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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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menhaden considerations for resource management

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
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
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 wisdom4
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 wisdom5
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 wisdom6
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 wisdom7
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 wisdom8
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 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
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.
menhaden facts
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
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
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; 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.
menhaden are food limited the implications
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.
implications for water quality
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
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.
facts competition
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
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
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 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 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.
menhaden impact on oysters
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.

menhaden impact on crabs
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.
menhaden facts summary
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
slide27

Ocean Associates, Inc.

Phone:703-534-4032

Fax:815-346-2574

Email:OceanAssociates@OceanAssoc.com

Ocean Associates, Inc.

4007 N. Abingdon Street

Arlington, Virginia USA 22207

http://www.OceanAssoc.com

Dr. John T. Everett

President

Ocean Associates, Inc.

4007 N. Abingdon Street

Arlington, Virginia USA 22207

JohnEverett@OceanAssoc.com

On the web at

http://www.OceanAssoc.com

http://www.OceansArt.us

http://www.ClimateChangeFacts.info

Tel: 703-534-4032