Assumption 2 



2. Being caught, handled, and marked one or more times has no effect 

 on an individual's subsequent chance of recapture and marked fish mix 

 completely with the unmarked population. 



Samples for marking and recaptures were taken over a 2-day period a 

 week apart during each survey. Recaptures of fish marked within the 

 sampling week were ignored for estimation purposes. It has been reasonably 

 assumed that the week period between marking and recapture has allowed 

 the marked fish to randomly mix within the population. In addition, all 

 fish were released within their area of capture. 



The number of specimens recaptured one or more times was examined 

 to see if any individuals may have been capture-prone and thus biased 

 the Jolly estimates. Similar proportions of capture frequencies were 

 noted for each year with most (88.2 - 94.8%) individuals recaptured only 

 once and very few (0.7% overall) recaptured more than twice (Table 10). 

 Therefore it is unlikely that the population estimates were biased by 

 variable catchability or the existance of particularly capture-prone 

 individuals. 

 Assumption 3 



3. A marked fish has an equal chance of being caught as an unmarked 

 fish. All emigration from the study area is permanent and therefore 

 indistinguishable from death in the model. 



This assumption was previously examined in detail in NUSCo (1980). 

 The phenomenon of non-permanent or temporary outmigration can lead to 

 overestimation of population and probability of survival using the Jolly 

 technique as the fish that temporarily leave the study area are not 

 subject to the same probabilities of survival and capture as those 



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