EMMETT and JAMIESON: TRANSPLANT OF NORTHERN ABALONE 



Table 2.— Recovery of live abalone in March 1985, recovery of abalone shells over the study period, and estimation 

 of M^^„ (from tagged shell recovery) and M^^ (from live tagged abalone recovery). Number recovered was after 

 / # tagged survivors \ 12 

 # initially tagged j 9 



Recovery 



9 months, so M = - In 



ered the shells of all tagged northern abalone that 

 had died. The recovery of live tagged abalone allows 

 estimation of maximal instantaneous natural mor- 

 tality (Afmax). assuming that divers recovered all the 

 living abalone. Values for M^^^ ranged from 0.10 to 

 0.27 for the three study sites; M^^^ ranged from 

 0.56 to 1.51 (Table 2). 



The movement of northern abalone from the lower 

 edge of the Macrocystis bed to deeper (5-11 m) 

 water shortly after the transplant (described above) 

 effectively increased the area of each transplant site 

 by threefold. Approximately 30% of recovered 

 northern abalone were found below the vegetation 

 zone at both transplant sites. This movement, 

 coupled with abalone losses, resulted in final abalone 

 densities of 1.27 m"- at site A and 0.73 m"- at 

 site B. 



Prior to final harvesting, divers searched beyond 

 the expanded boundaries of the sites for tagged 

 northern abalone. Little lateral movement of north- 

 ern abalone along the shoreline had occurred. At site 

 A, 11 tagged abalone (2.2% of the original tagged 

 number) were found outside the study area. Max- 

 imum distance from the site was 37 m, and one 

 tagged abalone was found at a depth of 18 m. At 

 site B, three tagged abalone were found outside the 

 site area, all in deeper water. The most extensive 

 movement was recorded at the control site. Ten 

 tagged abalone (2.2% of the tagged population) were 

 recovered outside the site boundaries; one abalone 

 had moved 125 m; and three abalone had crossed 

 a 50 m wide sandy channel. 



At sites B and C, a considerable proportion of the 

 transplanted or tagged population could not be 

 accounted for. The low recovery of tagged abalone 

 outside the boundaries of the sites suggests that 

 emigration is not the sole explanation. However, 

 searches conducted outside the site boundaries were 

 less intensive than those conducted within. 



Growth 



Figure 3 gives the length frequencies of tagged 

 northern abalone at each site at the initiation of the 

 study in June 1984 and upon recovery in March 

 1985. Differences between mean initial and final 

 lengths at each site were, in all cases, significantly 

 different (paired t-test, P < 0,05). The mean growth 

 of tagged northern abalone after 9 months was 7.1 

 mm at site A, 7.2 mm at site B, and 2.9 mm at site 

 C, the control site. Mean growth of untagged north- 

 ern abalone was 9.4 mm at site A and 9,9 mm at 

 site B, 



Growth rates of northern abalone were analyzed 

 by Walford plots, in which the initial length of in- 

 dividual tagged abalone (/(,) are plotted against the 

 length of the same individual at recovery in March 

 1985, 9 months later (l^). The numbers of data pairs 

 were 306, 167, and 126 at sites A, B, and C, respec- 

 tively. Table 3 summarizes parameters of the regres- 

 sion lines of Walford plots for each site as well as 

 the annual Brody coefficient and asymptotic length 

 calculated from these regression parameters (Ricker 

 1975). The annual Brody coefficient varied from 

 0.178 to 0.440, and was lowest at the control site. 

 Values for asymptotic length varied from 104 to 112 

 mm, also being lowest at the control site. 



Table 3.— Parameters for linear regression, annual Brody 

 coefficient (K). and asymptotic length (/_) as calculated from 

 Walford plots. 



99 



