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Status of Chesapeake Bay forage fish populations
&Investigations of factors
impacting prominent forage fish species
Selected results of a two-year CBSAC funded investigationRobert J. Wood and Edward D. Houde
March 24, 2003
Introduction• Forage fish importance• Multiple regional data sets utilized
ResultsStatus of the stocks
• Atlantic menhaden• Bay anchovy• Atlantic silverside
Factors influencing spatial & temporal patternsAnchovy
• Hydro-climatic influence on spawning migration & distribution• Potential bottom-up control (copepods)• Potential top-down control (ctenophores)
Menhaden• Climate influence on annual recruitment
Future work-implementation of results• Menhaden management• Ecosystem management
forage fishes
phytoplankton
zooplankton
Atlantic silverside
bay anchovy
Ecological importance
piscivorous fishes
Atlantic menhaden
menhaden+anchovy
Comprisea large proportionof the striped bass
diet
Data pertains to 150 - 450mm striped bass
Provided by John Walter & Anthony Overton
Fall Winter
Spring Summer
menhaden Spot
benthicInvertebrates(not crabs)
Str iped Bass Diet by Seasons (150-450mm)
menhaden
menhaden menhaden
Spot
anchovy
anchovy
anchovy
bluecrab
Spot
~ 60% ~ 60%
~ 75% ~ 40%
Fall Winter
Spring Summer
menhaden Spot
benthicInvertebrates(not crabs)
Str iped Bass Diet by Seasons (150-450mm)
menhaden
menhaden menhaden
Spot
anchovy
anchovy
anchovy
bluecrab
Spot
~ 60% ~ 60%
~ 75% ~ 40%
77.0 76.5 76.0 75.5
37.0
37.5
38.0
38.5
39.0
39.5
west longitude
north
latit
ude
Chesapeake Bay
Choptank River
Nanticoke River
United States
Canada
Atlantic Ocean
Potomac River
Rappahannock River
York River
James River
MDNR seineVIMS seineVIMS river trawlPatuxent trawlCalvert CliffsVIMS Bay trawl(random sites)
Fishery independent data sources
•Fishery-independent surveys•MDNR seine•VIMS seine•VIMS benthic trawl•TIES midwater trawl
•EPA/CBP zooplankton
•USGS hydrographic data
•USGS nutrient loading
•Gridded sea level pressure
•NMFS menhaden stock assessment SSB data
inde
x va
lues
1970 1980 1990 2000
-2-1
01
23
4
Potomac River (n=5)
1970 1980 1990 2000
-2-1
01
23
4
Upper Bay (n=4)in
dex
valu
es
1970 1980 1990 2000
-2-1
01
23
4
Choptank River (n=1)
1970 1980 1990 2000
-2-1
01
23
4
Nanticoke River (n=5)
Atlantic Menhaden (MDNR seine)
inde
x va
lues
1980 1985 1990 1995 2000
-1.0
-0.5
0.0
0.5
1.0
James River
inde
x va
lues
1980 1985 1990 1995 2000
-1.0
-0.5
0.0
0.5
1.0
Rappahannock Riverin
dex
valu
es
1980 1985 1990 1995 2000
-1.0
0.0
0.5
1.0
1.5
York River
Atlantic Menhaden (VIMS seine)
1970 1980 1990 2000
-2-1
01
23
4
Upper Bay (n=4)
MDRN seine (for comparison)
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
James River
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
Rappahannock River
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
York River
Atlantic menhaden VIMS trawl (fixed samples)
Year
Rel
ativ
e A
bund
ance
Inde
x
1988 1990 1992 1994 1996 1998 2000
-2-1
01
2
Chesapeake BayVIMS trawl (random samples)
inde
x va
lues
1970 1980 1990 2000
-2-1
01
23
4
Potomac River (n=5)
1970 1980 1990 2000
-2-1
01
23
4
Upper Bay (n=4)in
dex
valu
es
1970 1980 1990 2000
-2-1
01
23
4
Choptank River (n=1)
1970 1980 1990 2000
-2-1
01
23
4
Nanticoke River (n=5)
Bay Anchovy (MDNR seine)
inde
x va
lues
1980 1985 1990 1995 2000
-0.5
0.0
0.5
1.0
James River
inde
x va
lues
1980 1985 1990 1995 2000
-0.4
0.0
0.4
0.8 Rappahannock River
inde
x va
lues
1980 1985 1990 1995 2000
-0.4
0.0
0.4
0.8 York River
Bay Anchovy (VIMS seine)
1970 1980 1990 2000
-2-1
01
23
4
Upper Bay (n=4)MDRN seine (for comparison)
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
James River
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
Rappahannock River
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
York River
Bay Anchovy VIMS trawl (fixed samples)
Year
Rel
ativ
e A
bund
ance
Inde
x
1988 1990 1992 1994 1996 1998 2000
-2-1
01
2
Chesapeake Bay
VIMS trawl (random samples)
Data: Virginia Institute of Marine ScienceTrawl Survey Program, 1996-2000.
