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

This MERA file follows closely the document

The primary reference for this MERA case study is the 2015 stock assessment: Ziegler, P., and Welsford, D. 2015. An integrated stock assessment for the Heard Island and the McDonald Islands Patagonian toothfish (Dissostichus eleginoides) fishery in Division 58.5.2. WG-FSA-15/42. https://www.ccamlr.org/en/wg-fsa-15/52

Referred to as the ‘assessment report’ or ‘assessment’ herein


Fishery Characteristics

Longevity

Answered
Very short-lived (5 < maximum age < 7)
Short-lived (7 < maximum age < 10)
Moderate life span (10 < maximum age < 20)
Moderately long-lived (20 < maximum age < 40)
Long-lived (40 < maximum age < 80)
Very long-lived (80 < maximum age < 160)
Justification
The ‘moderately long lived’ option is a reasonably close match to the range stated in the assessment document 0.155 (Table 7, page 14)

Stock depletion

Answered
Crashed (D < 0.05)
Very depleted (0.05 < D < 0.1)
Depleted (0.1 < D < 0.15)
Moderately depleted (0.15 < D < 0.3)
Healthy (0.3 < D < 0.5)
Underexploited (0.5 < D)
Justification
The stock assessment estimates current spawning stock levels between 50% and 75% of unfished (Figure 14, page 26).

Resilence

Answered
Not resilient (steepness < 0.3)
Low resilience (0.3 < steepness < 0.5)
Moderate resilence (0.5 < steepness < 0.7)
Resilient (0.7 < steepness < 0.9)
Very Resilient (0.9 < steepness)
Justification
Steepness was assumed to be 0.75 (Table 7, page 14)

Historical effort pattern

Answered
Stable
Two-phase
Boom-bust
Gradual increases
Stable, recent increases
Stable, recent declines
Justification
Fishing mortality rate is not explicitly provided in the assessment report but is estimated (catch over vulnerable biomass) to be increasing rapidly in recent years.

Inter-annual variability in historical effort

Answered
Not variable (less than 20% inter-annual change (IAC))
Variable (maximum IAC between 20% to 50%)
Highly variable (maximum IAC between 50% and 100%)
Justification
There appears to be very little variability in fishing mortality rate around the underlying trend.

Historical fishing efficiency changes

Answered
Declining by 2-3% pa (halves every 25-35 years)
Declining by 1-2% pa (halves every 35-70 years)
Stable -1% to 1% pa (may halve/double every 70 years)
Increasing by 1-2% pa (doubles every 35-70 years)
Increasing by 2-3% pa (doubles every 25-35 years)
Justification
Since effort in the previous question was mimicking fishing mortality trends historically, stable catchability is assumed.

Future fishing efficiency changes

Answered
Declining by 2-3% pa (halves every 25-35 years)
Declining by 1-2% pa (halves every 35-70 years)
Stable -1% to 1% pa (may halve/double every 70 years)
Increasing by 1-2% pa (doubles every 35-70 years)
Increasing by 2-3% pa (doubles every 25-35 years)
Justification
Future fishing efficiency is assumed to be stable.

Length at maturity

Answered
Very small (0.4 < LM < 0.5)
Small (0.5 < LM < 0.6)
Moderate (0.6 < LM < 0.7)
Moderate to large (0.7 < LM < 0.8)
Large (0.8 < LM < 0.9)
Justification
The assessment maturity ogive implies 50% maturity at around half of asymptotic length.

Selectivity of small fish

Answered
Very small (0.1 < S < 0.2)
Small (0.2 < S < 0.4)
Half asymptotic length (0.4 < S < 0.6)
Large (0.6 < S < 0.8)
Very large (0.8 < S < 0.9)
Justification
Currently fishing selectivity first captures fish around 1/4 of asymptotic length.

Selectivity of large fish

Answered
Asymptotic selectivity (SL = 1)
Declining selectivity with length (0.75 < SL < 1)
Dome-shaped selectivity (0.25 < SL < 0.75)
Strong dome-shaped selectivity (SL < 0.25)
Justification
Selectivity is assumed to be dome-shaped with decreasing selectivity of larger individuals

Discard rate

Answered
Low (DR < 1%)
Low - moderate (1% < DR < 10%)
Moderate (10% < DR < 30%)
Moderate - high (30% < DR < 50%)
High (50% < DR < 70%)
Justification
Discarding is assumed to be very low.

Post-release mortality rate

Answered
Low (PRM < 5%)
Low - moderate (5% < PRM < 25%)
Moderate (25% < PRM < 50%)
Moderate - high (50% < PRM < 75%)
High (75% < PRM < 95%)
Almost all die (95% < PRM < 100%)
Justification
Inconsequential given the previous question, however discarding rate is thought to be high for most gears.

Recruitment variability

Answered
Very low (less than 20% inter-annual changes (IAC))
Low (max IAC of between 20% and 60%)
Moderate (max IAC of between 60% and 120%)
High (max IAC of between 120% and 180%)
Very high (max IAC greater than 180%)
Justification
Year class strength rarely varied more than 60% according to the assessment (Figure 10, page 23)

Size of an existing MPA

Answered
None
Small (A < 5%)
Small-moderate (5% < A < 10%)
Moderate (10% < A < 20%)
Large (20% < A < 30%)
Very large (30% < A < 40%)
Huge (40% < A < 50%)
Justification
No closures currently.

Spatial mixing (movement) in/out of existing MPA

Answered
Very low (P < 1%)
Low (1% < P < 5%)
Moderate (5% < P < 10%)
High (10% < P < 20%)
Fully mixed
Justification
Inconsequential given previous question.

