Bluff (Dredge) oysters

Maori name: Tio paruparu
Scientific name: Tiostrea chilensis
Availability: March to August
Weight:
Length: 6–8cm, reaching 10cm

 

Bluff (Dredge) oysters

Maori name: Tio paruparu
Scientific name: Tiostrea chilensis
Availability: March to August
Length: 6–8cm, reaching 10cm
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General

 

Location

They are endemic to New Zealand, where they are widely distributed around the coast, and form dense beds in gravel or coarse sand bottoms from 25 to 50 metres deep.

Attributes

Shell of varied colours from white to a dull purple-brown. The left shell is ridged and cupped while the right shell lies flat and has scaly layers. Inside, the shell is luminous, and the flesh has shades of white, grey, gold, and black. The creamy coloured meat is delicate and succulent, with a medium oil content.

Family

Bluff oysters, also known as Dredge oysters, belong to the Ostreidae family (oysters). There is a similar species in Chile.

Spawning

Bluff/Dredge oysters are hermaphrodites, and they spawn in summer. Larvae have a brief free-swimming stage before they settle on the sea floor.

Sustainability

Bluff oysters have been commercially fished in the Foveaux Strait since the late 1880s. Over that time, total landings of oysters have varied from 7.5 to 77 million oysters annually. Bonamia exitiosa, a parasite identified in 1986 and found globally, caused high mortality in the oyster population. In response, reduced catch limits were put in place, including a period of closure from 1993-1996. The fishery has since recovered and catch limits are now being increased. Regular monitoring for disease outbreaks is in place.

Fishing methods

The fishery is strictly controlled and only open from March to August when the oysters are in the best condition. They are harvested principally in Foveaux Strait and, in much smaller commercial quantities, in Tasman Bay and Golden Bay.

Nutrition

Bluff (Dredge) oysters are a good source

To quality for a 'good source' claim the food must contain at least 25% of the RDI.
The Recommended Dietary Intake (RDI) is considered to be the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97–98 per cent) healthy individuals in a particular life stage and gender group.

of Zinc

Zinc is necessary for normal immune system function, contributes to normal skin structure and the healing of wounds, the maintenance of bones, hair and nails

, Vitamin B12

Vitamin B12 is necessary for normal neurological function and it contributes to blood formation, energy metabolism and to the growth and development in children

, Vitamin C

Vitamin C is necessary for nomal connective tissue and blood vessel structure and normal neurological function

, Selenium

Selenium is necessary for normal immune system function and for the production of thyroid hormones and it contributes to the maintenance of hair and nails

and Iodine

Iodine is necessary for the production of thyroid hormones, for normal neurological function and for normal energy metabolism, and it contributes to the growth and development in children

; and a source

To quality for a 'source' claim the food must contain at least 10% of the RDI.
The Recommended Dietary Intake (RDI) is considered to be the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97–98 per cent) healthy individuals in a particular life stage and gender group.

of Vitamin D

Vitamin D is necessary for normal bone structure and the utilisation of calcium and phosphorus and it contributes to the maintenance of normal teeth

, Riboflavin (vitamin B2)

Riboflavin (vitamin B2) is contributes to the transport and metabolism of iron, to the release of energy from food and to the maintenance of normal vision

, Magnesium

Magnesium is necessary for normal nerve and muscle function and for teeth and bone structure and it contributes to normal energy metabolism

, Copper

Copper is necessary for nomal energy production and normal immune system function and it contributes to the transport and metabolism of iron

, Phosphorus

Phosphorus is necessary for normal teeth, bone and cell membrane structure and for energy metabolism

, Potassium

Potassium is necessary for water and electrolyte balance, it contributes to the functioning of the nervous system and normal muscle function; and to the normal growth and development of children

and Niacin (vitamin B3)

Niacin (vitamin B3) is necessary for the release of energy from food and for the normal structure and function of skin and mucous membranes, and contributes to the reduction of tiredness and fatigue

.

Seafood is a highly nutritious food and is a great source of protein

Protein is necessary for tissue building and repair, normal growth and development of bone in children and adolescents aged 4 years and over, and contributes to growth and maintenance of muscle mass

. Many species are low in saturated fat and a number of them are a good source of Omega 3

Omega 3 is a group of fatty acids that contribute to heart health

.

Tips

Bluff oyster flesh has shades of white, grey, gold and black. The meat is delicate and succulent, with a medium oil content. They are arguably best eaten fresh, raw and straight from the shell, however they can also be baked, barbequed, fried, poached, smoked, steamed, or used in a soup/chowder.

Buying & Storage Tips

The majority of Bluff oysters available in shops are in pottles, keeping the oyster meat fresh and tasty.

If you purchase live Bluff oysters, their shells should be tightly closed or close slowly when tapped. Live Bluff oysters should be stored in an open container with a damp cloth over them, in the fridge, and served within 48 hours of purchase.