| New Zealand sand flounder | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Pleuronectiformes |
| Family: | Pleuronectidae |
| Genus: | Rhombosolea |
| Species: | R. plebeia |
| Binomial name | |
| Rhombosolea plebeia (Richardson, 1843) | |
| Synonyms | |
The New Zealand sand flounder (Rhombosolea plebeia) is a righteye flounder of the genus Rhombosolea , found around New Zealand in shallow waters down to depths of 100 m.
New Zealand dab, pātiki, diamond, tinplate, square flounder. [2]
Like other flatfish, the larval sand flounder begins its life with an eye on each side of its head and a round body shape, swimming upright through the midwater. [3] As it grows out of this larval stage entering the juvenile stage one eye moves to the right side leaving the other blind and it takes on a flat diamond shape swimming flat/parallel to the ground. On the right side, the fish is a greenish brown dark colour or grey with faint mottling and on the left side (the side it lies on without eyes) it is white. [4] The average length of an adult sand flounder is 25–35 cm with the maximum being 45 cm. [5] In the day time, they lie on the seabed camouflaged almost perfectly in sand or mud; they have special pigment cells on their skin that can change colour to match their background, their protruding blue-green eyes being their only giveaway. [6] They swim in a flowing style with an undulating movement of the side fins and when threatened by predators their tail is used for propulsion. Technically the adult swims on its side with the continuous dorsal fin fringing one edge of its diamond shaped body and its extended anal fin on the other. It has no swim bladder and only leaves the seabed for courtship and spawning activities. [7]
Sand flounder are native to New Zealand so they are not found anywhere else in the world but they are found all over New Zealand. [8]
New Zealand sand flounder is found in a majority of coastal waters around New Zealand. Its largest population is found at Tasman Bay and on the East Coast of the South Island. [9] Around New Zealand they can be found in harbours, inlets, bays and open water. [8]
They prefer coastal areas and are found in waters up to 50m deep but rarely deeper. [9] They can be found in harbours, inlets, bays and open water. They are common on mudflats but seem to have no preference of bottom substrate as they are also found on sand, clay, pebbles and gravel bottoms. [8] They also can be found in estuaries. [10] When they are juveniles they are found in sheltered inshore areas such as estuaries, mudflats and sand flats where they will stay for around two years. They also prefer a temperate climate. [11]
The geographic location of the New Zealand sand flounder determines its spawning period. In the north, it has a long spawning period from March to December. In the south, spawning largely occurs in the spring. [12] A study in the Hauraki Gulf found sand flounder lay between 100,000 and 500,000 eggs when spawning. [9] The variation in the number of eggs laid was attributed to the difference in size of the female laying the eggs. [9]
After a period of time dependent on the temperature of the water (usually around a week), the larval sand flounder hatches. Larval sand flounders have a large yolk sac attached to their underside, providing nutrients to the fish until it is large enough to feed itself. At this stage, they are less than a half a centimetre in length. They have an eye on each side of their head and swim upright, as most fish do. As sand flounders grow they begin utilising external food sources such as seaweed spores and algae, and as they grow further, small shrimp and plankton.
The extra nutrients they receive from these new food sources enables them to grow to around one and a half centimetres by the time they are three weeks old. Above each eye of the sand flounder is a bar of cartilage, and at this stage of its development the cartilage above the left eye is absorbed and the eye begins to move from the side of the head, until it is next to the right eye. The unusual, twisted shape of the mouth of the sand flounder is due to the movement of the skull and bones as the left eye migrates to the right side of the body. While this slow process is occurring, the sand flounder begins to grow out to the side and flatten, losing its rounded shape. This metamorphism makes swimming as the larval sand flounder was able to difficult and exhausting. [13] The now juvenile sand flounders sink to the bottom and begin swimming as adult flatfish do, by undulating their side fins and for rapid acceleration, use their tail. [12]
The juvenile R. plebeia migrate to the shallow water of the estuaries and mudflats where they remain until they mature at two years old. Once R. plebeia reach a mature age and size, they migrate to deeper water of around 30 to 50 metres deep to spawn. [12] [2] After this first migration, they continue to migrate from shallow waters (0-50m) in spring and summer to deeper waters (50-100m) in autumn and winter. Male R. plebeia are smaller than female R. plebeia, maturing at a length of 10 cm, but can grow to 15–17 cm. The females grow faster, with mature size being 16–20 cm long, but they grow to 23–24 cm by age two. By age of three, female sand flounders grow to an average size of 30 cm. The average life span of flounder is three to four years. [12] This equates to being able to have two years of spawning.
