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

Abstract

Variations in the gonad index, gamete production, the density of post-settlement individuals (recruits), and the density of juveniles were measured for a population of the New Zealand abalone Haliotis iris during a 4-year study. Seasonal variation in a macroscopic gonad index was consistent with annual spawning and the appearance of recruits, but there was interannual variation in the frequency and magnitude of spawning, and the timing of recruitment. Rates of recruitment of H. iris measured by three different methods (suction, examination of substrata, and artificial collectors) were recorded as low (< 1 m -2 ) in deep (6-8 m) and shallow (1-2 m) habitats. After spawning, there was spatial variation in the density of recruits and the frequency of individuals on artificial collectors. However, densities of recruits were similar between shallow and deep habitats, although juveniles were more common in shallow habitat. In the shallow habitat, the low density of recruits measured in 1 year was reflected in a low density of juveniles censused a year later, but 1-year-olds were comparatively rare in deep habitat. Habitatrelated factors may affect recruitment in H. iris and may explain why levels of recruitment are lower than for other species of abalone whose recruitment has been examined. M95059

Seasonal reproductive anatomy and sperm storage in pleurocerid gastropods (Cerithioidea: Pleuroceridae)

“…Seasonal variation and cyclical reproductive activity is a common phenomenon in invertebrates (Berrie 1966;Webber 1969;Fankboner and Cameron 1985;Martel et al 1986;McShane and Naylor 1996), and our data demonstrate pleurocerids undergo a seasonal atrophy of accessory sexual organs. Atrophy of the pallial oviduct and ovipositor occurs in late summer, which likely allows resources to be allocated to somatic functions for surviving colder winter temperatures.…”

“…As such, allocating resources towards seasonally important somatic functions (e.g., increasing body size for defense vs. sexual functions during periods of reproduction) can be advantageous (Shanley and Kirkwood 2000;Kirkwood and Shanley 2005). Many marine and freshwater gastropods , display a cyclical waxing and waning of gametogenesis that often corresponds to increases and decreases in volume of the gonad (e.g., Webber and Giese 1969;McShane and Naylor 1996). This is known to occur not only in temperate species but in those that inhabit the tropics, where seasonal variation in temperature and food availability is much less pronounced, and it reflects synchrony in breeding times in order to maximize reproductive success.…”

Effect of Temperature, Diet, Light, and Cultivation Density on Growth and Survival of Larval and Juvenile White AbaloneHaliotis sorenseni(Bartsch, 1940)

“…White abalone have been estimated to live to between 20 and 40 y old (Tutschulte & Connell 1988b). By the last decades of the 20 th century, southern California populations of white abalone had a distribution skewed toward older individuals, possibly indicating episodic recruitment as found in other species (McShane & Naylor 1996). Declines in populations may have stemmed from fishing take and irregular recruitment attributed to environmental variation (Hobday & Tegner 2000, Shepherd et al1998).…”

Low Juvenile Pinto Abalone Haliotis kamtschatkana kamtschatkana Abundance in the San Juan Archipelago, Washington State

“…First, it is possible that pinto abalones undergo sporadic recruitment events and that we have sampled across a series of low-recruitment years. The New Zealand abalone Haliotis iris demonstrates spatiotemporal variation in reproductive effort and success (McShane and Naylor 1996). Irregular recruitment has also been observed in white abalone H. sorenseni (Hobday et al 2001).…”