Determining the postârelease mortality rate and best capture and ...
Determining the post‐release mortality rate and best capture and handling methods for haddock discarded in Gulf of Maine recreational fisheries
John Mandelman; Connor Capizzano; Doug Zemeckis; Micah Dean; Bill Hoffman; Nate Ribblett; Hugues Benoît; Nick Buchan; James Sulikowski; Steve Cadrin
Photo credit: Isaac Benaka
Introduction
Background • Team leveraged vast experience in acoustic telemetry, recreational groundfish fisheries, and tactical/analytical methods to investigate discard mortality (DM) • Recently funded studies on cod and cusk in this fishery
Primary Species
Introduction
Recreational Gulf of Maine Groundfish Fishery
For‐Hire Vessels Head/party boats
Charter boats
Atlantic cod (Gadus morhua)
Haddock (Melanogrammus aeglefinus)
Private Vessels Pollock (Pollachius virens)
Introduction
Gulf of Maine Haddock • Recreational haddock catches ranged from 29% to 68% of total annual removals [by weight] over last decade Recreational discards Recreational landings Commercial discards Commercial landings
NEFSC (2014)
Introduction
Recreational fisheries management and discard mortality • Increasing number of groundfish discards in recent years due to shifting management measures • DM assumption influences possession and size limits, among other reg. factors • Assumes 50% DM rate for haddock in recreational fishery • But…NO DIRECTED DISCARD MORTALITY RESEARCH
Introduction
Study objectives
1. Estimate longitudinal haddock DM in Gulf of Maine recreational fishery 2. Establish optimal catch‐ and‐release guidelines for this fishery
Methods
Field protocols • Haddock captured using standardized rod‐and‐reel setups and rigs • Range of angler experience levels employed (n = 75 anglers; 1:1 tackle split in effort/trip)
Methods
Field protocols • All capture‐related variables recorded (i.e. biological, environmental, and technical) • Injury score index applied
2
1 3
4
Methods Study Design 1. Large scale indexing of haddock haddock 2. Telemetry to validate index in subsample 3. Use index to estimate mortality on large scale to develop best capture and handling methods
variables
?
dead alive
Estimate DM
n=156 n=2,442
Subsample
Sample Mortality ???
Fishery‐scale DM estimate
???
Best capture‐and‐ handling methods
???
Methods
April – October 2015
Methods
Discerning live vs. dead haddock: Revised approach • Discriminant function: finds differences between the vertical and horizontal movement of positive and negative control haddock. Positive (i.e. known alive)
n = 13
Negative (i.e. known dead)
n = 3
Methods
Discerning live vs. dead haddock: Revised approach • Discriminant function is applied to post‐release detection intervals for each fish to determine if and when a mortality occurred
Methods
Analytical methods: Survival model development • Assessed covariates (a priori) o Angler experience o Handling time
o Tackle type
o Capture depth
o Temperature difference
o Length class
o Month of capture
o Injury score
o Season
o Fight time
o Total length
• Maximum likelihood and step‐wise forward model selection procedures • Only selected model with lowest AICc score
Methods
Analytical methods: Survival model development
• Season and total length (TL) still influence survival
Methods
Analytical methods: Survival model development • Low sample size of small haddock in the fall Model issues • Cannot predict when fishing mortality ends • Forces lines to be parallel, misjudges large haddock survival
Methods
Analytical methods: Survival model development
Scenario 1 Large haddock (≥ 43.2 cm) Acoustic and traditional tagging data
Scenario 2 All haddock (
John Mandelman; Connor Capizzano; Doug Zemeckis; Micah Dean; Bill Hoffman; Nate Ribblett; Hugues Benoît; Nick Buchan; James Sulikowski; Steve Cadrin
Photo credit: Isaac Benaka
Introduction
Background • Team leveraged vast experience in acoustic telemetry, recreational groundfish fisheries, and tactical/analytical methods to investigate discard mortality (DM) • Recently funded studies on cod and cusk in this fishery
Primary Species
Introduction
Recreational Gulf of Maine Groundfish Fishery
For‐Hire Vessels Head/party boats
Charter boats
Atlantic cod (Gadus morhua)
Haddock (Melanogrammus aeglefinus)
Private Vessels Pollock (Pollachius virens)
Introduction
Gulf of Maine Haddock • Recreational haddock catches ranged from 29% to 68% of total annual removals [by weight] over last decade Recreational discards Recreational landings Commercial discards Commercial landings
NEFSC (2014)
Introduction
Recreational fisheries management and discard mortality • Increasing number of groundfish discards in recent years due to shifting management measures • DM assumption influences possession and size limits, among other reg. factors • Assumes 50% DM rate for haddock in recreational fishery • But…NO DIRECTED DISCARD MORTALITY RESEARCH
Introduction
Study objectives
1. Estimate longitudinal haddock DM in Gulf of Maine recreational fishery 2. Establish optimal catch‐ and‐release guidelines for this fishery
Methods
Field protocols • Haddock captured using standardized rod‐and‐reel setups and rigs • Range of angler experience levels employed (n = 75 anglers; 1:1 tackle split in effort/trip)
Methods
Field protocols • All capture‐related variables recorded (i.e. biological, environmental, and technical) • Injury score index applied
2
1 3
4
Methods Study Design 1. Large scale indexing of haddock haddock 2. Telemetry to validate index in subsample 3. Use index to estimate mortality on large scale to develop best capture and handling methods
variables
?
dead alive
Estimate DM
n=156 n=2,442
Subsample
Sample Mortality ???
Fishery‐scale DM estimate
???
Best capture‐and‐ handling methods
???
Methods
April – October 2015
Methods
Discerning live vs. dead haddock: Revised approach • Discriminant function: finds differences between the vertical and horizontal movement of positive and negative control haddock. Positive (i.e. known alive)
n = 13
Negative (i.e. known dead)
n = 3
Methods
Discerning live vs. dead haddock: Revised approach • Discriminant function is applied to post‐release detection intervals for each fish to determine if and when a mortality occurred
Methods
Analytical methods: Survival model development • Assessed covariates (a priori) o Angler experience o Handling time
o Tackle type
o Capture depth
o Temperature difference
o Length class
o Month of capture
o Injury score
o Season
o Fight time
o Total length
• Maximum likelihood and step‐wise forward model selection procedures • Only selected model with lowest AICc score
Methods
Analytical methods: Survival model development
• Season and total length (TL) still influence survival
Methods
Analytical methods: Survival model development • Low sample size of small haddock in the fall Model issues • Cannot predict when fishing mortality ends • Forces lines to be parallel, misjudges large haddock survival
Methods
Analytical methods: Survival model development
Scenario 1 Large haddock (≥ 43.2 cm) Acoustic and traditional tagging data
Scenario 2 All haddock (
