Improving Fish Stock Assessments (1998)
Chapter: Appendix H
H— Information from Interstate Marine Fisheries Commissions and States
To aid the committee's deliberations, information was requested from the Atlantic, Gulf, and Pacific States Marine Fisheries Commissions. The committee specifically asked the commissions for information about what methods their states use to assess marine fish stocks in state waters (to compare with methods used by National Marine Fisheries Service [NMFS] and the regional fishery management councils). The commissions were also asked to relay their concerns about existing stock assessment methods. This information is shown below; they are the views of the commissions and their staff and do not necessarily coincide with the views of the committee. The response from the Atlantic States Marine Fisheries Commission was received first and was forwarded to the other commissions.
Commission and State Concerns and Comments Regarding Stock Assessments
Atlantic States Marine Fisheries Commission (ASMFC)
- The complexity of many stock assessments models leads to a lack of understanding among those who may not have a scientific background. More effort is needed to provide less technical explanations of stock assessment models and results.
- Discrepancies in model results due to incomplete characterization of input parameters lead to less effective and timely fisheries management, and lack of public confidence in the scientific process and expertise.
- Probability analysis should be included as a part of all stock assessments to provide an indication of the level of achieving management and rebuilding goals.
- Deficiencies in fisheries-dependent data bases limit the effectiveness of many stock assessments; i.e., catch at age, discards.
- Deficiencies in information concerning critical model parameters may limit stock assessments; i.e., fishing and natural mortality, bias in catch data, stock distribution, and life history parameters.
- Harvest regulations may affect input data. For example, the effect of size limits may be to truncate length-frequency data thereby affecting the model results.
- Biases in model results may occur due to equilibrium assumptions; i.e., yield-per-recruit modeling.
TABLE H.1 Stock Assessment Methods Used by the Atlantic States Marine Fisheries Commission
- Lack of information for stock identification may affect appropriateness of stock assessment models applied to various species.
- There is need for fisheries-independent data in stock assessment modeling, particularly as tuning indices for VPA analyses.
- Relatively simple models may overlook important parameters that the model is not robust to; i.e., sensitivity to changes in catchability.
- Little data is available on the functional relations among co-occurring exploited species and effects of fishing on shifts in ecological relations.
- Models used to forecast how management actions will change F do not always take into account economic and social factors.
- The quality of the input data affects the precision of the assessments.
Pacific States Marine Fisheries Commission (PSMFC)
There are fisheries on the West Coast that do not have the basic population data necessary to allow adequate assessment modeling. The thresher shark fishery is one example of a fishery that is being managed very conservatively due to the lack of funding for adequate assessments. We believe it is critical that efforts be initiated to develop the databases necessary to manage these fisheries.
Rockfish are targeted by both commercial and recreational fisheries off the West Coast. There has been concern, coast-wide, regarding the management of nearshore rockfish. These concerns have been discussed on a regional basis by the Canada-U.S. Groundfish Committee. This committee listed the following concerns.
- The lack of biological information and abundance for many nearshore rockfish species
- The generally poor track record of rockfish management coast-wide
TABLE H.2 Stock Assessment Methods Used by the State of Oregon to Manage Its Fisheries
|
Species Name |
Stock Assessment Model |
Comments |
|
Pink shrimp |
No formal assessment. Stock status is monitored using a retrospective, area-based index of recruitment. |
Managed by season and aggregate size limit |
|
Red sea urchin |
No formal assessment. Stock status is monitored using retrospective indices of size distribution and abundance. |
Managed by size limit and limited entry |
|
Dungeness crab |
None |
Managed by season, sex, and size limit |
|
Pacific herring, Yaquina Bay |
No formal assessment. Spawn deposition surveys conducted to establish harvest guidelines. |
Managed by harvest guideline, season, limited entry |
- The notable difficulty in managing nearshore species
- The longevity and vulnerability to over-exploitation associated with these species even when some biological parameters are known
Rockfish are managed by the Councils and the states. Most species occur in fisheries managed by different jurisdictions making it difficult to fully assess the populations and fishery impacts.
