Download Going Against the Flow - Non-Conventional Wisdom

Menhaden: Considerations
for Resource Management
Findings and views concerning current topics on the menhaden fishery
Dr. John T. Everett
So the first biological lesson of life is that life is competition. Competition is not only the life of trade,
it is the trade of life — peaceful when food abounds, violent when the mouths outrun the food.
Animals eat one another without qualm. Civilized men consume one another by due process of law.
Will and Ariel Durant, The Lessons of History
Reference
 Supporting citations for this presentation can be found in a paper
prepared for a Congressional hearing.
Everett, John T. May, 2008. Menhaden: Considerations for Resource
Management. Written Statement for U.S. House of Representatives,
Committee on Natural Resources, Subcommittee on Fisheries, Wildlife and
Oceans. Available: http://www.OceanAssoc.com/MenhadenHouse08.pdf
 Cover photo courtesy of William B. Folsom
(http://www.wfolsom.com)
 Purse seine photo with fish courtesy of Omega Protein, Inc.
http://www.omegaproteininc.com/
 Other photos courtesy OceansArt.us
(http://www.OceansArt.us)
Conventional Wisdom?
We, the (92) undersigned marine scientists, call on the National
Marine Fisheries Service to revise its methods and procedures
for setting optimum yield and annual catch limits to preserve
the key role of forage fish species as food for other species in
the marine food web.
Petition (2007) to NMFS to “Conserve Forage Fish Species in U.S.
Waters”
Atlantic menhaden are filter-feeder fish that help maintain the
water quality in the Chesapeake Bay
Maryland DNR Press Release (2005)
Conventional Wisdom?
 Atlantic menhaden help maintain water quality by
feeding on plankton and decaying plants. [They] filter
a volume of water equal to the entire bay in less than
one day.
 Juvenile fish are especially low, which is a key
indicator of a dwindling population.
 Many striped bass in the bay are suffering from
malnutrition and disease, and the declining Atlantic
menhaden population may be a big factor.
Atlantic Menhaden Conservation Act - HR 384. To prohibit
commercial fishing of Atlantic menhaden for reduction purposes in
inland, State, and Federal waters along the Atlantic coast of the United
States, and for other purposes.
Conventional Wisdom?
 Menhaden are filter feeders vital to the health of our Bays and near
shore waters….. they filter up to four gallons a minute. This
process holds in check red and brown tide as well as other algal
blooms. …. But one company, Omega protein …. is annually
catching billions of menhaden and converting them into cheap
industrial commodities, such as pet food, hog feed, and oils used in
paints, linoleum, and lipstick.
 Omega could wipe out this very important fish in a very short
period of time leaving no natural element to deal with algal blooms.
H. Bruce Franklin (2007), John Cotton Dana Professor of English and
American Studies; author of Menhaden: the most important fish in the sea.
Conventional Wisdom?
What is needed? An ecosystem approach to forage fish
management. Currently there is no framework in the U.S.
federal fishery policy to ensure that enough forage fish are
available as food for marine predators. The Network is
promoting the protection of forage fish as a first step towards
an ecosystem approach to fisheries management.
Forage Fish: The Most Important Fish In The Sea. Marine Fish Conservation Network
website (2008)
….the intense harvest of menhaden in the Bay is creating a
localized depletion of the primary forage fish.
Coastal Conservation Association (2006)
Conventional Wisdom?
 When considering predator-prey relationships, it is a key forage
species for many other species in the gulf. Menhaden eggs and
larvae are food for various filter-feeding and larval fishes and
invertebrates including but not limited to themselves, other
clupeids1, chaetognaths2, coelenterates3, mollusks4, and
ctenophores5.
 … the total bycatch in Texas waters from the commercial
menhaden industry is approximately 415,000 organisms per year.
…. The approximate number of red drum and sharks mortalities
associated with the current menhaden harvest is 1,600 and
31,000, respectively.
TPWD 2008 justification for proposed menhaden fishing regs.
(1) herring-like fish; (2) arrowworms; (3) jellyfish and anemones; (4) squid; and (5) jellyfish.
Conventional Wisdom?
 In Summary, we know from NMFS, state, Commission,
Chesapeake Bay Program, and university studies,
assessments, legislation and public writings that
menhaden
 maintain water quality by eating algae;
 young are in short supply, a bad sign;
 are at the base of the food chain;
 low stocks cause disease in striped bass;
 stocks are low; and
 fishing has high bycatch.
NOT!
Menhaden Facts
(These whales are filter feeders too)
 Menhaden can cause poor water quality, not cure it.
 Like most filter feeders, they do not eat many
plants, but specialize in animals.
 They mostly eat the animals that do eat the algae,
excreting them as fertilizer, making more algae.