The sand flounder feeds off a yolk-sac attached to its under surface until they are capable of fending for themselves. As an adult it is adapted to feed best at night on sand or mud. They are ambush predators, going unnoticed by camouflage and then attacking their prey when it comes near. They eat a variety of bottom-dwelling invertebrates such as crabs, brittlestars, shrimps, worms, whitebait, shellfish and tiny fishes located by touch and vision. [5] They also ingest mud detritus and seaweed while feeding. [3]
Sand flounder are a very important commercial fish in New Zealand which means that humans are a predominant predator for them. [8] Flat fishes including the sand flounder are good at camouflage which allows them to hide well from any predators. They are good at it because when they settle they wiggle their marginal fins throwing up a shower of sand or mud which lands on them and makes them almost undetectable. [14] In saying this sand flounders still get preyed on, some predators include tope, spined dogfish, Maori chief, ling and toadfish. [15] In a study done in the Avon-Heathcote Estuary they found that sand flounder were hosts of many different parasites including Nerocila orbignyi and Heteracanthocephalus peltorhamphi which were both found in less than one percent of fish sampled. They found trematode's in 24% of the sand flounder, Hedruris spinigera in 6%, and fungal patches on 13%. [16]
The New Zealand sand flounder is a popular fish caught by humans to eat. Recreational fishers catch the fish usually in beach seines, setnets or with spears. [5] The Maori used wooden spears to catch what they called ‘Patiki’ at night on mud flats. They would attract the ‘Patiki’ by light from a torch made of pine, spearing them with ease. [3] Commercially sand flounder are fished by trawl and setnet. [5] Sand flounder is very easy to cook and there are many ways to cook and serve it depending on preferences. At its simplest, it can be served beautifully after washing, drenching in flour and frying each side in a medium hot pan with oil/butter until the skin is crisp. [17] At the moment, sand flounder numbers are decreasing, but there is no evidence to show that the decline is rapid and they are still common in areas where they are found. So, because of this, they have been classed as Least Concern on the red list category and criteria. For these reasons, there is no current conservation effort to try save sand flounder, but as it is one of the most important commercial fishes in New Zealand ongoing research on the harvest levels and population numbers of this species is needed to make sure that they do not leave the Least Concern class and so that they know if they do, conservation efforts can be made. [8]
Flounders are a group of flatfish species. They are demersal fish, found at the bottom of oceans around the world; some species will also enter estuaries.
A flatfish is a member of the ray-finned demersal fish order Pleuronectiformes, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through or around the head during development. Some species face their left sides upward, some face their right sides upward, and others face either side upward.
The European plaice is a commercially important flatfish.
The hogchoker is a small flatfish found along the Atlantic coast of North America, ranging from Massachusetts and Florida to Panama. They prefer brackish water, and are abundant in many bays and estuaries north of the Carolinas. It is a member of the American sole family Achiridae. They are usually brown to dark brown in color, and lighter on their "blind side". The overall body color is often broken by a series of spots and thin stripes, which can be lighter or darker than the main body color. The fins and tail have fringed edges helping hide the fish from its prey. They mainly feed on small aquatic insects and invertebrates. They are regarded as "trash fish" by recreational fishermen and were fed to pigs but they have rather bony bodies which were sometimes difficult for the pigs to swallow, hence the vernacular name.
Demersal fish, also known as groundfish, live and feed on or near the bottom of seas or lakes. They occupy the sea floors and lake beds, which usually consist of mud, sand, gravel or rocks. In coastal waters they are found on or near the continental shelf, and in deep waters they are found on or near the continental slope or along the continental rise. They are not generally found in the deepest waters, such as abyssal depths or on the abyssal plain, but they can be found around seamounts and islands. The word demersal comes from the Latin demergere, which means to sink.
The yellowbelly flounder is a flatfish of the genus Rhombosolea, found around New Zealand. A different species from the genus Rhombosolea is found in Australia and also goes by the name yellow-belly flounder. The Māori people have commonly fished for R.leporina, and many other species of flatfish, throughout New Zealand's coastal waters for hundreds of years. The Māori name for this species is 'patiki totara'.
Yellow-eye mullet, also known as Coorong mullet, conmuri, estuary mullet, Forster's mullet, freshwater mullet, pilch, pilchard, Victor Harbor mullet, yelloweye, yellow-eyed mullet known are small, near-shore fish found in temperate waters of southern Australia from just north of Sydney, New South Wales to Shark Bay in Western Australia, around Tasmania, and New Zealand.
The New Zealand turbot, Colistium nudipinnis, is a righteye flounder of the subfamily Rhombosoleinae in the family Pleuronectidae, found around New Zealand in shallow enclosed waters.
