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Menhaden Muddle Series

By Charlie Hutchinson

The Menhaden Muddle Series is a collection of writings by Charlie Hutchinson, member of the Dorchester County chapter of the MSSA. Charlie began writing a series of articles designed to gain attention and put an end to the devastation of the atlantic menhaden by the reduction fishery. Charlie has published many of these articles and several more in local and state papers. Charlie is MSSA's lead on the menhaden issue and the menhaden muddle series explains the MSSA's position as well as what needs to be done to restore and sustain a healthy menhaden fishery.


Menhaden Muddle #15

CHESAPEAKE BAY ECOLOGICAL FOUNDATION, INC.

MENHADEN DECLINE AFFECTS GROWTH, HEALTH & MIGRATION OF ATLANTIC COAST STRIPED BASS

October 12, 2010

A five year study by the Chesapeake Bay Ecological foundation (CBEF) determined that ecological depletion (insufficient numbers to provide adequate prey for dependent predators) of Atlantic menhaden has affected the growth, health and migration of Atlantic coast striped bass. The CBEF, with assistance from East Carolina University, has examined over 7,000 striped bass from Maryland's section of the Chesapeake Bay (upper Bay) to Oregon Inlet, North Carolina since 2004.

Diminishing striped bass numbers culminated in threatened species status in the upper Bay in 1984 and a fishing moratorium in 1985. In 1990 the fishery reopened coast-wide. Within the upper Bay the 14" minimum size was raised to 18" and a harvest cap imposed for the first time. Within ocean waters the minimum size was set at 28". These actions protected unprecedented numbers of striped bass, dramatically increasing predation on menhaden and bay anchovy. The rapid expansion in numbers of striped bass greater than 18" has sustained the prey demand for all age classes of menhaden at record high levels since the mid 1990's.

During the early 1990's, coincidental with burgeoning striped bass predation on menhaden, adult menhaden were severely overfished off New England concurrent with intensive fishing by the purse seine reduction fishery (large scale harvest of fish for processing into products such as fish oil and meal) on sub-adults (ages 0-2) and adult menhaden (ages 3+) in the Virginia section of the Chesapeake Bay (lower Bay) and in ocean areas from New Jersey to North Carolina. The Omega Protein Corporation currently owns and operates the only remaining menhaden reduction fishery. This fishery, the largest on the Atlantic coast, competes with striped bass, fish eating birds and many marine predators for declining numbers of age-1+ menhaden. The excessive harvest of adult menhaden from New England waters coincided with chronically low reproduction of menhaden and the onset of health problems in Chesapeake Bay striped bass. The age structure of menhaden has been unnaturally skewed toward younger fish and only a remnant population of fish older than age 4 exists even though menhaden can live for more than 10 years.

Responding to mounting concern about the depletion of menhaden in the Chesapeake Bay, the Atlantic States Marine Fisheries Commission (ASMFC), which is responsible for the management of striped bass and menhaden, established (2006) an annual "Bay harvest cap" of 109,020 metric tons on menhaden reduction fishery landings from Virginia Bay waters. This measure has been ineffective in reducing harvest since reduction fishery landings in the lower Bay since 2006 have averaged approximately 30% below the harvest cap.

Data collected by the CBEF study indicates that malnutrition observed in upper Bay striped bass 16" to 24" is a consequence of declining populations of bottom dwelling species and the ecological depletion of bay anchovy and ages 0&1 menhaden. Studies of resident striped bass greater than 16" in Chesapeake Bay waters (year-round) and migratory striped bass greater than 28" in mid-Atlantic and Chesapeake Bay waters (late fall through spring) determined that menhaden constitute over 75% of their diet (by weight). Striped bass are the primary predator on menhaden from late fall through early spring.

Chesapeake Bay tidal waters provide the principal spawning and nursery areas for Atlantic coast striped bass. Historically, the Chesapeake Bay provided an ideal ecosystem for reproduction, survival and growth for high numbers of healthy striped bass. Natural productivity within the Chesapeake Bay has deteriorated over the past two decades due to severe declines in oysters, clams, crabs and populations of small forage fish — primarily bay anchovy and age-0 Atlantic menhaden.

