Shell/habitat dynamics in oyster restoration and fishery ma - PowerPoint Presentation

Slide1

Shell/habitat dynamics in oyster restoration and fishery management. Supported by the Chesapeake Bay Trust. Award period 1/23/2017-2/28/2018Collaborating investigators:Roger Mann*, Melissa Southworth, Marcia Berman, John Thomas, Tamia Rudnicky (all VIMS), James Wesson (retired, former VMRC), Mitch Tarnowski (MD DNR)

*

Roger Mann,

Virginia Institute of Marine Science

(

rmann@vims.edu

, 804-815-3550(cell))

p

resentation to

Chesapeake Bay Fisheries Goal Implementation Team

March 27, 2017Slide2

Reference points for oyster resource management:how did we get here and why the obsession with shell budgets? Set a goal of No Net Loss of living oysters or shell substrate: these apply to BOTH restoration efforts and fishery

management.

Recruitment (R) and growth dictate addition to the living component.

Natural mortality (M) and fishing mortality (F) dictate loss of oysters.M contributes to the shell substrate, F does not. High mortality rates result in low shell accumulation because contributing oysters are small – low mortality with oysters surviving to larger size contribute much more shell.Shell is lost to burial (B) and biological and chemical degradation (D). Shell loss rates are salinity dependent and independent of supply from mortality.Accreting reefs require equilibrium between shell addition and loss requires sustained recruitment, growth and survival of oysters to large size prior to death.Offsetting inadequate shell supply from natural processes through repletion (r) is NOT a single addition process – it requires continuing addition forever. Single replenishment action to suitable bottom IS NOT restoration. Examine the following shell budget diagrams where addition process are in BLUE and loss processes are in RED.

Mann

- GIT

–

3/27

/2017Slide3

Live oyster population characterized by density and demographicsExposed shell layer (brown shell) – substrate for recruitment Reef structure - buried shell mixed with sediment Recruitment,

R

,

and growth: S/R relationshipFishing mortality, F, with loss of shellNatural mortality, M, including disease adds shell to exposed poolLoss to burial, BLoss to biological degradation and chemical dissolution, D, salinity dependent

Replenishment,

r

D

escription of shell pools and processes.

Addition process , loss processes

Substrate enhances recruitment

Mann - GIT –

3/27/2017Slide4

Consider the following shell budget scenarios in management of both restoration and fisheries: which are stable and which are not, and more so which will accrete and rebuild habitat? Scenario #

1

2

3

4

5

6

Disease

-

+

+

-

+

+

Overfishing

-

-

-

+

-

-

Fishing

-

-

-

-

+

+

Repletion

-

-

+--+Stable?Y? NY? NNY?

Mann - GIT –

3/27/2017Slide5

Live oyster population characterized by density and demographicsExposed shell layer (brown shell) – substrate for recruitment Reef structure - buried shell mixed with sediment Recruitment, R,

and growth:

S/R relationship

Fishing mortality, F, with loss of shellNatural mortality, M, adds shell to exposed poolLoss to burial, BLoss to biological degradation and chemical dissolution, D, salinity dependent Replenishment, r

#1. Natural reef with accretion, no F, no r, shell accretes

As

M>(B+D

),

system stable

over extended periods.

Substrate enhances recruitment

Mann - GIT –

3/27/2017Slide6

Live oyster population characterized by density and demographicsExposed shell layer (brown shell) – substrate for recruitment Reef structure - buried shell mixed with sediment Recruitment, R,

and growth:

S/R relationship

Fishing mortality, F, with loss of shellNatural mortality, M, including disease adds shell to exposed poolLoss to burial, BLoss to biological degradation and chemical dissolution, D, salinity dependent Replenishment, r

#2. Natural reef, no F, no r, but increased M due to disease.

Decreased oyster longevity, lower shell addition rate to

e

xposed layer, no accretion as M<(B+D),

system fails

.

Decreased substrate enhancement

Mann - GIT –

3/27/2017Slide7

Live oyster population characterized by density and demographicsExposed shell layer (brown shell) – substrate for recruitment Reef structure - buried shell mixed with sediment Recruitment, R,

and growth:

S/R relationship

Fishing mortality, F, with loss of shellNatural mortality, M, including disease adds shell to exposed poolLoss to burial, BLoss to biological degradation and chemical dissolution, D, salinity dependent Replenishment, r

#3. Natural reef, no F, increased M

(

disease). Decreased oyster

longevity, lower shell addition rate to exposed layer, offset by

CONTINUAL

replenishment until M=(B+D),

system stable

.