Average bay anchovy trawl catch.
circles indicate catch number per 5 minute trawl.
Red
Recruitment in fish is often established in the early life stages (eggs-larvae)
Key
Influence of hydro-climatic factors on spring distribution of pre-spawning bay anchovy
1995
1996
1997
1998
1999
050
000
1000
0015
0000
2000
00
Cub
ic fe
et p
er s
econ
d
Annual average spring (February-May) discharge across the Bay mouth
Latit
ude
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
449
Maximum
1999
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
Northernstorm track
High
Pressure
Dry Spring
Latit
ude
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
397
Maximum
1998
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-77.5 -77.0 -76.5 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
Mid-Atlanticstorm track
High pressure
Wet Spring
March-May weather conditions Spring anchovy distribution
Despite strong spring discharge variability 1995-2000 spring bay anchovy population is distributed around a narrow salinity band 9 and 14 psu (ppt).
Dashed curve is a significant 2nd order polynomial fit for reference (r-square = 0.19)
Salinity
prop
ortio
n of
ann
ual s
prin
g ba
y an
chov
y ca
tch
0 5 10 15 20 25 30
0.0
0.2
0.4
0.6
0.8
95
95
95
9595
9696
96
96 97
97
9797
97
9798
98
98
98
9898 99
9999
99
99
99
00
0000
00
0000
For example, 60% of 1995 bay-wide TIES
anchovy catch found at 14 psu
Bar
nacl
e na
upliu
s
Cla
doce
ran
Cop
epod
ite+a
dult
cope
.
Cop
epod
egg
Cop
epod
nau
pliu
s
Dia
tom
Ost
raco
d
Poly
chae
teju
veni
le
Rot
ifer
Tint
inid
Uni
dent
ified
Uni
dent
ified
egg
0.0
0.05
0.10
0.15
0.20
0.25
Larval anchovy prey occurrence <7mm, n= 46
Food limitation•slow growth->predation•starvation
Source: Auth & Houde
Bar
nacl
e na
upliu
s
Cla
doce
ran
Cop
epod
cop
epod
ite/a
dult
Cop
epod
egg
Cop
epod
nau
pliu
s
Dia
tom
Ost
raco
d
Poly
chae
teju
veni
le
Rot
ifer
Tint
inid
Uni
dent
ified
Uni
dent
ified
egg
0.0
0.05
0.10
0.15
0.20
Larval anchovy prey occurrence 7-11mm, n= 63
Bar
nacl
e na
upliu
s
Cla
doce
ran
Cop
epod
cop
epod
ite/a
dult
Cop
epod
egg
Cop
epod
nau
pliu
s
Dia
tom
Ost
raco
d
Poly
chae
teju
veni
le
Rot
ifer
Tint
inid
Uni
dent
ified
Uni
dent
ified
egg
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Larval anchovy prey occurrence >11mm N= 102
2.5
3.0
3.5
4.0
4.5
1980 1985 1990 1995 2000
2
1
0
1
2
3
2.5
3.0
3.5
4.0
1980 1985 1990 1995 2000
-2-1
01
23Upper Bay Potomac
River
2.5
3.0
3.5
4.0
4.5
1980 1985 1990 1995 2000
-2
-1
0
1
2
1
2
3
4
5
1980 1985 1990 1995 2000
-2
-1
0
1
2 Lower Bay
James River
July Copepod abundance Annual anchovy abundanceA
nnua
l abu
ndan
ceA
nnua
l abu
ndan
ce
Bioenergetic approach
Consumption = Metabolic loss + Waste + Growth
C = Cmax x P-value x f(T)
Cmax= a x (Weight of fish)b
Cmax = max feeding rate standardized to grams of fish (g*g-1*d-1)a = intercept of the weight dependence functionb = weight dependence coefficient
f(T) = water temperature dependence function for warm water fishes
Patterns in anchovy consumption
Larval Anchovy Sampling(tucker trawl)
Source: Jung & Houde-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
1995 7/23 Total Catch = 13187
