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6. DATA COLLECTION METHODS


6.1 VARIABLES, SOURCES AND METHODS
6.2 RECORDING A VARIABLE
6.3 DATA COLLECTION METHODS

The choice of method is influenced by the data collection strategy, the type of variable, the accuracy required, the collection point and the skill of the enumerator. Links between a variable, its source and practical methods for its collection (Table 6.1, Table 6.2 and Table 6.3) can help in choosing appropriate methods. The main data collection methods are:

· Registration: registers and licences are particularly valuable for complete enumeration, but are limited to variables that change slowly, such as numbers of fishing vessels and their characteristics.

· Questionnaires: forms which are completed and returned by respondents. An inexpensive method that is useful where literacy rates are high and respondents are co-operative.

· Interviews: forms which are completed through an interview with the respondent. More expensive than questionnaires, but they are better for more complex questions, low literacy or less co-operation.

· Direct observations: making direct measurements is the most accurate method for many variables, such as catch, but is often expensive. Many methods, such as observer programmes, are limited to industrial fisheries.

· Reporting: the main alternative to making direct measurements is to require fishers and others to report their activities. Reporting requires literacy and co-operation, but can be backed up by a legal requirement and direct measurements.

6.1 VARIABLES, SOURCES AND METHODS


6.1.1 Data sources
6.1.2 Linkage among variables, sources and methods

The choice of the many methods for collecting fishery data will depend on the variables to be measured, the source and the resources available. In many cases, there is a natural way to collect particular variables. For example, relatively static variables, like vessel length or engine size, are often best collected through a registration system. Highly dynamic variables, like catch or effort, may often be best obtained through daily records, such as logsheets.

For the same variable, the methods can be different depending on the type of fishery. For example, for a large-scale fishery, catch data would be best collected from logbooks, whilst in a small-scale fishery interviews and/or questionnaires would often be the best method. The sources (fishers, processors etc.) are also an important factor for the choice and design of methods. Buyers, processors and other intermediaries are likely to keep their own sales records, which should be used as the basis of data forms. Small-scale fishers often do not keep any records, and data acquisition in this case would be restricted to one-to-one interviews, but the interview structure could be more flexible.

Data collection should be conducted at intervals sufficiently frequent for the management purpose. For example, data for stock monitoring have to be collected constantly, while household data can be at much longer time intervals. In general, frequently collected data will probably have to rely on fishers or industry personnel providing the data. Less frequent data can use enumerators since the costs of collection are much lower.

There are cases when fishery data collection programmes cannot be operated on a regular basis because of operational limits. These cases include small scale fishing operations in many inland or remote marine areas, where fishing operations are spread over a large area with part-time fishers using a large array of fishing gears and techniques, sometimes in many different habitats. Under these circumstances, a number of alternative approaches can be taken to assess the fisheries, including:

· limited scope census or sample-based pilot surveys;
· household surveys or surveys for fish consumption
· trade patterns;
· logbook systems.
All of these can be used for cross-checking landings data as well as providing production and socio-cultural information.

Many variables can be collected by more than one method and at different points from fishers to consumers. Where possible, data should be collected from several sources to crosscheck for errors. For example, catch data collected through logbooks can be cross-checked against reported landings based on sales slips, data collected by interview at landing sites and even consumer or trade data.

In almost all cases, many different variables can be collected simultaneously. For example, length frequency, species composition, average weight and first sale price can all be obtained when vessels land their catch. Collecting of data for different purposes reduces costs and thus due account should be made of this aspect when planning the data collection programme.

There are strong links between types of data, where they can be obtained and the methods, which are available for their collection. This section provides a guide for selecting data collection methods in relation to the data type and source, and gives some indication of what types of data can be collected simultaneously.

6.1.1 Data sources

Harvest: at the level where fish are caught. The most direct approach to the fishery data (e.g. catch, effort).

Post harvest: levels through which fish are prepared for market. This may include middle person, fish auction, cold storage, processing farms and transport of products.

Market: all situations where fish are commercially transferred. It may include the fish market at landing port, transaction (secondary market) of products among brokers, processing farms and consumers' market.

Consumers: at the level where the products are finally consumed.

Government-related agencies: any agencies or institutes forming part of government (including the inter-governmental level). It would include various agencies outside of fisheries (e.g. custom, coast guard and meteorology department).

