the story of edible oysters. what are oysters? marine / estuarine animal shell (mollusc) bivalves (2...
TRANSCRIPT
“PLANKTON TO PLATE”
The story of edible oysters
What are oysters?Marine / estuarine animal Shell (mollusc) Bivalves (2 shells)Omnivore (eats both phytoplankton
and zooplankton)Size: 8cm-36 cm
(depending on the species)
Immobile after the oyster larvae has settled
What is the purpose of the shell ?The shell is the only protection for the oyster from predators
Helps the oyster retain moisture when the tide drops.
A mini-habitat for other living things to grow.
Where do they come from?
Adults
Spat -juveniles
SpermEgg
Fertilised egg
Free swimming larvae
Oysters swopping sexesAll oysters start off life as malesOysters become adults when they are 1 year old, and produce sperm
in their first year of spawningAs oysters grow older, they switch from being males, and become
femalesIn their 2nd and 3rd years of life, these female oysters produce eggsOver 75% of prime eating oysters are females
How do oysters feed?Oysters are filter feeders They filter suspended
sediment and plankton
• Oysters trap suspended sediment & plankton on mucus on their gills• This material is transported to the mouth and then enters the stomach• Waste is excreted through the anus
Identifying the parts of an oyster All species of oysters share the same common anatomical parts. Protecting
the animal there is a right shell and a left shell. The right shell is the top shell. The left shell is the one attached to the substrate and is called the bottom shell or cup.
Can you identify the internal parts?
1
2
3
4
1. Stomach 2. Heart 3. Mouth-Hinge 4. Adductor Muscle - used to open and close shell
Oyster Predators Oysters have several predators, including: Carnivorous sea snails (e.g. Mulberry whelk, Oyster drill) Sea stars that open oyster shells by exerting continued pressure on the
shellsMud crabs that open oyster shells using their strong pincers. Australian Pied Oystercatcher , a marine bird that has a beak adapted for
prising open oyster shells Fish including stingrays
What do we know so far?Anatomy of the oysterFilter the estuary waterProvide habitats for other organismsImportant in the estuary food chain.
Growing oystersWater quality is very important
to growing oysters.
What washes off the land influences the water.
Therefore, what happens within a catchment can impact on the quality and health of local oysters.
Oysters are not fed or treated with any chemicals throughout their lifetime.
Farming OystersWhat does an
oyster farm look like?
The Sydney rock oyster (Saccostrea glomerata) is considered a gourmet's delight and is the main focus of oyster production in NSW
Four different cultivation methods exist:1) Stick culture where larvae settle on sticks2) Tray culture where oysters are grown
in trays that are laid on racks 3) Basket culture where oysters are grown
in containers that are attached to long-lines made of rope
4) Raft culture which allows stacked trays of oysters to hang from a floating structure
Getting StartedOyster farming is the most valuable aquaculture industry in New
South Wales
NSW production valued at $42.3m
Food safety Healthy oysters are sold by farmers when water
quality tests indicate that water quality is good.
Eating oysters from rocks is not safe as you don’t know how clean the water is.
Eating a contaminated oyster can make you sick.
Fresh oyster:• Proper storage- cold dry environment – refrigerate• Closed shell• Scrub and rinse shell• Shuck (open the shell)• Bed on ice – keep cold!• Eat immediately.
The way of the oyster farmer
Hatchery Spat Grading Growing
Line building Maintenance Harvest Sales Transport
Source: Oysters SA http://www.oysterssa.com.au/thesaway2.php?id=82
Plankton to platethe story of edible oysters
What is the correct
sequence from plankton
to plate?
2.
1.
3.
4.
5.
6.
7.
8.
9.
10.
13.
12.
11.
Why are oysters important to the health of an estuary?
Water quality is improved as oysters
remove material
from water column
Oysters filter the
suspended sediment &
plankton from the water
Oysters build
healthy tissue,
which is very
nutritious
Sediment & other
particles wash from the land to waterways
Food for thought! The oyster has been referred to as the canary of the waterways because its health is determined by
the health of the water in which it grows.
What affects healthy oysters?
Water too
warm.
Water too
fresh
Water pollute
d
Water too warm?Warming sea temperatures
Climate change leads to shift of species
Could lead to the introduction of marine pests and other animals that compete for food and space
‘Ocean acidification’ – oyster shells (made from calcium carbonate) could dissolve as oceans become more acidic
Impacts on oysters and the oyster industry from Climate ChangeStrengthening of the East Australian CurrentRainfall changesIncreasing frequency of heat wavesSea level riseAcidification of sea water
Water too fresh?Urban development has increased the
amount of freshwater that runs-off the land into the waterways
This freshwater run-off contains pollutants that are washed off the land
Freshwater bloats oysters, reducing the quality of this seafood
Water too dirty Sediment washed off the land can smoother
oysters and other marine animals and plans such as seagrass
Pollution comes in many forms. Most notably for oysters is effluent from sewage overflows, cattle accessing creeks, birds and dog-poo
Increased nutrients from fertilisers washing off farms and gardens may cause high algal growth and can result in very low oxygen levels in the water when the algae decompose
Chemical contamination from industrial leaks or chemical dumping
Contaminants that enters an estuary will affect an oysters health
Water-based pollution -Oil and fuel spills from boats
Land-based pollution -Stormwater run-off-Sewage overflows-Cattle effluent in creeks-Fertilisers -Pesticides -Dog poo-Sediments displaced due to erosion
‘Oyster health
declines’
Click here to investigate
the issues facing our estuaries
further
One Oyster...40.8 calories.
Carbohydrate -10.2 grams fat calories -10.4 grams protein calories -20.2 grams
vitamin B12 (120 percent of your daily recommended value)
rich in three minerals: zinc, copper and selenium(33-55% of daily requirement)
The Oyster Plate
low calorielow fat low-cholesterolsource of vitamin B12. complete protein (having all the essential amino acids in the proper
proportions)
GOOD FOR YOU!
Recap and ReviewThe anatomy of an oysterThe oyster environmentRole of the oyster – its place in the estuary food webOyster farmingNutritional valueEating oysters
END of PRESENTATION
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