Population dynamics and fishery management of the paua,Haliotis irisI. Population structure, growth, reproduction, and mortality

Abstract

The biology of an unfished population of the paua, Haliotis iris Martyn, in Peraki Bay, Banks Peninsula, was studied from 1973 to 1976. In February 1976 the population consisted of about 179 000 animals on 4.5 km of coastline. The length/frequency distribution was strongly skewed to the left, indicating an accumulation of old individuals and a recent history of low recruitment. Growth of animals <70 mm long was determined from changes in length frequency, and of larger animals by the analysis of tag returns. The mean parameters of the von Bertalanffy growth equation for the study population are K = 0.163 and L = 131.9 mm. Both are lower than those reported for paua in a more typical habitat near Kaikoura. The annual instantaneous natural mortality rate, as estimated by several methods from population size structure and individual growth rate data, is about 0.1. Spawning was monitored during the breeding seasons of 4 years. Spawning on Banks Peninsula failed to occur during 2 years, and the failure during 1 year was geographically widespread. No explanation for these spawning failures can be offered. The length at first maturity was the same at Peraki Bay and Kaikoura, despite a much lower growth rate and fecundity at Peraki Bay. Recruitment was 2000-5000 2-year-olds per year and either recruitment is largely independent of local spawning success or significant spawning occurs outside the currently accepted breeding season.

Variation in spawning and recruitment ofHaliotis iris(Mollusca: Gastropoda)

“…This is considered unlikely because the density of juveniles from the shallow habitat is the highest recorded for the species (McShane et al 1994). The low levels of recruitment of H. iris observed in our study is consistent with results obtained by Sainsbury (1982) which he attributed to natural recruitment failure. Furthermore, surveys of juvenile habitat off southern New Zealand (> 41°S) found no juvenile H. iris at more than 60% of the 300 sites searched (McShane 1993, unpubl.…”

“…The perimeters of crosssections of gonad and digestive glands were traced onto paper with the aid of a dissecting microscope equipped with a camera lucida, and their areas were used to calculate a macroscopic gonad index by sex (Shepherd & Laws 1974). This procedure has been successfully used in previous studies of reproduction in H. iris (Poore 1973;Sainsbury 1982).…”

“…It co-occurs with a congener//, australis but at much greater densities (McShane et al 1994). In relation to other species of abalone, particularly H. rubra in Australia, H. iris appears to have low rates of recruitment (Sainsbury 1982). We define recruits as recentlysettled individuals which occupy exposed reef surfaces such as those covered by non-geniculate coralline algae, and we define juveniles as immature individuals (< 80 mm shell length) which occupy cryptic habitat such as the undersurfaces of boulders.…”

“…Haliotis iris is an abalone endemic to New Zealand waters (Sainsbury 1982). It co-occurs with a congener//, australis but at much greater densities (McShane et al 1994).…”

Effect of recombinant vertebrate growth hormones on growth of adult abalone, Haliotis kamtschatkana

“…Decreased growth rate appears not just to be the result of general decline in metabolism among older animals, but rather to be at least partly due to the competitive demand of the gonad for energy. In support of this, a number of authors have reported decreased growth rates for abalone specifically during periods of gonad production (Shepherd and Heam, 1983;Keesing and Wells, 1989), and negligible growth during most of the year except for a growth spurt after spawning (Cox, 1962;Foster, 1967;Poore, 1972;Sainsbury, 1982;Keesing and Wells, 1989). The present study took place over 10 weeks from April to July, which corresponds to the time of gametogenesis and negligible somatic growth in H. hmtschatkuna (Paul et al, 1976).…”