The winter flounder, also known as the black back, is a right-eyed ("dextral") flatfish of the family Pleuronectidae. It is native to coastal waters of the western north Atlantic coast, from Labrador, Canada to Georgia, United States, although it is less common south of Delaware Bay. It is the most common near-shore (shallow-water) flounder in the waters from Newfoundland down through Massachusetts Bay, reaching a maximum size around 61 cm in length and 2.25 kg in weight. The species grows larger on Georges Bank, where they can reach a length of 70 cm and weight of 3.6 kg. Although winter flounder historically supported large commercial and recreational fisheries, biomass and landings have decreased since the 1980s.
Glyptocephalus cynoglossus, known in English by a variety of common names including the witch, witch flounder, pole flounder, craig fluke, Torbay sole and grey sole, is a species of flatfish from the family Pleuronectidae. It occurs on both sides of the North Atlantic Ocean on muddy sea beds in quite deep water. In northern Europe it has some importance in fisheries as a food fish.
Platycephalus fuscus, the dusky flathead or black flathead, is a large predatory fish and the largest member of the family Platycephalidae. Dusky flathead are a largely estuarine species and are found in estuaries, estuarine lakes and coastal bays on the east coast of Australia, from Cairns in Queensland to the Gippsland Lakes in Victoria. They occur over sand, mud, gravel and seagrass and can inhabit estuarine waters up to the tidal limit.
Rhombosolea is a genus of righteye flounders. The four species in this genus can be found in the waters around New Zealand and southern Australia.
The European flounder is a flatfish of European coastal waters from the White Sea in the north to the Mediterranean and the Black Sea in the south. It has been introduced into the United States and Canada accidentally through transport in ballast water. It is caught and used for human consumption.
The lined sole is a ray-finned flatfish found in the Western Atlantic. Its common length is 17 cm. Often considered a trash fish in commercial trawling, it is of little or no economic value.
Paralichthys lethostigma, the southern flounder, is a species of large-tooth flounders native to the eastern and gulf coasts of the United States. It is a popular sports fish and is the largest and most commercially valuable flounder in the western North Atlantic Ocean and Gulf of Mexico. It is a "left-eyed flounder", meaning the left side is pigmented and is the "up side".
Coastal fish, also called inshore fish or neritic fish, inhabit the sea between the shoreline and the edge of the continental shelf. Since the continental shelf is usually less than 200 metres (660 ft) deep, it follows that pelagic coastal fish are generally epipelagic fish, inhabiting the sunlit epipelagic zone. Coastal fish can be contrasted with oceanic fish or offshore fish, which inhabit the deep seas beyond the continental shelves.
The American smooth flounder is a flatfish of the family Pleuronectidae. It is a demersal fish that inhabits shallow inshore salt and brackish waters at depths of up to 27 metres (89 ft). Its native habitat is the temperate waters of the northwestern Atlantic, from Ungava Bay in Quebec, Canada to Rhode Island, United States. It can grow up to 30 centimetres (12 in) in length.
Juvenile fish go through various stages between birth and adulthood. They start as eggs which hatch into larvae. The larvae are not able to feed themselves, and carry a yolk-sac which provides their nutrition. Before the yolk-sac completely disappears, the tiny fish must become capable of feeding themselves. When they have developed to the point where they are capable of feeding themselves, the fish are called fry. When, in addition, they have developed scales and working fins, the transition to a juvenile fish is complete and it is called a fingerling. Fingerlings are typically about the size of fingers. The juvenile stage lasts until the fish is fully grown, sexually mature and interacting with other adult fish.
The bay whiff is part of the family Paralichthyidae. This family is known as "left-eye flounders". They are one of the most common flatfish of the Gulf of Mexico. They are benthic ambush predators with the ability to camouflage themselves on or just below the surface. They are often solitary animals with few individuals. They vary in color from light to dark in life and are brownish in color after death. They have two dark spots on the caudal peduncle and a light spot under the pectoral fin. The average size of the Bay whiff is 15 cm and the maximum recorded length is 20 cm. The lateral line is straight along the body. It has a large mouth. The opercle on the blind side has no cirri. Their pelvic fins are also asymmetrical.
Pseudorhombus arsius, the largetooth flounder, is a species of left-eyed flatfish, that is the dark side with the eyes on the adult fish is the left side of the fish's body, from the family Paralichthyidae. As Rhombus polyspilos it was named as the type species of the genus Pseudorhombus. It is an Indo-Pacific species and is fished for by both recreational and commercial fisheries.
