Implications of Bycatch, Discards, and Size Limits on Reference Points in the Pacific Halibut Fishery

2015 ◽  
Author(s):  
S Martell ◽  
I Stewart ◽  
J Sullivan
Keyword(s):  
Reference Points ◽  
Pacific Halibut ◽  
The Pacific ◽  
Size Limits

Economic Overfishing

Overfishing ◽  
2012 ◽  
Author(s):  
Ray Hilborn ◽  
Ulrike Hilborn
Keyword(s):  
United States ◽  
Sustainable Management ◽  
The United States ◽  
Pacific Halibut ◽  
The Pacific ◽  
Biological Problem

Is overfishing only a biological problem? The Pacific halibut fishery has long been considered the outstanding success of sustainable management. The International Pacific Halibut Commission was formed in 1923 by the United States and Canada to jointly manage the halibut stock on the Pacific...

Interannual stability from ensemble modelling

2018 ◽  
Vol 75 (12) ◽  
pp. 2109-2113 ◽  
Author(s):  
Ian J. Stewart ◽  
Allan C. Hicks
Keyword(s):  
Stock Assessment ◽  
Base Case ◽  
Single Model ◽  
Sensitivity Testing ◽  
Ensemble Modelling ◽  
Temporal Correlations ◽  
Pacific Halibut ◽  
Simple Simulation ◽  
The Pacific ◽  
Hippoglossus Stenolepis

Ensemble modelling for fisheries analyses is increasing and may improve on single-model approaches through better representation of uncertainty, reduced potential for bias, and greater stability in results. Stability, defined here as deviations from model estimates as each year of data are added, may be due to the use of multiple models (rather than periodic changes to a single base-case model) and from the buffering effect of characterizing the central tendency with a set of models. However, stability against the addition of new data, although logically appealing, has not been explored for fisheries stock assessment. We use the Pacific halibut (Hippoglossus stenolepis) ensemble as an example and provide a simple simulation to explore the general behavior of results from an ensemble of models. Counterintuitively, we found the models in the halibut example showed high temporal correlations among deviations. However, we found that a small number of models with low among-model deviation correlations could show a stability benefit. Among-model deviation correlations may be a useful diagnostic for analysts developing ensembles or for those performing sensitivity testing of single-model assessments.

Age validation of four rockfishes (genera Sebastes and Sebastolobus) with bomb-produced radiocarbon

2020 ◽  
Vol 71 (10) ◽  
pp. 1355
Author(s):  
Craig Kastelle ◽  
Thomas Helser ◽  
Todd TenBrink ◽  
Charles Hutchinson ◽  
Betty Goetz ◽  
...  
Keyword(s):  
Age Determination ◽  
Gulf Of Alaska ◽  
Age Validation ◽  
Pacific Halibut ◽  
The Pacific ◽  
Hippoglossus Stenolepis ◽  
Deep Water Species ◽  
Growth Zones ◽  
Shortspine Thornyhead ◽  
Water Species

In rockfish (Family Scorpaenidae), age determination is difficult and the annual nature of otolith growth zones must be validated independently. We applied routine age determination to four species of Gulf of Alaska rockfish: two shallower-water species, namely harlequin rockfish (Sebastes variegatus) and redstripe rockfish (Sebastes proriger), and two deep-water species, namely shortspine thornyhead (Sebastolobus alascanus) and shortraker rockfish (Sebastes borealis). The estimated ages (counts of presumed annual growth zones in the otoliths) were then evaluated with bomb-produced radiocarbon (14C) and Bayesian modelling with Markov chain Monte Carlo simulations. This study successfully demonstrated the level of accuracy in estimated ages of redstripe rockfish (a 35% probability of underageing, and ~5% probability of overageing) and harlequin rockfish (a 100% probability that they were underaged by ~3 or 4 years). Measured Δ14C in shortspine thornyhead and shortraker rockfish otoliths was lower and increased later than expected. Hence, incorrect age determination could not be evaluated. This is likely caused by dissimilar environmental and biological availability of 14C between these two species and the Pacific halibut (Hippoglossus stenolepis) reference chronology, or underageing of these two species.

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