About this document
This is a prototype of an automatic report that documents how the user specified the operating model and their various justifications.
Introduction
Describe the history and current status of the fishery, including fleets, sectors, vessel types and practices/gear by vessel type, landing ports, economics/markets, whether targeted/bycatch, other stocks caught in the fishery. Arrowtooth Flounder are an important component of the bottom trawl fishery, although they are also encountered by hook and line fisheries, particularly those targeting Pacifc Halibut (Hippoglossus stenolepis). Information cover management areas 3CD (West Coast Vancouver Island), 5AB (Queen Charlotte Sound), 5CD (Hecate Strait), and 5E (West Coast Haida Gwaii). Prior to the introduction of freezer trawlers in the mid-2000s, most of the historical catch of Arrowtooth Flounder is understood to have been discarded at sea. This was largely due to proteolysis. Catch data prior to the introduction of at-sea observers in 1996 were considered too unreliable for inclusion in the assessment due to unknown quantities of discarding at sea. The assessment fits a female only Bayesian age-structured model to catch,survey and age-composition data from the years 1996-2014.Management advice is provided in the form of decision tables. They are managed as a coastwide stock, with a TAC of 15,000t and catch of 10,679t in 2014. there is a information in the short time series of available data to resolve the population scale/ productivity. The magnitude of catch and discards prior to1996 is a major source of uncertainty.
Describe the stock’s ecosystem functions, dependencies, and habitat types. The second largest groundfish TAC in British Columbia after Pacifc Hake(Merluccius productus).
Provide all relevant reference materials, such as assessments, research, and other analysis. Grandin, C. and Forrest, R. 2017. Arrowtooth Flounder (Atheresthes stomias) Stock Assessment for the West Coast of British Columbia. DFO Can. Sci. Advis. Sec. Res. Doc. 2017/025. v + 87 p.
Fishery Characteristics
Longevity
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Answered
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Very short-lived (5 < maximum age < 7)
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Short-lived (7 < maximum age < 10)
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Moderate life span (10 < maximum age < 20)
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Moderately long-lived (20 < maximum age < 40)
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Long-lived (40 < maximum age < 80)
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Very long-lived (80 < maximum age < 160)
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Justification
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The maximum observed age is 25y for females and 20y for males (p2, Grandin and Forrest 2017). Posterior estimates for M is 0.314, so I included the Moderate life span.
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Stock depletion
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Answered
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Crashed (D < 0.05)
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Very depleted (0.05 < D < 0.1)
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Depleted (0.1 < D < 0.15)
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Moderately depleted (0.15 < D < 0.3)
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Healthy (0.3 < D < 0.5)
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Underexploited (0.5 < D)
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Justification
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The credibility interval is broad, reflecting the uncertainty in posterior estimates of B0 (Figure23,Table6). The median posterior projected estimate of 2015 relative biomass is 0.596 (0.367–0.936) (Figure23,Table11).
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Resilence
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Answered
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Not resilient (steepness < 0.3)
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Low resilience (0.3 < steepness < 0.5)
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Moderate resilence (0.5 < steepness < 0.7)
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Resilient (0.7 < steepness < 0.9)
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Very Resilient (0.9 < steepness)
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Justification
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Table 5.Posterior (2.5th percentile, Median, and 97.5th percentile) and MPD from the Reference Case.
Steepness(h) 0.688, 0.874, 0.975, and 0.916. However, Umsy is not estimated correctly (see fig. 9) so I included Low resilience as well.
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Historical effort pattern
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Answered
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Stable
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Two-phase
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Boom-bust
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Gradual increases
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Stable, recent increases
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Stable, recent declines
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Justification
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see fig 22. I couldn’t mimic the relative fishing effort
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Inter-annual variability in historical effort
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Answered
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Not variable (less than 20% inter-annual change (IAC))
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Variable (maximum IAC between 20% to 50%)
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Highly variable (maximum IAC between 50% and 100%)
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Justification
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Model shows low variability in F (see fig. 2). However, authors suggest that the historical catch series need to reconstructed in order to include appropriate uncertainty (p.21).
