Catch per unit effort
Encyclopedia
In fisheries and conservation biology
, the catch per unit effort (CPUE) is an indirect measure
of the abundance
of a target species. Changes in the catch per unit effort are inferred to signify changes to the target species' true abundance. A decreasing CPUE indicates overexploitation
, while an unchanging CPUE indicates sustainable harvesting
.
CPUE has a number of advantages over other methods of measuring abundance. It does not interfere with routine harvesting operations, and data area easily collected. The data are also easy to analyse
, even for non-specialists, in contrast to methods based on transect
s. This means that decisions about stock management
can also be made by the people doing the harvesting. The best practice
is to standardise the effort employed (e.g. number of traps or duration of searching), which controls for
the reduction in catch size that often results from subsequent efforts.
Although CPUE is a relative measure of abundance, it can be used to estimate absolute abundances. The main difficulty when using measures of CPUE is to define the unit of effort.
Conservation biology
Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction...
, the catch per unit effort (CPUE) is an indirect measure
Proxy (statistics)
In statistics, a proxy variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained...
of the abundance
Abundance
Abundance may refer to:In science and technology:* Abundance , the opposite of scarcities* Abundance , growing food with plentiful resources that will not run out -- sunshine, CO2, and waste or brine water....
of a target species. Changes in the catch per unit effort are inferred to signify changes to the target species' true abundance. A decreasing CPUE indicates overexploitation
Overexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Sustained overexploitation can lead to the destruction of the resource...
, while an unchanging CPUE indicates sustainable harvesting
Sustainability
Sustainability is the capacity to endure. For humans, sustainability is the long-term maintenance of well being, which has environmental, economic, and social dimensions, and encompasses the concept of union, an interdependent relationship and mutual responsible position with all living and non...
.
CPUE has a number of advantages over other methods of measuring abundance. It does not interfere with routine harvesting operations, and data area easily collected. The data are also easy to analyse
Analysis
Analysis is the process of breaking a complex topic or substance into smaller parts to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle , though analysis as a formal concept is a relatively recent development.The word is...
, even for non-specialists, in contrast to methods based on transect
Transect
A transect is a path along which one records and counts occurrences of the phenomena of study .It requires an observer to move along a fixed path and to count occurrences along the path and, at the same time, obtain the distance of the object from the path...
s. This means that decisions about stock management
Stock management
Stock management is the function of understanding the stock mix of a company and the different demands on that stock. The demands are influenced by both external and internal factors and are balanced by the creation of Purchase order requests to keep supplies at a reasonable or prescribed...
can also be made by the people doing the harvesting. The best practice
Best practice
A best practice is a method or technique that has consistently shown results superior to those achieved with other means, and that is used as a benchmark...
is to standardise the effort employed (e.g. number of traps or duration of searching), which controls for
Controlling for a variable
Controlling for a variable refers to the deliberate varying of the experimental conditions in order to see the impact of a specific variable when predicting the outcome variable . Controlling tends to reduce the experimental error...
the reduction in catch size that often results from subsequent efforts.
Although CPUE is a relative measure of abundance, it can be used to estimate absolute abundances. The main difficulty when using measures of CPUE is to define the unit of effort.