July Meeting - World Record Size Register
We've heard stories about the one that got away, but we are interested in the ones that did not!
There are over 250 New Zealand shells listed in our register of largest NZ shells. Check your collections for any unusually large shells - you could be a record breaker! Records will also be kept of sinistral shells of any size for species that are not normally sinistral. The register can also be used as an up to date quick reference for the current species names and authors, and to identify which species are endemic to New Zealand.
Bring along to our July meeting any shells that you think may be possible contenders for world record size status or club records. Shells do not have to be up to any quality standard at all, ie lack of operculum is ok, and for bivalves having only one valve present is perfectly acceptable. Regale us with your stories about how you obtained the "big one".
Martin Walker, Peter Poortman, and Luen Jones shall inform us of the history (going back 40 years), philosophy, some good practical reasons behind such a focus on size, the CSAMI initiative, and perhaps a look at the online registry. We will have a measure-up, with measuring equipment supplied.
Proposed categories include the largest ...
. New Zealand : Gastropoda, Pelecypoda, Scaphopoda, Amphineura (dried), Cephalopoda (shell only), any other classes, fossil mollusc.
. Smallest mature : Volutidae, Cassidae, Struthiolaria papulosa and heaviest self-collected shell.
. Worldwide : Gastropoda, Pelecypoda, Scaphopoda, Amphineura (dried), Cephalopoda (shell only), any other classes, fossil mollusc.
. Other : Landsnail, freshwater gastropod, freshwater bivalve, smallest mature lip on any species normally immature at that size (eg a Cypraea tigris mature at 45mm), largest nautiloid, favourite Gerontic specimens.
. Sinistral : Any sinistral shell for species that are not usually sinistral (size not a factor).
. Worldwide Operculum : i) calcareous ("shelly") and ii) chitinous (brown and leathery).
This will be held on Tuesday, 8 July at Epsom Community Centre, 202 Gillies Avenue, Epsom. You are welcome to arrive from 7:00 pm onwards with the meeting commencing at 7:30 pm. Come along ... this is going to be another enjoyable meeting night with the opportunity for new knowledge, amazement, stories and humour along the way!
If you are unable to attend the meeting, check our website for further details regarding the world record size register, or contact Peter Poortman or Luen Jones direct.
Apologies - our previously advertised "movie night" has been transferred to August's meeting whilst we obtain and edit DVD material.
Shell Auction - Wellington - 11/October/2008
View lots from 10:00am, auction starts at 1:00pm.
Location is the Salvation Army Building, 1st Floor Social Hall, 8 Jessie Street, Central Wellington
Carparking is available on the western side of the building (parking permits will be issued on the day). Lift access available if required. If wet there is an internal garage access for loading purchases.
Auction list is due out mid/late August.
We wish safe travel to those attending the Australian Shell Shows.
We need your articles for the next edition of Poirieria. Any scientific studies, personal stories/anecdotes, observations, trips you have made, etc would make for great reading. Please forward any ideas you have for an article to Tony and Jenny Enderby, PO Box 139, Leigh 0947 or telephone 09) 422 6127.
For those who could not make last month's meeting you missed another great night. Bruce Hayward was incredibly informative on his discussion on impacts of marine invaders and human activities on coast marine ecosystems in Auckland. His talk related to impact by fresh water run-off, sewage, heavy metals and other pollutants, TBT poisoning from anti-fouling paint, sediment run-off (which has increased mangrove populations by 1000% in the Manukau and Waitemata Harbours), and shipping (at least 70 species of marine invaders have been introduced through shipping).
