Report prepared by the Chesapeake Bay Ecological Foundation, Inc. at the request
of the Secretary of the Maryland Department Of Natural Resources submitted to
the Maryland Department Of Natural Resources
CHESAPEAKE BAY FORAGE BASE COLLAPSE
AND INTERACTIONS OF STRIPED BASS & ATLANTIC MENHADEN
The Atlantic coast striped bass fishery re-opened in 1990 following a five year
moratorium. New restrictions adopted by the Atlantic States Marine Fisheries
Commission (ASMFC) established an annual quota and raised the striped bass minimum
size limit in the Chesapeake Bay from 12” (age-2), to 18” (age-4).
These measures altered the striped bass population’s size structure and
dramatically increased their forage demand in the Bay. Forage size Atlantic
menhaden (ages 0-2), an essential part of the striped bass diet, subsequently
declined 74% over the past decade and are no longer found throughout the Bay
in sufficient numbers or adequate size to supply the forage demand of striped
bass. Striped bass consumed larger prey and 300% more menhaden in the Bay prior
to the menhaden purse seine (reduction) fishery concentrating its efforts in
Virginia’s portion of the Bay during the mid-1960s. From 1955 to 1965,
the annual menhaden purse seine (reduction) fishery harvest from the Bay averaged
107 million pounds or approximately 11% of the total coastal landings, during
the 1990s average menhaden purse seine (reduction) fishery landings increased
to 379 million pounds or approximately 58% of the total coastal landings. Most
of the Bay’s striped bass now suffer from poor nutrition and approximately
50% of the population is infected with a disease called Mycobacteriosis. The
ASMFC has allowed age-2 menhaden to be overfished by the purse seine fishery,
which annually reduces their numbers to a level inadequate to serve the vital
ecological role they once played along the coast and in the Bay.
An outbreak of disease among striped bass has coincided with the decline of
their forage base. Striped bass with sores and lesions (Ulcerative Dermatitis)
were first documented in 1994 by Dr. Eric May, Maryland Department of Natural
Resources (MD-DNR). In 1997, James Price, president, Chesapeake Bay Ecological
Foundation, notified the MD-DNR and the U.S Fish & Wildlife Service that
12% of the 190 striped bass examined in a Striped Bass Cooperative Survey had
external sores and lesions. Most of the striped bass had no fat in their body
cavities and showed signs of poor nutrition. Dr. Steve Jordan, MD-DNR, reported
that striped bass collected in the 1998-2002 fall surveys had: “Weight
at length, tissue moisture and lipid levels (that) were not significantly different
from wild fish starved for two months at Horn Point Laboratory were not characteristic
of values obtained from wild fish in 1990-1991”. Since 1997,
striped bass have shown a high prevalence of anomalies (skin abrasions, lesions,
or bacterial infections). By 2002, a MD-DNR striped bass pound net tagging survey
found that 17% of the striped bass had external anomalies, the highest percentage
since the bay-wide survey began in 1997. Anomalies are cause for concern because
they indicate nutritional stress and disease. Fishery scientists and pathologists
from the University of Maryland and Virginia Institute of Marine Science (VIMS)
have warned fishery managers that Mycobacteriosis has infected approximately
50% of the striped bass population, with one strain known to cause death. A
University of Maryland study by Dr. Anthony Overton from 1998 to 2001 indicates
Mycobacterium infections in striped bass originated in the Bay, affecting the
health and survival of both resident and migratory fish. A 2003 report by Victor
Crecco, Connecticut Marine Fisheries Division, that analyzed striped bass mortality
and tagged-based exploitation rates found a dramatic rise in natural mortality
rates after 1997 for 18 inch plus striped bass from the Chesapeake Bay. This
could suggest that natural mortality from starvation and disease has reduced
the number of older male striped bass in the Bay.
The ASMFC has failed to take action that could prevent growth overfishing
by the menhaden purse seine (net that encircles large numbers of fish) fishery.
Growth overfishing is defined, according to research funded by the National
Oceanographic and Atmospheric Administration (NOAA) as “When fishing pressure
on smaller fish is too heavy to allow the fishery to produce its maximum poundage.”
