Abstract. - Populations of the 

 New Zealand (NZ) black-footed aba- 

 lone Haliotis iris were examined in 

 two important fishing areas. Size- 

 frequencies were compared among 

 three regions around Stewart Island 

 in the extreme south of NZ, three 

 regions of the Marlborough Sounds 

 in the northern part of the South 

 Island, and a site closed to commer- 

 cial fishing in the North Island. Von 

 Bertalanffy growth parameters were 

 estimated from shell growth rings of 

 subsamples from all regions. Mark- 

 recapture data were available for 

 two regions, and independent esti- 

 mates of von Bertalanffy parameters 

 were calculated. Total mortality was 

 estimated from catch curves and also 

 from length-frequencies using the 

 method of Fournier and Breen 

 (1983). Yield-per-recruit (YPR) and 

 egg-per-recruit (EPR) were calcu- 

 lated and two reference levels of fish- 

 ing mortality, F 0] and F 25 %, were 

 estimated. Analyses showed that, 

 despite previous evidence to the con- 

 trary, rings are not laid down annu- 

 ally in the regions we examined. For 

 two fishing regions, the estimated 

 current fishing mortality rates are 

 greater than both F 01 and F 25 %, 

 suggesting that the current fishery 

 is more intense than can be sustained 

 in the long term. YPR and EPR do 

 not appear to be greatly affected by 

 changing the minimum legal size. By 

 decreasing F to F (ll , however, equi- 

 librium egg production would in- 

 crease from 18% to a more satisfac- 

 tory level with little change in YPR. 

 We discuss management strategies 

 and argue that it would be prudent 

 to decrease fishing mortality, there- 

 by maintaining higher egg produc- 

 tion at little sacrifice of YPR. 



Population Structure, 



Ageing, and Fishing Mortality of 



the New Zealand Abalone Haliotis iris 



David R. Schiel 



Ministry of Agriculture and Fisheries. Fisheries Research Centre 

 P O Box 297, Wellington. New Zealand 



Present address: Department of Zoology. University of Canterbury 

 Christchurch 1, New Zealand 



Paul A. Breen 



Ministry of Agriculture and Fisheries. Fisheries Research Centre 

 P O Box 297, Wellington. New Zealand 



Manuscript accepted 9 August 1991. 

 Fishery Bulletin, U.S. 89:681-691 (1991). 



The fishery for the abalone Haliotis 

 iris (called "paua" in New Zealand) 

 is now one of the largest abalone fish- 

 eries in the world, yet the biological 

 basis for its management has only 

 recently been examined in detail. 

 Both the minimum legal size (MLS) 

 for fishing and the permissible catch 

 level were arbitrarily set for histor- 

 ical reasons that did not take into 

 account the best yield and egg pro- 

 duction of the fishery. Recent re- 

 search has aimed at assessing whether 

 the present levels of fishing are sus- 

 tainable. 



Individual Transferable Quotas 

 (ITQs) for paua were implemented in 

 1986 and a Total Allowable Commer- 

 cial Catch (TACC) was set in each of 

 seven Quota Management Areas 

 (QMAs), based on the previous catch 

 histories of commercial fishers 

 (Schiel 1991). The total catch of paua 

 for the entire country is currently 

 1193 tons (whole weight). 



Haliotis iris is a shallow-water 

 species, endemic to New Zealand 

 (NZ). It occurs around the entire 

 coastline, but is most abundant in the 

 cooler waters from Cook Strait south- 

 wards. It is found predominantly at 

 depths of < 5m (Schiel, unpubl. data). 

 Fishing is restricted to free-diving, 

 and no underwater breathing appara- 

 tus is allowed. Paua reach 195mm 

 (shell length) and the MLS is 125 mm. 



The commercial value of the fishery 

 has increased dramatically during the 

 last five years (Schiel 1991). There 

 are also a large recreational fishery 

 and a continuing importance of both 

 paua meat and shell to the indigenous 

 Maori people. 



The history of abalone fisheries 

 worldwide shows that management 

 is difficult and that populations are 

 often overfished, causing a precip- 

 itous drop in commercial landings 

 (Sloan and Breen 1988). The diffi- 

 culties in management arise from the 

 spatial patchiness and sedentary 

 nature of abalone (Poore 1972b, 

 Shepherd 1986, Sluczanowski 1986), 

 an uncertain relationship between 

 standing stock and recruitment 

 (Prince et al. 1988, Breen 1991), and 

 often a paucity of useful information 

 on growth and mortality (Shepherd 

 and Breen 1991). These uncertainties 

 also apply to the NZ paua fishery, 

 which occurs over most of the coast- 

 line including many remote places 

 with rough sea conditions and dif- 

 ficult access. 



Although the fishing of paua goes 

 back to pre-colonial times (Best 

 1929), there is a relatively small his- 

 tory of research on the fishery (Schiel 

 1991). Growth and mortality rates 

 have been studied for only a few sites 

 in the South I. (Poore 1972a, 

 Sainsbury 1982). Estimates of basic 



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