U.S. Dept Commerce/NOAA/NMFS/NWFSC/Publications

NOAA-NMFS-NWFSC TM-31: Data Collection -- Groundfish (cont): 

7.1 Introduction

The working group's main purpose in preparing this Technical Memorandum was to describe the existing systems in Washington, Oregon, and California for data collection and data processing of shoreside landings and associated effort for the commercial groundfish fisheries. The groundfish fisheries off the U.S. Pacific coast face common management problems, and in many cases involve stocks that are fished by fleets based in more than one state. There are broad similarities between the groundfish fisheries in each state. Each state has landings that are dominated by trawl fishers (ranging from about 75% of the landed biomass in California to 96% in Oregon). The bulk of the landings occurs at relatively few discrete ports in each state. Even in California, where the fishery is spatially most diffuse, approximately 70% of the landed biomass of groundfish occurs at just five ports in the northern half of the state. The states also share many of the same important species and species groups. Sablefish, Dover sole, Pacific hake, and a diverse group of rockfish, including thornyhead and widow rockfish, are important in all of the fisheries.

Thus, there is potential that increased standardization of the commercial groundfish data systems of the Pacific states would either improve the information available to fisheries managers or allow the same information to be collected more efficiently. We believe that an important preliminary step to improving and evaluating potential benefits of adopting any further standardization of coastwide protocols was to prepare the description of the existing systems contained in the preceding chapters. Much can be learned by considering the similarities among the state systems and exploring why differences exist. Also, the preceding chapters collectively represent an important source document for users of the groundfish data produced by the individual states. Many important characteristics of the various databases and estimated quantities documented in the previous chapters would be difficult for users to uncover in a reasonable period of time. This review of the general sampling designs and data systems used by the three states will be useful for those involved in the production and management of fisheries data in other regions.

7.2 Similarities and Differences Among the State Systems

The commercial groundfish data systems that have evolved in the three states have the following major components: 1) fish receipt systems in which landings are reported by market categories, 2) logbook systems in which fishing hours and locations of fishing are reported, and 3) sampling programs in which the composition of landings in various market categories is evaluated. The data collection systems for fish receipts are fundamentally similar in each of the states. The fish receipt systems are intended to function as complete censuses of the quantities of commercially landed groundfish. In practice some landings certainly go unreported, and there can be undetected errors in data entry. Dealers are required to submit receipts (also called fish tickets) at the time fish are sold. These receipts include the weight in each of a number of market categories and the values of those categories. Some market categories are essentially equivalent to single species, other market categories (particularly for rockfish) represent mixtures of different species, with the exact composition unknown, and still others represent subcategories within a species (e.g., different size classes). All three states stress rapid initial data entry so that reported landings can be forwarded to PacFIN (Pacific Fisheries Information Network) for use in in-season quota management. Data entry is then followed by various methods of error screening and correction.

The major practical difference among the states in their fish receipt systems is that different numbers of market categories, representing differential amounts of sorting, are defined. For example, in California, rockfish are landed in 57 categories as of 1992, while only six rockfish market categories are defined in Oregon. In California, market orders are often made for specific types of rockfish, which has led to subsorting of categories prior to actual sampling visits by port biologists. We suspect that these same market forces could cause the frequency of such subsorting to increase in Oregon and Washington in the future.

Logbooks originated as a method for monitoring fishing effort (hours of fishing). These data are important for defining the geographic location of both catch and effort. A standardized and mandatory trawl logbook is used coastwide, compliance is monitored, and the resulting data are computerized and maintained by all three states. Although logbooks exist for other components of the groundfish fishery, in most cases these are voluntary or there are compliance problems. In general these other logbooks are not integrated into the groundfish data systems, and much of the information is neither computerized nor maintained in long-term agency databases. Because a standardized trawl logbook is used, the raw data for all three states are similar. In each state, the original logbooks contain estimates of the species composition and magnitude of the catch on a tow-by-tow basis, along with information on the location of tows, gear used, depth fished, fuel used, ports of departure and landing, and other related information. Some differences arise in the way logbook data are edited, keypunched, and processed because of differences in how the data are currently being used and how they have been used in the past. For example, in California and Oregon, the logbook data are matched with the fish receipt data to produce an adjusted logbook database, with total trip landings for a market category matching the landings for that trip in the fish receipt database. This approach allows allocation of accurate information on retained catch from individual trips recorded on fish receipts to specific locations, as might be desired in the preparation of environmental impact statements or for a Geographic Information System (GIS). Washington does not match the logbook data to fish receipts on a trip-by-trip basis, and thus does not produce an adjusted logbook database. Furthermore, the particulars of how fish receipts without matching logbooks are handled differ between California and Oregon. Another difference among the states is in the precision with which location of catch data are keypunched.

