CARLINE: PRODUCTION BY WILD BROOK TROUT 



of age trout was important; they averaged 449c 

 of the total. 



Among populations the influence of age trout 

 on total production was evident when production 

 by individual age-groups was considered in rela- 

 tion to their biomass (Figure 7). Age trout had 

 a marked^ effect on the slope of the relationship 

 between B and P when all age-groups were com- 

 bined. The linearity of these relationships was 

 due to similarity in growth rates within and 

 among populations. If growth rates had declined 

 with increasing biomass, the relationship be- 

 tween B and P would have been curvilinear. 



There was no single parameter that could 

 adequately describe levels of recruitment because 

 numbers of trout hatched within ponds and num- 

 bers of immigrants were different in each popula- 

 tion. If densities of fall fingerlings or spring 

 yearlings were used as indexes of recruitment, 

 mean annual production among populations and 



o 



100 



200 



MEAN BIOMASS OF ALL COHORTS (kg/ha) 



tr 

 o 

 I 

 o 

 t_> 

 _l 

 < 



3 

 Q 



a 



z 



120 -i 



100 



80 



60 



p 40 



o 



3 



a 



o 



£ 



°- 20 



z 



20 40 60 



MEAN BIOMASS OF INDIVIDUAL COHORTS (kg/ha) 



80 



FIGURE 7. — Relationships between mean annual biomass and 

 annual production. Production and biomass of all cohorts are 

 combined in upper panel. In lower panel each point represents 

 a single cohort. Lines fitted by inspection. 



recruitment were directly related (Figure 8). 

 Although age trout made up a substantial 

 portion of total production in Hoglot and Maxwell 

 springs, production of just age 1 and older trout 

 was also related to recruitment. 



The ratio of annual production to mean annual 

 biomass (PIB) has been called "turnover rate" 

 and "efficiency of production." The PIB ratio is, 

 in fact, the weighted mean growth rate of the 

 population. Population production is the sum of 

 G x B for each year class, hence, dividing total 

 production by the sum of year class biomasses 

 yields population growth rate, weighted according 

 to the biomass of each age-group. 



Among populations annual PIB ratios for age 1 

 and older trout varied by more than 100^ (Table 

 11). The PIB ratio in 1969 at Clubhouse Springs 

 ( 0.63) was probably underestimated. Growth rates 



300 



200 



100 



z 



2 o 



i- 



o 



3 

 O 



o 



Q- 



MAXWELL SPRINGS 



HOGLOT SPRINGS 



.— age I* 



CLUBHOUSE SPRINGS 



" 



-age 



< 



< 



5 



300 



200 



'00 



1250 2500 



MEAN DENSITY OF SPRING YEARLINGS (No /ha) 



MAXWELL SPRINGS 



HOGLOT SPRINGS 



CLUBHOUSE SPRINGS 



_ 



age I*- 



age 0- 



s 



" 



1000 2000 



MEAN DENSITY OF FALL FINGERLINGS (No ./ha) 



3000 



FIGURE 8. — Mean annual densities of spring yearlings and fall 

 fingerlings in relation to mean annual production of age and 

 age 1 and older trout. 



761 



