Rusty Swafford

1
Biological Design Considerations for Beneficial
Use Marshes
Rusty Swafford NOAA/ National Marine Fisheries
Service Habitat Conservation Division
2
Shrimp Production in the Gulf of Mexico is
Dependent upon Wetlands
3
Salt Marsh Value inAnnual Shrimp
Production(based on brown shrimp model in marsh
with 50 vegetated edge and 50 open water)




1,307 / ac (at 2/lb)
Assuming similar values for white shrimp
4

• Creation of habitats through beneficial uses
  should not be conducted in an information vacuum.
• Understanding how habitats function for living
  marine resources and how to re-create these
  functions is critical.

5
Wetland Sampling Methods
6
Estimating Nekton Population Sizes in Gulf Coast
Wetlands a Landscape Perspective
1
0.8
Standardized Density
0.6
0.4
0.2
0
10
5
3
1
1
5
25
50
15
Edge
Distance from Marsh Edge (m)
Fine-scale model of brown shrimp densities in
salt marshes
7
The goal of BU habitat creation is to increase
the net productivity of the existing open water
habitat being replaced. In order to achieve
this, the structure and function of habitats
must be considered in the BU design.
8
Spatial patterns of land and water in natural
salt marshes differ from those in many created
marshes
9
Key Research Findings (Minello and Rozas
2002)

• Densities in created marsh 50 less than natural
  marsh
• BU will have negative effects if solid marsh is
  created

10
Key Research Findings (cont.)

• Shrimp and crabs need at least 1 creek/acre or
  equivalent edge area to equal productivity of
  open water
• 6 creeks/acre or equivalent area need to equal
  natural marsh
• Large increases as site goes from 0 to 20-25
  edge/open water
• Increases tend to level off from 25 to 70
  edge/open water
• More than 70 open water populations quickly
  decrease

11
Annual shrimp production 346 lbs/ac 0.32 shrimp
prod./1 const.
Galveston Island State Park Terraces
Constructed at 2150/ac
Jumbile Cove Marsh Islands Constructed at
4808/ac
Annual shrimp production 290 lbs/ac 0.12 shrimp
prod./1 const.
12
BU Design Considerations

• Complexity is critical to biological
  productivity.

• Edge should be a high priority in BU design for
  salt marshes.

13
BU Design Considerations (cont.)

• To increase frequency and duration of flooding on
  the BU site, low marsh elevations should be
  targeted
• Presents an engineering and economic challenge
  from both a functional and maintenance
  standpoint.
• Active management and maintenance is key to a
  successful BU site

14
Example BU Design to Maximize Fisheries Use
15
TAKE HOME MESSAGE
If you want to create a successful BU site, need
to rethink the Pump it, Dump it and Leave it
mentality of the past.