Sources of spatial and temporal variation in...
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Sources of spatial and temporal variation in recruitment Larval production Larval dispersal Settlement Post-settlement Sources of spatial and temporal variation in recruitment Larval production Larval dispersal Settlement Post-settlement 1. How many propagules are produced (spores, eggs, larvae…) Determinants: 1. Reproduction by adults - relatively little work has been done on this - why?? - problem of tracking or identifying source of highly dispersive offspring - poor stock-recruitment relationships - presumed local decoupling (remember, only true if…?) Sources of spatial and temporal variation in recruitment Poor stock-recruitment relationships from fisheries statistics:
Transcript of Sources of spatial and temporal variation in...
Sources of spatial and temporal variation in recruitment
Larval production
Larval dispersal
Settlement
Post-settlement
Sources of spatial and temporal variation in recruitment
Larval production
Larval dispersal
Settlement
Post-settlement
1. How many propagules are produced (spores, eggs, larvae…)
Determinants:
1. Reproduction by adults - relatively little work has been done on this - why??
- problem of tracking or identifying source of highly dispersive offspring
- poor stock-recruitment relationships
- presumed local decoupling
(remember, only true if…?)
Sources of spatial and temporal variation in recruitment
Poor stock-recruitment relationships from fisheries statistics:
importance of local production
to local recruitment
dispersal distance
(=% settlers produced locally)
Importance of local production varies as a function of a species’ average dispersal distance
What determines the number of propagules (larvae) produced by a population?
Example: surfperch populations track benthic productivity
Perch recruitment
Population responses:4 surfperch
species
Benthic productivity
Surfperch production
(Holbrook et al. 1997 Ecological Applications)
Ocean climate change
Population/environmental effects on larval quality
Example 1: Spatial variation in environmental quality(productivity) and larval quality (MacFarlane and Norton 1998, Fishery Bulletin)
0
20
40
60
80
100
protein totallipids
esters triacyl-glycerol
s
cholesterol polarlipids
BodegaPioneerAscension
Larval condition of Sebastes jordani (shortbelly rockfish) among three submarine canyons:
Example 2:
Larvae produced by older females grow faster and survive better
(Steve Berkeley 2004 Ecology; 2004 Fisheries)
black rockfish, Sebastes melanops
similar relationships between larval condition /performance and size of oil globule (=energy stores)
suggests age-based energy allocation by females
Sources of spatial and temporal variation in recruitment
Larval dispersal
Larval production
Larval production
Larval dispersal
Settlement
Post-settlement
?????
Where do the larvae from a particular site go?
Where do the larvae that arrive at a particular site come from?
Propagule Duration (hr)
Indirect estimate: pelagic duration as a proxy for dispersal potential?
Dis
pers
al D
ista
nce
(km
)
Shanks et al. 2003 Ecological Applications
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
0.01 0.1 1 10 100 1000 10000
Predicted by passive dispersal
Propagule Duration (hr)
Dis
pers
al D
ista
nce
(km
)
Shanks et al. 2003 Ecological Applications
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
0.01 0.1 1 10 100 1000 10000
Indirect estimate: pelagic duration as a proxy for dispersal potential?
Propagule Duration (hr)
Dis
pers
al D
ista
nce
(km
)
Shanks et al. 2003 Ecological Applications
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
0.01 0.1 1 10 100 1000 10000
Indirect estimate: pelagic duration as a proxy for dispersal potential?
Propagule Duration (hr)
Dis
pers
al D
ista
nce
(km
)
Shanks et al. 2003 Ecological Applications
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
0.01 0.1 1 10 100 1000 10000
Invertebrates, algaefish
Indirect estimate: pelagic duration as a proxy for dispersal potential?
Western North American Coastal Fish Time in Larval Stagemidpoint (range)
Shanks et al. 2003AVERAGE = 94 days
Time in the larval stage (fish)
Propagule Duration (hr)
Dis
pers
al D
ista
nce
(km
)
Shanks et al. 2003 Ecological Applications
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
0.01 0.1 1 10 100 1000 10000
Indirect estimate: pelagic duration as a proxy for dispersal potential?