Size of a future potential MPA

Answered
None
Small (A < 5%)
Small-moderate (5% < A < 10%)
Moderate (10% < A < 20%)
Large (20% < A < 30%)
Very large (30% < A < 40%)
Huge (40% < A < 50%)
Justification
A hypothetical 10-20% future MPA is considered.

Spatial mixing (movement) in/out of future potential MPA

Answered
Very low (P < 1%)
Low (1% < P < 5%)
Moderate (5% < P < 10%)
High (10% < P < 20%)
Fully mixed
Justification
Mixing is assume to be unknown.

Initial stock depletion

Answered
Very low (0.1 < D1 < 0.15)
Low (0.15 < D1 < 0.3)
Moderate (0.3 < D < 0.5)
High (0.5 < D1)
Asymptotic unfished levels (D1 = 1)
Justification
The assessment assumes the stock is ‘unfished’ in the first historical year.


Management Characteristics

Types of fishery management that are possible

Answered
TAC (Total Allowable Catch): a catch limit
TAE (Total Allowable Effort): an effort limit
Size limit
Time-area closures (a marine reserve)
Justification
1. Describe what, if any, current management measures are used to constrain catch/effort.

TAC control is the current approach.

2. Describe historical management measures, if any.

Coming soon!

3. Describe main strengths and weaknesses of current monitoring and enforcement capacity.

Coming soon!

4. Describe and reference any legal/policy requirements for management, monitoring and enforcement.

Coming soon!


TAC offset: consistent overages/underages

Answered
Large underages (40% - 70% of recommended)
Underages (70% - 90% of recommended)
Slight underages (90% - 100% of recommended)
Taken exactly (95% - 105% of recommended)
Slight overages (100% - 110% of recommended)
Overages (110% - 150% of recommended)
Large overages (150% - 200% of recommended)
Justification
I assume that enforcement is relatively good and TACs are taken exactly.


TAC implementation variability

Answered
Constant (V < 1%)
Not variable (1% < V < 5%)
Low variability (5% < V < 10%)
Variable (10% < V < 20%)
Highly variable (20% < V < 40%)
Justification
I assume that enforcement is relatively good and TACs are taken exactly.


TAE offset: consistent overages/underages

Answered
Large underages (40% - 70% of recommended)
Underages (70% - 90% of recommended)
Slight underages (90% - 100% of recommended)
Taken exactly (95% - 105% of recommended)
Slight overages (100% - 110% of recommended)
Overages (110% - 150% of recommended)
Large overages (150% - 200% of recommended)
Justification
For hypothetical TAE management I assume similar quality to TAC control.


TAE implementation variability

Answered
Constant (V < 1%)
Not variable (1% < V < 5%)
Low variability (5% < V < 10%)
Variable (10% < V < 20%)
Highly variable (20% < V < 40%)
Justification
For hypothetical TAE management I assume similar quality to TAC control.


Size limit offset: consistent overages/underages

Answered
Much smaller (40% - 70% of recommended)
Smaller (70% - 90% of recommended)
Slightly smaller (90% - 100% of recommended)
Taken exactly (95% - 105% of recommended)
Slightly larger (100% - 110% of recommended)
Larger (110% - 150% of recommended)
Much larger (150% - 200% of recommended)
Justification
For hypothetical minimum size limit management I assume similar quality to TAC control.


Size limit implementation variability

Answered
Constant (V < 1%)
Not variable (1% < V < 5%)
Low variability (5% < V < 10%)
Variable (10% < V < 20%)
Highly variable (20% < V < 40%)
Justification
For hypothetical minimum size limit management I assume similar quality to TAC control.


Data Characteristics

Available data types

Answered
Historical annual catches (from unfished)
Recent annual catches (at least 5 recent years)
Historical relative abundance index (from unfished)
Recent relative abundance index (at least 5 recent years)
Fishing effort
Size composition (length samples)
Age composition (age samples)
Growth (growth parameters)
Absolute biomass survey
Justification
1. Provide the time series (specify years, if possible) that exist for catch, effort, and CPUE/abundance indices.

The assessment makes use of a wide range of fishery data. Given the assessment a calibrated index estimate of Absolute biomass is also available.

2. Describe how these data collected (e.g., log books, dealer reporting, observers).

3. Describe what types of sampling programs and methodologies exist for data collection, including the time-series of available sampling data and quality.

4. Describe all sources of uncertainty in the status, biology, life history and data sources of the fishery. Include links to documentation, reports.


Catch reporting bias

Answered
Strong under-reporting (30% - 50%)
Under-reporting (10% - 30%)
Slight under-reporting (0% - 10%)
Reported accurately (+/- 5%)
Slight over-reporting (less than 10%)
Justification
There is some history of IUU but it is not substantial compared with the reported catches.


Hyperstability in indices

Answered
Strong hyperdepletion (2 < Beta < 3)
Hyperdepletion (1.25 < Beta < 2)
Proportional (0.8 < Beta < 1.25)
Hyperstability (0.5 < Beta < 0.8)
Strong hyperstability (0.33 < Beta < 0.5)
Justification
The possibility for hyperstability in the fishery dependent indices is included.


Available data types

Answered
Perfect
Good (accurate and precise)
Data moderate (some what inaccurate and imprecise)
Data poor (inaccurate and imprecise)
Justification
Overall the data are considered of very good quality.


Version Notes

The package is subject to ongoing testing. If you find a bug or a problem please send a report to so that it can be fixed!




tcar_-2019-11-26-10:25:40

Open Source, GPL-2 2019