Post on 06-Apr-2022
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
OAC Meeting, June 11, 2018 2
Terms of Reference (TORs)
OAC Meeting, June 11, 2018 3
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
OAC Meeting, June 11, 2018 4
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
OAC Meeting, June 11, 2018 5
Terms of Reference
NOAA Code 129Harvest reporting “NOAA codes”
OAC Meeting, June 11, 2018 7
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
OAC Meeting, June 11, 2018 8
“Depletion” analyses
OAC Meeting, June 11, 2018 9
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)
OAC Meeting, June 11, 2018 13
• 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
OAC Meeting, June 11, 2018 14
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
OAC Meeting, June 11, 2018 15
Terms of Reference (TORs)
OAC Meeting, June 11, 2018 16
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
OAC Meeting, June 11, 2018 17
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