For management purposes, it is necessary to assign landings to an area of capture. In Washington and Oregon, this is done for the trawl fishery using logbook data because information on area of capture in the logbooks is more accurate and complete than in the landing receipt data. In California, landings are assigned to the same area in which they are landed. The proximate explanation for the different approach in California is that there has been a backlog of logbook data to be keypunched for a number of years. As a consequence, logbook data could not be used in a timely fashion. This backlog, however, is the result of a choice in how limited resources were used. This choice can be best understood by considering how the composition and behavior of the California fishing fleet differs from that in the other two states.

The vessels operating in California are generally smaller and fish closer to their home ports than the fleets in Oregon and Washington. The greatest number of vessel-months of fishing are made in California, but with the smallest average landings per trip, whereas the fewest vessel-months of fishing with the largest average landings per trip are made in Washington (GMT 1991). These differences are seen within the trawl fleet and are further accentuated by the greater importance of non-trawl gear in California, which is usually operated from smaller vessels. It is also the case in California that major ports are generally located far from the boundaries of International North Pacific Fisheries Commission (INPFC) areas for which landings are reported. 

Although both Oregon and Washington use logbook data to assign landings to specific management areas, they do this in substantially different ways. In Oregon, logbook data are matched to the fish receipt data to identify the catch location for individual landings. In Washington, fish receipts and logbook records are not matched on a trip-by trip basis. Instead, the distribution by area of catch for each market category is calculated from the hailed weights in the logbooks. This distribution is used to apportion landings to areas. A similar approach is used by Oregon to allocate landings for those cases where a fish receipt record cannot be matched in the logbook database. In Washington, logbook data are used to apportion landings to areas much more rapidly than is the case in Oregon.

Each of the states have programs for sampling portions of the groundfish fishery. Each state samples rockfish landings and participates in coastwide sampling programs for sablefish. Oregon and California participate in a federally organized sampling program for lingcod that started in 1991, while Washington samples lingcod as part of an ongoing state sampling program. Oregon and California also participate in a federally organized sampling program for shore-processed Pacific hake. Each of the states also has sampling programs for species that have special importance locally. Differences among the states' sampling programs generally reflect the relative importance of different species or groups of species to each of the states' fisheries.

In each state the primary purpose of the rockfish sampling program is to provide information on the species composition of rockfish market categories, which often consist of several to many species. This allows total landings to be estimated for individual species. Sampling is also done to provide information on age, length and sex compositions, and other biological information for targeted species.

The sampling process for determining species compositions of landings of rockfish is similar in California and Oregon. In Oregon, estimates of species composition are made for each market category by port, quarter, gear, and area of capture. Data are partitioned similarly for estimates in California, except that all landings from a given port are assumed to have occurred in a single known area. The samples consist of two or more fixed-weight clusters (basket subsamples) selected from a market category contained within a boat trip. The fish in these samples are then counted and individually identified. There is no attempt in this sampling scheme to completely describe individual trips, because all market categories are not sampled on each trip.

The sampling approach to determine species compositions of rockfish landings in Washington differs fundamentally from that used in the other two states. The sampling plan reflects greater attention to the process of assigning species-specific landings to management areas. Only landings of market categories that can be assigned to an individual Pacific States Marine Fisheries Commission (PSMFC) statistical catch area are sampled. The sampler will examine the landings from a trip for a given market category and record the PSMFC area and, based on a visual examination, the species composition of that market category. The estimated landings by species for the sampled landings are then used to obtain estimates for each area within a given time period. In California and Oregon, the sampled landings from a trip could come from more than one PSMFC area.