Pacific Ocean Reef FishesLarval Duration Estimates
10
20
30
40
50
60
70
< 1 1-7 31-90 > 90Perc
ent
of S
peci
es
Tropical (n= 298 spp)
Temperate (n= 60 spp)
Larval Duration (days) 8-30
Carr and Syms 2006, CA Fishes book
Gen
etic
di
ffer
ence
Geographic distance (kilometers)
Slope tells you something about average dispersal
populations nearby one another
populations further apart
shortlow
long
high
Indirect estimate: genetic differentiation as indication of gene flow/dispersal?
Gen
etic
dif
fere
nce
Dispersal and Genetic differentiation
8000 200 400 600
low
high
Geographic distance (kilometers)
Copper rockfish
CA snails
High dispersal
Rosethorn rockfish
Intermediate dispersal
CA corals
Low
dis
pers
al
Fish: 20-300 kilometers
Palumbi 2003Kinlan and Gaines 2003
Larval dispersalBased on geneticdifferences
Inverts: <1-100 kilometers
Num
ber o
f spe
cies
Different estimates, similar results
Dispersal distance of fish larvae = 20 - 300 km
Time in larval stage Genetic distance
Time as larvae (hr)
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
0.01 0.1 1 10 100 1000 10000
Dis
pers
al d
ista
nce
Dispersal distance of invert larvae = 1 - 100 km
What influences how many of the propagulesproduced reach a given site?
2) Survivalthey can’t get there if they don’t survive
1) Dispersal (advection)what determines patterns of transport
(large and small-scale processes)
3) Depletion (by settlement)fewer available as they settle elsewhere
currents —e.g., California Current
Dispersal (advection) of propagules --what determines patterns of transport?
1. Large-scale (biogeographic) processes
Example: Doyle 1984, Gaines 1997
Gen. Hypothesis: larval supply limits biogeographic ranges
Specific Hypothesis:
Test:
Result:
More evidence for importance of Large-scale (biogeographic) processes:
Example: Cowen 1985 Jour. Mar ResearchTemporal (episodic) variability in current patterns
Normal year (La Nada)
El Nino
General Hypothesis: Change in current patterns influences spatial patterns of sheepheadrecruitment
Normal year (La Nada)
El Nino
General Hypothesis: Change in current patterns influences spatial patterns of sheephead recruitment
Specific Hypothesis: More recruitment in the northern part of the range when there are el Nino currents.
California sheepheadSemicossyphus pulcher
“Protogynous hermaphrodite”
Role of aggressive social interactions with dominant (alpha) male
Conservation story: Catalina versus other Channel Islands
Test: Use annual otolith increments and settlement mark to back-calculate what year individuals settled…
Use this to construct strength of year-class recruitment
Back to sources of variation in larval delivery…
Specific Hypothesis: More recruitment in the northern part of the range when there are el Nino currents.
Example: Cowen 1985 Jour. Mar ResearchTemporal (episodic) variability in current patterns
0 0 0
0ND
ND ND
0ND
10
20
10
20
20
20
10
10
30
40
75 77 79 81 83
Year
San Nicolas Is.
Is. Guadalupe
Cabo Thurloe
Is. San Benito
Result:
A. windward and leeward patterns around islands
Dispersal (advection)--- what determines patterns of transport?
2) Small-scale (localized) processes
- local retention? Implications for “openness” of marine populations
- two cool examples:Swearer et al. 1999 Nature -St. Croix, CaribbeanJones et al. 1999 Nature -Lizard Island, Australia
Pattern: Spatial variation in recruitment of blue head wrasse, Thalassoma bifasciatum, around St. Croix Island
Caselle & Warner, 1996
Mon
thly
rec
ruit
dens
ity
(fis
h/m
2 )
Monthly recruit
density (fish/m2)
0
1.0
2.0
1.5
0.5
N
1.0
2.0
1.5
0.50
5 kmcurrent
windLarval dispersal with
patch depletion?
Larval retention within island wake?
General Hypothesis: Patterns of larval transport (delivery and retention) causes spatial pattern of recruitment
Swearer et al.1999; St. Croix, Caribbean
Sources of chemical signatures in St. Croix:
Christiansted
Cruzan Rum, Hess Oil, Vialco
Salt River Canyon
Groundwater
Specific hypothesis:
New tool in the toolbox: otolith microchemisty(“flight recorders”)
Monthly relative recruitment intensity
Mea
n ca
noni
cal f
acto
r 1
Dis
pers
al
R
eten
tion
Butler Bay (Leeward) Jack's Bay (Windward)
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.5 3.0
Northstar (Leeward)
1.0 2.0 2.5 0.0 1.0 2.00.5 1.51.52.25 3.25
Multivariate measure of relative abundance of elements in otoliths
Result:
Conclusion:
B) Internal waves
Dispersal (advection) what determines patterns of transport?
