

Evaluating the significance of changes in available for- 

 age for predators is another aspect of the impacts of a fish- 

 ery on nontarget species. At the present state of the art 

 of ecology, even if changes in food availability could be 

 predicted with reasonable precision, it would still be diffi- 

 cult to anticipate the exact responses of predator popula- 

 tions to those changes. Predators respond to the size, den- 

 sity and distribution of prey, as well as to the overall 

 amount of prey available. Potential responses include be- 

 havioral changes as well as changes in overall population 

 size. In addition, the possibility of a shift of predators 

 to alternative prey species should be considered. For the 

 practical development of ecosystem oriented management, some 

 careful consideration needs to be given to which parameters 

 of predator prey relationships should in fact be measured, 

 what kind of data are practical to collect, and what kind of 

 indicator information needs to be observed to be able to pre 

 diet overall population responses. Small scale perturbation 

 experiments might be considered as one possible method for 

 investigating how predators and prey respond to changing den 

 sities . 



Treating a fishery as an additional predator in an eco- 

 system may be a useful perspective for consideration of the 

 impacts of a fishery on target and nontarget species. 



In the same context, a fishery can be viewed as a preda- 

 tor that lacks the regulating feedback that controls natural 

 predator populations in an ecosystem. OY formulations could 

 be designed to mimic natural controls on a predator by using 

 appropriate functions of measured ecosystem parameters such 

 as threshold values for the density of the target species, 

 its other predators, or some indicator species, by very strict 

 limited entry formulations, or by compensating for increased 

 capture efficiency with reduced effort. 



Risk Assessment 



One approach to evaluating the impact of proposed fish- 

 ing levels on populations of marine mammals and of endangered 

 species is to assess the probabilities that adverse impacts 

 on those populations would result from various harvest levels 

 Probabilities of adverse impacts, or lack of them, are the 

 risk levels associated with particular activities. The de- 

 tailed information on the fishing industry and on social and 

 economic ramifications of proposed management measures found 

 in almost all FMPs demonstrates that levels of economic risk 

 can be evaluated. 



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