The use of visual estimates in Washington allows a higher sampling rate and more frequent complete sampling of all market categories within a trip than would be possible following the sampling protocols used in California and Oregon. The approach in Washington allows more information to be compiled on a trip-by-trip basis, but there may be a greater potential for sampler selection bias. There is, however, evidence that samplers can estimate the species composition of a trip reasonably well by visual inspection. Currently, it is not feasible to compare objectively the sampling schemes used by each state, because the relative variability in the resulting estimates from each state is unknown. While the species compositions are very accurate for sampled clusters in California and Oregon, and the within-trip variability is known to be low, relatively limited numbers of trips are sampled due to the increased time needed to process these subsamples.

The greater fragmentation of rockfish landings into different gear types and market categories in California sometimes leads to unsampled "cells" (market category/port/quarter combinations) (Pearson and Almany 1995). This has led to a process by which unsampled landings in particular categories are assumed to be similar to other categories or the same category sampled in other locations and places. The frequency of unsampled "cells" is less in the other two states, although it is not uncommon for non-trawl gear in Oregon. When this situation occurs in Washington, the species composition is left as "unknown." In Oregon, sample data are "borrowed" to fill in missing cells as in California, although the process differs in the details of its application.

Washington and Oregon determine biological characteristics of the rockfish landings, such as age, sex, and length compositions of the catch, by taking special samples of targeted species. California, by contrast, collects this information by examining fish in a subset of the samples used for determining species compositions. Although only targeted species are sampled for purposes of age determination, the sex and length are recorded for all of the fish in the California species-composition samples. In part, this difference may be due to the greater diversity of the catch in California. One consequence of the biological sampling program used in Washington and Oregon is that boat trips with relatively small landings may go unsampled because of the difficulty in obtaining a sufficient number of fish for a sample. 

Age and length compositions are widely used in stock assessments of groundfish, but currently none of the states provide such estimates or the raw data to the PacFIN system. California regularly produces estimates of age and length compositions for rockfish, thornyhead, and Dover sole for the trawl fishery, weighting the samples by the size of the market category landings. Oregon produces estimates of age and length compositions by special request for species included in their biological sampling program. The Oregon calculations are done using weighted or unweighted estimators, depending upon how the researcher requests the information. Washington also generates age compositions by special request, and produces weighted or unweighted estimates as deemed appropriate by an individual analyst. Routine generation of age or length compositions is not done as part of any of the federal sampling programs. When needed, age compositions have been generated from the raw data by particular scientists who are involved in assessments concerning stocks sampled through the federal programs.

7.3 Logistical Constraints

Attempts to improve data collection and processing systems need to keep in mind the physical constraints of the systems and the limits of personnel and money that inherently constrain most sampling programs. Historically, one problem faced by the port sampling programs has been that data requests from outside parties have often been generated in isolation from one another. In practice, however, it is the same people who sample Pacific hake, rockfish, and sablefish, and any increase in sampling intensity for one of these species usually results in less sampling of the others. There is a clear and urgent need for coordinated management of all the data requests being made of these sampling programs.

The dynamic nature of the groundfish fishery needs to be kept in mind as data systems are designed and revised. Because the fishery is changing rapidly and will continue to do so, it is unreasonable to view the evaluation of sampling designs and estimation methods as a one-time task. Choices about how to "fill in" unsampled ports and market categories, or where and when to allocate sampling effort, will need to accommodate the changes in the fishery.

Finally, we note that the features of the U.S. Pacific coast groundfish fishery, like those of most fisheries (e.g., Tomlinson 1971), prevent us from often obtaining truly random samples. Although analysis of existing data could suggest possible ways to improve sampling, any such analyses should keep in mind the reality of the sampling situation as distinct from the ideal models on which discussions in many sampling texts are based. In virtually all cases, samples and subsamples that are treated as being selected at random are in some sense being selected systematically. Subsamples taken within trips are deliberately selected from different parts of the catch, and within time periods there are usually attempts to sample trips spread out over time; however, for a given trip it is often more efficient to sample more than one market category. Also, some portions of the fishing fleets may be over- or underrepresented because of the relative ease of obtaining samples. All of these facts could act to make calculated means and totals and their variances differ from actual ones in a systematic fashion. The danger of introducing such unforeseen biases should always be kept in mind when considering ways to improve the sampling programs. Because the fisheries differ among the states, an approach that works well in one state might well have serious problems in another state.

