AN EXPOSITION ON THE DEFINITION OF FISHING EFFORT' 



Brian J. Rothschild- 



ABSTRACT 



The term "fishing effort" is well defined in population dynamics literature. The term as 

 defined in the population dynamics literature is, however, difficult to reconcile with broader 

 definitions of fishing effort, particularly those having economic implications. The present 

 paper discusses the distinction between the definitions and gives some examples in the 

 context of allocating inputs, the capacities of fishing boats, and several stocks to the catch 

 in a manner which maximizes profits. Managerial behavior is also an important input 

 to the fishing process; this is discussed in a decision theory format where decision quality 

 can be measured relative to entropy in the decision environment affording a comparison 

 among decision environments in terms of information and an imputed valuation of a bit 

 of information under various circumstances. The conventional measures of the quality 

 of the decision environment are often based upon expected catch. Alternate measures 

 are discussed which include the expected loss or the risk involved in the decision process. 



The deployment of fishing effort is one of the 

 fundamental components of fishery management. 

 While fishing effort has been rather precisely 

 defined in the population dynamics literature, ef- 

 fort has not been well defined in its broadest con- 

 text. This paper considers the definition of fish- 

 ing effort with special reference to the develop- 

 ment of techniques which are useful not only for 

 the definition of effort in the usual strategic 

 sense, but for the definition of effort in the tact- 

 ical and operational sense as well. This defini- 

 tion is requisite for considering fishing as a total 

 system (see Rothschild, 1971). 



The transformation of wild stocks of fish into 

 the "catch" is generally considered to be medi- 

 ated by the quantity of fishing effort expended 

 in the process of harvesting the catch. The 

 measurement of the magnitude of fishing effort 

 is of central importance to the theory of the dy- 

 namics of exploited fish populations because the 

 various "optimal" catches which are developed 

 in this theory must ultimately be related to op- 



^ Adapted from a paper presented at the International 

 Symposium on Fisheries Economics, sponsored by the 

 Organization for Economic Cooperation and Development 

 in Paris, France, November 29-December 3, 1971. 



^ National Marine Fisheries Service, Northwest Fish- 

 eries Center, 2725 Montlake Boulevard East, Seattle, WA 

 98112. 



timal quantities of fishing effort. On one hand 

 it seems quite obvious that fishing effort should 

 be related to quantities that can be thought of as 

 "inputs" to the fishing process, quantities such 

 as hours fished, fuel consumed, number of fish- 

 ermen, etc. Therefore, it is at least to some ex- 

 tent somewhat paradoxical that the basic defi- 

 nition of fishing effort which is used in popula- 

 tion dynamics, and commonly used in most fish- 

 ery management applications, does not necessar- 

 ily refer to any of these usual "inputs." Fishing 

 effort is defined in terms of the catch; that is, 

 one unit of real or nonnominal effort is simply 

 the numerical fraction of the average popula- 

 tion that is caught. In order to emphasize this 

 point, consider two fishing fleets. Each fleet 

 fishes on separate populations which are in every 

 respect identical. The fleets make identical 

 catches and, therefore, each removes identical 

 fractions of the average populations from each 

 population. By definition, then, these two fleets 

 both exert the same amount of fishing effort. The 

 fact that "inputs" are not implicit in the theory 

 can be seen by identifying the first fleet as con- 

 sisting of 100 modern trawlers and the second as, 

 perhaps, 10 pleasure yachts that have been mod- 

 ified just enough to enable them to catch fish. 

 Even though both fleets exert equivalent amounts 

 of fishing effort, their inputs — indexed by, say. 



Manuscript accepted April 1972. 



FISHERY BULLETIN: VOL. 70. NO. 3, 1972. 



671 



