Southeast Data, Assessment, and Review SEDAR 41 Stock Assessment Report South Atlantic Gray Triggerfish April 2016 SEDAR 4055 Faber Place Drive, Suite 201 North Charleston, SC 29405 Please cite this document as: SEDAR. 2016. SEDAR 41 – South Atlantic Gray Triggerfish Assessment Report. SEDAR, North Charleston SC. 428 pp. available online at: http://sedarweb.org/sedar-41. Table of Contents Pages of each Section are numbered separately. Section I: Introduction .................................................................................. PDF page 4 Section II: Data Workshop Report ............................................................... PDF page 30 Section III: Assessment Workshop Report .................................................. PDF page 247 Section IV: Research Recommendations ..................................................... PDF page 395 Section V: Review Workshop Report ........................................................ PDF page 400 SEDAR Southeast Data, Assessment, and Review SEDAR 41 South Atlantic Gray Triggerfish SECTION I: Introduction April 2016 SEDAR 4055 Faber Place Drive, Suite 201 North Charleston, SC 29405 April 2016 South Atlantic Gray Triggerfish Executive Summary SEDAR 41 addressed the stock assessments for South Atlantic gray triggerfish and red snapper. The assessments consisted of four in-person workshops, as well as a series of webinars. Two Data Workshops (DW) were held in Charleston, SC, the first August 4-8, 2014 and the second August 4-6, 2015. The SEDAR 41 Assessment Process was conducted through a combination of an in-person workshop, held December 14-17, 2015 in Morehead City, NC, and a series of webinars held from October 2015 to February 2016. The Review Workshop (RW) took place March 15-18, 2016 in North Charleston, SC. The Stock Assessment Report is organized into six sections. Section I is the Introduction which contains a brief description of the SEDAR Process, Assessment, and Management Histories for the species of interest, and the management specifications requested by the Cooperator. Section II is the Data Workshop Report. It documents the discussions and data recommendations from the Data Workshop Panel. Section III is the Assessment Report. This section details the assessment model, as well as documents any changes to the data recommendations that may have occurred after the Data Workshop. Consolidated Research Recommendations from all three stages of the process (data, assessment, and review) can be found in Section IV for easy reference. Section V documents the discussions and findings of the Review Workshop. Finally, Section VI is the Addenda and Post-Review Workshop Documentation which consists of any analyses conducted during or after the RW to address reviewer concerns or requests. It may also contain documentation of the final RW-recommended base model, should it differ from the model put forward in the Assessment Report for review. The final Stock Assessment Report (SAR) for South Atlantic Gray Triggerfish was disseminated to the public in April 2016. The Council’s Scientific and Statistical Committee (SSC) will review the SAR for its stock. The SSCs are tasked with recommending whether assessments represent Best Available Science, whether the results presented in the SARs are useful for providing management advice, and developing fishing level recommendations for the Council. An SSC may request additional analyses be conducted or may use the information provided in the SAR as the basis for their fishing level recommendations (e.g. Overfishing Limit and Acceptable Biological Catch). The South Atlantic Fishery Management Council’s SSC will review the assessment at its May 2016 meeting, followed by the Council receiving that information at its June 2016 meeting. Documentation on SSC recommendations is not part of the SEDAR process and is handled through each Council. During the March 2016 RW, the RW Panel evaluated outputs and results from the Beaufort Assessment Model (BAM), the primary assessment model that implements a statistical catch-at- age framework; and a secondary, surplus-production model (ASPIC) used to help evaluate model uncertainty and provide a comparison of assessment results. Low contrast in Gray Triggerfish landings and indices of abundance caused ASPIC results to be considered non-informative by the RW. An error with the Southeast Reef Fish Survey (SERFS) chevron trap survey age SEDAR 41 SAR Section I 2 Introduction April 2016 South Atlantic Gray Triggerfish composition data used in the base configuration of the BAM model was discovered during the RW. Based on the magnitude of changes to the data, results, and model diagnostics developed from the Assessment Workshop (AW) base model as well as concerns about overfitting the