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
0 15 30
208
0 15 30
875
0 15 30
1057
0 15 30
9670 15 30
790
0 15 300 15 300 15 30
180
0 15 30
335
0 15 30
2004
0 15 30
2916
0 15 30
1121 0 15 30
21
0 15 30
8
0 15 30
540 15 30
393 0 15
435
0 15 30
19
0 15 30
3790 15 30
164
0 15
97
15 30
260 15 30
200
0 15 30
189
0 15 30
80 15 30
45
0 15 30
65
0 15 30
460 15 30
2 2
0 15 30
1
0 15 30
1 0 15 30
5
0 15 30
4
0 15 30
7
0 15 30
5
278269
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
1995 7/23 Total Catch = 13187
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
0 15 30
208
0 15 30
875
0 15 30
1057
0 15 30
9670 15 30
790
0 15 300 15 300 15 30
180
0 15 30
335
0 15 30
2004
0 15 30
2916
0 15 30
1121 0 15 30
21
0 15 30
8
0 15 30
540 15 30
393 0 15
435
0 15 30
19
0 15 30
3790 15 30
164
0 15
97
15 30
260 15 30
200
0 15 30
189
0 15 30
200
0 15 30
189
0 15 30
80 15 30
45
0 15 30
65
0 15 30
460 15 30
2 2
0 15 30
1
0 15 30
1 0 15 30
5
0 15 30
4
0 15 30
7
0 15 30
5
0 15 30
4
0 15 30
7
0 15 30
5
278269
Larval AnchovyConsumption
average = 0.007 g/ m3 x d
Prey densityaverage = 0.03 g/m3
1995 – dry & poor recruitment
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
1995 7/23 Mean Prey surplus = 0.016 g/m^3
0.8
1.2<7mm
Upp
erM
id-B
ayLo
wer
7-11mm
Upp
erM
id-B
ayLo
wer
>11mm
Upp
erM
id-B
ayLo
wer
Growth Rates Larval Size Class
mm
/ da
y
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
-76.6 -76.5 -76.4 -76.3 -76.2 -76.1 -76.0
37.0
37.5
38.0
38.5
39.0
39.5
1998 8/5 Mean Prey surplus = 0.065 g/m^3
0.8
1.2<7mm
Upp
erM
id-B
ayLo
wer
7-11mm
Upp
erM
id-B
ayLo
wer
>11mm
Upp
erM
id-B
ayLo
wer
Growth Rates Larval Size Class
mm
/ da
y
Larval AnchovyConsumption
average = 0.005 g/ m3 x d
Prey densityaverage = 0.08 g/m3
1998 - wet & good recruitment
Predicting October recruitment from July larval abundance and Consumption Surplus
Year
Oct
ober
anc
hovy
abu
ndan
ce
1995 1996 1997 1998 1999
010
020
030
0
Year
Oct
ober
anc
hovy
abu
ndan
ce
1995 1996 1997 1998 1999
010
020
030
0
Variance accounted for = 61%
Oct YOY +July larval abundance
Oct YOY +July larval abundance +July prey surplus
Variance accounted for = 83%
Predict Predictors
Predict Predictors
0
1
2
3
1985 1990 1995 2000 1985 1990 1995 2000
CB2.2CTENOPHORES
CB3.3CCTENOPHORES
CB4.3CCTENOPHORES
CB5.2CTENOPHORES
CB6.1CTENOPHORES
CB6.4CTENOPHORES
Bay-wide Ctenophore trendsImportant predator of larval anchovy and copepods
Cte
noph
ore
Log
Abun
danc
e in
Jul
y
WT5.1CTENOPHORES
1
2
3
0
Data Source: Now defunct Chesapeake Bay Program Zooplankton monitoring program
0
1
2
3
1985 1990 1995 20000
1
2
3
1985 1990 1995 2000 1985 1990 1995 2000
CB2.2CTENOPHORES
CB3.3CCTENOPHORES
CB4.3CCTENOPHORES
CB5.2CTENOPHORES
CB6.1CTENOPHORES
CB6.4CTENOPHORES
Bay-wide Ctenophore trendsImportant predator of larval anchovy and copepods
Cte
noph
ore
Log
Abun
danc
e in
Jul
y
WT5.1CTENOPHORES
1
2
3
0
Data Source: Now defunct Chesapeake Bay Program Zooplankton monitoring program
Predation:
PC1 loadings for site-specific analyses of annual July bay anchovy, Acartia tonsa, and Mnemiopsis leidyi(ctenophore) abundances, and temperature and salinity (integrated over surface-most 3 meters).