7.4 Opportunities for Standardization 

The PacFIN system is one source of aggregated data, estimates, and original data that are used in fishery assessments and for other purposes. Currently, the PacFIN system provides access to original fish receipt data for Washington, Oregon, and California in a standardized form. Other data are provided to PacFIN in an aggregated format or as estimates for specified strata. Within the context of this revised PacFIN system, we believe that greater comparability of estimates could be achieved by standardizing routine calculations across the states before the aggregated or estimated quantities are provided to PacFIN. Even when calculations differ between the states because of variations in sampling design or characteristics of the data, consideration for the same sets of issues and concerns in each state could make data more compatible across state boundaries. Further pooling of ideas and experiences for common data-processing problems (e.g., how to assign landings to areas) could potentially increase the quality of the data and could prevent the use of different ad hoc procedures by the individual states for the same problems.

One area for possible standardization is in estimating species compositions for unsampled market category, time period, and gear combinations. A first step would be to evaluate the current approaches and possible alternatives. Another example where standardization is possible is in the calculation of variances for estimated species compositions. The current revisions to PacFIN will allow variance estimates (coefficients of variation) for estimated proportions to be included in the species-composition records in the system. Although other measures of performance are possible (e.g., sampling rates per ton of landings or estimated confidence intervals), we think that regular reporting of these variances within the revised PacFIN system provides the most immediate potential for providing information on the quality of the species-composition data. Large coefficients of variation may indicate small sample sizes and incomplete sampling coverage, and small coefficients of variation may reflect strata that have been 'over-sampled.' However, unless the estimators used by the different states account for the same sources of variation and make logically compatible assumptions, it will be difficult to compare the estimates objectively.

California and Oregon have essentially identical sampling programs for species composition, and unless the characteristics of the data are quite different, these states should probably calculate variances in the same way. In any case, given the similarity of the sampling programs, it seems reasonable that the same considerations and alternatives should be addressed in each state. Sen (1984, 1986) discussed various potential estimators in light of the California system as it existed in the early 1980s. Crone (1992a, 1992b, 1995) has discussed variance estimators for the Oregon system. These existing studies could form the foundation for adopting a common approach to variance estimation. 

Although the species-composition sampling program in Washington differs substantially from that used in Oregon and California, similar issues and considerations need to be addressed in estimating variances for the species compositions. For example, there is still the need to combine the within-trip (and market category) component of the variance with the between-trip component. In Washington, the within-trip component arises from differences between the sampler's visual estimate and the actual composition for the trip.

For some purposes (e.g., environmental impact assessments that require geographic information on catch locations, and stock assessments that require age and length compositions), researchers require types of data that are not in the PacFIN system or data that are in their original unprocessed and unaggregated form. For these data, adoption of coastwide standards could also provide benefits. Such standard databases could facilitate the use of original data by stock assessment scientists and other researchers. A common format would reduce the amount of documentation and learning required to use the data and avoid unnecessary pitfalls. The resources needed to develop, maintain, and document the standards would be considerable. Such a system would have to be dynamic to accommodate the changing nature of the fisheries it would support. The most significant impediment to standardization may well be the inevitable hesitancy of the current users within each state to support and develop a system that focuses primarily on general problems common to all of the states and secondarily on state-specific problems.

Although complete standardization may be unobtainable, standardization in some areas could be achieved. We believe that there would be benefits by standardization of the logbook databases to make detailed information on catch and effort available from the entire region. The creation of uniform processed logbook databases could facilitate GIS applications of the data for fishery management, environmental impact assessments, and fundamental research. This would need to be done with care so that useful information available in the existing databases for some states (e.g., precise positions, individual tow information, and adjusted catches) is not lost in the quest for uniformity. Another concern is that the confidentiality of information provided by individual vessels would need to be maintained.

Complete standardization of species composition and biological sample databases is currently impossible because each of the states collects the information in different ways. At this point, attention may be better directed at considering the differences in how the data are collected and summarized, and whether standard approaches are advisable.