Another issue is the lack of total catch information in many fisheries. Landing tickets give managers information on those species landed, but very limited data exist for West Coast fisheries total catch. Regulatory and economic discards are virtual unknowns. We believe an effective observer program is essential for the future health of these fish stocks and their attendant fisheries. A voluntary pilot program funded by the West Coast trawl industry is an important start to gather this data. Two states in the region provided information about the stock assessment methods they use: Oregon (Table H.2) and Alaska (Tables H.3 to H.5).
Alaska Department of Fish and Game (ADF&G)
- Often we fail to recognize that most samples taken for stock assessment are not random samples. Statistical models behind estimates from stock assessment are built with the concept of samples being representative of populations because these samples were randomly drawn. In stock assessment, samples are almost never randomly drawn. More diagnostic testing should be built into stock assessments to determine if our non-randomly drawn samples are, or are not, representative.
- Extrapolation of results from VPA (virtual populations analysis) to manage fisheries in the current year is a poor substitute for annual surveys and mark-recapture experiments. Since these extrapolations reflect past, not current information, results of VPA lag behind actual trends in abundance. Ancillary information from indices such as mean CPUE (catch per unit effort) to compensate adds another layer of assumptions and considerable danger.
- Sampling (handling) fish affects their subsequent behavior in ways that could bias stock assessments based on that behavior. Again, more diagnostics are needed to determine influences of handling.
- The lack of age structures for most shellfish species has thwarted the development of assessment models for years. For the past three years, ADF&G has focused on development of length-based methods for shellfish stock assessments under a range of data situations (e.g., trawl survey, pot survey, no survey). During the next few years ADF&G will continue to apply these methods to various stocks around the state. ADF&G also plans to
TABLE H.3 Methods Used to Assess Alaska Shellfish
|
Species Name/Area |
Stock Assessment Model |
Comments |
|
Red king crab Southeast Alaska |
Catch-survey analysis (CSA) |
For CSA methods, see Collie and Kruse (in press) |
|
Bristol Bay |
Length-based analysis (LBA) |
For LBA methods, see Zheng et al. (1995a,b) |
|
Kodiak Prince William Sound, Cook Inlet, Alaska Peninsula, Pribilof Islands, Norton Sound. |
CSA, trawl survey, area-swept estimator Trawl survey, area-swept estimator |
Plans: LBA |
|
|
Plans: CSA (historical pot surveys) and LBA (ongoing trawl surveys) |
|
|
Adak |
None |
Plans: catch-length analysis (CLA) - see Zheng et al. (1996) for methods |
|
Blue king crab St. Matthew and Pribilof Islands |
Trawl survey, area-swept estimator |
CSA in progress |
|
Prince William Sound |
None |
CPUE index from experimental fishery |
|
Golden king crab Southeast Alaska, Prince William Sound, Dutch Harbor, Adak |
None |
Plans: GIS analysis of fisheries with on-board observer data |
|
Tanner crab Southeast Alaska |
None |
CPUE model used to project attainment of fixed quota |
|
Cook Inlet, Kodiak, Alaska; Peninsula, Bering Sea |
Trawl survey, area-swept estimator |
LBA in progress for Bering Sea, LBA planned for Kodiak |
|
Snow crab; Bering Sea |
Trawl survey, area-swept estimator |
Needs: growth and M estimates |
|
Hair crab Bering Sea |
Trawl survey, area-swept estimator |
Needs: growth and M estimates |
|
Dungeness crab Southeast Alaska, Yakutat, Kodiak, Alaska Peninsula |
None |
CLA possible in future |
|
Prince William Sound, Cook Inlet |
Pot survey, index of abundance |
CSA possible in future |
|
Pink shrimp Cook Inlet, Kodiak, Alaska |
Trawl survey, area-swept estimator; |
LBA in progress for Cook Inlet |
|
Peninsula |
None |
CLA possible in future |
|
Southeast Alaska |
|
|
|
Weathervane scallop Prince William Sound, Cook Inlet |
Dredge survey, area-swept estimator |
Plans: develop age-structured model |
|
Yakutat, Kodiak, Dutch Harbor, Bering Sea |
None |
Plans: GIS analysis of onboard fishery observer data |
|
Sea cucumber Southeast Alaska |
Dive survey, surplus production model |
Needs: growth and recruitment |
|
Elsewhere |
None |
estimates |
|
|
Needs: sampling, basic biological information |
|
|
Sea urchin Southeast Alaska |
Dive survey, surplus production model |
Needs: growth and recruitment |
|
Elsewhere |
None |
estimates |
|
|
Needs: sampling, basic biological information |
|
|
Intertidal clams Cook Inlet (Kachemak Bay) Elsewhere |
Transect surveys None |
Plans: develop age-structured model |
|
Miscellaneous other shellfish species (crabs, shrimps, clams, etc.) |
|
|
|
Statewide |
None |
Needs: basic biological information and sampling programs |
- develop fishery-based assessments for fisheries with onboard observers in a GIS framework. Despite progress, stock assessments are not possible for the majority of Alaskan shellfish stocks due to a lack of basic biological information and funds for sampling programs.