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Historical fishing efficiency changes
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Answered
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Declining by 2-3% pa (halves every 25-35 years)
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Declining by 1-2% pa (halves every 35-70 years)
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Stable -1% to 1% pa (may halve/double every 70 years)
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Increasing by 1-2% pa (doubles every 35-70 years)
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Increasing by 2-3% pa (doubles every 25-35 years)
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Justification
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Since their introduction, freezer trawlers have taken an increasing proportion of the total Arrowtooth Flounder catch, increasing from 7.0% in 2005 to 65.8% and 79.8% in 2013 and 2014, respectively (p2)
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Future fishing efficiency changes
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Answered
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Declining by 2-3% pa (halves every 25-35 years)
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Declining by 1-2% pa (halves every 35-70 years)
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Stable -1% to 1% pa (may halve/double every 70 years)
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Increasing by 1-2% pa (doubles every 35-70 years)
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Increasing by 2-3% pa (doubles every 25-35 years)
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Justification
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There has also beena recent increasein catch from 2010–2014, which is due tofour freezer trawlers joining the feet. Withtheir ability to freeze the catch a short time after capture, the freezer trawlers have accessed wider markets thanthe smaller shoreside boats (p2)
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Length at maturity
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Answered
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Very small (0.4 < LM < 0.5)
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Small (0.5 < LM < 0.6)
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Moderate (0.6 < LM < 0.7)
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Moderate to large (0.7 < LM < 0.8)
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Large (0.8 < LM < 0.9)
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Justification
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5.6/25 = 0.224 (Age-at-50%-maturity for females /maximum observed age)
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Selectivity of small fish
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Answered
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Very small (0.1 < S < 0.2)
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Small (0.2 < S < 0.4)
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Half asymptotic length (0.4 < S < 0.6)
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Large (0.6 < S < 0.8)
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Very large (0.8 < S < 0.9)
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Justification
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the estimated age-at-50%-harvest in the trawl fishery (median =9.40y) was consistent with the fishery age composition data (Figure3) but that these data may not be representative of ages in the freezer trawl fleet due to lack of age samples.
Authors suggest: 1) selectivity ogive = maturity ogive (Scenario 12); 20 age-at-50%-harvest = 6y (Scenario 13) (p18)
here: 5.6/25 = 0.224 (Age-at-50%-maturity for females /maximum observed age)
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Selectivity of large fish
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Answered
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Asymptotic selectivity (SL = 1)
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Declining selectivity with length (0.75 < SL < 1)
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Dome-shaped selectivity (0.25 < SL < 0.75)
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Strong dome-shaped selectivity (SL < 0.25)
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Justification
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all the selectivities were Asymptotic (see fig 17)
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Discard rate
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Answered
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Low (DR < 1%)
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Low - moderate (1% < DR < 10%)
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Moderate (10% < DR < 30%)
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Moderate - high (30% < DR < 50%)
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High (50% < DR < 70%)
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Justification
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Before 2016 there were no limits on catches or discards of Arrowtooth Flounder. Unfortunately, due to rapid proteolysis of the flesh, the fishery was not profitable and a large drop in catch is evident after 2005 (Figure2) when the test fishery ended abruptly. There has also been a recent increase in catch from 2010–2014, which is due to four freezer trawlers joining the feet. With their ability to freeze the catch a short time after capture, the freezer trawlers have accessed wider markets than the smaller shore side boats (p2).