Support industry: industries which provide materials and services for fisheries, but are not directly involved in fisheries business (e.g. ship building industry, fishing gear suppliers).

6.1.2 Linkage among variables, sources and methods

The linkage between variables, sources and methods are shown in three tables. These tables intend to give some guidance for selecting collecting methods and sources, and design a data collection system. The tables also would give ideas about what types of data can be collected simultaneously at the same source with the same method.

Table 6.1 The different types of data that can be collected from the various data sources. Numbers in brackets refer to relevant sections in the main text.

Main Data Types

Sources

Harvest

Post Harvest

Market
(including retails)

Consumers

Government related agencies & institutions

Support Industry

Catch (4.3.1.1)







Effort (4.3.1.2)





+

+

Vessel/gear data (4.3.1.4)






+

Operations data (4.3.1.4)







Compliance data (4.3.1.5; 4.3.1.6)



+




Biological data (4.3.2)







Environmental data (4.3.2.4)







Market data (4.3.3.1; 4.3.4.5)






+

Costs and earnings data (4.3.3.3)




+

+

+

Trade data (4.3.3.11; 4.3.3.12)


+

+




Fisherfolk data (4.3.4)







Household data (4.3.4)






+

Institutions data (4.3.3.5; 4.3.4.3)








Table 6.2 The different data collection methods that can be used for the different sources.

Method/sources

Harvest

Post Harvest

Market

Consumers

Government

Support Industry

Registration (6.3.1)







Questionnaires (6.3.2)





+


Interviews (6.3.3)








Open-ended (6.3.3.1)







Structured (6.3.3.2)





+

+

Observations (6.3.4)








Observers (6.3.4.1)







Inspectors (6.3.4.2)







Scientific research (6.3.4.3)







Data logging (6.3.4.4)







Reporting (6.3.5)








Harvest (6.3.5.1)







Post harvest (6.3.5.2)





+


Sales (6.3.5.3)







Trade (6.3.5.4)



+



+

Strong linkage: major relation (source)
Secondary linkage: secondary source or important validation source
+ Possible source or secondary validation source
Table 6.3 The different types of data that can be collected by the various data collection methods.


Registration
(6.3.1)

Questionnaires
(6.3.2)

Interviews
(6.3.3)

Direct Observations
(6.3.4)

Reporting
(6.3.5)

Open-ended
(6.3.3.1)

Structured
(6.3.3.2)

Observers
(6.3.4.1)

Inspectors
(6.3.4.2)

Scientific research
(6.3.4.3)

Data logging
(6.3.4.4)

Harvest
(6.3.5.1)

Post harvest
(6.3.5.2)

Sales
(6.3.5.3)

Trade
(6.3.5.4)

Complete enumeration













Catch (4.3.1.1)








+


+



Effort (4.3.1.2)













Vessel/gear data (4.3.1.4)








+





Operations data (4.3.1.4)






+







Compliance data (4.3.1.5; 4.3.1.6)













Biological data (4.3.2)





+





+



Environmental data (4.3.2.4)








+





Market data (4.3.3.1; 4.3.4.5)










+



Costs and earnings data (4.3.3.3)













Trade data (4.3.3.11; 4.3.3.12)













Fisherfolk data (4.3.4)













Household data (4.3.4)













Institutions data (4.3.3.5; 4.3.4.3)













Sampling













Catch (4.3.1.1)









+

+

+


Effort (4.3.1.2)









+




Vessel/gear data (4.3.1.4)









+




Operations data (4.3.1.4)









+




Compliance data (4.3.1.5; 4.3.1.6)









+




Biological data (4.3.2)






+



+




Environmental data (4.3.2.4)









+




Market data (4.3.3.1; 4.3.4.5)













Costs and earnings data (4.3.3.3)











+


Trade data (4.3.3.11; 4.3.3.12)













Fisherfolk data (4.3.4)









+


+


Household data (4.3.4)













Institutions data (4.3.3.5; 4.3.4.3)










+



Strong linkage: major relation (source)
Secondary linkage: secondary source or important validation source
+ Possible source or secondary validation source

6.2 RECORDING A VARIABLE

It is important to assess the degree of precision required for the measurement of each variable. This will affect the method of collection, the design of the recording form and later analyses. For example, catch can be recorded in 1, 10, 100, 1000 kg or other units. Total estimated catch can be disaggregated into species by relative proportions or each species mass can be estimated separately. Fishers' age can be recorded by year categories or locally derived groups such as "apprentice", "active" or "semi-retired". However, there is little point in requesting a captain to report and record the catch from a haul to the nearest kilogram, when his estimates are only accurate to the nearest tonne. If more precise measurements are required, the catch will have to be weighed on landing.