Note: for 1985-2000, ctenophore data was collected in Maryland waters only and mainstem bay anchovy abundance is available only for the upper Bay.
anch
ovy
A.to
nsa
cten
oph
surf.
tem
psu
rf.sa
lin
-0.4
0.2
Upper Bay (CB3.3c)
anch
ovy
A.to
nsa
cten
oph
surf.
tem
psu
rf.sa
lin-0.6
0.0
Choptank (ET5.2)
anch
ovy
A.to
nsa
cten
oph
surf.
tem
psu
rf.sa
lin
-0.4
0.2
Potomac (LE2.2)
A.to
nsa
cten
oph
surf.
tem
psu
rf.sa
lin-0.6
0.0
Upper-mid Bay (CB4.3)
A.to
nsa
cten
oph
surf.
tem
psu
rf.sa
lin-0.6
0.2
Mid-Bay (CB5.2)
Multivariate analyses reveal strong trophic patterns related to salinity
Year
PC
1 S
core
1985 1990 1995 2000
-1.0
-0.5
0.0
0.5
1.0
1.5Upper Bay (CB3.3c)Upper-mid Bay (CB4.3c)Mid Bay (CB5.2c)Choptank (ET5.2)Potomac (LE2.2)Lower Bay anchovy abundance
Figure 8. Principle component one associated with the loadings depicted in Figure 7. For comparison, a bay anchovy abundance index is presented for lower Chesapeake Bay (Virginia mainstem).
Year
PC
1 S
core
1985 1990 1995 2000
-1.0
-0.5
0.0
0.5
1.0
1.5Upper Bay (CB3.3c)Upper-mid Bay (CB4.3c)Mid Bay (CB5.2c)Choptank (ET5.2)Potomac (LE2.2)Lower Bay anchovy abundance
Figure 8. Principle component one associated with the loadings depicted in Figure 7. For comparison, a bay anchovy abundance index is presented for lower Chesapeake Bay (Virginia mainstem).
Stage-based bay anchovy stock/flow population model. Graph presents 480 month run with all factors held constant except daily instantaneous larval mortality rates (randomly varied between 0.15 and 0.25.
Stage-specific stock/flow model of theChesapeake Bay anchovy stock
Annual NMFS Menhaden SSB estimates
Rec
ruitm
ent
0 20 40 60 80 100
010
000
2000
030
000
4000
050
000
Annual NMFS Menhaden SSB vs. MDNR YOYRicker SSB-recruitment curve
residual
Ricker-modeled spawning stock biomass (SSB) – recruitment relationship.Residuals assumed to represent variability forced by environmental factors.
Influence of climate on Atlantic menhaden recruitment in Chesapeake Bay
Temporal synoptic indexRealistic characterization of weather patterns
Azores-BermudaHigh
warm subtropical air advected northward
Gulf moisture& storm track
10 m/s
Individual weather variables model (one predictor chosen: March temperature)R
icke
r cur
ve re
sidu
als
65 70 75 80 85 90 95-200
000
3000
0 r-squared = 0.22Menhaden recruitmentmodel fitted recruitment
Synoptic circulation model (one predictor chosen: March frequency/Azores-Bermuda High
Year (19xx)
Ric
ker c
urve
resi
dual
s
65 70 75 80 85 90 95-200
000
2000
0
r-squared = 0.44Menhaden recruitmentModel fitted recruitment
Future work
• Quantify the effect of bay anchovy grazing on the zooplankton population
• Construct a formal menhaden recruitment predictive model and test its utility as a management tool
• Further explore anchovy predator-prey interactions and the effect of climate variability on them
• Incorporate predator and prey abundance information into the bayanchovy population model
• Estimate the effect of observed forage fish population variability on the ecosystem utilizing Ecopath and Ecosim modeling
inde
x va
lues
1970 1980 1990 2000
-2-1
01
23
4
Potomac River
4.0
4.5
5.0
1970 1980 1990 2000
-2-1
01
23
4
Upper Bay River
4.6
4.8
5.0
5.2
Load
ing
(Kg/
Mo)
1970 1980 1990 2000
-2-1
01
23
4
Choptank River
2.0
2.4
2.8
3.2
water year/all months1980 1985 1990 1995 2000
1.0
1.5
2.0
James River
3.2
3.6
4.0
4.4
Load
ing
(Kg/
Mo)
water year/all months
Phosphorus (USGS)Menhaden index
inde
x va
lues
Dashed red lines represent the general trend P loadings modeled by lowess smoothing. F-values varied according to time series length (0.2 used for <20 years, 0.25 for shorter time series). P loadings were based on water years calendar (October-November).
