankton. Dina Leech and Scott Ensign of the University of North Carolina at Chapel Hill’s (UNC-CH) Institute of Marine Science, and fishing brothers Herbert and Bobby Byrum, are trying to discover whether there are enough zooplankton to support a river herring fishery in the Chowan River Basin.

In response to the rate of decline among river herring in recent years, the N.C. Marine Fisheries Commission implemented a statewide moratorium on all harvest of river herring effective September 2007.

Concerns about river herring span the coast from Maine to Florida. The Atlantic States Marine Fisheries Commission has drafted an amendment to the Interstate Fishery Management Plan for Shad and River Herring that recently circulated through respective states for public comment. Amendment 2 focuses specifically on river herring and the need for more collective monitoring and management.

“It’s an East Coast effort to determine what issues are addressing the entire fishery,” says Sara Winslow, northeast district manager for DMF.

SCANT SURVIVORS

Back in 2007, when Mitchell, Taylor and Pratt applied for the two-year grant to study river herring abundance, they suspected that a moratorium was pending. That’s what made their research even more crucial.

With sonar technology — which, similar to commercially available fish-finders, uses high-frequency sound to estimate locations of fish — the team hoped to find a reliable method, other than fishing, to provide river herring population estimates for fishery managers.

“Sonar technology has worked well in other fisheries,” Mitchell says.

In fact, Taylor recently organized the first meeting of a group called the Carolina Acoustics Working Group, which drew individuals from North and South Carolina who use sonar and other acoustic technology for marine research.

In Spring 2008, Mitchell and Taylor made daily trips to three designated areas of the Chowan River and Western Albemarle Sound during a seven-week period between late March and early May when river herring tend to be most abundant.

Alewife and bluebacks have slightly different spawning cycles, and this and other state-funded projects only monitor bluebacks to infer generalities about river herring.

Using hydroacoustic gear strapped on the side of the boat, they identified areas that appeared to have herring. The acoustic signals allowed them to get an idea of the size and numbers of fish, and therefore predict the species. Unfortunately, white perch and menhaden appeared quite similar to blueback herring on the sonar detection screen.

To solve that problem, Mitchell and Taylor radioed coordinates to Pratt’s fishing boat, where Pratt and his crew set gill nets and counted the herring from the catch. From the abundance in Pratt’s nets, they were able to predict the percentage of the acoustic data that were herring, Taylor explains.

Preliminary results show that the acoustics can adequately map locations of fish, Mitchell says. “The sonar did its job. The problem is that river herring were a very small proportion of the total catch — a little more than 10 percent.”

It also will be useful to compare data gathered by DMF in Spring 2008 with the acoustic results, Mitchell says. “DMF operates a few of its own pound nets, simulating commercial fishing.”

Pratt, who has fished in the Chowan for nearly 50 years, wonders whether DMF sampling areas are truly representative of herring abundance.

“Hopefully our results will show a higher concentration of fish than the state data shows,” Pratt says.

Taylor says two products will come out of their 2008 results. The first will be a map of the overall distribution of fish throughout the survey regions in each of the project’s seven weeks.

“This will be useful for people to understand how fish are distributed and moving through the Sound and into its tributaries,” Taylor says.

The second product will be an estimate of the total number of river herring in the western Albemarle Sound during the project period.

The team’s other goals for 2009 — in addition to comparing data from other projects and contributing useful observations of the herring population status — are to reduce costs and increase efficiency of the testing process.

“The primary objective is to design a monitoring program that will reduce manpower costs and still get accurate estimates of abundance,” Taylor says. “This study is a cost-benefit analysis as well. There are benefits of acoustics, but like all survey methods, it still costs money.”

The team also may slightly change the boundaries of the sampling regions based on 2008 results. Hightower and CMAST faculty member Jeff Buckel, both past participants on Sea Grant- and FRG-funded projects, are providing technical support for the two-year study.

FISH FOOD

The last time zooplankton — tiny algae-eating organisms that drift in the water column — were analyzed as a river herring food source in the Chowan River Basin was in the 1980s, according to Dina Leech. At that time, researchers found that the concentration of the tiny prey was very low and not plentiful enough to support a healthy river herring population.

Leech, Ensign and the Byrum brothers have conducted monthly sampling since March 2008 to re-assess the availability of zooplankton as part of another FRG project.

Based on attempts to overlap with 1980s study regions, and suggestions by the Byrum brothers who have fished for herring in the Chowan for more than 40 years, the team selected four sampling sites: two on the main stem of the Chowan River below Holiday Island; and one each on the mouths of Wiccacon and Bennett’s creeks — tributaries that flow into the Chowan.