Since Arrowtooth Flounder were not managed with quotas before1996,there was little incentive for skippers to record discards. Therefore the quantity of discards in the pre-1996 period is highly uncertain
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Post-release mortality rate
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Answered
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Low (PRM < 5%)
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Low - moderate (5% < PRM < 25%)
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Moderate (25% < PRM < 50%)
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Moderate - high (50% < PRM < 75%)
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High (75% < PRM < 95%)
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Almost all die (95% < PRM < 100%)
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Justification
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I need to ask
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Recruitment variability
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Answered
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Very low (less than 20% inter-annual changes (IAC))
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Low (max IAC of between 20% and 60%)
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Moderate (max IAC of between 60% and 120%)
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High (max IAC of between 120% and 180%)
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Very high (max IAC greater than 180%)
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Justification
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process error = 0.8 (p15)
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Size of an existing MPA
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Answered
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None
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Small (A < 5%)
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Small-moderate (5% < A < 10%)
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Moderate (10% < A < 20%)
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Large (20% < A < 30%)
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Very large (30% < A < 40%)
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Huge (40% < A < 50%)
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Justification
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No justification was provided
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Spatial mixing (movement) in/out of existing MPA
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Answered
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Very low (P < 1%)
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Low (1% < P < 5%)
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Moderate (5% < P < 10%)
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High (10% < P < 20%)
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Fully mixed
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Justification
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No justification was provided
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Size of a future potential MPA
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Answered
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None
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Small (A < 5%)
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Small-moderate (5% < A < 10%)
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Moderate (10% < A < 20%)
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Large (20% < A < 30%)
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Very large (30% < A < 40%)
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Huge (40% < A < 50%)
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Justification
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No justification was provided
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Spatial mixing (movement) in/out of future potential MPA
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Answered
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Very low (P < 1%)
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Low (1% < P < 5%)
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Moderate (5% < P < 10%)
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High (10% < P < 20%)
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Fully mixed
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Justification
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No justification was provided
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Initial stock depletion
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Answered
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Very low (0.1 < D1 < 0.15)
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Low (0.15 < D1 < 0.3)
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Moderate (0.3 < D < 0.5)
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High (0.5 < D1)
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Asymptotic unfished levels (D1 = 1)
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Justification
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The magnitude of catch and discards prior to1996 is a major source of uncertainty in this assessment that could provide critical information about the scale and productivity of this stock.
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Management Characteristics
Types of fishery management that are possible
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Answered
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TAC (Total Allowable Catch): a catch limit
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TAE (Total Allowable Effort): an effort limit
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Size limit
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Time-area closures (a marine reserve)
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Justification
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1. Describe what, if any, current management measures are used to constrain catch/effort.
They are managed as a coastwide stock, with a TAC of 15,000t and catch of 10,679t in 2014
2. Describe historical management measures, if any.
Arrowtooth Flounder has been managed on a status-quo basis in recent years, with an annual allocation of 15,000tforthegroundfshtrawl feet since 2006.Before that time, there were no limits on catches or discards of Arrowtooth Flounder.
3. Describe main strengths and weaknesses of current monitoring and enforcement capacity.
Prior to the introduction of freezer trawlers, most of the historical catch of Arrowtooth Flounder is understood to have been discarded at sea in large quantities due to proteolysis of the fesh if catches were not landed and frozen quickly after capture. Prior to the introduction of 100% at-sea observer coverage in theBritish Columbia groundfsh feetin1996, reporting of Arrowtooth Flounder discards in fishery logbooks was voluntary. Since Arrowtooth Flounder were not managedwithquotasbefore1996,there was little incentive for skippers to record discards. Therefore the quantity of discards in the pre-1996 period is highly uncertain
4. Describe and reference any legal/policy requirements for management, monitoring and enforcement.
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TAC offset: consistent overages/underages
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Answered
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Large underages (40% - 70% of recommended)
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Underages (70% - 90% of recommended)
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Slight underages (90% - 100% of recommended)
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Taken exactly (95% - 105% of recommended)
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Slight overages (100% - 110% of recommended)
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Overages (110% - 150% of recommended)
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Large overages (150% - 200% of recommended)
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Justification
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Since 2006, an annual allocation of 15,000t is given to the groundfish trawl fleet. However, Table 1 and Figure 2 show that the TAC is not taken
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