2. Small-scale (localized) processes
Alan Shanks 1983, MEPS
ONSHORE TRANSPORT
- onshore currents caused by tidal action
- form at interface of salinity, temperature (= density) strata
- occur on 14-day frequency- form surface slicks above trough with
warm water
Shanks sampled larvae as waves passed by and detected concentrations above troughs, identified internal waves as mechanism for onshore transport of larvae!
Example: Norris 1963, Ecological Monographs
Opal eye (Girella nigricans)
Pattern #1: recruitment related to tide pool temperature; warmer = more recruits
General hypothesis:
C) Interaction between larval behavior and physical/oceanographic processes
2. Small-scale (localized) processes
Specific hypothesis:
Opal eye settles in response to warm water cues
Pattern #2: coast-wide, recruitment inversely related to upwelling
General Hypothesis: mechanism of larval delivery: interaction among…
- internal waves- thermal / structural cues- upwelling http://oceanexplorer.noaa.gov
“Structure - schooling”Long larval duration(3 - 4 months)
“Benthic - solitary”Shorter larval duration(1-2 months)
Black-&-yellow rockfish
Gopher rockfish
Kelp rockfish
Black rockfish
Yellowtail rockfish
Olive rockfish
(1998) (1999) (2000)El Nino La Nina La Nada
Mid-water complexLong larval duration(3 - 4 months)
Benthic complexShort larval duration(1-2 months)
Kelp, Black-&-yellow, and Gopher rockfish
Olive, Yellowtail and Black rockfish
1007550250
255075
100
Rel
ativ
e A
bund
ance
1986 1992
1.0
0.5
0.5
1.0
0
Prop
ortio
n
Lenarz et al. 1995 CalCOFI
Carr and Syms 2006
Benthic complexShort larval duration(1-2 months)
Relaxation
(1998) (1999) (2000)
El NiñoLa Niña
La Nada
Fish
per
240
m3
0
4
8
12
16
20 Kelp, Black-&-yellow, and Gopher rockfish
Black-&-yellow rockfish
Gopher rockfish
Kelp rockfish
Mid-water complexLong larval duration(3 - 4 months)
Upwelling
10
30
50
70
(1998) (1999) (2000)
El NiñoLa Niña
La Nada
Fish
per
240
m3
Olive, Yellowtail and Black rockfish
Black rockfish
Olive rockfish
Yellowtail rockfish
Pattern: Interannual variation in rockfish recruitment - midwater vs. benthic species
Num
ber
of f
ish
per
tran
sect Midwater complex
Benthic Complex
0
10
20
30
40
50
60
70
80
1999 2000 2001 2002 2003 2004 2005
Year
-1
0
1
2
3
Cumulativeupwelling
indexanomaly
(thru June)
Pattern also hold for smaller-scale, more frequent events
Arnold Ammann, thesis research at UCSC
SMURFs = “Standardized Monitoring Units for the Recruitment of Fishes”
May June July August
Num
ber o
f fis
hpe
r sam
plin
g un
it Benthic complexn = 363
0.5
0.30.4
0.20.10.0
Mid-water complexn = 227
Num
ber o
f fis
hpe
r sam
plin
g un
it
0.5
0.30.4
0.20.10.0
Tem
pera
ture
(°C
)
May June July AugustYear 2000
9
10
11
12
13
14
Pattern also hold for smaller-scale, more frequent events Pattern: Interannual variation in rockfish recruitment - midwater vs. benthic species
Num
ber
of f
ish
per
tran
sect Midwater complex
Benthic Complex
0
10
20
30
40
50
60
70
80
1999 2000 2001 2002 2003 2004 2005
Year
-1
0
1
2
3
Cumulativeupwelling
indexanomaly
(thru June)
Pattern: following storms there is catastrophic loss of kelpbed area, followed by quick, widespread recruitment and recovery
3 Hypotheses…
HA1– whole plants carried to reef, then release spores
Determinants of larval delivery, continued…
3. Episodic eventse.g. storms (Reed 1988 Ecology)
(but broad-scale, uniform pattern of recruitment inconsistent with pattern predicted by plant swept across reef)
Macrocystis sporophylls at base of plant
Pterygophora
HA3– storms cause propagule transport to distant locations (for kelps)
(but previous work indicated that dispersal was on the order of 1 meter)
b) 3 Hypotheses:
HA2– “seed bank” of dormant spores(but out-plant studies by Reed suggests very short longevity -rapid loss to grazers)
Test:
Current SandKelp 10 m 100 m 1000 m
Results:
calm conditions storms
Settlementof sporeson slides
10 m 100 m 1000 m 10 m 100 m 1000 m
Conclusion: During storms, long range dispersal can occur, spores get mixed, advected up into the water column, transported away
What influences how many of the propagulesproduced reach a given site?