At first, the team only sampled near the surface, finding relatively small zooplankton, some less than one millimeter in size. “We did surface tows half a meter down from the surface, slowly driving the boat for a given time period,” Leech says. They would then rinse tow contents into a cup and preserve them in formalin, to be counted back in the lab.

Herring are visual predators and are more likely to eat larger, more visible prey, which also have more nutritional value. Suspecting there might be larger zooplankton lower in the water column, the team sampled at the bottom, using a modified bilge pump, or a hose attached to a hand pump.

In deeper water, the researchers found larger zooplankton, and smaller ones carrying eggs.

Every day, the zooplankton move up and down the water column. “The larger ones go deeper in the day to avoid predation and back up at night to feed on algae at the surface,” Leech explains.

Based on preliminary counts, the team estimates less than one to two of the tiny animals per liter from April to May 2008, but much higher numbers from June to July of between 50 and 100 animals per liter.

The next step was to inspect the guts of river herring for zooplankton content. But, no river herring were found at their sampling sites.

“We are finding so many zooplankton compared to the 1980s study, but we have no idea why,” Leech says. “One interesting possibility is that the cause is fewer fish.”

The team coordinated with Winslow to use some juvenile herring collected by DMF’s sampling program, but DMF hasn’t found many either.

From the limited gut contents the team has analyzed so far, it appears that the remaining herring are getting their fill of zooplankton.

“One of the things we want to do is extend it another year,” Leech says. “We want to add additional sites in the lower Chowan and into Albemarle Sound to overlap more with DMF sites.”

Taylor, along with Michael Piehler of UNC-CH’s Institute of Marine Sciences, is providing technical assistance on the zooplankton project. He says knowing if there is sufficient prey in the region will be useful to compare with estimates of river herring abundance from the acoustic FRG.

Herbert Byrum, who with his brother has also been operating pound nets for one of DMF’s river herring projects, says he hopes this study will help reveal what is causing river herring declines.

STATEWIDE EFFORTS

The 2007 N.C. River Herring Fishery Management Plan indicates a long list of topics to be researched: predation by species like striped bass, herring bycatch in ocean fisheries, water quality and status of critical habitat areas, blockages to historic spawning areas, and loss of fry and juveniles from industrial, municipal and agricultural water use.

Despite recent budget cuts across the board for government programs, Winslow says the N.C. General Assembly has given significantly more funding for river herring in 2007 and 2008 compared to the last 25 years.

To replace commercial landing data, DMF is using funds to re-evaluate spawning area surveys, monitor water quality, and to work with pound net fishermen like the Byrum brothers. The Albemarle-Pamlico National Estuary Program also received state funds for river herring, which it will share with DMF for research.

NOAA’s National Marine Fisheries Service (NMFS) also provided a small federal aid grant for N.C. herring research, Winslow says. The money goes towards DMF’s juvenile sampling program using seines in Albemarle Sound.

Clearly, North Carolina is not ready to give up on this historic resource.

FACING THE FUTURE

Although river herring are so much a part of the state’s heritage, some question the high cost of research on a resource that may never again bring in the revenue it once provided.

“Some say why spend the money on research, when the fishery wasn’t bringing in much money anyways,” Mitchell says, referring to the abysmal catches in the years just prior to the fishery’s closure.

Taylor says the collective goal of the two river herring FRG projects is to find out how successful river herring fishery management efforts can be.

“We’re all interested in determining if Western Albemarle can support recovery of that stock,” Taylor says.

Based on early results from the zooplankton assessment project, it is still unclear if the food source is enough to support a healthy river herring population.

But researchers, fishermen and N.C. residents still have hope that the herring can rebound, and that the fishery will eventually reopen, Mitchell says.

“When moderated, fishing is one of the few truly sustainable industries on Earth,” he says.

“Hopefully, we’ll get back the ability to catch herring sooner than 25 years from now,” says Pratt, referring to some estimates of how long it may take before the moratorium is lifted.

“People in North Carolina have been used to eating herring all their life. They’d like to be able to get a few,” Herbert Byrum says.

For more information on FRG projects, go online to ncseagrant.ncsu.edu.

To find out more about the past, present and future of river herring, check out “Fish of Yesterday, Fish of Tomorrow” by Jim Wilson. The article appeared in the October 2007 issue of Wildlife in North Carolina magazine, and is available online from the N.C. Wildlife Resource Commission: www.ncwildlife.org.

For Draft Amendment 2 to the Interstate Fishery Management Plan for River Herring, go online to www.asmfc.org and follow links to “Shad and River Herring” under managed species. The period for public comment ended Jan. 1. Final review and approval are planned for May 2009.

This article was published in the Winter 2009 issue of Coastwatch.

For contact information and reprint requests, visit ncseagrant.ncsu.edu/coastwatch/contact/.