Many invasive species are rare and only occasionally encountered with unknown impacts. Some invasive species are common but in very restricted localities with limited impacts, eg the barnacle Balanus amphitrite in Orakei Basin and shelly worm Ficopomatus enigmaticus at Otara Power Station cooling water intake. Some invasive species have an initial population explosion with subsequent number drop, eg. the file shell Limaria orientalis. This was first noticed in 1972 in the Waitemata and by the mid 1970s was found under every intertidal rock in the area, by the 1990s-2000s it was mostly sub-tidal. The parchment worm, Chaetopterus arrived in inner Hauraki Gulf in 1996, by the late 1990s it had formed subtidal beds through much of the gulf causing huge drifts of washed up tubes. By the mid 2000s this density has much reduced. The Asian paddle crab Charybdis japonica arrived in the Waitemata ca 2000 and by 2002-2005 was commonly seen at low tide, in 2007 rarely seen at low tide. The club tunicate Styela clava was noticed in 2002 but incorrectly identified. In 2005 it was found in Viaduct Harbour and identified as Styela clava, however by then it was already widespread with a population explosion in the mid 2000s. In May 2007 the sea squirt Pyurastolonifer praeputiale was seen on the rocks of Twilight Beach. This is a major low tidal zone forming species already smothering Perna and other native species. There is the potential for significant change to the northern New Zealand inter-tidal ecosystem. The invasive species with the most dramatic physical effect is the Pacific oyster, Crassostrea gigas. It was found in the 1960s in the Kaipara and Mahurangi Harbours and by 1970 through to current had taken over the intertidal and rocky shores of northern New Zealand. In the 1980s the formation of oyster banks on tidal mud and sand flats caused swimmers discomfort, with dead shells washing up and burying sand beaches affecting sun bathing and beach activities. In the 1950-1960s the sea grass Zostera died out due to a fungal pathogen. In 2000s this sea grass is recolonising in the Waitemata Harbour flats.
A survey of benthos in the Waitemata Harbour was undertaken in the 1930s by Powell. This survey was redone in the 1990s. Out of 45,000 specimens, 420 species were found from 153 stations with summer and winter samplings. When compared to Powell's results the following changes were discovered: changes in covering of horse mussel bed (natural colonisation that lasted 6 years), disappearance of olive shells (killed by TBT anti-fouling paint), disappearance of Tawera (Rangitoto Channel dredging), loss of turret shell population around North Head (mud accumulation had buried substrate), file shell become prominent (invasive overseas species), Asian date mussel thickets (invasive overseas species - introduced 1978), small Theora bivalve becomes dominant member of muddy, shallow areas of the harbour (invasive overseas species - introduced 1972).
A further study was undertaken by Bruce Hayward and Margaret Morley on Theora lubrica. This consisted of 26 monthly samples taken between 1997 and 1999 from a low tidal study site using a 1mm sieve with a 0.5sqm quadrant. It was discovered that the Theora live in the top 3cm of sand, there is no evidence of tidal migration by different sized individuals. It was concluded that there was a lower growth rate in winter, summer populations grow fast (lives 2-3 months), spawning intermittently, winter slow growth rate (live 6-8 months), density highly variable, decline in spring, lower numbers over summer, higher densities in winter, with an inverse relationship with the mud crab densities - crab predation played a major role in determining the density of the Theora especially in summer.
The Asian date mussel Musculista senhousia was first seen in the Waitemata Harbour in 1968 and quickly spread up the East Coast and is now found on the West. It smothers the sea floor and native biota. They colonise in the Autumn and live for 22 months. The adults die Feb/March causing a feeding frenzy for whelks, cushion stars, fish and ducks. If not recolonised the thickets quickly break up and wash away. In another study off Cheltenham, the subtidal ecosystem was tracked as an Asian date mussel colony died, was invaded by suspension feeders, soon followed by predator crabs. Over the following two years progressively returned to its pre-mussel, low diversity, low density sand-dwelling association.
A five year study was completed on microfossils in the Tamaki and Rangitopuni Estuaries. For each study cores were taken for analysis looking at grain size, pollen, Cs isotopes and heavy metals for dating. It was found that foraminifer Ammonia was declining and agglutinated forms were taking over. This change also coincided with loss of molluscs and occurred at Lucas Creek in the late 1800s (deforestation) and in Tamaki in the 1950s (urbanisation). It was concluded that freshwater run-off was the major factor in the changing harbour ecosystem. Councils have now implemented rainwater gardens, stormwater run-offs and holding tanks to try and make a difference.
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