- Budgets are declining while the complexity of and conflicts with the fishery management process are increasing. This situation will inevitably lead to a reduction in the quality of stock assessment data. This problem is most acute for stocks where fisheries are developing.
Gulf States Marine Fisheries Commission (GSMFC)
The stock assessment team of the Gulf States Marine Fisheries Commission has reviewed the documents provided by your office and generally offer complete concurrence with the thirteen points raised by the Atlantic States staff. Three comments (which to me represent emphasis) forwarded by GSMFC stock assessors were:
- Environmental Concerns. Natural climatological phenomena obviously play a role in success/failure of fishery management measures. While this is taken for granted in a functional sense, there is no practical way to account for these influences in current modeling practices. (Related or similar to ASMFC #5.)
- Human Dimensions. Almost totally lacking in stock assessment proceedings is the reactive capability of the fishers. It is typical for fishers to act or react unpredictably to management measures. (Related or similar to ASMFC #12.)
- Local vs. Regional Management. Spotted seatrout is an example. While regional management is desirable from an interstate transport perspective, status of local trout stocks can be drastically different within a relatively small geographic region. Regional managers may know very little about the condition of these local stocks. (Imbedded in ASMFC #s, 2, 5, 6, 8, 9, 10, and 13.)
TABLE H.4 Methods Used to Assess Pacific Salmon
|
Species Name/Area |
Harvest Policy |
Stock Assessment Methods |
|
Chinook salmon |
|
|
|
Southeast Alaska |
Preseason quota based on constant harvest rate applied to preseason forecasted abundance with Pacific Salmon Commission Chinook Technical model |
Cohort analysis of coded wire tag recoveries from hatchery indicator stocks; wild stock escapement enumeration with weirs, mark-recapture, aerial surveys, foot surveys |
|
Yakutat |
Fixed escapement goal |
Weir counts |
|
Copper River |
Fixed escapement goal |
Aerial survey counts |
|
Upper Cook Inlet |
Limited directed commercial fishing, reduce bycatch, sport fisheries managed for fixed escapement goals |
Sonar counts, weir counts, aerial surveys |
|
Kodiak/Chignik |
No directed commercial fishing, fixed escapement goal |
Aerial surveys, weir count |
|
Bristol Bay |
Fixed escapement goal |
Sonar counts, aerial surveys |
|
Kuskokwim River |
Commercial fishery quota ranges |
Test fishery catches, commercial fishery CPUE |
|
Yukon River |
Commercial fishery quota ranges |
Test fishery catches, commercial fishery CPUE, mark or recapture, postseason run reconstruction |
|
Coho salmon |
|
|
|
Southeast Alaska |
Scheduled closures of troll fishery based on CPUE of inside fisheries and early escapement; postseason evaluation of escapement relative to goals and harvest rates for indicator stocks |
Fishery CPUE, indicator stock assessments (weir counts, mark-recapture of juveniles, exploitation rates CWT marking), fishwheel catches, aerial surveys |
|
Yakutat |
Fixed escapement goals |
Weir counts, aerial surveys |
|
Copper, Bering River |
Fixed escapement goals |
Weir counts |
|
Upper Cook Inlet |
Stocks in Northern/Central District systems caught incidental to directed sockeye fishery. |
Fishery CPUE, limited weir count |
|
|
Directed Westside set net fishery limited to two openings per week and reduced if CPUE low |
|
|
Kodiak |
Fixed escapement goal |
Aerial survey, weir count |
|
Chignik |
Fixed escapement goal |
Aerial survey, weir count |
|
Alaska Peninsula |
Fixed escapement goal |
Aerial survey, weir count |
|
Bristol Bay |
Fixed escapement goal |
Sonar count, aerial survey |
|
Kuskokwim River |
Reduced fishing periods when run strength is weak |
Test fishery CPUE |
|
Yukon River |