 They start out with teeth, so they can catch animals.
 They morph into filter feeders as juveniles, and for a
few months can filter small algae and animals, then
morph again to larger algae and animals.
 Schooling allows them to exhaust and catch
copepods and other evasive small animals.
Menhaden Facts - Stock Health
 Abundance is in the range of natural variation
 Menhaden are not overfished and overfishing is not
occurring
 Adults compete with and eat their young
 Abundance is self-regulating when stocks are high
relative to food
 As the Spawning Stock Biomass (SSB) rises, the # of
juveniles falls
 When adults diminish there is more food for the young,
and less predation
 The coastwide index of juveniles shows the first 20
years of data (4.3) and the last 20 (4.3) are the same.
Metric Tons
(000)
SSB and Statewide Juvenile Index
Juv. Index
450.0
7.0
400.0
6.0
350.0
5.0
300.0
250.0
200.0
SSB
Juv. Index
150.0
4.0
3.0
2.0
100.0
50.0
19
55
19
58
19
61
19
64
19
67
19
70
19
73
19
76
19
79
19
82
19
85
19
88
19
91
19
94
19
97
20
00
20
03
0.0
1.0
0.0
Menhaden Facts
 Menhaden are not at the base of the food
chain. They are omnivores, but for most of
their lives they focus on animals.
 Even many of their prey are in the second or
third tier above plants.
 Much is made of the studies that indicate
menhaden can filter all the water in an
estuary every day, or every few days.
 If you are a copepod, or a little fish or oyster
larva, this is not beneficial at all.
Menhaden Facts - The Soup
Consider - all the water filtered every day….
 Menhaden concentrate where the food is; near algae bands because grazers, and the animals that eat them will be there
 With each menhaden in a school swimming at 2 ft./sec., one
copepod jump length apart, each prey quickly tires
 In the soup are the eggs, larvae, and very young of every
creature with a planktonic stage. Think fish, oysters, shrimp,
crabs….Are there enough breeders to overcome predation?
 Before menhaden can filter and when they are most abundant,
they use teeth to catch copepods, eggs, and larvae
 Like their movie cousins, they may also target prey as juveniles
 With grazing pressure removed, well-fertilized algae can
blossom and lead to harmful algal blooms.
Movie: young herring particulate feeding. A juvenile herring attacks four times in a row
(50% timelag). In the third attack the copepod is visible between the wide opened sides of
the mouth. The opercula are spread wide open to compensate for the pressure wave
which would alert the copepod to trigger a jump. (Source: Uwe Kils 1992/Wikipedia)
Menhaden Are Food-Limited
the Data
 GSMFC & ASMFC: menhaden are limited by available food
 Average weight of age 3 fish fell 60% from 1976 to 1978,
through 1984, during high abundance
 Average weight is strongly related to biomass (for age 3;
P=0.00003).
 During 1955-1975 each fish weighed 32% more (149 gm), than
for the latest 20 years (112 gm) (P=0.0002).
 Each fish weighed much more 50 years ago when there were
few state fishing restrictions
 Even then, they were constrained by food availability.
Juvenile Abundance Vs Weight at Age
Grams
600.0
Index
7.0
Weight Age 1
Weight Age 2
Weight Age 3
500.0
6.0
Juv Index
5.0
400.0
4.0
300.0
3.0
200.0
2.0
100.0
1.0
0.0
55
9
1
0.0
65
9
1
75
9
1
85
9
1
95
9
1
05
0
2
Menhaden Are Food-Limited
the Implications
 The data indicate zooplankton are over-harvested
 Being underweight, menhaden are hungry and feeding
 As schooling filter feeders, they out-compete other zooplankton
users
 Algae provides little energy for Age 1 fish; only they can eat it
 Oysters have normal growth, confirming menhaden do not rely
on algae
 Young fish near menhaden are also probably hungry
 Larvae need steady food: high metabolism; little mobility or fat
 Menhaden can create a bottleneck for other species and their
own young to find food
 Poor recruitment is not a sign of trouble if adult stocks are high.
Implications for Water Quality
 Zooplankton are over-harvested, algae are more
abundant; harmful algal blooms are easier
 Increased algae shade submerged plants
 Ammonia-N increases several fold, even miles away
from schools
 Menhaden accumulate significant nitrogen
 Estuary nitrogen increases are linked to reduced fish
removals
 Abundant m
contribute to poor water
quality.
And About Those Fish Kills
(Speculation)
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Fish kills are often blamed on too much algae
Why are filter feeders usually present?
They find and eat zooplankton feeding on algae
The algae grazers are rapidly cleared and excreted as
ammonia; digestion is complete in a few hours
Unconstrained and fertilized, algae bloom, doubling
every few hours, exhaust their nutrients, and die
Decomposition bacteria, doubling every quarter hour,
consume the oxygen and cause the menhaden to die
Whether menhaden in bays, or herring in the Great
Lakes, this is the likely mechanism
More menhaden is not the answer.