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
James River
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
Rappahannock River
Year
Rel
ativ
e A
bund
ance
Inde
x
1980 1985 1990 1995 2000
-2-1
01
2
York River
Atlantic silverside VIMS trawl (fixed samples)
Year
Rel
ativ
e A
bund
ance
Inde
x
1988 1990 1992 1994 1996 1998 2000
-2-1
01
2
Chesapeake BayVIMS trawl (random samples)
inde
x va
lues
1980 1985 1990 1995 2000
-0.5
0.0
0.5
1.0
James River
inde
x va
lues
1980 1985 1990 1995 2000
-0.5
0.0
0.5
1.0
Rappahannock Riverin
dex
valu
es
1980 1985 1990 1995 2000
-0.5
0.0
0.5
York River
Atlantic Silverside (VIMS seine)
Kane et al., 1998
Rhodes, et al., 2001
Concerns for the general health & condition of …Atlantic menhaden
menhaden lesionsisolated mass mortality events
resident striped bassstriped bass lesions & poor condition
YOY recruitment continues
continued YOYupstream migration
Figure 1a. April average bay anchovy catch map (zero catches excluded) for the VIMS trawl survey, 1996-2000. Open circles indicate catch number per 5 minute trawl. The scale for circles sizes for all plots (1a-i) are consistent and indicated in the upper left. For comparison, the largest catch for each monthly map is also provided. Sampling stations during the period of record are indicated by small closed circles in the lower to middle Bay.
Mortality >> recruitment
Longitude
Latit
ude
3738
3940
3738
3940
-76.2 -76.0 -75.8
3738
3940
1999
=100 bayanchovies
Dry year Bay-wide distribution
stormtrack
Longitude
Latit
ude
3738
3940
3738
3940
3738
3940
=100 bayanchovies
1998
-76.2 -76.0 -75.8
stormtrack
Wet year Bay-wide distribution
inde
x va
lues
1980 1985 1990 1995 2000
0.4
0.8
1.2
1.6
James River
4.4
4.6
4.8
5.0
1980 1985 1990 1995 2000
0.5
1.0
1.5
2.0
Mattaponi River (York river tributary)
2.6
2.8
3.0
3.2
3.4
Load
ing
(Kg/
Mo)
inde
x va
lues
1980 1985 1990 1995 2000
0.5
1.0
1.5
2.0
Pamunkey River (York river tributary)
3.2
3.4
3.6
3.8
Load
ing
(Kg/
Mo)
water year all months
Dashed red lines represent the general trend P loadings modeled by lowess smoothing. F-values varied according to time series length (0.2 used for <20 years, 0.25 for shorter time series). P loadings were based on water years calendar (October-November).
Phosphorus (USGS)Menhaden index
LongitudeLa
titud
e
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
=100 bay anchovies
1999
Dry year Bay-wide distribution
Northern storm track
High
Pressure
LongitudeLa
titud
e
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
=100 bay anchovies
1995
LongitudeLa
titud
e
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
=100 bay anchovies
1997
LongitudeLa
titud
e
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
=100 bay anchovies
1996
LongitudeLa
titud
e
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
-76.5 -76.3 -76.1 -75.9
3738
3940
=100 bay anchovies
1998
Wet year lower bay distribution
Mid-Atlanticstorm track
High Pressure
Early hatched young-of-the-year (YOY)
begin upstream migration
Peak spawning
YOY recruitment
peaks
Enhanced YOYupstream migration
Mortality > recruitment(in the lower Bay)
YOYDistributed
throughout tidal tributaries once
again
Coastal influx ?
Enhanced catchability ?
inde
x va
lues
1970 1980 1990 2000
-2-1
01
23
4
Potomac River (n=5)
1970 1980 1990 2000
-2-1
01
23
4
Upper Bay (n=4)
Atlantic Silverside (MDNR seine)in
dex
valu
es
1980 1985 1990 1995 2000
-0.5
0.0
0.5
1.0
James River
inde
x va
lues
1980 1985 1990 1995 2000
-0.5
0.0
0.5
1.0
Rappahannock River
Atlantic Silverside (VIMS seine)
Annual bay anchovy (open circles) and July Acartia tonsa abundance indices were derived from MDNR & VIMS seine surveys, and CBP zooplankton sampling programs, respectively. Lowess smoothed (f = 0.5) curves plotted for each time series.
1970 1980 1990 2000
-2-1
01
23
Upper Bayp-value = 1.4 x 10 –5 r-squared = 0.75
1980 1985 1990 1995 2000
-2-1
01
2
Rappahannock Riverp-value = 1.2 x 10 -5 r-squared = 0.79
York Riverp-value = 1.1 x 10 -4 r-squared = 0.79
1980 1985 1990 1995 2000
-2-1
01
2
James Riverp-value = 2.4 x 10 -6 r-squared = 0.90
Anchovy abundanceJuly A. tonsa abundance
1980 1985 1990 1995 2000
-2-1
01
2
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