Since the mid 1960’s, the menhaden purse seine (reduction) fishery, which
processes fish into meal and oil, concentrated its effort in Virginia’s
portion of the Bay, harvesting mostly small, immature fish. This intensive fishery
is the largest commercial fishing operation on the Atlantic coast. Fishery scientists,
fishermen and the environmental community are concerned that menhaden are being
overfished causing a depletion of forage size menhaden
and damage to the Chesapeake Bay’s ecosystem.
ASMFC’s Interstate Fishery Management Plan (FMP) for Atlantic menhaden
fails to comply with national standards specified in the Magnuson Act, e.g.
The first standard to “…prevent overfishing while achieving, on
a continuing basis, the optimum yield for each fishery.” Optimum yield,
according to research funded by NOAA, is defined as “the amount of fish
which will provide the greatest overall benefit to the nation”. The Atlantic
Menhaden FMP doesn’t limit the number or size of fish that can be caught
by the menhaden purse seine fishery. Omega Protein Corporation, based in Houston,
Texas, has a monopoly over the menhaden purse seine (reduction) fishery in the
Chesapeake Bay, and has been allowed to overfish age-2
menhaden in the Bay and nearby coastal waters. This massive removal of menhaden
from the Bay has been equal in biomass to five times Maryland’s annual
commercial seafood harvest. During the past decade, 48% of the purse seine (bait)
fishery harvest and 87% of the purse seine (reduction) fishery harvest from
the Chesapeake Bay by numbers were forage size menhaden (ages 0-2). Approximately
45% of the estimated total populations of ages 2-4 menhaden, which represent
over 99% of the spawning stock biomass, are removed annually by the purse seine
fishery. The Bay’s annual menhaden purse seine (reduction) fishery
landings have averaged 315 million pounds since 1965. Historically, this huge
biomass of menhaden was an integral component of the Bay’s ecology. Atlantic
menhaden improved water clarity by consuming an enormous amount of nutrients,
and provided essential forage for older striped bass, bluefish and weakfish.
The purse seine (reduction) fishery has influenced the age structure of menhaden
over the past four decades by harvesting excessive numbers of age-2 forage size
menhaden, altering the predator-prey relationship of striped bass and menhaden
in the Chesapeake Bay and along the Atlantic coast. A bioenergetics (diet and
growth) modeling study by Jennifer Griffin, (2002) examined striped bass data
collected by MD-DNR from 1955-1959, before the purse seine (reduction) fishery
concentrated their efforts in the Bay. Griffin stated: “Atlantic menhaden
was the primary prey of striped bass in the Chesapeake Bay in the early 1950s…predation
demand was only slightly below prey supply throughout the modeled year for all
ages”. Hartman and Brandt’s (1995) bioenergetics modeling study,
conducted from 1990 to 1992, concluded: “Total prey demand by age-3 striped
bass exceeded supply by 80%, while demand by age-4 through age-6 striped bass
was 101-103% higher than supply”. Overton (2001) suggested prey supply,
availability and size were not able to support production of older striped bass
in the Bay.
The estimated Atlantic coast population of forage size menhaden (ages 0-2)
averaged 795 billion from 1955 to 1959. Bioenergetics modeling using data for
the same time period estimated menhaden comprised 77% of the Bay’s ages
3-6 striped bass diet (Griffin 2001). Forage size menhaden declined to an average
of 544 billion fish during 1990-1992 and according to Hartman and Brandt’s
bioenergetics modeling data, they comprised 65% of the Bay’s ages 3-6
striped bass diet. Forage size menhaden declined to an average of 233 billion
fish from 1998 to 2001. Overton’s bioenergetics modeling study reported
that menhaden comprised 21% of the Bay’s ages 3-6 striped bass diet during
1998 to 2001. The Atlantic coast population of forage size menhaden (ages 0-2)
declined to 158 billion fish in 2000, 80% less than from 1955-1959, according
to population estimates by the National Marine Fisheries Service (NMFS). Increased
predation and overfishing by the purse seine fishery contributed to the decline
of the Atlantic menhaden population in the Bay during the 1990s, causing consumption
by older striped bass in the Bay to shift from menhaden to bay anchovy, blue
crab and alternative prey in an attempt to survive. Bioenergetics modeling studies
completed in 2001 indicate that by the time the Bay’s striped bass reach
age-6, they annually consume 38% less forage and weigh approximately 40% less
than they did from 1955 to 1959.
