Fishing effort is generally defined in terms of the time spent searching for fish (search duration) and/or the amount of fishing gear of a specific type used on the fishing grounds over a given unit of time e.g. a fishing operation, fishing activity, day or fishing trip. The measure of effort (unit of fishing effort) depends on the fishery and type of gear used. The impact of a unit of fishing effort on the fish populations and the ecosystem in general differs amongst vessels and fishers and depends on the gear deployed. As a result, effort statistics often need to be qualified (e.g. by vessel type, engine power, seasonal effect). When two or more kinds of gear are used or when the same gear is used for example by different classes of vessel, the respective efforts must be adjusted to some common standard before being aggregated across all classes. This common standard is sometimes referred to as effective fishing effort. Standard measures of effort for each ISSCFG category (Annex M) of fishing gear are listed in Table 1.

Table 1: Standard measures of effort for each category of fishing gear. Refer also Report of technical workshop on global harmonization of Tuna fisheries statistics, March 2018, Session 6.2 and Appendix 8.

Standards for fishing effort reporting (STATLANT questionnaires)

Varying levels of precision of fishing effort are identified in reporting forms used in STATLANT questionnaires and data should be provided for each of these levels. The three main levels of precision are defined as categories A, B and C where:

• Category A refers to a detailed unit of measure, e.g. hours fished or number of sets, etc. These units of measure will vary with the gear used. For possible combinations of gear and effort see Annex N I.
• Category B refers to number of days fished, i.e., the number of days on which fishing took place. For those fisheries in which searching is a substantial part of the fishing operation, days in which searching occurred, but no fishing took place should be included in "days fished" data.
• Category C refers to number of days on ground in addition to days fishing and searching; here all other days while the vessel was on the ground should be indicated.
• Another category (Category D in STATLANT form B21) uses the percent of pro-rated effort to estimate the percentages of the catches when data are incomplete.

The effort may be nominal, reflecting the simple total of effort units exerted on a stock in a given time period. Effort may also be standard or effective when corrected to take account of differences in fishing power and efficiency and ensure direct proportionality with fishing mortality and this relates usually to a specific fishery and gear. If more than one gear is considered, standardization in relation to one of them is necessary. For biologists, a good measure of fishing effort should be proportional to fishing mortality. For economists it should be proportional to the cost of fishing.

FAO. 1997. Fisheries management. FAO Technical Guidelines for Responsible Fisheries No. 4. Rome, FAO. 82 pp. (also available at http://www.fao.org/3/a-w4230e.pdf).

FAO. 2019. FAO technical workshop on global harmonization of Tuna fisheries statistics. Rome, 19-22 March 2018. FAO Fisheries and Aquaculture Report No. 1239. Rome, FAO. 55 pp. (also available at http://www.fao.org/3/CA3132EN/ca3132en.pdf).

Selected combinations of gear and effort (former ANNEX N.I)