Ezo Abalone Research Articles

Microsatellite DNA markers of Ezo abalone ( Haliotis discus hannai): a preliminary assessment of natural populations sampled from heavily stocked areas

Reproductive success of released animals becomes a growing interest in the context of stock enhancement program and conservation biology. In the case of the Ezo abalone (Pacific abalone; Haliotis discus hannai), limited information is available about the extent of interbreeding between natural and released hatchery populations. This study aimed to develop microsatellite DNA markers from Ezo abalone to address the issue. We developed 38 microsatellite markers that worked well in three full-sib families established from wild caught abalone. Of these, nine markers, with which alleles could be scored easily and accurately, were applied to two population samples derived from coastal areas where intensive releases of hatchery-produced abalone seedlings have been carried out. Multilocus estimates of genetic population differentiation calculated based on the nine markers ( F ST analogue θ and R ST analogue ρ) rejected a null hypothesis of genetic homogeneity between the populations ( θ=0.048, P<0.00001; ρ=0.029, P=0.0051). Although both populations conformed to Hardy Weinberg's equilibrium at almost all of the nine loci, the results of simulation analysis for variance of relatedness coefficient provided evidence of nonrandom mating in each population, possibly caused by the cumulative effect of stocking on the genetic make-up. The population analysis presented here is preliminary; but we consider that the microsatellite markers are potentially an efficient means to examine the reproductive contribution of released abalone to natural resources.

Purification and Characterization of a Novel Extracellular .BETA.-1,3-Glucanase Produced by Bacillus clausii NM-1 Isolated from Ezo Abalone Haliotis discus hannai.

A novel extracellular alkaline stable β-1,3-glucanase produced byBacillus clausii NM-1 isolated from the ezo abaloneHaliotis discus hannai was purified by ammonium sulfate precipitation, DEAE-Sepharose FF ion exchange chromatography and Sephacryl S-200HR gel filtration. The molecular weight of the purified enzyme was estimated to be 71 kDa from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme was very stable at pH 5.3 to 11.5 but unstable at pH 4.0 to 4.5. The optimum temperature and thermostability of the enzyme increased in the presence of CaC1, The enzyme hydrolyzed R-1,3-glucan from marine organisms, but did not show activity against any other β-1,3-glucans. The major hydrolysis products of β-1,3-glucan fromLaminaria digitata andEisenia bicyclis were laminaritriose and laminaritetraose, respectively. The N-terminal amino acid sequence of the purified enzyme was similar to that of several β-1,3-glucanases in the glycoside hydrolase family 16.

Dietary Changes in the Abalone, Haliotis discus hannai, and Relationship with the Development of the Digestive Organ

The feeding habits of the Ezo abalone, Haliotis discus hannai, changed with growth. Three major changes in the feeding of H. discus hannai were identified by reviewing recent studies on the feeding habits of this species. The first change occurred at the time of the metamorphosis, namely a shift from lecithotrophy to particle feeding. In the second change, when the shell length (SL) reached values of about 0.6–0.8 mm, post-larvae were able to digest diatom diets and they grew more rapidly on efficiently digested strains. The final change consisted of a shift from a biofilm-dominated diet to a macroalgal-dominated diet. Post-larval abalone (> 1.8 mm SL) were able to utilize juvenile macroalgae efficiently. These changes in the feeding habits were closely related to ontogenetic changes in the digestive enzyme activities and the development of the radula morphology.

Ocean ranching of abalones and scallops in northern Japan

Ezo abalone, Haliotis discus hannai, is one of the most important species for ocean ranching along the rocky shores of Hokkaido. The number of juveniles produced from hatchery and natural seed in 1980 is estimated at 1,150,000 and 798,000 respectively. The juveniles are released in rocky areas of the Sea of Japan around Hokkaido every year. At Otaru, Yoichi, and Furubira, for example, 5,000 to 20,000 juveniles are released annually and they grow to 75 mm in shell length in 2 to 3 years. The recapture rates for abalone are 5–10% for hatchery and 20–25% for natural seed. The giant ezo scallop, Patinopecten yessoensis, is one of the most important species on gravel-bottomed habitats in Hokkaido. This species is maricultured on a large scale in Funka Bay and Lake Saroma and is propagated in the Okhotsk Sea, the Nemuro Channel, and at other areas on Hokkaido's coasts. The propagation has been especially successful in Sarufutsu on the Okhotsk Sea. Mariculture production of this species in Hokkaido has increased rapidly, from 5,625 tons in 1971 to 69,532 tons in 1977. This rapid increase, however, has resulted in a number of problems, such as reduced growth rates, diseases, and higher death rates. Toxins produced by plankton, Protogoniolax sp. and Dinophysis fortii, resulted in a sharp decrease in the production in 1979 and 1980. On the other hand, propagation of the species has developed with the availablity of large-scale seedbeds, nursery culturing, and improvements in transportation. The production by propagation showed a rapid increase from 8,231 tons in 1971 to 68,774 tons in 1980. Propagation, however, has recently faced problems similar to those encountered in mariculture: tardiness in growth, underdevelopment of the gonad, and generation of parasites.

Studies on propagation of Ezo abalone, Haliotis discus hannai Ino-II. The appearance and growth of 0-year-old Ezo abalone.

Studies on the appearance and growth of 0-year-old Ezo abalone, were made from September 1974 to November 1975 in Toyoura, which were seed-transplanted grounds in south Hokkaido. The same studies were made from November 1976 to December 1977 in one part of Okushiri Island, which is the source of seed supply for Toyoura. In Toyura, 0-year-old abalones began to appear in November, and ceased to grow for five months since December. They acquired the first annulus on shells of 21 to 22mm in length. The viability of young abalones was quite low, probably owing to the low water temperature of 0 to 1°C in early March. In Okushiri Islang, young abalones born in that year were found in December, with 3.1 mm-long shells. They continued to grow by 2mmin length per month from June of the next year to December, and then stopped growing and acquired the first annulus on 16.8mm-long shells. In spite of the good water condition for abalone survival in winter, always above 3°C in temperature, the growth rate there was lower than in Binosaki, the poorest place in shell growth in Toyoura.