Maryland Oyster Stock Assessment Update

June 11, 2018Annapolis, MD

1OAC Meeting, June 11, 2018

Today’s presentation

• Describe the data and methods we are using to conduct the stock assessment

• Provide an overview of the review process

• Describe the timeline for the completion of the stock assessment

• No results will be presented today because they are not final until after they have been evaluated by the Peer Review Committee

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Terms of Reference (TORs)

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Oyster Assessment Terms of Reference :

1) Complete a thorough data review: survey data, reported harvest and effort data, studies and data related to population rates (growth, mortality and recruitment), available substrate, shell budgets, and sources of mortality.

a) List, review, and evaluate the strengths and weaknesses of all available data sources for completeness and utility for stock assessment analysis, including current and historical fishery-dependent and fishery-independent data.

b) Identify the relevant spatial and temporal application of data sources. c) Document changes in data collection protocols and data quality over time. d) Justify inclusion or elimination of each data source

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Inventory of Available Data

Terms of Reference #1 & 2

We are using data for 1999-present.

(√) indicates primary role in the analysesNo check mark indicates primarily used for qualitative comparison

Input category Data Source

Recruitment Fall dredge survey (√), Hatchery-reared spat (√), Natural seed (√), Patent Tong surveys, Peer reviewed studies

Habitat Bay Bottom Survey (√), Yates Survey, Current sonar surveys, Shell plantings (√), Artificial substrate plantings (√), Peer reviewed studies (√)

Harvest Dealer buy tickets (√), Monthly harvester reports (√), Bushel tax forms

Natural mortality Fall dredge survey (√), Peer reviewed studies, DNR and other analyses (√)

Abundance trends Fall dredge survey (√), Patent Tong surveys

Growth Peer-reviewed studies(√), Fall dredge survey

Catchability Peer-reviewed studies(√), other DNR analyses and studies

2) Develop stock assessment model or index based approach that estimates biological reference points and documents status of the stock relative to estimated reference points. To the extent possible, quantify sources of uncertainty within model.

a. Depletion analyses – Buy ticket datab. Trend analyses – Fall dredge surveyc. Population dynamics stock assessment model

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Terms of Reference

NOAA Code 129Harvest reporting “NOAA codes”

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Index-based approach (Uses survey or fishery data without a complicated model)

• Often used when there is not a lot of data.• Limited information about the population and how it reacts to fishing. • When using an index approach, the goal is to keep some population

measure (e.g. oyster density) within a given range. Fishing harvest rules are loosened or tightened to keep it within range.

• Can be used as a cross-check for model-based approaches.

Model-based approach • Can estimate population size• More complex models can incorporate data from many sources and

allow for exploration of how differing fishing levels may impact the population over time.

• More complex models also allow us to explore how things we are unsure of impact model estimates.

Stock Assessment Background

Stock Assessment Approaches

• Uses reported harvest and effort to estimate the number of oysters alive at the beginning of the harvest season and the fraction that were harvested

• We are using the Buy Ticket data and conducted analyses for each NOAA code and year where enough data were available

• We are using harvest per license per day as our index of abundance and a censored regression to account for the daily harvest limits

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“Depletion” analyses

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Trend analyses using the fall dredge survey

Assessment Model

Spat

Small AdultSmall Box

Market Adult

Harvest

Market Box

Decay

Broad Creek – Live Oyster Model Fits (Damiano 2017)Lo

g In

dex

Year

• Observed —Predicted

Model results: Total abundance of adults (age 1+)For the Choptank and Little Choptank Rivers (Damiano 2017)

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• Biological reference points identify levels of fishing that will maintain the population abundance at a desired level.

• Two types of biological reference points:1. Target reference point defined by managers through the public process

Benchmark that identifies our goal2. Threshold reference point defined by the stock assessment

Benchmark that identifies do not want to be

• Reference points for biomass/abundance and fishing mortality

Stock Assessment Background

What are biological reference points?

• Abundance• Goal – not allow abundance to decrease below the lowest levels

observed• Threshold reference point for market-sized oysters (>3 in)• Set to the minimum abundance estimated during 1999-2018

• Harvest mortality• Goal – maximize sustainable harvest of oysters knowing that shell is an

important resource• Threshold reference point for fraction of market-sized oysters harvested• Estimated as the fraction of market-sized oysters that can be removed

each year that allows for the highest possible long-term harvest

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Reference Points

3) Compare estimates of stock status generated by index and model-based approaches. Justify selected approach.• We are comparing the results of the different approaches and how well

their assumptions are met

4) Include sanctuaries and restoration efforts in sanctuaries in the development of stock assessment approaches. • We are conducting analyses for almost all NOAA codes in Maryland,

including ones with sanctuaries• Repletion and restoration efforts are included in the population dynamics

assessment model (hatchery-reared spat, natural seed, shell plantings, artificial substrate)

5) Examine how hatchery plantings (aquaculture and public fishery) impact spawning potential in fishery.• We hope to compare estimates of abundance from the assessment

models to numbers planted and harvested from aquaculture• Hatchery plantings on public bars are included in the population dynamics

assessment model

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Terms of Reference (TORs)

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Peer Review

Selection of Peer Reviewers• A list of potential reviewers was developed by Dr. Larry Jacobson,

Supervisor of the Invertebrate Task, Population Dynamics Branch, Northeast Fisheries Science Center, NOAA (now retired)

• Reviewers from that list were contacted and asked about their willingness and availability for reviewing the Maryland Oyster Stock Assessment

• Peer reviewers are being contracted through the Atlantic States Marine Fisheries Commission

Peer reviewers• Dr. Paul Rago (Chair) – Former Chief of the Population Dynamics

Branch of the NEFSC (retired)• Dr. Daphne Munroe, Assistant Professor, Haskins Shellfish Laboratory,

Rutgers University• Dr. Dan Hennen, Operations Research Analyst, NEFSC

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Important dates

Peer review – late August, 2018

Presentation of peer review to the OAC – November meeting, 2018

Final Stock Assessment report to Maryland General Assembly – December 1, 2018