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Data |
Management Applications |
Limitations |
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ESSENTIAL |
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1) Total annual landings |
Able to monitor trends in landings and adjust fishing effort up or down according to trend |
Cannot be sure whether trend results from changing resource abundance, changing effort or environmental changes leading to e.g. variability in availability |
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2) Annual fishing effort by fleet e.g. days fished; number of traps; etc. |
a) Can calculate average catch rate (catch/effort), which better index of abundance than catch. b) Can observe trends in fleet size and effort, indicating changing interest in or dependence on fishery |
a) Catch rate can also be affected by other factors apart from abundance e.g. availability, changes in fishing practice, density of fishing effort. Therefore must be interpreted cautiously |
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3) Destination (market) of landings and average price per unit mass for i) domestic market and ii) export market |
Together with trends in fishing effort, gives indication of economic conditions in fishery, may also indicate whether effort likely to increase or decrease |
Profit = income - expenditure. Without information on expenditure, have only incomplete information on profitability of fleet and fishery as a whole |
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4) Number of fishers and shore-based workers within each fleet |
Indicates social importance of the fishery |
Does not give information on the standard of living of the fishers and their dependents |
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HIGHLY DESIRABLE |
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5) Length and/or age composition of catch (this can frequently be obtained for the industrial fishery directly from the processing factory or company) |
a) Fishing pressure reduces the average size of the population, and such changes provide an index of the impact of fishing on the population b) Potential yield from a population varies with size at capture. This information facilitates design of fishing gear and fleets to optimize yields c) Gives indication of recruitment variability |
May be costly to obtain, but time series of good information on catch, effort and size composition of the catch provide the basis for high level single-species assessments |
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6) Total bycatch and discards by species |
Fisheries may affect not only the target species but also other species and the environment. Management strategies should consider the impact of the fishery on the ecosystem as a whole |
Direct effects of fishing on other species and the environment are easier to estimate than indirect affects (e.g. food chain affects). To be useful, however, estimates of bycatch and discards should be part of a broader management plan for the ecosystem as a whole |
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7) Costs and profitability of fishing |
Management measures are usually designed to reduce the effort or efficiency of fishing. They therefore often affect the cost of fishing. Managers should have information on costs and profitability to take into consideration when formulating management strategies |
May not always generate the true economic importance to the sector, hence there is often a need to incorporate costs and profitability of exports and value added products |
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8) Dependence of fishers and shore-based workers, and their socio-economic conditions |
Important information for estimating the social impact of changes in management of the fishery (e.g. reducing effort, changing closed season, etc.) |
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DESIRABLE |
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9) Fisheries independent information on e.g. adult biomass, juveniles or pre-adults |
Properly designed and implemented biomass surveys can give more accurate (less biased) information than relying on fishery catch per unit effort. Estimates of pre-recruit stages can be useful in providing advance warning of likely adult abundance |
Can be very costly and time-consuming to obtain statistically valid estimates |
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10) Changes in critical habitats or the environment that could affect fish production and yield |
Fishing mortality is only one factor affecting the abundance of fish populations. If changes in the environment of the population are having an important impact on fish production, this should be taken into account in management |
In many cases the relationship between fish abundance and production and the environment is not well understood. This uncertainty often makes it very difficult to use environmental information effectively in fisheries management |
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11) The spatial characteristics of fishing |
Marine populations are normally unevenly distributed over their range, and fisheries operate in the regions of highest concentration. This can lead to local depletions and indices of abundance or of fishery performance that do not take spatial distribution into account can be misleading. Monitoring the spatial characteristics therefore can improve the accuracy of information |
Spatial information is difficult and can be costly to obtain, but is being facilitated by technology such as GPS and vessel monitoring systems |