Sometimes decisions on the units of measure are complicated by the type of data to be collected. Data values may need to be represented by codes (e.g. sea state, degree of job satisfaction), which should be standardised.

6.3 DATA COLLECTION METHODS


6.3.1 Registration
6.3.2 Questionnaires
6.3.3 Interviews
6.3.4 Direct observations
6.3.5 Reporting

6.3.1 Registration

A register is a depository of information on fishing vessels, companies, gear, licenses or individual fishers. It can be used to obtain complete enumeration through a legal requirement. Registers are implemented when there is a need for accurate knowledge of the size and type of the fishing fleet and for closer monitoring of fishing activities to ensure compliance with fishery regulations. They may also incorporate information related to fiscal purposes (e.g. issuance or renewal of fishing licenses). Although registers are usually implemented for purposes other than to collect data, they can be very useful in the design and implementation of a statistical system, provided that the data they contain are reliable, timely and complete

6.3.1.1 Registration data types

In most countries, vessels, especially commercial fishing vessels, and chartered or contract fishing vessels are registered with the fisheries authorities. Data on vessel type, size, gear type, country of origin, fish holding capacity, number of fishers and engine horsepower should be made available for the registry.

Companies dealing with fisheries agencies are registered for various purposes. These companies may not only include fishing companies, but also other type of companies involved in processing and marketing fishery products. Data, such as the number of vessels, gear type and vessel size of registered fishing companies, should be recorded during such registration. Processing companies should provide basic data on the type of processing, type of raw material, capacity of processing, and even the source of material.

Fishing vessels and fishing gears may often be required to hold a valid fishing licence. Unlike vessel registers, licences tend to be issued for access to specific fisheries over a set period of time. Because licences may have to be periodically renewed, they can be a useful way to update information on vessel and gear characteristics.

6.3.1.2 Registry design

A registry must not only capture new records, but be able to indicate that a particular record is inactive (e.g. a company has ceased operations) or record changes in operations (e.g. a company's processing capacity has increased). If licences must be renewed each year, data collected from licensing is particularly useful, as records are updated on an annual basis.

Registry data also contain criteria for the classification of fishing units into strata. These classifications are usually based on assumptions and a priori knowledge regarding differences on catch rates, species composition and species selectively.

In general, vessel registers are complex systems requiring well-established administrative procedures supported by effective data communications, data storage and processing components. As such, they predominantly deal with only certain types and size of fishing units, most often belonging to industrial and semi-industrial fleets. Small-scale and subsistence fisheries involving large numbers of fishing units are often not part of a register system or, if registered, are not easily traced so as to allow validation or updating.

6.3.2 Questionnaires

In contrast with interviews, where an enumerator poses questions directly, questionnaires refer to forms filled in by respondents alone. Questionnaires can be handed out or sent by mail and later collected or returned by stamped addressed envelope. This method can be adopted for the entire population or sampled sectors.

Questionnaires may be used to collect regular or infrequent routine data, and data for specialised studies. While the information in this section applies to questionnaires for all these uses, examples will concern only routine data, whether regular or infrequent. Some of the data often obtained through questionnaires include demographic characteristics, fishing practices, opinions of stakeholders on fisheries issues or management, general information on fishers and household food budgets.

A questionnaire requires respondents to fill out the form themselves, and so requires a high level of literacy. Where multiple languages are common, questionnaires should be prepared using the major languages of the target group. Special care needs to be taken in these cases to ensure accurate translations.

In order to maximise return rates, questionnaires should be designed to be as simple and clear as possible, with targeted sections and questions. Most importantly, questionnaires should also be as short as possible. If the questionnaire is being given to a sample population, then it may be preferable to prepare several smaller, more targeted questionnaires, each provided to a sub-sample. If the questionnaire is used for a complete enumeration, then special care needs to be taken to avoid overburdening the respondent. If, for instance, several agencies require the same data, attempts should be made to co-ordinate its collection to avoid duplication.

The information that can be obtained through questionnaires consists of almost any data variable. For example, catch or landing information can be collected through questionnaire from fishers, market middle-persons, market sellers and buyers, processors etc. Likewise, socio-economic data can also be obtained through questionnaires from a variety of sources. However, in all cases variables obtained are an opinion and not a direct measurement, and so may be subject to serious errors. Using direct observations (6.3.4) or reporting systems (6.3.5) for these sorts of data is more reliable.

Questionnaires, like interviews, can contain either structured questions with blanks to be filled in, multiple choice questions, or they can contain open-ended questions where the respondent is encouraged to reply at length and choose their own focus to some extent.

To facilitate filling out forms and data entry in a structured format, the form should ideally be machine-readable, or at least laid out with data fields clearly identifiable and responses pre-coded. In general, writing should be reduced to a minimum (e.g. tick boxes, multiple choices), preferably being limited to numerals. In an open-ended format, keywords and other structuring procedures should be imposed later to facilitate database entry and analysis, if necessary.

6.3.3 Interviews

In interviews information is obtained through inquiry and recorded by enumerators. Structured interviews are performed by using survey forms, whereas open interviews are notes taken while talking with respondents. The notes are subsequently structured (interpreted) for further analysis. Open-ended interviews, which need to be interpreted and analysed even during the interview, have to be carried out by well-trained observers and/or enumerators.

As in preparing a questionnaire, it is important to pilot test forms designed for the interviews. The best attempt to clarify and focus by the designer cannot anticipate all possible respondent interpretations. A small-scale test prior to actual use for data collection will assure better data and avoid wasting time and money.

Although structured interviews can be used to obtain almost any information, as with questionnaires, information is based on personal opinion. Data on variables such as catch or effort are potentially subject to large errors, due to poor estimates or intentional errors of sensitive information.

6.3.3.1 Open-ended interviews

Open-ended interviews cover a variety of data-gathering activities, including a number of social science research methods.

Focus groups are small (5-15 individuals) and composed of representative members of a group whose beliefs, practises or opinions are sought. By asking initial questions and structuring the subsequent discussion, the facilitator/interviewer can obtain, for example, information on common gear use practices, responses to management regulations or opinions about fishing.

Panel surveys involve the random selection of a small number of representative individuals from a group, who agree to be available over an extended period - often one to three years. During that period, they serve as a stratified random sample of people from whom data can be elicited on a variety of topics.

6.3.3.2 Structured interview

Generally, structured interviews are conducted with a well-designed form already established. Forms are filled in by researchers, instead of respondents, and in that it differs from questionnaires. While this approach is more expensive, more complicated questions can be asked and data can be validated as it is collected, improving data quality. Interviews can be undertaken with variety of data sources (fishers to consumers), and through alternative media, such as by telephone or in person.

Structured interviews form the basis for much of the data collection in small-scale fisheries.

In an interview approach for sample catch, effort and prices, the enumerators work according to a schedule of landing site visits to record data. Enumerators can be mobile (that is sites are visited on a rotational basis) or resident at a specific sampling site. Their job is to sample vessels, obtaining data on landings, effort and prices from all boat/gear types that are expected to operate during the sampling day. The sample should be as representative as possible of fleet activities. Some additional data related to fishing operations may be required for certain types of fishing units, such as beach seines or boats making multiple fishing trips in one day. For these, the interview may cover planned activities as well as activities already completed.

In an interview approach for boat/gear activities, the enumerators work according to a schedule of homeport visits to record data on boat/gear activities. Enumerators can be mobile (that is homeports are visited on a rotational basis) or resident at a specific sampling site. In either case, their job is to determine the total number of fishing units (and if feasible, fishing gears) for all boat/gear types based at that homeport and number of those that have been fishing during the sampling day.

There are several ways of recording boat/gear activities. In many cases, they combine the interview method with direct observations. Direct observations can be used to identify inactive fishing units by observing those that are moored or beached, and the total number of vessels based at the homeport are already known, perhaps from a frame survey or register. Often enumerators will still have to verify that vessels are fishing as opposed to other activities by using interviews during the visit.

