Fishing effort in capture fisheries is generally defined in terms of the amount of fishing gear of a specific type used on the fishing ground(s) over a given time period (e.g. duration of a fishing operation, fishing activity or fishing trip).  Any time spent searching for the aquatic organism(s) of interest is also taken into consideration. Fishing effort may be reported as nominal fishing effort or effective fishing effort.

Nominal fishing effort is used to quantify the unadjusted (i.e. unstandardized) total effort exerted on the aquatic organism(s) of interest in a given time period. Nominal fishing effort has a meaning that is easily understood by fishers, fishery managers and other users of fishery statistics, and is derived directly from logbook data or available statistics. However, the impact of a unit of fishing effort on populations of aquatic organisms and the ecosystem depends on the characteristics of the  fishing vessel (if used), the knowledge and skills of fishers, the characteristics of the fishing gear and the way the gear is operated. As a result, total effort is often adjusted (i.e. standardized) to account for such variations including differences in fishing power and efficiency in order to better quantify the impact of fishing on fishing mortality (e.g. Millischer et al., 1999; Marchal et al., 2002). When two or more types of gear are used or when the same gear is used for example by different classes of fishing vessel, the respective measures of effort must be adjusted to a common standard before such measures can be aggregated. The adjusted measure of effort is referred to as the effective fishing effort. Unlike nominal fishing effort, effective fishing effort is a means to account for variability in the efficiency of capturing the aquatic organisms of interest, such as differences in fisher skill and technology among fishing vessels (e.g. engine size, vessel length, electronic equipment), fishing fleets and métiers (from McCluskey and Lewison, 2008). 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.

Measures of fishing effort and associated catch per unit of effort generally underpin advice on the sustainable development and management of capture fisheries and such measures provide key inputs to stock assessment models and management strategy evaluation simulations. CWP recognizes that fishing effort statistics are often required as detailed, disaggregated data and national and regional fishery organizations publish effort statistics in various forms. Thus, it is recognized that the concepts and definitions used to quantify fishing effort may differ between organizations. In addition, adequate data on fishing effort may be difficult to obtain for some fisheries, and also fishing effort may be under-reported or unreported. As a result, fishing effort statistics compiled at national or regional levels usually reflect local and national requirements for, and limitations in collecting fishery data and statistics. In turn, variability in the way fishing effort statistics are collected and reported at local and national level may limit the compatibility of effort statistics and the exchange and wider use of these data in regional and global contexts.

Measures of fishing effort may also be dependent on, or independent of the type of fishing gear used. Gear-dependent measures are specific to the type of fishing gear used (e.g. number of hooks set, trawl tow duration) while gear-independent measures apply to all types of fishing gear (e.g. number of days fished, number of fishing trips).

In 2019, CWP established an ad-hoc task group to review and further develop fishing effort concepts for use in collecting statistical data on fishing effort from capture fisheries (FAO, 2019). In 2023, CWP endorsed the recommendations of the task group (FAO, 2022). The various components of fishing effort are described in the fishing effort concepts diagram and these concepts are defined in the associated glossary. Standard measures of fishing effort for use in collecting statistical data were also revised. The diagram, glossary and standard measures are interim and may be subject to further revisions by CWP.