204 



DRAFT 



management activities identified in the OFIC report, but this matrix recognizes that a 

 specific cause of biological impact can be associated with more than one activity. 



The effect of each biological impact in the matrix is presented as the relative survival 

 change (percent) in each life history parameter. For example, if siltation reduces egg 

 survival by 45 % , the matrix entry would be -45 % . If a factor has a direct negative 

 impact on one parameter that results in a related change in another parameter, it would 

 be reflected in the matrix. For example, if a 45% reduction in egg survival results in a 

 10% increase in juvenile survival because of reduced juvenile rearing densities, matrix 

 entries would be -45% for egg survival and -1-10% in juvenile survival. This approach 

 allows the incorporation of compensatory survival relationships in the evaluation of the 

 environmental and management factors. 



The final measure of the biological impact of each factor on salmonid production is the 

 percent change in recruits to adult. With this approach, the evaluation is based on the 

 change in total salmonid production that occurs because of the activity being evaluated. 

 For a given factor, the recruits to adult (RTA) relationship is estimated under baseline 

 and impacted conditions as: 



RTA = (adult spawners) x (eggs/adult) x (egg survival) x 

 (juvenile survival) x (survival to adult). 



The percent change in RTA (PRTA) is then calculated as: 



PRTA = -100 X [1 - (RTA impacted / RTA baseline)]. 



The empirical data used to calculate the percent change in salmonid production (PRTA) 

 is not presented in the matrix. The purpose of the matrix is to present the direction and 

 magnitude of changes in population parameters and production. A supportive table for 

 each matrix would present ^e associated empirical data. The column and row headings 

 of this table would be the same as the corresponding matrix, however the entries would 

 be the empirical measures, under baseline and impacted conditions, of adult spawners, 

 fecundity per adult, egg survival, juvenile survival, survival to adult, and recruits to 

 adult. 



The following table provides an illustration of the possible format of an alternative 

 matrix using this methodology (Table 1). In the first column are the identified causes 

 of biological impact and all of their various combinations (to examine cumulative 

 effects). In the second column are the potential activities or sources that contribute to 

 the identified impact. In columns 3-7 are the relative survival changes (percent) of the 

 five population parameters. The final column reports the total relative change (percent) 

 in salmonid production (recruits to adult) associated with the identified biological 

 impact. To complete an accurate evaluation of the relative impacts of the various 

 environmental and management factors, a separate matrix would have to be generated 

 for each species and basin combination. 



15 



