identification, conservation & management of estuarine nurseries for economically important...
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Identification, conservation &
management of estuarine nurseries for economically
important finfish
K.L. Heck, Jr.S.P. PowersF. J. Fodrie
“One of the greatest long term threats to the viability of commercial and
recreational fisheries is the continuing loss of marine, estuarine, and other
aquatic habitats.” Magnuson-Stevens Act 1996.
Ecosystem Restoration of Nursery Habitats is Difficult
Alligator Point marsh, Galveston Bay
If Function Isn’t Easily Restored: Emphasize Protection
Tidal Creeks & Mud Flats
Seagrass-nGOM Mangrove forests
Coastal Nurseries:Which Ones to
Focus on?
Kelp forests
Oyster reef- nGOM
Salt Marsh-nGOM
Wetlands
Is there a problem with nursery role concept?
Nursery role of certain marine habitats is appreciated by scientists, managers, & public as a general concept.
“Seagrass beds serve as nursery grounds for many speciesthat spend their adult lives in other areas.” Nybakken, 1993.
Main problem: the nursery role concept is too broad to give direct guidance to conservation and management.
Nursery role hypothesis
• “A habitat is a nursery for juveniles of a particular species if its contribution per unit area to the production of individuals that recruit to adult populations is greater, on average, than production from other habitats in which juveniles occur” (Beck et al. 2001, Bioscience).
Growth
Density
Survival
Juvenile Habitat Adult Habitat
Movement
Growth
Density
Survival
Species of Current and Growing Economic Importance for Which We
Will Quantify the Nursery-Role of Gulf of Mexico Seagrass Beds
Targeted Species
Opportunistic Collections
Gray snapper, Lutjanus griseus
Flescher, D.
Gag, Mycteroperca microlepis
Baumeier, E.
Lane snapper, Lutjanus synagris
Ontogenetic Habitat Shifts shown by these species
Juveniles in Seagrass Beds Adults on Offshore Reefs
OntogeneticShift
QuestionsWhich northern Gulf of Mexico seagrass meadows are the sources of recruits to adult populations of gray and lane snapper, and gag, on Alabama reefs?
Do different source seagrass meadows vary in their contribution (i.e., their nursery value) to adult stocks on off-shore reefs?
Human (1993)
Methods: Otolith Chemistry as a Natural Tag of Juvenile Habitat
Trace and minor elements incorporated into otolith structure from water
Metabolically inert once formed
Can be used to discriminate among stocks or as a natural tag of juvenile habitat
=
Approach: Age-0 Fish in 2006 and 2007
Sample juveniles
Multi-element chemical and isotopic analysis of otoliths
LA-ICPMS
20 mm
MS
LA
AL
FL
Gulf of Mexico
AL Art. Reefs
Southwest GulfC
lass
ifica
tion
%
0
20
40
60
80
1996 1997 1998 1999 2000
Age-0 Red Snapper Classification Success using DFA (from Patterson et
al. in prep)North Central Gulf
Cla
ssif
icat
ion
%
0
20
40
60
80
1996 1997 1998 1999 2000
Northwest Gulf
Cla
ssifi
catio
n %
0
20
40
60
80
1996 1997 1998 1999 2000
Total Area = 3,108 km2
Sites of Adult Captures—Alabama Artificial Reefs
Largest AR program in U.S.
LA
ALMS FLArea Shown
Estimated over 20,000 structures deployed
Very high snapper landings per area of shelf
AR Program dates to 1950s
Approach: 2007-08 1 & 2 Year Old Sub-Adult Sampling
Juvenile Region Estimates using DFA(red snapper from Patterson et al. in
prep)AL Adults LA Adults
TX Adults
Progress to Date
2006 Juvenile Surveys
• Summer/Fall 2006 = 297 tows in 9 “regions”
• 5-m otter trawl • Also recorded:
-community composition-depth-temperature-salinity-bottom type
Fall 2006 Fish Collections by “Regions”
Region Gag Grey Snapper Lane Snapper Speckled Trout
Chand. Is. 8 280 75 2
Gulf Is. 6 84 364 19
Miss. Sound 2 80 9 323
Perdido Bay 4 199 38 64
Mobile Delta 0 83 0 47
Pensacola Bay 0 156 30 30
Choctaw. Bay 0 92 53 5
St.Andrew’s Bay 2 21 13 13
St. Joe Bay 5 47 13 1
2006 Otolith Prep and Analyses
• All otoliths dissected and cleaned from specimens collected during fall 2006 (ultimately want ~ 30 otoliths species-1 site-1)
• To date: ca. 195 otoliths mounted and polished
- ca. 95 gray snapper, 75 lane snapper, 38 gag
• To date: 45 otoliths analyzed via LA-ICPMS (all gray snapper, representing all regions considered) - Trace elements: analyses at SIO- Stable isotopes: analyses will be at UA
Beginning the 2006 Library of Otolith Fingerprints for gray
snapper (DFA Results)
-6
-4
-2
0
2
4
6
8
-20 -15 -10 -5 0 5 10
Score 1
Sco
re 2
Chand Is
Ship Is
Horn Is
PB Is
GBS
PAP
Mob Del
B St John
Big Lag
Pen B
SRS
Choc B
SAS
SJB
• There is likely to be variation in nursery quality among seagrass meadows in our 9 “regions”
• We can predict much of this variation and use this information to prioritize habitat conservation and restoration efforts
Implications of our Nursery Habitat Research
Juvenile Distributions and Habitat Utilization
• Product of Density * Area Gives a Measure of “Expected Contribution” from 2006
*Florida Bays Include Big Lagoon, Pensacola Bay Choctawhatchee Bay, St. Andrews Bay and St. Joes Bay
Fish Catch Rates (Relative Densities)
0
10
20
30
40
Chand Is Miss Sound Mobile Bay Perdido Florida Bays
# fis
h pe
r 2-
min
tow
Gray Snapper
Lane Snapper
Gag
Speckled Trout
Segrass Cover, 2003 Estimates (USGS 2004)
0
2000
4000
6000
8000
Chand Is Miss Sound Mobile Bay Perdido Florida Bays
hect
ares
Progress to Date--Beginning the 2006 Library of Otolith
Fingerprints for Lutjanus griseus
-20
-10
0
10
20
-12 -4 4 12
Score 1
Sco
re 2
26MG
55MN
63CU
112CD
Classification Success
Site % CorrectChand Is 100Ship Is 100Horn Is 75PB Is 100GBS 67PAP 100Mob Del 100B St John 75Big Lag 50Pen Bay 100SRS 50Choc Bay 100SAS 50SJB 67TOTAL 80
Fall 2006 GOMHC Fish Collections “Sites”
Site Gag Gray Snapper Lane Snapper Speckled TroutChand Is 8 280 75 2Cat Is 0 0 0 0Ship Is 0 23 82 3Horn Is 4 27 139 16PB Is 2 34 143 0GBS 0 31 9 109Mid Bay 1 2 0 10GB/PAP 1 47 0 204Mob Del 0 83 0 47Lit Lag 0 6 3 11B St John 1 76 6 46Perd B 0 0 0 0Big Lag 3 117 29 7Pen B 0 111 28 1SRS 0 45 2 29Choc 0 92 53 5SAS 2 21 13 13SJB 5 47 13 1
Approach: Age-0 Fish in 2006 and 2007
Sample juveniles
Multi-element chemical analysis of otoliths
SF-ICP-MS
20 mm