Another bumper crop of young striped bass in Maryland’s portion of the Chesapeake comes as menhaden — one of their main sources of food — appear to have had another poor year of reproduction in the state.
This is fueling continued speculation that the mushrooming number of young striped bass is outpacing one of their most important food supplies, at least in some parts of the Bay.
Many striped bass, especially in parts of Maryland, have been unusually thin and covered with sores in recent years. Some believe the poor condition is stems from a 79 percent drop in the Atlantic coast menhaden population since 1991.
Menhaden are one of the Bay’s most important species, both ecologically and economically. They graze large amounts of algae out of the water as they grow, and eventually become a major food source for larger fish.
Menhaden also support the Bay’s largest commercial fishery, measured by weight. Though not consumed by humans, the fish are used for oil, animal feed and other products.
Critics say the Atlantic States Marine Fisheries Commission, which represents all East Coast jurisdictions and is responsible for managing species that migrate across state lines, has focused on the commercial fishery rather than on menhaden’s ecological role.
“We’re concerned that the population has been low for so long that it’s going to take a while for it to recover,” said Jim Price, president of the Chesapeake Bay Acid Rain Foundation and a leading critic of ASMFC’s menhaden management. “By having this intense fishery in Virginia, it certainly reduces the number of menhaden at a time that we need all the forage we can get.”
Price said Maryland’s juvenile menhaden index for 1999 — though improved from last year — still remained far below the long-term average. The index, a predictor of the future menhaden stock, has been below average every year since 1991.
Scientists are divided whether the decline of menhaden jeopardizes striped bass; many note that rockfish are opportunistic feeders that will eat almost anything.
But a scientific peer review of the ASMFC’s menhaden plan raised many management questions, and called for establishing quotas on the commercial menhaden catch and taking into consideration the ecological role menhaden play.
Although the peer review panel said it found no evidence that the overall menhaden population was at risk, it said fishing pressure could cause seasonal menhaden depletions in some areas, such as parts of the Chesapeake, where most of the Atlantic menhaden catch takes place.
The ASMFC this summer took comments on potential changes in the way it manages menhaden. It’s expected to recommend changes and take them out for additional comment in the next year.
A focal point of many comments was the makeup of the ASMFC’s Menhaden Management Board. ASMFC is divided in a number of boards, each of which develops management strategies for a particular species. The menhaden board is unique in that it is the only panel that includes representatives — half of the board’s membership — from the fishing industry it regulates.
“There is one overriding comment that I’ve heard, and that was ‘change the board structure,’” said Joe Desfosse, the ASMFC fishery management plan coordinator who conducted public hearings along the coast during the summer and reviewed more than 1,000 written comments.
Concerns about the relationship of menhaden to striped bass and other predators has helped spur scientists to begin rethinking how they manage fish.
Concerns aren’t limited to menhaden: There are questions about predator-prey relationships among many species, including whether predation on blue crabs has increased in recent years.
“The striped bass–menhaden issue is the easiest for the public to grasp, but it’s a complex food web,” said Derek Orner, a biologist with the National Oceanic and Atmospheric Administration’s Chesapeake Bay Office.
The Congressional intent is to allocate $500,000 for NOAA’s Bay Office to begin a study of “multispecies” interactions within the Chesapeake.
Also, the ASMFC is planning a workshop next year to examine multispecies issues throughout the coast. That could result in a series of research recommendations, and potentially even management actions.
Historically, fish stocks have been managed individually to support fisheries, without regard to their relationships with other species. Management plans therefore aim to identify the maximum allowable catch of a particular fish — in this case menhaden — without taking into account that growing stocks of striped bass, bluefish, weakfish and other predators may require more prey.
“The prey biomass needed to sustain those species needs to be higher than it was 15 years ago,” said Phil Jones, of the Maryland Department of the Environment. “We need to keep an eye on this. Menhaden are obviously an important ecological species.”
Still, he and others note that food web interactions are tremendously complex, and it’s rare when one species is totally dependent on another. While striped bass may prefer menhaden, they are also opportunistic feeders.
“Striped bass just eat too many different things,” said Herb Austin, a biologist with the Virginia Institute of Marine Science who has studied the rockfish diet. “Menhaden have been low before when striped bass were abundant in past times.”
Austin said that during fishing tournaments this year, VIMS scientists who examined fish saw few striped bass with sores and none of the skinny fish that were observed in Virginia two years ago. Striped bass measuring 18–24 inches had body fat, which seemed to indicate they were in good health, he said.
In Maryland though, up to 15 percent of the fish caught have had lesions, which some believe could be an indicator of stress in the food chain, although it may not be related at all.
Confusing the issue further is that even as the overall number of menhaden remains small, the number of large fish — those which make up the potential “spawning stock” for the species — remains high. No one knows why their reproduction has been so low in recent years.
While no one can fully explain the problem with menhaden reproduction, Bill Goldsborough, a fisheries scientist with the Chesapeake Bay Foundation, said he believes there is growing agreement that fundamental changes are needed in the way the species is handled.
“We know that regardless what the recruitment level is, we need to manage this species more comprehensively — that is, for the wider range of benefits that it provides society — than we have in the past,” Goldsborough said. “And I think in a couple of years, that is likely to change.”