SSC Report to NEFMC
SSC Report to NEFMC
Portsmouth, NH January 31, 2018 Lisa Kerr, SSC Vice‐Chair
Topic
• Atlantic Halibut OFLs & ABCs 2018‐2020
Halibut: Background • During 2015 operational assessment process, the peer review panel rejected the stock assessment for halibut. • NEFMC contracted Dr. Paul Rago to conduct an analysis to develop catch advice in absence of an approved benchmark stock assessment. • Proposed a method that uses catch, discards, and survey information to develop catch advice, called First and Second Derivative (FSD) approach.
Halibut: Background • Simulation testing and comparative analyses were performed to show the stability and characterize the uncertainty of the FSD method. • A subcommittee of the SSC reviewed the Halibut Report and concluded: • FSD is the best scientific information available. • Scientifically valid as a basis for catch advice.
Halibut: SSC Deliberations Sources of Uncertainty: • Stock structure and stock identity of Atlantic halibut. • US management area may not be a unit stock. • Selection of appropriate indices. • If resource is shifting in its distribution, stock dynamics estimated using only data from U.S. waters could be incomplete.
Halibut: SSC Deliberations Sources of Uncertainty: • Discard mortality assumptions: • Analysis used gear specific discard mortality estimates. • In some cases (eg. gillnet), data were dated or not specific to halibut in this area. • Prevalence of high‐grading in trawl and gillnet fisheries. • Assumptions impact estimates of removals and can have unaccounted for impacts.
Halibut: SSC Deliberations Sources of Uncertainty: • State harvest assumption • Preliminary Maine 2017 data suggests landings were lower than assumed in PDT’s bridge year estimate • SSC concurred with PDT recommendation to keep the previously set assumption
Halibut: SSC Deliberations Recommendations: • SSC recommends the stock be classified as overfished. • Despite positive trends, overall picture is still that the population is lower than it was historically. • SSC notes that overfishing status is unknown, which aligns with both Dr. Rago’s comments and the PDT advice. • FSD does not allow for a determination of the overfishing status as an OFL cannot be determined using this method.
Halibut: Model Performance First and Second Derivative (FSD) Model Estimates
Halibut: Summary • FSD is the best scientific information available and is scientifically valid as a basis for catch advice. • OFL for Atlantic Halibut is unknown. • ABC for Atlantic Halibut should not exceed 137 mt in 2018 – 2020. • Uncertainty around this catch advice ranges from 121 – 154 mt. (137 mt = median value). • SSC recommended ABC be held constant for specification period.
Halibut: Summary • Existing bridge year assumption should be kept despite indications that 2017 harvest may be lower than projected. • Research recommendations: • Investigating stock structure and how this may impact population dynamics. • Investigating species and gear specific discard mortality to improve the data poor approach for setting catch advice used for this specification setting process.
Questions?
Portsmouth, NH January 31, 2018 Lisa Kerr, SSC Vice‐Chair
Topic
• Atlantic Halibut OFLs & ABCs 2018‐2020
Halibut: Background • During 2015 operational assessment process, the peer review panel rejected the stock assessment for halibut. • NEFMC contracted Dr. Paul Rago to conduct an analysis to develop catch advice in absence of an approved benchmark stock assessment. • Proposed a method that uses catch, discards, and survey information to develop catch advice, called First and Second Derivative (FSD) approach.
Halibut: Background • Simulation testing and comparative analyses were performed to show the stability and characterize the uncertainty of the FSD method. • A subcommittee of the SSC reviewed the Halibut Report and concluded: • FSD is the best scientific information available. • Scientifically valid as a basis for catch advice.
Halibut: SSC Deliberations Sources of Uncertainty: • Stock structure and stock identity of Atlantic halibut. • US management area may not be a unit stock. • Selection of appropriate indices. • If resource is shifting in its distribution, stock dynamics estimated using only data from U.S. waters could be incomplete.
Halibut: SSC Deliberations Sources of Uncertainty: • Discard mortality assumptions: • Analysis used gear specific discard mortality estimates. • In some cases (eg. gillnet), data were dated or not specific to halibut in this area. • Prevalence of high‐grading in trawl and gillnet fisheries. • Assumptions impact estimates of removals and can have unaccounted for impacts.
Halibut: SSC Deliberations Sources of Uncertainty: • State harvest assumption • Preliminary Maine 2017 data suggests landings were lower than assumed in PDT’s bridge year estimate • SSC concurred with PDT recommendation to keep the previously set assumption
Halibut: SSC Deliberations Recommendations: • SSC recommends the stock be classified as overfished. • Despite positive trends, overall picture is still that the population is lower than it was historically. • SSC notes that overfishing status is unknown, which aligns with both Dr. Rago’s comments and the PDT advice. • FSD does not allow for a determination of the overfishing status as an OFL cannot be determined using this method.
Halibut: Model Performance First and Second Derivative (FSD) Model Estimates
Halibut: Summary • FSD is the best scientific information available and is scientifically valid as a basis for catch advice. • OFL for Atlantic Halibut is unknown. • ABC for Atlantic Halibut should not exceed 137 mt in 2018 – 2020. • Uncertainty around this catch advice ranges from 121 – 154 mt. (137 mt = median value). • SSC recommended ABC be held constant for specification period.
Halibut: Summary • Existing bridge year assumption should be kept despite indications that 2017 harvest may be lower than projected. • Research recommendations: • Investigating stock structure and how this may impact population dynamics. • Investigating species and gear specific discard mortality to improve the data poor approach for setting catch advice used for this specification setting process.
Questions?
