Menhaden: Considerations for Resource Management

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Menhaden Considerations for Resource Management

• Findings and views concerning current topics on
  the menhaden fishery
• Dr. John T. Everett

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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)

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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)

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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.

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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.

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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)

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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.

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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!

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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.

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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.

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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.

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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)
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Menhaden Are Food-Limitedthe 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 P0.00003).
• During 1955-1975 each fish weighed 32 more (149
  gm), than for the latest 20 years (112 gm)
  (P0.0002).
• Each fish weighed much more 50 years ago when
  there were few state fishing restrictions
• Even then, they were constrained by food
  availability.

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Menhaden Are Food-Limitedthe 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.

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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.

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And About Those Fish Kills (Speculation)

• 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.

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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)
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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.

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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.

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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.

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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
• more food flows to the competitors
• predators are nutritionally unaffected
• there are fewer hungry menhaden mouths
• nitrogen is removed from the system.

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Menhaden Impact on Oysters

• 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.

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Menhaden Impact on Crabs

• 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.

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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

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• Dr. John T. Everett
• President
• Ocean Associates, Inc.
• 4007 N. Abingdon Street
• Arlington, Virginia USA 22207
• JohnEverett_at_OceanAssoc.com
• On the web at
• http//www.OceanAssoc.com
• http//www.OceansArt.us
• http//www.ClimateChangeFacts.info
• Tel [phone]