Increased substrate enhancement

This is the reality

o

f sanctuaries!

Mann - GIT –

3/27/2017Slide8

Live oyster population characterized by density and demographicsExposed shell layer (brown shell) – substrate for recruitment Reef structure - buried shell mixed with sediment Recruitment, R,

and growth:

S/R relationship

Fishing mortality, F, with loss of shellNatural mortality, M, adds shell to exposed poolLoss to burial, BLoss to biological degradation and chemical dissolution, D, salinity dependent Replenishment, r

#4. Overfishing, no disease, no r, but F removes shell such

That M<(B+D),

system fails

as substrate disappears.

Decreased substrate enhancement

Mann - GIT –

3/27/2017Slide9

Live oyster population characterized by density and demographicsExposed shell layer (brown shell) – substrate for recruitment Reef structure - buried shell mixed with sediment Recruitment, R,

and growth:

S/R relationship

Fishing mortality, F, with loss of shellNatural mortality, M, including disease adds shell to exposed poolLoss to burial, BLoss to biological degradation and chemical dissolution, D, salinity dependent Replenishment, r

#5. Natural reef, no r, but with fishing, F, and increased M (disease).

Decreased oyster longevity in those not fished, lower shell addition

rate to exposed layer, no accretion as M<(B+D),

system fails

.

Decreased substrate enhancement

Mann - GIT –

3/27/2017Slide10

Live oyster population characterized by density and demographicsExposed shell layer (brown shell) – substrate for recruitment Reef structure - buried shell mixed with sediment Recruitment, R,

and growth:

S/R relationship

Fishing mortality, F, with loss of shellNatural mortality, M, including disease adds shell to exposed poolLoss to burial, BLoss to biological degradation and chemical dissolution, D, salinity dependent Replenishment, r

#6. Natural reef, limited fishing, F, and increased M (disease).

Decreased oyster longevity, lower shell addition rate to exposed layer

balanced by

CONTINUAL

replenishment until M=(B+D),

system stable

.

Continual substrate enhancement

This is the reality

o

f fisheries

!

Mann - GIT –

3/27/2017Slide11

Shell budget scenarios: long term observations in VA.Scenario #

1

2

3

4

5

6

Disease

-

+

+

-

+

+

Overfishing

-

-

-

+

-

-

Fishing

-

-

-

-

+

+

Repletion

-

-

+--+Stable?YNYNNYMann - GIT – 3/27/2017Scenario #6 applies everywhere in VA except a limited number of reefs in James River which

e

xhibit very high recruitment to offset impact of reduced longevity on shell supply. All other

s

ystems have varying levels of shell replenishment to maintain substrate cover. Slide12

Objectives for the current study. Develop salinity dependent shell budgets for tributary – scale restoration sites in Maryland and Virginia under the 2014 Chesapeake Bay Program Agreement and for actively fished and rotational harvest reefs in Maryland and Virginia. Analysis of shell amounts required to maintain sufficient shell and reef habitat based shell budgets derived from deliverable #1.Estimates of future shell resource needs for different areas and/or management types. Develop a report that outlines how to apply this methodology to other areas in the Bay

.

Mann - GIT –

3/27/2017Slide13

Progress since beginning of project (~7 weeks)The MD DNR survey database for monitoring (live oysters plus shell) has been obtained and is being reformatted at VIMS to as near as possible to format of VMS/VMRC monitoring database to facilitate analysis (Thomas, VIMS). VIMS database for survey map coordinates (shape files)are being reformatted to allow item #3 - below. (Southworth, VIMS)Writing of scripts to analyze/condense survey data to provide location dependent time series of live oyster and shell data in common format (Thomas & Mann, VIMS)Items 1 through 3 above are requirements to development of rate budgets for live and shell components of the “graphic budgets” displayed in prior slides –

this activity is planned for April-May period.

We have engaged VIMS CCRM expertise in GIS graphic development to portray all of these results in a parallel presentation format to complex databases (Marcia Berman plus support from Tamia

Rudnicky). This builds on long term collaboration between Mann lab ad CCRM – Google VOSARA for an example. We will build from this template in the project effort. Questions? Mann - GIT – 3/27/2017