The ASMFC continues to focus on increasing the striped bass stock without considering
the ecological impact striped bass forage demand has on other species. Atlantic
menhaden are no longer available as an abundant source of forage; Maryland and
Virginia juvenile indices and pound net catch per effort in the Potomac River
and Maryland’s portion of the Bay are at their lowest level on record.
Predation rates on blue crab, the most important fishery for the Bay’s
watermen, have dramatically increased; Overton’s bioenergetics modeling
study reported that blue crab contributed more than 17% to the diet of ages
4-6 striped bass from 1998 to 2001. Blue crab spawning stock abundance also
declined over the past decade, according to Virginia and Maryland trawl surveys;
estimates for 2000 and 2001 are the lowest on record. Also, Overton reported
that age-3 striped bass consumption of bay anchovy increased 500% over the past
decade and at the same time bay anchovy declined to the lowest level on record,
according to finfish surveys conducted by the MD-DNR and Virginia Institute
of Marine Science. Most alarming is that increased predation on bay
anchovy has reduced their total biomass and limited the crucial role they play
in the Bay’s food web.
Under the Atlantic Coastal Fisheries Cooperative Management Act, Virginia and
North Carolina do not comply with the goal and fail to achieve primary objectives
of ASMFC’s Atlantic menhaden FMP, to “protect and maintain…the
forage base” and “the important ecological role Atlantic menhaden
play along the coast”. In 2002 the purse seine (bait) fishery harvest
was approximately 65 million pounds; the purse seine (reduction) fishery harvest
was 382 million pounds, of which 80% were forage size menhaden (ages 0-2). NMFS
landings data verify that age-2 menhaden are being overfished
by the Virginia purse seine fishery in the Chesapeake Bay region of the Atlantic
coast. According to research funded by NOAA, overfishing is defined as “harvesting
at a rate greater than that which will meet the management goal”. During
the past decade the purse seine fishery has annually removed approximately 45%
of the estimated Atlantic coast population of age-2 menhaden with 65% of the
harvest being taken from the Chesapeake Bay region. These findings confirm that
the purse seine fishery continues to significantly deplete age-2 menhaden even
though recent population estimates are more than 50% below 1955-1959 levels.
A bioenergetics modeling study, conducted by Hartman and Brandt from 1990 to
1992, suggests that growth conditions for striped bass are now much less favorable
than they once were in the Chesapeake Bay “…management measures
that permit increased escapement and presumably increased migration of age-1
and older menhaden to the Chesapeake Bay will benefit the production of striped
bass, bluefish and weakfish”. Overton stated: “The consumption of
Atlantic menhaden has declined significantly from 1959 to 2001 concurrent with
a greater dependence on benthic pathways (bottom dwelling organisms) as an energy
source for striped bass. Managers must consider new approaches such as managing
the abundance and health of prey for top predators”.
The NMFS and the ASMFC are making a mistake by attempting to maintain
a declining purse seine (reduction) fishery that targets forage size menhaden
(ages 0-2) while trying to rebuild stocks of predator species that depend on
menhaden as an essential portion of their diet. The striped bass recovery is
at risk because their forage base has collapsed and most of the striped bass
in the Bay suffer from poor nutrition and disease. The ASMFC and NMFS need to
implement management measures to maintain the forage base for coastal predator
species in order to achieve the ecological objectives and goals of their FMPs.
This would help restore the striped bass forage base and the Chesapeake Bay’s
ecosystem, since menhaden play a vital role in top-down control consuming zooplankton
and phytoplankton, the bay’s primary production. The purse seine fishery
should not be allowed to remove excessive numbers of immature menhaden; they
should be directed to target the older age-3 plus menhaden.
Written by James E. Price President
Dec.11th 2003