SERFS combined chevron trap and video (CVID) survey, the RW Panel felt that the proposed base model parameterization was inappropriate to provide information on Gray Triggerfish stock status or benchmarks. The RW Panel recommended that further modeling is needed to fit the corrected age data and to resolve the fit to the CVID survey. During the assessment process several data and modeling topics received a lot of discussion. Some of these topics included: • Southeast Region Headboat Survey (SRHS) Data Evaluation : After the 2014 DW, a working paper was submitted questioning the validity of data collected during the early years of the SRHS. The assessment was delayed in order to investigate these potential issues. Prior to the 2015 DW, the SEFSC did a comprehensive evaluation of the SRHS program that indicated no evidence of chronic, widespread misreporting, no evidence of an apparent temporal pattern in potentially misreported data, and minimal spatial patterns in potentially misreported data. • Marine Recreational Information Program (MRIP) Access Point Angler Intercept Survey (APAIS) adjustment: Starting in wave 2 of 2013, the MRIP APAIS implemented a revised sampling design. To address this new survey design change, a Calibration Workshop was held in 2014. The final report recommended an additional calibration for catch estimates and recommended an interim ‘simple ratio’ method using 2013 data. SEDAR 41 was the first time this method was used in a South Atlantic SEDAR assessment. • Ageing : Gray triggerfish dorsal spines are difficult to age and issues pertaining to ageing lead to the cessation of the SEDAR 32 Gray Triggerfish Stock Assessment in August 2013. Additional ageing workshops and webinars were held between the National Marine Fisheries Service Beaufort and South Carolina Department of Natural Resource ageing labs. Prior to the start of SEDAR 41, a decision was made that one lab would read all spine samples due to higher within laboratory reader consistency. The DW Panel also discussed using increments vs. calendar ages. Members of the Assessment Team noted that calendar ages were necessary for a catch at age model, so the DW Panel developed a set of criteria to convert increments to calendar ages. • Natural mortality : Both the DW and AW panels had lengthy discussions about natural mortality. The final recommendation was to use the Charnov et al. (2013) age-varying natural mortality curve scaled to the Then et al. (2015) point estimate for those ages fully recruited to the fishery. SEDAR 41 was the first time the Then et al. (2015) estimator has been used in a South Atlantic SEDAR assessment. • Southeast Reef Fish Survey (SERFS) Chevron Trap and Video Indices – Independence and Selectivity: The AW Panel recommended combining the trap and video indices into one index (CVID) since the data are collected from the same sampling platform (e.g. cameras are mounted on the traps). Age composition data were not available for the SEDAR 41 SAR Section I 3 Introduction April 2016 South Atlantic Gray Triggerfish video index, so the selectivity for the combined CVID index was informed by age composition of gray triggerfish caught in chevron traps. • Use of Fishery Independent (FI) and Fishery Dependent (FD) Indices : The DW Panel recommended a series of FI and FD indices for use in the model. During model development, the AW Panel found there were conflicts between the FI and FD indices. The AW Panel recommended using only the FI index (CVID) in the base run. Sensitivity runs explored the effects of including both the FI and FD indices and only the FD indices. • Stock Recruitment Curve and Steepness: Attempts were made to estimate steepness resulting in a value near its upper bound. Estimates of annual recruitment from the model were on the asymptotic portion of the stock-recruitment curve. The AW Panel decided to assume this asymptote represented an average recruitment by fixing steepness at 0.99, acknowledging this would require using spawning potential ratio (SPR) benchmarks to determine stock status rather than MSY-benchmarks. • Upweighting the CVID Index: The AW Panel recommended upweighting the CVID index by a factor of 6 to ensure a good fit to the index. The RW Panel had concerns that this caused the model to ‘overfit’ the survey. The estimates of abundance at age in the first year of the assessment were the lowest in the assessment time series, despite being relatively early in the exploitation history. The low abundance estimates were produced, in part, by closely fitting to the first year of the CVID survey, which was the lowest in the survey time series. The RW Panel recommended further investigation was needed to resolve the model fit to the CVID survey. • SERFS Revised Chevron Trap Age Compositions: