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Collection of fisheries data usually has more than one objective. Fisheries biologists, economists, sociologists, managers, politicians, industrialists, etc. may all require different information. Some basic fisheries data, however, will be of interest to all groups.

The first objective of fisheries data collection is the regular publication of a yearbook or Annual Fisheries Statistics by the government. The publication presents the overall description of the fisheries sector, and it will usually be supplemented by a number of other publications on specialised topics.

An overall description of the sector is the first prerequisite for any rational management of the fishery. The publication should cover biological, technical, demographic, economic and sociological data. In additional to the annual publication, various profiles of the fisheries sector are useful as general information for decision-makers in fisheries management and development. The reports on the fisheries sector must be supplemented by reports on the current stage and the historical development of the resources. Routinely collected data may also be used in research, when supplemented with other data.


Decision-makers in fisheries, at all levels, must posses an overall knowledge of the fisheries sector, including the overall fisheries statistics usually published as the “Yearbook of Fisheries Statistics” or “Annual Fisheries Statistics”.

Such annual publications will contain tables with number of fishers, number of fishing vessels and particulars of vessels and fishing gears, fisheries infrastructure, production by species, gear and area in value and weight, import and export, legislation, trends in production and development, etc. Obviously, one objective of data collection is to produce these yearbooks.

However, the yearbook does not always contain the type of detailed information needed for prediction of the effect of management and development decisions. These details comprise landings in weight and value by species (or species group) and by fleet (vessel/gear category, fishing effort), variable costs, fixed costs and earnings of the fishing operations, investments and employment. More detailed data will usually be published in reports from scientists and administrators to the government or to international fisheries bodies. Some results may be published as scientific papers or books.

Eventually, summaries of information will be distributed through the press or the Internet, either through the initiative of data managers or scientists, or through a request from the press itself. The information derived must be distributed or published, and preferably published in different ways to different target groups. If data are not published or made accessible in some form, there is little point in collecting them.

In 1997 FAO published “Fisheries management”, No. 4 in the series of “FAO Technical Guidelines for Responsible Fisheries”. This publication allocates around 30% of its pages to “Management data and information requirement and use”. Many of the data types mentioned are information from processed data, such as the results of fish stock assessment. This type of data does not belong to the type of database dealt with in the present manual, which is constructed to deal with the collection and storage of raw data, not processed data.

The overall objective of data collection cannot be defined in an exact manner, due to the multitude of data needs. There is no single objective, but a suite of objectives, some of which may not go together very well. So the overall objective can be described only in very general terms, such as:

“To create a fisheries management information system”


“To meet the requests from the public on information about the fishing sector, with special emphasis on the information needed for a rational decision-making in fisheries management and development”.

This may in turn lead to all kinds of specialised (but routinely collected) data for special scientific, inspection, control, enforcement and protection purposes, but the fundamental pillars of the fisheries management information system are the catch and effort data, and vessel registration.

An Example of an Objective: Estimation of Total Landings

It is useful to have an example of an objective of data collection, by which the concepts can be illustrated. A very common and important objective, the estimation of the total landings by value and by weight, is used here to develop an example data collection programme.

Total landings may be all species, all fleets and all seasons combined. However, total combined landings will usually not be considered a sufficiently detailed description of fisheries production, and so landings are divided on several levels.

Landings will usually be divided into:

  • Administrative geographical areas (e.g. provinces of a country);

  • Landing places;

  • Fishing fleets (Vessel category, see definition in Section 3.1.3);

  • Commercial landings groups (e.g. species groups, see definition in Section 5.3);

  • Fishing seasons;

  • Fishing grounds.

For the scientific analysis of fisheries resources, total landings are often required by species (or stock). For fish stock assessment methods such as VPA (Virtual Population Analysis, see Section 3.2.2) the total number of individuals caught by age and/or size group is required. Several methods of resource evaluation, however, use the CPUE (catch per unit of effort, for example kg caught per day) as the basic input, but methods based on absolute values (total catch) are preferable compared to methods based on relative values (CPUE).


2.2.1 Directorate of Fisheries

The production of an Annual Fisheries Statistics report is naturally the responsibility of a ministry (i.e. the national fisheries management authority). In the following, we shall refer to this government body as the “Directorate of Fisheries”.

The Directorate of Fisheries usually assumes the responsibility for registration of fishing vessels, and thereby they will be responsible for maintaining a vessel register. The directorate will usually maintain a number of other databases on production, quality and prices of sea products.

Basic catch and effort data is usually also the responsibility of the Directorate of Fisheries. The basic catch data comprise weight and value of landings by administrative unit (for example province), by fleet (vessel/gear category) and by commercial group of landings (for example, species group and size group).

2.2.2 Fisheries Research Institute

The “Fisheries Research Institute” will often be a part of the ministry responsible for fisheries, although it may also be found under another government department, a section of a university or an independent research institute. In any case, the Fisheries Research Institute must have a close relationship with the Directorate of Fisheries, which may be facilitated if it is a part of the same ministry. The research institute will have the responsibility to collaborate closely with the Directorate of Fisheries on exchange of data, analysis of data and reporting.

The Fisheries Research Institute will often have the obligation to perform resource evaluations and/or bio-economic analyses for the Ministry of Fisheries or for international bodies. The input for scientific analyses is usually a combination of basic catch and effort data combined with other routinely collected scientific data.

The research institute will have the responsibility to present the scientific information in a form, which can be applied by the managers and other decision-makers. It will also have responsibility to combine the scientific data with the basic fishery statistics collected by the Directorate of Fisheries, for the regular publication of reports on the state of the fishery.

2.2.3 Other Agencies

Other types of data from the fisheries sector, which are not specific to fisheries, will be the responsibility of institutions not under the ministry dealing with fisheries. Such data may comprise demographics, infra-structural and institutional data, imports and exports, information on taxation, household data, coast guard (or harbour police) registrations, meteorological data and so on. These agencies, departments, institutes and organisations have the same responsibility as the fisheries directorates and institutes, to deliver information to the public.

Data collected by a government agency should not be considered the property of the agency in question, but should be available to all concerned government agencies, and summaries of data should be available to the public. Similarly, the private industry must have the obligation to deliver basic, accurate information to the government agencies. These obligations must be secured by adequate fisheries legislation.

Some information from individual private entrepreneurs, however, must be treated as confidential. It is important that the industry has a guarantee that confidential information is not passed on to competitors or other parties who have no legal rights of access. This might be achieved by publishing only summary information on the industry, in such a form that the information cannot be traced back to individual entrepreneurs.


The concept of “stock” is rather complicated and there is no consensus among scientists on how to define it. A full discussion of the stock concept in the context of fisheries management is given in Begg et al. (1999). A living stock could be defined as a group of animals from one species, which share a common gene pool. For the management of fisheries, however, this definition is academic rather than practical. Therefore, we shall try to identify more operational concepts. For management of fisheries, it is the concept of “management unit” rather than stock that is useful. A management unit is a resource for which it is possible to make predictions, or, in other words, something for which we can give answers to “What-if questions”.

The first problem encountered in a typical tropical country, is that of the definition of stocks. More than 500 species of fish, cephalopods and shrimps may be included in the list of sampled species of commercial interest. Each of the species could consist of a number of “stocks”. Thus in practice, a sampling programme is often not able to apply the stock concept rigorously. The programme has to replace the concept of a “stock”, with the concept of a “management unit”.

According to the agreed international standards, “reference points” are an important concept in implementing a precautionary approach to fishing. Reference points are closely related to the stock concept. Annex II of the UN Agreement on Straddling and Highly Migratory Fish, distinguishes between “target reference points” and “limit reference points” for fish stocks. The relevant paragraphs are:

Two types of precautionary reference points should be used: Conservation or limit reference points and management or target reference points. Limit reference points set boundaries, which are intended to constrain harvesting within safe biological limits within which the stocks can produce maximum sustainable yield. Target reference points are intended to meet management objectives.

Precautionary reference points should be stock-specific to account, inter alia, for the reproductive capacity, the resilience of each stock and the characteristics of fisheries exploiting the stock, as well as other sources of mortality and major sources of uncertainty.

Fishery management strategies shall ensure that the risk of exceeding limit reference points is very low. If a stock falls below a limit reference point or is at risk of falling below such a reference point, conservation and management action should be initiated to facilitate stock recovery. Fishery management strategies shall ensure that target reference points are not exceeded on average.

The fishing mortality rate, which generates maximum sustainable yield, should be regarded as a minimum standard for limit reference points. For stocks, which are not overfished, fishery management strategies shall ensure that fishing mortality does not exceed that which corresponds to maximum sustainable yield, and that the biomass does not fall below a predefined threshold. For overfished stocks, the biomass, which would produce maximum sustainable yield, can serve as a rebuilding target.

Therefore, fishing mortality rates, biomass, or other measures should be regarded as indicators of the status of the stock in relation to predefined reference point limits, that should be avoided, or targets, that should be aimed at, in order to achieve the management objective. The identification of reference points requires a time series of scientific data, often over many years.

A key concept in some reference points is the Spawning Stock Biomass (SSB), which is defined as the number of individuals multiplied by the fraction of mature individuals for each age group, summed over all age groups. Another important concept is the “recruit”, which is a juvenile fish entering the exploited part of the stock.

With a few rare examples, the identification of the relationship between parent stock (SSB, spawning stock biomass) and subsequent recruitment (R) has remained elusive for marine fishes. The only point on the stock-recruitment (S/R) curve known for certain is the origin of the curve. If there are no parents, there will be no offspring, otherwise the curve is rarely estimated with certainty. The precautionary approach dictates that unless it is scientifically demonstrated that there is no relationship between the parent stock and subsequent recruitment, such a relationship should be assumed to exist, even if the data are ambiguous. Figure 2.3.1 shows the characteristic shape of a stock-recruitment curve. The broken straight line through the origin is the “replacement line”, which defines the survivorship needed to replace the spawning stock in the future. The slope of the replacement line depends on the fishing mortality. The higher the fishing mortality is, the fewer recruits will survive to become “parents”, and replacement line will, thus, be steeper.

