Presentation on theme: "Identification, conservation & management of estuarine nurseries for economically important finfish K.L. Heck, Jr. S.P. Powers F. J. Fodrie."— Presentation transcript:
Identification, conservation & management of estuarine nurseries for economically important finfish K.L. Heck, Jr. S.P. Powers F. 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 species that 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 BedsAdults on Offshore Reefs Ontogenetic Shift
Questions Which 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
Age-0 Red Snapper Classification Success using DFA (from Patterson et al. in prep)
Total Area = 3,108 km 2 Sites of Adult Captures—Alabama Artificial Reefs Largest AR program in U.S. LA AL MS FL Area 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
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” RegionGagGrey SnapperLane SnapperSpeckled Trout Chand. Is.8280752 Gulf Is.68436419 Miss. Sound2809323 Perdido Bay41993864 Mobile Delta083047 Pensacola Bay015630 Choctaw. Bay092535 St.Andrew’s Bay22113 St. Joe Bay547131
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)
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
Progress to Date--Beginning the 2006 Library of Otolith Fingerprints for Lutjanus griseus