As noted above, Washington uses a fundamentally different sampling approach for determining rockfish species composition than the other states. A comparison of the sample selection approaches would require collecting information in each of the states on costs and lost sampling opportunities, as well as information regarding the magnitude of the within-trip variability associated with the sampling program in Washington. Substantial resources, both money and manpower, would be needed to develop and conduct a research study that addresses these very important issues regarding optimal features of commercial fishery sampling designs.

Currently, only California generates standard reports with estimated age and length compositions. The other states support software for generating these compositions but respond to specific requests and allow flexibility in the algorithms used, the major option being whether to weight the samples by the size of the landings. The analytical approaches used in Oregon and Washington provide additional flexibility by allowing a suite of estimation procedures to be employed that best accommodate the sample data. However, a rational choice among estimation methods could require extensive analysis of the original data, a consideration of how they were collected, and substantial knowledge regarding sampling theory and application. Consequently, we believe that a review of this issue would result in considerable benefit, perhaps leading to general recommendations and standardization in analysis.

The consequences of the different methods for collecting biological sample data among individual states also need evaluation. In Oregon and Washington, special biological samples are taken for targeted rockfish species. In California, biological data are collected for all rockfish appearing in species-composition samples. The California sampling approach allows some evaluation of changes in the population structure of minor species (e.g., Pearson and Ralston 1990), but reduces effort that could be exerted toward major species. The difference among the states may be reasonable, given the greater diversity of the landed rockfish species in California. However there would be value in quantifying the actual costs and benefits associated with the biological sampling programs currently in place in each of the states.

Another possible area for standardization concerns how landings are allocated to area of catch. The three states use different approaches, and only Washington takes area of catch into account in the choice of species-composition samples. The approach of each state seems reasonable in isolation, but in no case is it known how the estimates would vary using an alternative approach. Standardization across all three states would require major changes to the data-processing systems used in at least two of the states. However, existing data could be used to evaluate the sensitivity of the results generated from a particular approach. 

7.5 Other Opportunities to Improve the System or Increase Efficiency

There are potential improvements to the data collection systems that do not necessarily require more standardization. One example is the process by which species compositions for rockfish in California are derived for market category, port, time period, and gear combinations for which there are no sample data. Although the process used in the past is reasonable, there are other equally plausible approaches. This is an area that has recently been explored by analysis of existing data (D. E. Pearson, NOAA, NMFS, Southwest Fisheries Science Center, Tiburon Laboratory, 3150 Paradise Drive, Tiburon, CA 94920. Pers. commun., December 1995). The emphasis of these analyses has been to identify certain types of samples that should be collected, or places where sampling effort could be reduced. This is critically important because the large number of market category/gear combinations in California appears to be market driven, may increase over time, and similar fragmentation may well occur in Oregon and Washington. 

In Oregon and California, rockfish species-composition samples consist of two or more subsamples (clusters) from a market category. These subsampling protocols are also part of the lingcod and sablefish sampling programs. This is done primarily to allow the within-trip (and market category) component of the variance to be estimated. However, it is known through analysis of existing data that this component of the variance is usually small for rockfish, and this second-stage variability is likely small for lingcod and sablefish as well. In the past, for species-composition sampling of rockfish landings, the cost of selecting a second subsample for each sample was considered negligible because identifying trips to sample, rather than time spent sampling, was often limiting. However, with the increasing numbers of market categories and landings by small non-trawl vessels, this may no longer be true (B. A. Erwin, California Department of Fish and Game, 411 Burgess Drive, Menlo Park, CA 94025. Pers. commun., November 1995).

The absence of replicate subsamples would require additional assumptions to be made in variance calculations so that the within-trip component of the variance could be determined without compromising the validity of the estimates. There may be relatively little danger in this when the within-trip component of the variance is relatively small. Changes in sampling procedures involved in a multistage approach should not be adopted until investigations are conducted that address optimal sample-size allocations at each stage of the design.

Another opportunity to improve the system is to use existing information to regularly report performance measures for sampling programs. This could include coefficients of variation or variances for each derived or estimated quantity. 