The pure interview approach can be used in those cases where a pre-determined sub-set of the fishing units has been selected. The enumerator's job is to trace all fishers on the list and, by means of interviewing, find out those that had been active during the sampling day. For sites involving a workable number of fishing units (e.g. not larger than 20), the interview may involve all fishing units.

Sometimes it is possible to ask questions on fishing activity which refer to the previous day or even to two days back. This extra information increases the sample size significantly with little extra cost, ultimately resulting in better estimates of total fishing effort. Experience has shown that most of the variability in boat/gear activity is in time rather than space.

6.3.4 Direct observations

6.3.4.1 Observers

Observers can make direct measurements on the fishing vessels, at landing sites, processing plants, or in markets. The variables that enumerators can collect include catch (landing and discards), effort, vessel/gears, operations, environmental variables (e.g. sea state, temperature), biological variables (e.g. length, weight, age), the values and quantities of landings and sales.

In practice, observers do not only make direct measurements (observations), but also conduct interviews and surveys using questionnaires. They might also be involved in data processing and analysis. The tasks of an observer are difficult and adequate training and supervision are therefore essential.

Clear decisions need to be made on the nature and extent of data collected during any one trip. Often, the amount of data and frequency of collection can be established analytically with preliminary data.

Preferably, observers should only collect data, not carry out other activities, such as enforcement, licensing or tax collection. This should help to minimise bias by reducing the incentives to lie. Problems in terms of conflicts between data collection and law enforcement, for example, can be reduced by clear demarcation, separating activities by location or time. This becomes a necessity for at-sea observers. Their positions on fishing vessels and the tasks that they perform depend significantly on a good working relationship with the captain and crew, which can be lost if they are perceived as enforcement personnel.

The major data obtained through at-sea observers are catch and effort data, which are often used for cross checking fishing logs. At the same time, the at-sea observers can collect extra biological (fish size, maturity, and sex), by-catch and environmental data, as well as other information on the gears, fishing operations etc. Frequently, discards data can only be collected by at-sea observers.

The main data obtained from observers at landing sites, processing plants and markets include landing (amount, quality, value and price), biological (size, maturity), and effort (how many hauls, hours fishing) data. For the large-scale fishery where a logbook system is used, data collected at landing sites could be used to crosscheck data recorded in logbooks. Data collected from processing plants include quantities by species and, especially in modern factory practices, the batch number of raw materials, which can sometimes be traced back to fishing vessels. These data if collected can be used to validate landing data.

Collecting data to estimate raising factors for converting landed processed fish weight to the whole weight equivalent may be necessary. By sampling fish before and after processing, conversion factors may be improved. Potential seasonal, life history stage and other variations in body/gut weight ratios suggest date, species, sex and size should be recorded in samples.

Economic and demographic data at each level (e.g. input and output of various products to and from market and processors) are usually obtained by interview and questionnaire. However, the data directly collected by enumerators can also be the major source as well as supporting data for those collected through other methods.

While product data in processing plants can be collected through questionnaire (6.3.2) or interview (6.3.3), enumerators can directly collect many physical variables (weight, number, size etc.) more accurately. Automatic scales, through which a continuous stream of fish passes, can record the weight of fish mechanically or through computerised sensors. Similarly, mechanical or automatic weighing bins for whole frozen or defrosted fish, prior to entry to a processing line or cold store, can be used to record weights for each batch. Otherwise, boxes need to be counted and sub-sampled to ensure their fish contents are correctly identified and weighed.

Fish is often landed in bulk together with non-fish materials (e.g. ice, brine slurry, packing material and pallets). It can be very difficult to estimate the total fish weight, let alone weight by species, product and size grade. Methods need to be established to record whether non-fish material is included in any weighing process (e.g. are scales set to automatically subtract pallet weight?). In the case of processed fish in sealed boxes, it may be that sampling to determine an average weight and then box or pallet counting is sufficient. Alternatively, each box or pallet is weighed and a note taken whether box and pallet weight should be subtracted at a later data when processing the data.

Complete landings of all catch in relation to a vessel's trip (i.e. emptying of holds) is preferred since records can then be matched against logsheets. However, in some circumstances off-loading in harbours, at the dock or at sea may only be partial, some being retained on board until the next off-loading. In this case, records should be maintained of both catch landed and retained on board.

