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Conchology Section |
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Conchology Section |
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Mrs Joan Willan.
Several members attended the funeral service of our life member Joan Willan, held at the All Souls Anglican Church at Clevedon on the 19th. August 2002. Joan was a member of the Section for over 35 years. Our sympathy is extended to her son Dr. Richard Willan, the Curator of Molluscs at the Darwin Museum Australia, who is also a life member of our club.
Greetings from the President.
We welcome a new member, Ms. Eva Trombik, of Mt Eden Ak. to the Shell Club.
At the August meeting our President, Doug Snook, and our Vice President, Bruce Hazelwood, took us on a world tour with the family Volutidae. This family has between 300-400 different species, (some of which are considered sub species.)
Volutes are predators and feed on a variety of invertebrates including other molluscs. As there is no pelagic (free swimming) larval stage, the embryos hatch as small crawling snails. This characteristic explains the variety of different forms known from numerous isolated habitats.
New species are still being discovered: mainly those from deeper water; and some 30 species are known to have an operculum. Fortunately for NZ shell collectors, our neighbour Australia has about one third of all known species.
Bruce spoke on the NZ species and his display of specimens included: a pristine deep water Provocator mirabilis (Finlay 1926) with a protoconch apical spine; a rare form of Provacator mirabilis albino: Alcithoe knoxi (Dell 1956) Alcithoe benthicola (Dell 1963); Alcithoe wilsonae (Powell 1933); Alcithoe fissurata (Dell 1963).
Doug's 100 specimens included: a huge baler shell, Melo amphora (Lightfoot 1786); Cymbiola thatcheri (McCoy 1868) from the Chesterfield reefs, Australia; a rare endemic to New Caledonia, Voluta rossiniana (Bernardi 1859) and a Lyna lyraeformis (Swainsoni from Kenya).
Other members displays included specimens of hedleyi by Heather Smith and ostenfeldi by Nancy Smith.
Next Meeting: Tuesday 10th September 7:30 pm at the Museum.
Entrance by the rear Admin door between 7:15-7:30pm. We regret there can be no late admittance due to security regulations. Mystery door prizes!
Committee Meeting - dinner provided - will be held at 6 pm.
Speakers: Mr. Jean Paul Van Weert. We are privileged to have one of our new members, Jean Paul, to speak on his shelling experiences as far a field as South Africa. Jean Paul hails from Holland and is in NZ on a working holiday and hopes to stay for 1-2 years. He has currently flown home to attend his sister's wedding but promises to return in time to speak at out meeting!
SHELL CONVENTION
Shell Auction Sunday 10th November 2002 (Schedule to arrive with the next newsletter).
Free Trading Tables 10am-12:30 pm.
Monday 11th a day trip is planned.
Tuesday 12th free time or visit collections, also the Club Meeting at Auckland Museum at 7-30 pm, with Mike Hart speaking about Aitutaki, Cook Is.
Merv Cooper of Perth Shell Distributors, PO Box-186, Hawthorne, W.A. (email: mac@perthshells.com) is researching Columbarium shells. He wants to purchase/exchange specimens from NZ. Also needs photos and research info.
Library News: Librarian, Gladys Goulstone (38A Church Rd. Mangere Bridge, Ak.) ph. (AK) 634-2823. Please return books to Mataapuna as soon as possible or to Gladys at the next meeting, or mail them to her address above.
Poirieria: T. and J. Enderby, P.O Box 139 Leigh, require articles for the next Poirieria issue. Queries; ph.09-422-6127 or Email: enderby.t.j@xtra.co.nz (Back copies available.)
Field trip report:
Main product half pearls.
Adult Haliotis iris needed for breeding are brought in by van from New Plymouth. For some unexplained reason, paua don't like flying. They cannot be collected locally because MoF won't issue a permit. However owner Stewart says he is planning to get a permit to stock an educational aquarium. It just might have a few paua in it! Paua are haemophiliac so need careful handling, any cut results in them bleeding to death. The adults have to be examined to find out the level of maturity of the gonads and sperm. This cannot be done by injection due to me lack of blood clotting. He may have found a way to do this. One of several trade secrets. Paua can be induced to spawn by adding hydrogen peroxide to the water. This increases the oxygen levels in the water which acts as a trigger.
The eggs are produced in millions. One million fit in a tablespoon. The larvae are very particular where they settle. They prefer certain microscopic algae or Corallina paint in the wild. They are also attracted to rocks where adult paua have been, possibly to feed on the mucus slime left behind. They are larvae for 12 days then need to settle within a critical 24 hours. They will go down to a site but if it is not suitable go up to the surface again. Those that cannot find a site to settle will die. Once settled they metamorphose and develop a shell. At the farm they achieve a 20% settlement rate.
The farm operates a closed circuit sea water system. Keep your hands out of me water! This avoids the necessity of a resource consent for discharge. Sea water is brought in by tanker then filtered. The water is tested at regular intervals weekly? for salinity, pH and nitrite. Tap water added to replace that evaporated. Baking soda can be added with confidence as sea water only allows a certain level of buffering. The nitrite comes from the paua faeces and is controlled by bacteria turning it to harmless nitrate. The powerful air pressure (pump?) foams off impurities. Protein skimmers are used and any remaining debris from dead paua is blown off. The faeces are allowed to settle in a purifying tank between filters and are then hosed off. The filters in all the tanks have to be manually cleaned at present. Stewart is working on a design to do it automatically.
The micro algae are cultured in one shed, lots of bubbling jars. It starts in small bottles moving on to tanks as it doubles in quantity. It cannot be stored so if not needed at the tank stage has to be discarded. They culture 2 spp. "A" is slower growing and settles on the surfaces, "B" sp. the faster growing one, stays in the water circulation. The largest tanks of "A" when ready are lifted by fork lifts to the paua tanks allowing time to settle on the surfaces prior to adding the paua larvae. In 3 weeks the larvae metamorphosed and developed a shell 2mm long. Algae B is added as needed to maintain optimum growth rates. Larvae grow best if kept in moving water which reduces how much they swim using up the egg yolk. The half buttons are inserted under the mantle, 3 to each paua. Can be harvested in 1 year minimum. Each quality half pearl is worth $180.
Holy grail would be to develop a way of making a whole pearl. Despite much research, rumours and speculation it has not been done yet. In oyster the pearl is inserted with a piece of mantle from another specimen. This cannot be done in paua because of the bleeding. The paua animal is sold but is not very profitable. When harvested the pearls have to be cut out of the shell.
Water temperatures- paua stop eating at over 20 degrees and hibernate in less than 15 degrees. He keeps the water at 16-17 degrees which achieves steady growth. The adults are fed on Gracilaria chilensis this has no holdfast. It has high nutritional value. The paua don't like the local stuff- too prickly, so it has to come from Ohiwa. Stewart was hand feeding them with bits of Ecklonia. They put out the foot to draw it in. Some are specially growing as an investment for grandchildren, coloured tags. Gracilaria is able to use nutrients in fresh water run off to use in "dry" periods afterwards. This gives it an advantage over other algae unable to do this such as Ulva. Stewart has designed a space saving tank it appeared to have vertical surfaces but he would not be drawn.
He sells units for people to start their own farms. You need an air conditioned shed without contaminants - concrete or asbestos. & $12000 + $2000 + building. Has sold 10 units around Auckland. At present cannot supply enough to the market. Developing a bigger shop and working on getting access to cruise ships, unique NZ product.
