1. SEDAR 49 Assessment Review Workshop: Gulf of Mexico ABC Control Rule and DLM Theory in a Nutshell November 1, Jeff Isely, Skyler Sagarese, Matthew Smith
Southeast Fisheries Science Center,
Sustainable Fisheries Division,
Miami, FL

2. Gulf of Mexico ABC Control Rule
Tier 1: A quantitative assessment provides both an estimate of OFL based on MSY or its proxy, and a probability density function of OFL that reflects scientific uncertainty.

3. Gulf of Mexico ABC Control Rule
Tier 2: An assessment exists but does not provide an estimate of MSY or its proxy. Instead, the assessment provides a measure of OFL based on alternative methodology. Additionally, a probability density function can be calculated to estimate scientific uncertainty in the model-derived OFL measure. This density function can be used to approximate the probability of exceeding the OFL, thus providing a buffer between the OFL and ABC.

4. Gulf of Mexico ABC Control Rule
Tier 3: No assessment is available, but landings data exist. The probability of exceeding the OFL in a given year can be approximated from the variance about the mean of recent landings to produce a buffer between the OFL and ABC. Recent historical (reference period) landings are without trend, landings are small relative to stock biomass, or the stock is unlikely to undergo overfishing if future landings are equal to or moderately higher than the mean of recent landings. For stock complexes, the determination of whether a stock complex is in Tier 3a or 3b will be made using all the information available, including stock specific catch trends.

5. Gulf of Mexico ABC Control Rule
Tier 3
Data poor species
Not enough information to conduct a traditional assessment
OFL is based on best scientific information available
Base stock status on expert opinion
Base management on stock status
Landings only
Establish a reference period

6. Gulf of Mexico ABC Control Rule
Tier 3A
Based on expert evaluation of best scientific information available
Assumes:
Recent historical landings (reference period) are without trend
Landings are small relative to stock biomass
Stock is unlikely to undergo overfishing if future landings slightly exceed mean of recent landings
OFL = Mean of reference period landings + 2SD
ABC = Mean + 1SD* * Depending on risk of overfishing

7. Gulf of Mexico ABC Control Rule
Tier 3B
Based on expert evaluation of best scientific information available
Assumes recent historical landings (reference period) may be unsustainable.
OFL = Mean of reference period landings
ABC = % of Mean of reference period landings

11. Data Limited Approach
Catch only
Recent Landing or reference period
No Data Limited Approach
(given GOM ABC Control Rule)
Existing ABC Control Rule

12. Catch plus additional information
Data Limited Approach
Catch plus additional information
Adjust OFL and ABC based on Landings and trends
Specific models in the toolbox consider
CPUE
Annual Mean Length
Annual Mean Age
Life History
Growth

16. Data Limited Approach Catch and Index CPUE Annual Mean Length
Annual Mean Age
Life History

21. Data Limited Model Approach
Compare Recent Index to Reference Index
Adjust OFL and ABC based on index

27. SEDAR49 Approach Catch only
Maintain status quo for Tier3A or Tier3B ABC Control Rule
If Index
Adjust based on Index