EMMETT and JAMIESON: TRANSPLANT OF NORTHERN ABALONE 



at all sites. The similar ratio of tagged to untagged 

 northern abalone at the initiation and end of the 

 study demonstrated that both tagged and untagged 

 animals had similar survival rates. 



Breen (1986) calculated M, from population size 

 structure and growth rate estimates, to be 0.05- 

 0.24 for H. kamtschatkana at eight sites in British 

 Columbia. These values are consistent with esti- 

 mates of M, derived from a variety of techniques, 

 of 0.05-0.40 for abalone populations in Australia and 

 New Zealand (Shepherd et al. 1982; Sainsbury 1982). 

 In California, estimates of Af (partly based on dead 

 shell recovery) are higher, ranging from 0.36 to o° 

 for four native species of Haliotis (Tutshulte 1976; 

 Hines and Pearse 1982). The highest estimates are 

 from areas that experience sea otter, Enhydra 

 lutris, predation. Estimates of M calculated from 

 data given by Tegner and Butler (1985) are 0.40 and 

 0.55 for two transplanted populations of red aba- 

 lone, H. rufescens. 



In the present study, estimates of M based on 

 recovered, tagged shells {M^,„) are similar to values 

 determined for abalone populations from similar 

 latitudes in British Columbia (Breen 1986) and 

 southern Australia (Shepherd et al. 1982). Values 

 of M determined from the recovery rate of live aba- 

 lone (M^ax) are higher than most values of M re- 

 ported in the literature. It is likely that M^^y^ esti- 

 mates of instantaneous natural mortality are high 

 because some abalone probably emigrated or re- 

 mained hidden within the sites. However, while un- 

 recovered abalone would still be able to contribute 

 to population reproduction, they would not likely be 

 available for harvest; the after-harvest population 

 density would be too low to encourage the return 

 of fishermen, and the animals might remain well hid- 

 den. Effectively, these abalone can be considered 

 removed from the harvestable biomass, and since 

 there are only two categories, available and unavail- 

 able animals, in most cost-benefit and/or exploita- 

 tion models, unrecoverable abalone should be con- 

 sidered unavailable abalone. For this reason M^^^ 

 is an appropriate term for use in models assessing 

 the economic feasibility of abalone transplants and 

 in other situations where animals are established in 

 an area for the purpose of future exploitation. 



A considerable proportion of tagged and/or trans- 

 planted northern abalone were unaccounted for at 

 sites B and C. The difference in percent recovery 

 of live abalone at the two transplant sites (72% 

 versus 39%) was due primarily to these abalone, as 

 approximately the same number of shells were col- 

 lected at each site. There are several explanations: 

 1) difficulty in locating abalone due to complex bot- 



tom topography, 2) physical removal of abalone 

 from the site by mobile predators such as octopus 

 and sea stars, 3) the destruction of shells by pred- 

 ators such as crabs, 4) emigration, and 5) transport 

 of shells from the site by waves or currents. 



In California, Tegner and Butler (1985) attributed 

 abalone loss during transplant experiments to both 

 predation and emigration, citing the recovery of 

 shells in all directions outside the study site as 

 evidence of random dispersal of live animals. In the 

 present study, searches outside the sites at the ter- 

 mination of the study suggested little emigration of 

 tagged abalone, except at the control site. Although 

 no studies have been done on the natural movement 

 of Haliotis kamtschatkana, the mean distance 

 moved in a year by tagged ormers (Haliotis tuber- 

 culata) in France was only 6.7 m for the 68% of the 

 population that showed any evidence of movement 

 (Clavier and Richard 1984). That study also showed 

 that smaller abalone tended to be less mobile. Hines 

 and Pearse (1982) reported that marked abalone 

 shells drifted 2-3 m in three months. The degree 

 of shell drift due to wind or current action is ob- 

 viously site specific and probably only occurred at 

 the more exposed control site in the present study. 



Three fundamental questions concerning the 

 feasibility and benefit of transplanting abalone from 

 exposed areas remain: 1) the number and extent 

 of abalone in exposed coastal areas has not been 

 established, 2) the population dynamics and the 

 reproductive contribution from such populations to 

 the total coastal stock remain unknown, and 3) the 

 potential of transplanted abalone to enhance popula- 

 tion reproduction and ultimately recruitment at 

 specific transplant sites has to be determined on a 

 site-by-site basis. 



ACKNOWLEDGMENTS 



This study was carried out in conjunction with 

 the West Coast Abalone Harvesters Association 

 (W.C.A.H.A.). Eric Wickham, Bob Harrington, and 

 Guy Whyte of the W.C.A.H.A. and Thomas Shields 

 of Archipelago Marine Research were responsible 

 for much of the initial planning of this project. We 

 thank Dave Johnstone and Mark Bath of the 

 W.C.A.H.A. for their participation in all phases of 

 the field work; their experience as abalone divers 

 and their firsthand knowledge of the study area 

 made the field program run smoothly and efficient- 

 ly. Paul Breen of the New Zealand Minister of 

 Agriculture and Fisheries offered many useful com- 

 ments throughout the study and provided the equa- 

 tions for the economic feasibility model. Howard 



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