Catch incidental to fall chum fishery, stock not fully exploited |
Test fishery CPUE, sonar count |
|
Pink salmon |
|
|
|
Southeast Alaska |
Fixed escapement goals |
Aerial survey |
|
Prince William Sound |
Fixed escapement goals |
Aerial survey, hatchery stock identification based on CWT |
|
Lower Cook Inlet |
Fixed escapement goals |
Aerial survey |
|
Kodiak |
Fixed escapement goals |
Aerial survey |
|
Chignik |
Fixed escapement goals |
Aerial survey |
|
Alaska Peninsula |
Fixed escapement goals |
Aerial survey |
|
Bristol Bay, Norton Sound |
Production highly variable, markets not well developed |
None |
|
Chum salmon |
|
|
|
Southeast Alaska |
Generally catches incidental to pink salmon, except for hatchery terminal harvest |
Aerial surveys, poor quality due to presence of pink salmon |
|
Prince William Sound |
Generally catches incidental to pink salmon, except for hatchery terminal harvests |
Aerial surveys, poor quality due to presence of pink salmon |
|
Kodiak |
Generally catches incidental to pink salmon, except for hatchery terminal harvests |
Aerial surveys, poor quality due to presence of pink salmon |
|
Alaska Peninsula |
Generally catches incidental to pink salmon |
Aerial surveys, poor quality due to presence of pink salmon |
|
Bristol Bay |
Harvests incidental to directed sockeye fishery |
Nushagak sonar, aerial survey |
|
Kuskokwim River |
Fixed escapement goal |
Sonar count, test fishery catches, weir counts, aerial survey |
|
Yukon River |
Fixed escapement goals, in river allocation plan, subsistence priority summer run fishery is market limited |
Sonar count, test fishery catches |
|
Norton Sound |
Fixed escapement goal, large-run fisheries are market limited |
Lower counts, aerial surveys, weir counts |
|
Kotzebue Sound |
Fixed escapement goal |
Sonar count, aerial survey, test fishery catches |
|
Sockeye salmon |
|
|
|
Southeast Alaska |
Fixed escapement goals, interception fishery limited by quota |
Weir count, mark-recapture |
|
Yakutat |
Fixed escapement goal |
Weir count, aerial survey |
|
Copper/Bering River |
Fixed escapement goal |
Sonar count, aerial survey |
|
Upper Cook Inlet |
Fixed escapement goal |
Sonar count, test fishery catches |
|
Kodiak |
Fixed escapement goal |
Weir count, test fishery catches |
|
Chignik |
Fixed escapement goal |
Weir count, test fishery catches |
|
Alaska Peninsula |
Fixed escapement goal, June interception quota set on Bristol Bay sockeye preseason forecast and chum cap |
Weir count, aerial survey, test fishery catches |
|
Bristol Bay |
Fixed escapement goal |
Lower count, sonar count, aerial survey, test fishery catches |
TABLE H.5 Methods Used to Assess Pacific Herring
|
Area |
Harvest Policy |
Stock Assessment Methods |
|
Southeast Alaska |
Fixed harvest rate with threshold |
Age-structured analysis tuned to biomass estimated with spawn deposition surveys |
|
Prince William Sound |
Fixed harvest rate with threshold |
Age-structured analysis tuned to biomass estimated with spawn deposition surveys, aerial surveys |
|
Lower Cook Inlet |
Quota based on historical catches that maintained stable abundances; quota increments or decrements based on in-season abundance indices |
Aerial surveys |
|
Kodiak |
Quota based on historical catches that maintained stable abundances; quota increments or decrements based on in-season abundance indices |
Aerial surveys |
|
Bristol Bay |
Fixed harvest rate with threshold |
Aerial surveys |
|
Kuskokwim Bay |
Quota based on historical catches that maintained stable abundances; quota increments or decrements based on in-season abundance indices |
Aerial surveys |
|
Norton Sound |
Quota based on historical catches that maintained stable abundances; quota increments or decrements based on in-season abundance indices |
Aerial surveys |
TABLE H.6 Stock Assessment Methods Used by the Gulf States Marine Fisheries Commission