Most striped bass greater than 12" aggregate in the main stem of Maryland's mid-Bay region from late spring through early fall. As a result of menhaden size distribution in the upper Bay during this time period, large numbers of menhaden over 10" are available as prey for striped bass greater than 24": Most menhaden less than 10" inhabit lower salinity regions of the Bay and tributaries and are unavailable to 16" to 24" striped bass inhabiting the Bay's main stem. Consequently, in the main stem of the upper Bay from spring through early fall, striped bass over 24", which can ingest menhaden over 10", have more body fat than striped bass 16" to 24" which must select smaller, less available menhaden. These findings are substantiated by relative body fat levels which averaged approximately three times higher in striped bass greater than 24". From spring through fall, millions of age 1 menhaden (less than 10") are caught annually in the lower Bay and nearby coastal waters by the menhaden purse seine reduction fishery.

The weight of striped bass approximately 14" to 18" caught in the Choptank River varies with annual abundance of age-0 menhaden: During years of low abundance of age-0 menhaden the average weight of striped bass caught during the fall can be less than 70% of their historical weight — a level symptomatic of starvation. Within the Chesapeake Bay, striped bass length-at-age and weight-at-length have decreased, a significant percentage of striped bass have mycobacterial infections and striped bass natural mortality rates have risen.

The study revealed that large numbers of striped bass greater than 28" that historically migrated from summer habitat in New England waters during the fall to feeding grounds in coastal ocean waters off Virginia and North Carolina now arrive in the upper Bay from fall through winter and remain through the spring spawning season — a previously undocumented event. This unprecedented shift in established feeding patterns by migratory striped bass indicates that menhaden are ecologically depleted on their coastal feeding grounds. Consequently, migratory striped bass greater than 28" (80% females) are now competing with resident upper Bay striped bass for over-wintering sub-adult menhaden. Body fat accumulated by adult striped bass is used for gonadal development as post-spawning fat indices are near zero for both male and female striped bass. Sub-adult menhaden are also crucial for rebuilding body fat of resident striped bass 16" to 24" during spring through early summer. This body fat helps striped bass inhabiting the main stem of the upper Bay to maintain their health during summer through early fall when menhaden consumption by striped bass approximately 16" to 24" is greatly reduced and bottom dwelling prey represent most of their diet. Large numbers of striped bass in this size range suffer from malnutrition during summer through early fall.

CBEF studies of striped bass food habits determined that increasing the supply of menhaden less than 10" through harvest restrictions could mitigate nutritional stress on 16" to 24" striped bass. Also, closure of the Exclusive Economic Zone (three to 200 miles off the Atlantic coast) to menhaden harvest could improve spawning stock survival and increase prey availability in coastal waters for migratory striped bass. Optimistically, ASMFC decisions that address menhaden overfishing will eventually resolve the fundamental problem - ecological depletion of Atlantic menhaden.

Previous Menhaden Articles:

Menhaden Muddle #33
AN OPEN LETTER TO THE COMMISSIONERS OF THE MENHADEN BOARD

Menhaden Muddle #32
WHAT'S UP WITH OMEGA PROTEIN?

Menhaden Muddle #31
MORE VIEWPOINTS ON MENHADEN ECONOMICS

Menhaden Muddle #30
THE OUTFALL FROM BEANTOWN

Menhaden Muddle #29
ANOTHER INCONVENIENT TRUTH

Menhaden Muddle #28

Menhaden ALERT

End Overfishing of Menhaden

Menhaden Muddle #27
NEXT MOVES ON MENHADEN

Menhaden Muddle #26
A CRITIQUE...

Menhaden Muddle #25
SOME MANAGEMENT MEASURES FOR CONSIDERATION

Menhaden Muddle #24
ASMFC'S Challenge

Menhaden Muddle #23
ASMFC'S Dilemma

Menhaden Muddle #22

Menhaden Muddle #21

Menhaden Muddle #20

Menhaden Muddle #19

Menhaden Muddle #18

Menhaden Muddle #17

Menhaden Muddle #16
What would Izaak do?

Menhaden Muddle #15

Menhaden Muddle #14

Menhaden Muddle #13
Menhaden Unmuddled?

Menhaden Muddle #12
What's next for Menhaden Management?

Menhaden Muddle #11

Menhaden Muddle #10

Menhaden Muddle #9

Menhaden Muddle #8

Menhaden Muddle #7

Menhaden Muddle #6

Menhaden Muddle #5

Menhaden Muddle #4

Menhaden Muddle #3

Menhaden Muddle #2

Menhaden Muddle #1


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