6.3.4.2 Inspectors

Inspectors are a kind of enumerator involved in law enforcement and surveillance (for fishing regulations, sanitary inspections, labour control, etc.). They may work at sea on surveillance vessels, at landing sites on shore, at processing factories and at markets. In general, scientific data are better collected by enumerators who are not directly involved in law enforcement. Nevertheless, many variables collected by the inspectors are very useful, and include landings, operational information, effort, landing price, processing procedure and values of product to the market and processors. Inspectors are also useful in collecting employment data.

Inspectors may play an important role in verification. In many cases, reports can be physically checked with observations. For example, random samples of boxes can be taken to check box contents (species, product type and size grade) against box identification marks. Inspectors need to be skilled in such sampling strategies.

As with enumerators/observers, inspector data should be treated with caution because of the high chance of sampling bias. This potential bias of data collected by law-enforcement officers should be considered in analyses.

6.3.4.3 Scientific research

Ecological research methods can be undertaken independent of commercial fishing operations to measure variables related to fish populations or the environment. Such research can be carried out by institutional research vessels or by industry or institutions using commercial fishing vessels. The objective is to obtain observations on biological (e.g. stock abundance or spatial distribution and fish size, maturity and spawning activities) and environmental (e.g. salinity and temperature) variables. It is important that this type of research is carried out periodically in order to obtain time sequential data.

Similarly, socio-cultural research methods can be used to obtain specific information useful to management. Although these methods may not often be considered routine, they provide important data and should be considered for infrequent data collection where possible.

Key informants are individuals with specialised knowledge on a particular topic. They may include academic specialists, community leaders, or especially skilled fishers. Interviews are usually begun with a set of baseline questions, but the interviewer expects to elicit new and perhaps unexpected information by requesting that the key informant expand on his or her answers to these initial questions. This method is ideal for obtaining in-depth descriptive data on beliefs and practices, including historical practices.

Participant-observation is a technique whereby the researcher spends an extended period of time (from weeks to years, depending on the objective and the context) living with a target community, both observing their behaviour and participating in their practices. During this time, the researcher will be conducting formal and informal open-ended interviewing on a variety of topics. This is a good method for learning about the actual processes of decision-making, as opposed to the formal procedures. Cultural and institutional rules are rarely followed to the letter, and there are usually informal standards for an acceptable leeway. However, information on these standards can often only be obtained through participant-observation.

6.3.4.4 Data logging

Automatic Location Communicators (ALC) automatically log data through positioning and communications technology. They allow remote observation through recording of fishing activities at sea, and could replace logbooks and observers/inspectors on the bridges of fishing vessels. However, ALCs will be deficient in one simple respect: entry of data on the catch remains the responsibility of the captain.

Many data on fishing operations can be automatically recorded from bridge instrumentation. Position, speed, heading, deployment of gear through links to electronic instruments are likely to become more common in future. Once gathered, such data may be automatically transmitted to databases through satellite or ground communications.

The technology that combines vessel position and a catch assessment for management authorities through remote means is generally known as a Vessel Monitoring System (VMS). Confidentiality is the key to the widespread acceptance of VMS, as information on current fishing grounds, and therefore security of position information, is a major concern.

However, vessel positions, activities and catch reporting through these systems, directly to databases and thence to reports that either aggregate data or remove vessel identifiers are becoming possible. Since it will be relatively simple to check remotely sensed position against recorded position, logsheet records should become more representative of real vessel activities at sea.

6.3.5 Reporting

In most complete enumeration approaches, fisheries staff do not directly undertake data collection, but use external data sources. Most commonly, these sources are data forms completed by the fishing companies themselves, middle persons, market operators, processors and even trading companies and custom offices. Such methods are almost exclusively used for semi-industrial and industrial fisheries and institutions.

Fishing companies are often a good source of information regarding basic data on catches and fishing effort. Regular submission of basic data is a part of the fishing licensing process. Data submitted by companies are often in the form of logbooks or landings declarations. Logbooks should contain detailed information on individual fishing operations, including fishing grounds, type and duration of operation, catch by species and other types of data relating to weather and sea conditions. Landings declarations usually deal with grouped data presented as summaries of fishing trips and catch by species.