7.6 Recommendations

In our discussion of opportunities above, there are many implicit recommendations. An overarching recommendation is that more resources be devoted to analyzing existing procedures on an ongoing basis. These analyses need to be coordinated across the states to avoid redundancy and so that the approaches are acceptable to all parties involved. This kind of work would need to be directed by a coordinating group involved in coastwide sampling. It is clear that implementation of such work would require specialized skills and substantial efforts. The same coordinating group could also track ongoing sampling programs and intermittent data requests, and make recommendations to the agencies regarding priorities of different sampling programs. We strongly recommend that critical investigations be established to address the inherent issues of limited sampling resources and tradeoffs between data collection programs and the dynamic nature of the U.S. Pacific coast groundfish fishery.

Within the many specific areas where we have recognized potential opportunities for standardization and improvement, a few stand out as being critical areas for immediate work.

- We believe that variance estimates associated with all species   compositions should be estimated and that the methods used should be reviewed   coastwide with a view towards standardizing assumptions, at least at the   conceptual level.    
- Substantial efficiencies, both statistical and financial, would likely   result from a detailed and thorough analysis of the costs and benefits of the   different approaches used by the individual states to sample and estimate   species compositions of rockfish landings and age compositions of landings   associated with targeted species of groundfish.    
- A critical evaluation of the methods used by the different states to   allocate landings to fishery management areas (e.g., PSMFC areas) is urgently   needed to ensure that stock assessments appropriately consider the spatial   attributes of the sample information and, most importantly, to ensure that   management advice is based on accurate representations of the sample data.     
- We recommend that the logbook databases be scrutinized in a much more   rigorous and timely fashion than currently is done. We feel that there likely   exists a great deal of information in these logbooks that can benefit current   stock assessments and the overall management of the groundfish fisheries off   the U.S. Pacific coast. For example, changes in the spatial demographics of   the fishing fleet and the targeted fish populations could be monitored using   data contained in fishers' logbooks, and it may be possible to derive usable   estimates of relative abundance (i.e., catch-per-unit-effort) that   subsequently could be used to 'gauge' the reliability of the output produced   from stock assessment modeling procedures.    

This chapter was written with input from all of the authors of this document. We also thank Alec MacCall, Bill Lenarz, and Rick Methot for fruitful discussion regarding some of the issues addressed here.

7.8 Citations

Crone, P. R. 1992a. Sampling design and statistical considerations for the commercial rockfish fishery of Oregon, Part 1 ­ Species composition. Report to the Oregon Department of Fish and Wildlife, Contract 91-54, 97 p. (Available from Oregon Department of Fish and Wildlife, 2040 SE Marine Science Drive, Newport, OR 97365.)

Crone, P. R. 1992b. Sampling design and statistical considerations for the commercial rockfish fishery of Oregon, Part 1 ­ Species composition, Report Addendum. Report to the Oregon Department of Fish and Wildlife, Contract 91-54, 50 p. (Available from Oregon Department of Fish and Wildlife, 2040 SE Marine Science Drive, Newport, OR 97365.)

Crone, P. R. 1995. Sampling design and statistical considerations for the commercial groundfish fishery of Oregon. Can. J. Fish. Aquat. Sci. 52:716-732.

Groundfish Management Team (GMT) for U.S. Pacific Coast. 1991. Report to the Pacific Fishery Management Council, E.10, 57 p. (Available from Pacific Fishery Management Council, 2130 SW Fifth Avenue, Suite 224, Portland, OR 97201.) 

Pearson, D. E, and G. Almany. 1995. The effectiveness of California's rockfish port sampling program. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFC-218, 50 p.

Pearson, D. E, and S. Ralston. 1990. Trends in landings, species composition, length-frequency distributions and sex ratios of 11 rockfish species (Genus Sebastes) from central and northern California ports (1978-1988). U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFC-145, 85 p.

Sen, A. R. 1984. Sampling commercial rockfish landings in California. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-SWFC-45, 95 p.

Sen, A. R. 1986. Methodological problems in sampling commercial rockfish landings. Fish. Bull., U.S. 84:409-421. 

Tomlinson, P. K. 1971. Some sampling problems in fishery work. Biometrics 27:631-641. 

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