There is no single model on the relationship between SSB and recruitment. The observations show large variation around any SSB/R curve, so scientists are not in a position to predict future recruitment with any accuracy. They are only able to tell the probability distribution of the future recruitment, and only then, if a long time series of SSB/R observations is available (Figure 2.3.2).

Figure 2.3.1

Figure 2.3.1 Illustration of the “Stock Recruitment Relationship”, “Replacement line”, and “Equilibrium Spawning Stock Biomass”. The slope of the replacement line depends on the mortality of the fish. The figure shows how the stock approaches an equilibrium, if the replacement line remains constant (B1/R1, B2/R2, … BEquilibrium/REquilibrium).

A target reference point is defined by the policy for the fisheries sector. It may aim at, for example, the maximum economic yield. Precautionary approach reference points are reference points selected so that the probability of exceeding a limit reference point is very small. Thus, fishing mortality limit reference points should always be larger than the precautionary approach fishing mortality (FPA). Notice that, when expressed as fishing mortalities, the reference points must satisfy the condition: Ftarget < FPA < Flimit.

For the tropical fish stocks it is often not possible to apply the methodology of reference points as outlined above, for the simple reason that the information on stock and recruitment, as well as fishing mortalities and other population parameters are not available.

Figure 2.3.2 shows typical information needed for the calculation of reference points, namely a long time series of recruitment estimates. This type of data is usually available for stocks in temperate waters, where the number of species is much less than in tropical waters, and where the definition of stocks is simpler (although still problematic in many cases).

If a data collection programme is to implement international standards for responsible fishing, it has to choose reference points that can be calculated by aid of the data currently available. The basic data collected is first of all catch rates (kg/day by fleet, season, fishing grounds and species group), also called CPUE (Catch Per Unit of Effort). Thus, possible candidates for reference points must be derived from, for example, catch rates.

Figure 2.3.2

Figure 2.3.2 Time series of recruitment. Information required for the use of international standard reference points.

The definition of reference points is difficult in the case where long time series of data are not available. The situation for many tropical countries is that of paragraph 2 in ANNEX II of Straddling and Highly Migratory Fish Stocks (UN, 1995):

“When information for determining reference points for a fishery is poor or absent, provisional reference points shall be set. Provisional reference points may be established by analogy to similar and better-known stocks. In such situations, the fishery shall be subject to enhanced monitoring so as to enable revision of provisional reference points as improved information becomes available”.

In some cases, only provisional reference points can be applied, which are defined with respect to CPUE data (catch rates). The definition of reference points could include socio-economic aspects. For example, the value of the catch per day of all major vessel types could be collected. This information combined with cost data could estimate the profitability or rates of return on investment. Profitability is one measure for the performance of an individual member of a fishing fleet. This and other measures of performance are of utmost importance when deciding on investment in a fishing vessel. The profitability also reflects the status of the resources. Catch rates and profitability are linked to the stock biomass, and should also signal when the biological reference points are exceeded.

Investments in the entire fisheries sector should be based not only on the profitability of single vessels, but also on the profitability of total fleets. One may, from the profitability, conclude that a certain vessel type is a promising object for investment, but it does not say how many vessels should be invested in. For these decisions total catch, total effort and total number of vessels in each major fleet must be known.

A certain number of vessels correspond to a certain investment, and therefore it should be possible to convert a precautionary approach fishing mortality (FPA) into a “precautionary investment policy”. The precautionary approach, which is usually expressed in terms of fishing mortality, can approximately be expressed as a number of vessels. The number of vessels together with the activity level of the vessels, gives the effort, which in turn can be converted into fishing mortality. This allows investment to be used as an indicator to guide decision making in preventing overcapacity, for example.

Figure 2.3.3

Figure 2.3.3 Illustration of the search for alternative reference points based on bio-economics.

In the tropics, it is not possible to carry out fish stock assessments for all commercially important living stocks. Even if the stock concept is replaced by the management units, there are still too many units to assess all of them. Therefore, the solution is to select a small group of representative species, and carry out a first stock assessment based on data from only one year (i.e. the minimum period covering the seasonal effects).

Figure 2.3.3 illustrates the search for alternative reference points, based on bio-economics. The curve kg/day (or value/day) is the link between biology and economics. The break-even point indicates the level of fishing effort, where the catch per day is so low that the fishers can no longer maintain a subsistence level from fishing (assuming alternative employment is not available). The break-even point may be reached when fisheries are poorly managed. Reaching this point for the major fleets of a nation will cause unemployment and bankruptcies in the fishing industry. “Optimum Fishing Effort” is a better management target, as it represents the long term maximum sustainable yield (or income) to the industry. However, the precautionary approach suggests that the management target of effort should be less than the “Optimum Fishing Effort”, as this target level may result in stock collapse, due to the large random (unpredictable) variations of fish stock biomass.

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