2) Survivalthey can’t get there if they don’t survive
1) Dispersal (advection)what determines patterns of transport
(large and small-scale processes)
3) Depletion (by settlement)fewer available as they settle elsewhere
Determinants of larval delivery, continued…
Larval depletion - ecological filtersPredation Gaines and Roughgarden 1987 Science
Pattern: from year-to-year, recruitment of B. glandula was negatively correlated with kelp abundance offshore
barnaclerecruitment
(no. / cm2 / wk)
kelp canopy area (m2)
General Hypothesis:
Presence of kelp decreases larval supply.
Specific Hypothesis:
Larval abundance should be lower on inside edge of kelp bed thanoutside it
CurrentShore inshore
Kelp offshore
X X
Cyprid larvae - the settlement stage for Barnacles
Results:
No.competent
larvaeper hr
inshore offshore
Confirmed: 70 times greater concentration offshore than inshore!
Nauplius larvae - pre-settlement stage - released by adults
No.competent
larvaeper hr
inshore offshore
Opposite pattern!
Shore nauplii
Kelp
cyprids
Test: sample larval concentrations with plankton pump inshore and offshore of kelp bed
Possible general hypotheses for pattern:
1) simple hydrodynamic effects (of kelp)
water slows down – particles sinkLarvae get entrained in kelp
2) predation by kelp-associated planktivores
Test: looked at distribution of particles that were same size and shape as barnacle larvae but that were not living or edible= molts of larval barnacles!
No.cypridmoltsPer
volume
inshore offshore
Results:
Larval depletion - ecological filtersPredation Gaines and Roughgarden 1987 Science
New general hypothesis: predation by juvenile rockfish filters cyprids
Specific hypothesis: If rockfish are reducing the number of cyprids, there should be a NEGATIVE relationship between abundance of juvenile rockfish (Sebastes) and Balanus glandula recruitment.
Year rockfish density# observed / min
Balanus recruitment #/cm2
kelp bed area
1983 0.7 3.7 8,500 m2
1984 7.2 1.4 33,000 m2
1985 236 0.05 46,500 m2
Larval depletion – ecological filters“recruitment shadow” Gaines et al. 1985 Oecologia
General Hypothesis: as a bath of larvae pass over a site, settlement causes there to be a decrease in the # of larvae available to settlement down current:
Predictions:
Tests:
III III
propagules
1) cyprid concentration should decrease with distance
2) settlement should decrease
2) followed settlement at Hopkins Marine Station at three sites along a unidirectional current
1) counted cyprid concentration (supply) in water column
Larval depletion – ecological filters“recruitment shadow” Gaines et al. 1985 Oecologia
Results:
cypridconcentration
I II III
site
settlementrates
#/cm2/day
I II III
site
Results were consistent with “larval depletion hypothesis”, but other hypotheses not rejected (assumption that change in cyprid # = depletion)
Particularly likely alternative:
hydrodynamic -- difference in cyprid # caused by hydrodynamic reasons(e.g., greater water movement/exchange at site 1 → more water → more cyprids → more settlement)
SUMMARY: Processes affecting larval supply
4. Mortality and Depletioni) predation
ii) hydrodynamic influence of kelp/submerged macrophytes
iii) larval depletion
3. Episodic events - storms
2. Physical oceanographic processesi) large/biogeographic scale processes
ii) intermediate scale processesa) internal waves
b) upwelling
1. Variable productioni) species traitsii) environmental variation (in productivity)
