EMMETT and JAMIESON: TRANSPLANT OF NORTHERN ABALONE 



SITE C 

 x=78 7t|IO 

 n = 438 



iLo^ ^ 



50 60 70 80 90 100 110 120 



SHELL LENGTH (mm) 



x = 81.6* 9.3 

 n= 126 



50 60 70 80 90 100 110 120 



SHELL LENGTH (mm) 



Table 5 summarizes these economic parameters 

 for values of M^^ ranging from 0.10 to 1.00. These 

 data indicate that a reasonable value for the inter- 

 nal rate of return (i.e., >20%) would be obtained at 

 •^max values of 0.80 or less. Transplants to site A 

 but not site B would show a reasonable rate of 

 return. 



This model can be generalized to estimate eco- 

 nomic returns for variable abalone seed costs in 

 the case of transplanting hatchery- reared seed 

 to the wild. Figure 4 summarizes internal rates 

 of return for 20 mm hatchery seed of variable 

 cost, a 4.5 yr growth period, planting costs of $0.20 

 per abalone, and harvest costs of $0.40 per kg. 

 All other assumptions are the same as the model 

 given above. Under these price assumptions, M^^ 

 values must be less than 0.6 to show a reasonable 

 rate of return if seed costs are ^$0.10 per abalone. 

 At M^^ values greater than 0.8, transplanted 

 abalone seed will not yield a reasonable rate of 

 return unless seed costs are extremely low (<$0.02 

 per abalone). 



Figure Z.-Continued-(U[a.rch 1985  Tj) of the study. 



Harvest costs were similarly estimated at $1,575. 

 Fixed costs were not included and were assumed to 

 be zero. This information is used in the following 

 simple economic model which examines the rate of 

 economic return as a function of M^^ (instantane- 

 ous natural mortality estimated from recovery of 

 live abalone). 



Assuming that 5,000, 80 mm abalone are trans- 

 planted, they reach legal size (100 mm and 340 g) 

 in two years, and can be sold at a price of $11 kg"^ 

 Then 



gross return = $11 kg ' x 0.34 kg abalone"' x 

 5,000 abalone x e"''^, where t 

 = 2, M = M^ 



gross return-harvest costs, where 

 harvest costs = $1,575 

 net return-initial costs, where ini- 

 tial costs = $1,500 



1 



net return 

 profit 



discounted 

 profit 



net return 



1 -I- d 



initial 



internal rate 

 of retiu-n 

 (IRR) 



costs, where d = discount rate = 

 10% 



gretun, rate _ ;l_o, whorO rotum 



rate = (In (net return/initial 

 costs))/i. 



Table 5, — Summary of economic returns from 

 transplanting abalone, assuming 2 years to recov- 

 ery. Calculated from ttie economic model given in 

 text. IRR = Internal rate of return; f = 2 years. 



DISCUSSION 



In this study northern abalone transplanted from 

 exposed areas to more sheltered habitat grew faster 

 than nontransplanted controls. These results cor- 

 roborate the observations of Breen (1986) that 

 "surf" abalone retain the potential to grow well 

 when placed in more productive habitat. These ob- 

 servations suggest that abalone are, to some degree, 

 food limited in exposed habitats which have little to 

 no canopy-forming algae. 



Because northern abalone varied in size in differ- 

 ent sections of the source area, the initial size of non- 

 transplanted abalone at the control site was signif- 

 icantly less than that of the transplanted abalone 

 (Fig. 3). This bias would be expected to reduce the 

 difference in growth rate between the abalone at 



101 