Facts: Competition
 Menhaden are food constrained, expanding to
the limit of nutrition as recreational and
commercial fisheries reduce their predators
 Their relative abundance exceeds the
evolutionary history of their ecosystems
 They compete with almost all young fish for
copepods and other zooplankton
 Including their own young
 If they are starving,
so is everything else.
Movie: young herring feeding. Slow-motion macrophotography
video (50%) of juvenile Atlantic herring (38 mm) feeding on
copepods - the fish approach from below and catch each copepod
individually. In the middle of the image a copepod escapes
successfully to the left. (Source: Wikiedia)
Menhaden Facts and a Guess
Can the disease in East Coast striped bass be due to
too few menhaden?
All studies show that menhaden are just part of the diet
of all the predators, usually a minor part
 Menhaden stocks are not overfished and overfishing
is not occurring. In fact they are protected in much of
their range
 Turning to conjecture; 1) the high abundance of
menhaden may be spreading disease through
crowding and 2) their eating of the things that eat the
algae, and excreting them as ammonia, may be
turning estuaries into cesspools, spreading disease.
Facts: Localized Depletion
 There is no science affirming the concept
 Atlantic menhaden is a unitary stock. They move north (spring)
and south (fall) and intermix in winter
 Nicholson: “all menhaden do not return to the same area they
occupied the previous year”
 Local depletion cannot endure with a migratory stock
 It does not matter to predators:
 bay anchovy and other forage are usually more important
 predators are large, mobile and discern prey from afar.
 Opinion: if there were localized depletion, it would be a good
thing. The algae eaters would quickly recover and the oyster and
crab larvae would have a chance to settle. And baby striped bass
would have something to eat.
Menhaden Facts - Bycatch
 Menhaden has about the lowest bycatch of any
fishery, including recreational
 Bycatch varies by area-from none to a few %
 About half is croakers and catfish, with very few
sportfish
 Scientists often classify any non-menhaden as
bycatch, including some jellyfish, and other
clupeids that are reduction targets elsewhere
 ASMFC & GSMFC: Bycatch is not a problem.
Menhaden Facts - Value
 Menhaden have value as forage and as input for
important nutrition, health, and industrial products
 Menhaden have costs as:
 predators of fish and shellfish eggs, and larvae
 major consumers of animals that eat algae
 competitors with all other zooplanktivores, and since their
weight is depressed, food for all is limited.
 When menhaden are harvested:
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more food flows to the competitors
predators are nutritionally unaffected
there are fewer hungry menhaden mouths
nitrogen is removed from the system.
Menhaden Impact on Oysters
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Atlantic menhaden population is within natural variation
MD Ches Bay oysters are at 1% of historic levels
The ratio of menhaden to oysters is up by 100X
Oyster growth rates are unchanged (have food)
Natural mortality rate is up from 10% to 90%
Above are clues menhaden predation on oyster larvae
is too high for the depressed stocks to overcome.
Note: oysters have adequate food, menhaden do not.
This verifies they have different diets: algae vs.
animals.
Menhaden Impact on Crabs
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Atlantic menhaden are within natural variation
MD Ches Bay blue crabs: depressed; poor recruitment
Baby crabs exposure to menhaden lasts weeks
Crabs up to at least Stage 4 (9mm) are vulnerable
Menhaden are skinny; they share the same food
Above are clues menhaden competition with, and
predation on, crab larvae (zoeae) and juveniles is too
high for the depressed stocks to overcome.
 Relationships with other problematic species also bear
scrutiny.
Menhaden Facts - Summary
 Menhaden become filter feeders as juveniles.
This does not mean they then eat plants
 Menhaden are omnivores. If it is the right size,
and they can catch it, it will be eaten
 They turn algae eaters into fertilizer. More
menhaden & clean water are incompatible goals
 The fishery is “clean”, by any bycatch standard
 Menhaden are at ecosystem carrying capacity
 Ecosystem-based management must consider
what “forage fish” eat
 For oysters and crabs, think outside the box
Ocean Associates, Inc.
Ocean Associates, Inc.
4007 N. Abingdon Street
Arlington, Virginia USA 22207
http://www.OceanAssoc.com
Phone:703-534-4032
Fax:815-346-2574
Email:[email protected]
Dr. John T. Everett
President
Ocean Associates, Inc.
4007 N. Abingdon Street
Arlington, Virginia USA 22207
[email protected]
On the web at
http://www.OceanAssoc.com
http://www.OceansArt.us
http://www.ClimateChangeFacts.info
Tel: 703-534-4032