catch per unit effort

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.{{cite book |editor=Kirsten M. Silvius, Richard E. Bodmer & José M. V. Fragoso |year=2004 |title=People in Nature: Wildlife Conservation in South and Central America |publisher=Columbia University Press |isbn=978-0-231-12783-7 |author=Pablo E. Puertas & Richard E. Bodmer |chapter=Hunting effort as a tool for community-based wildlife management in Amazonia |pages=[https://archive.org/details/peopleinnaturewi0000unse/page/123 123–136] |chapter-url=https://books.google.com/books?id=Ghr7KupbQacC&pg=PA124 |url=https://archive.org/details/peopleinnaturewi0000unse/page/123 }}

CPUE has a number of advantages over other methods of measuring abundance. It does not interfere with routine harvesting operations, and data are easily collected. The data are also easy to analyse, even for non-specialists, in contrast to methods based on transects. 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.{{cite book |author=William J. Sutherland |year=2000 |title=The Conservation Handbook: Research, Management and Policy |publisher=Wiley-Blackwell |isbn=978-0-632-05344-5 |chapter=Monitoring |pages=36–64 |chapter-url=https://books.google.com/books?id=u04eZtdAPXUC&pg=PA50}}

Although CPUE is a relative measure of abundance, it can be used to estimate absolute abundances.{{cite book |author=J. R. Skalski, Kristen Elaine Ryding & Joshua J. Millspaugh |year=2005 |title=Wildlife Demography: Analysis of Sex, Age, and Count Data |publisher=Academic Press |isbn=978-0-12-088773-6 |chapter=Analysis of population indices |pages=359–434 |chapter-url=https://books.google.com/books?id=Jp_FzZkKKB4C&pg=PA389}} The main difficulty when using measures of CPUE is to define the unit of effort.{{cite book |author=Working Party on Marine Mammals |title=Mammals in the Seas |series=FAO Fisheries Series, Number 5 |volume=1 |publisher=Food and Agriculture Organization |year=1978 |isbn=978-92-5-100511-8 |chapter=General aspects of population biology |pages=142–154 |chapter-url=https://books.google.com/books?id=-lqiLtuWSa8C&pg=PA146}} CPUE is also often nonlinearly related to abundance, making interpretation more difficult.{{Cite journal |last1=Harley |first1=Shelton J |last2=Myers |first2=Ransom A |last3=Dunn |first3=Alistair |date=2001-09-01 |title=Is catch-per-unit-effort proportional to abundance? |url=http://dx.doi.org/10.1139/f01-112 |journal=Canadian Journal of Fisheries and Aquatic Sciences |volume=58 |issue=9 |pages=1760–1772 |doi=10.1139/f01-112 |bibcode=2001CJFAS..58.1760H |issn=0706-652X}}