The advantage of using reports is that data are compiled by agents other than fisheries staff and sometimes can be made available in pre-processed computerised format directly from the company's records, thereby reducing administration costs. Confidentiality of information (such as fishing grounds and catch rates) should be part of the agreement for data submission, and statistical outputs of the survey should not contain information related to individual fishing vessels or companies. However, there are also risks of under-reporting or of deliberate distortion of data, especially fishing ground, catch and revenue related information.

6.3.5.1 Harvest

The collection of data from all vessels within a fishery sector is sometimes needed usually from large-scale fisheries. Normally each vessel will be required to record their catch and effort data for every trip on a specially designed logbook. Because it is a painstaking task, usually only essential data are required. For various reasons, the data collected by this method could be inaccurate and thus validation from time to time by inspectors is important.

6.3.5.2 Post harvest

Data from post harvest operations are often used for obtaining information on landings, biology, markets, costs and earnings. Where logsheets, landings records and market reports are not available, reliable information can often only be obtained from processing factories. Reports by the processors generally include quantities and value of fish received and the resulting products. Additional information may include the origin of catch (fishing and transport vessels) and size categories of fish.

Monitoring off-loading catch in processed or whole round form requires considerable attention to detail and much depends on the relationship between the fishery authority and vessel captains or companies. It may be that sufficient trust has been developed to allow vessel or company off-loading records to be used directly, perhaps with random spot checks.

In some circumstances, off-loading may proceed directly to a processing factory or cold store (particularly by conveyor of bulk fish such as small pelagics, tuna etc.). Detailed landings can still be recorded as long as each batch is marked with its source (vessel name and trip identifier).

Most factories will maintain records of fish (by species, product type and size grade) that enter processing directly or cold store. They will also maintain information on their output and sales, including destination and price, although such data may be much more difficult or impossible to obtain unless legally required. Data forms will need to be customised to the type of processing and the factory management system.

6.3.5.3 Sale

Market transaction records may form a feasible way of collecting landings with complete enumeration, particularly in large fleets of small-scale vessels that land in central locations. All invoices, sales slips or sales tallies should be designed with care as to content, style and availability to ensure completeness of coverage. Given the potential volume of paper work, simplicity and brevity will often be the most important criteria.

The primary identifier on records should be the name of the vessel (including all carrier vessels unloading from more distant fleets) that sold the catch, and the date or trip number, since vessels may make more than one sale from one landing. Total weight by species or commercial group, and price should be collected. Ideally, further data should be obtained on fishing ground and level of fishing effort, although often this is not possible.

In similar fashion to logsheets and landings sheets, sales records should be prepared in appropriately identified forms in multiple copies as required. Copies are likely to be required for the market administration (if necessary), the seller, the buyer and the fishery authority.

General sales records, such as volume of sales and prices by product type, provide useful information for bio-economic analyses and a source of data on catch and landings when all other avenues for data collection are unavailable. Three information sources on general sales are usually available: market, processing factory and export data. However, these data must always be treated with care. The further away the data sources are from the primary source, the more errors will be introduced, and the more details (e.g. fishing ground, fishing effort) will be lost.

In addition to these, direct surveys of fishing companies may provide vital details upon which overall fisheries management and administration can be based. Annual fisheries statistical surveys can be voluntary or compulsory. If voluntary, responses will depend on the level of co-operation between the private sector and the authorities. If compulsory, legislation is required and can be drafted in various forms, such as Companies or Statistics Acts.

6.3.5.4 Trade

Trade data refers to information from customs or similar sources on trade. These data are used in socio-economic indicators and, in some exceptional cases, support landings data.

Information on exports and imports is published in most countries. It is particularly important where export or import taxes are payable, or export incentives given. Of course, export and import data is of limited use in estimating the total production of fish unless there are also means to establish the proportion of catch that is used in domestic consumption. However, in some particular cases, the trade data are the main source for estimating landings (e.g. shark, tunas). If trade data are used for validating or estimating landings, the quantities will usually need converting to whole weight.

The lack of detail in export data can be a problem simply because of the form in which they are collected. Export categories recorded by the authorities (not usually in co-operation with fishery authorities) can mask much of the information required. Canned fish, frozen fish, fresh fish, dried fish and fishmeal may be the only relevant categories for export authorities. Together with accurate raising factors, these data can be used for total fish production. This method of estimation is fairly accurate when there is a small local market. However, unless they are broken down by species and linked back directly to sources of data closer to the harvest sector, they provide little value for fishery management purposes.


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