Blue Crab Habitat and Spamming

Despite its fearsome appearance and aggressive nature, the Blue Crab is greatly cherished in the South Carolina lowcountry. Many gourmets prefer the blue crabs sweet meat over all other locally-caught seafood. This interesting animal is often sought by recreational fishermen and it also supports a considerable commercial fishery. The blue crab requires both inshore brackish waters and high salinity ocean waters to complete its life cycle. They are common from Massachusetts to Texas and a few have been reported as far north as Nova Scotia and as far south as Uruguay. The Chesapeake Bay, North Carolina and Louisiana support the largest blue crab fisheries.
 
Although other small swimming crabs in this family (Portunidae) occur locally, only the blue crab is of any commercial or recreational importance in South Carolina. The blue crab's scientific name, Callinectes sapidus, translates to "savory beautiful swimmer." Swimming is accomplished by skulling the oar-like fifth pair of legs, the swimming legs. These paddles usually rotate at 20 to 40 revolutions per minute, but they quickly disappear into a blur as the animal darts away.

Walking is accomplished with the three pair of thin walking legs. Blue crabs almost always walk sideways clearing a path with their sharp lateral spines. The blue crabs most prominent features are the large and powerful claws which are used for food gathering, defense, digging and sexual displays. If not handled properly, blue crabs can inflict severe injury. Male crabs can be distinguished from females by the shape of the abdomen. The male has a Tshaped abdomen which is held tightly against the body until maturity when it becomes somewhat free. The immature female has a triangle-shaped
abdomen which is tightly sealed against the body.

The mature female's abdomen becomes rounded and can be easily pulled away from the body after the final molt. Large males, often called "Jimmies" by fishermen, usually have brilliant blue claws and legs. The mature females or "sooks" can be distinguished by the bright orange tips on their claws. Males typically grow larger than females, sometimes reaching seven or eight inches in point-to-point width. Some males have been reported to grow to about ten inches.

Mating and Spawning
Mating generally occurs in brackish water from February to November with peaks in March to July and in October and November. Females mate only during the final molt when they are in the soft shell condition, but males are believed to mate several times. Researchers have determined that blue crabs release chemical signals called pheromones which attract their mates. Two to three days prior to mat-ing, the male will "cradle carry" the soon-to-shed female after a rather elaborate courtship ritual. These crabs are called "doublers." The male is usually one to two inches larger than its mate.

The male protects the soft female when she is vulnerable to predators. After mating, he will continue to carry her until her shell hardens. After mating, females migrate to higher salinity water in the lower reaches of the estuary or in the ocean. Spawning occurs in near shore ocean water about one or two months after mating in spring or summer. Females that mate in fall or winter usually spawn the following spring.

Females produce up to two million eggs, but only about one egg per million will survive to become an adult. Eggs are carried under the abdomen until they hatch. The egg mass is bright orange at first and becomes darker as the embryos mature and consume the egg yolk. Females carrying an egg mass are called "sponge crabs," and are protected by law in South Carolina. If captured, they must be returned to the water immediately. Sponge crabs usually first appear in early April and are common until August or September. Eggs hatch after about two weeks into zoea larvae which are 1/100-inch long. During the next month there are six or more larval stages before reaching the megalopal stage. 

The megalopae, which is about 1/10-inch wide, begin to migrate into the nutrient-rich estuarine waters. Very soon after settling in the saltmarsh creeks, the megalopae transform into the "first crab" stage. Crabs hatched in April or May become two to three inches wide by Nov- ember and five inches or larger by August the following year. Crabs hatched in early fall will be only -inch in width by winter. After one year, these crabs will be only three to four inches wide and will not mature until the following spring. A few crabs may live for three years but most live for less than a year. South Carolina law requires that captured crabs less than five inches in width be returned to the water.

Growth and Molting
Blue crabs, like all arthropods, must periodically shed their hard exoskeleton in order to grow. The smallest crabs shed every three to five days, juvenile crabs every 10 to 14 days and those 3 inches and larger every 20 to 50 days. Experienced crabbers can quickly spot crabs about to molt. Five to ten days before molting, a narrow white line appears just within the thin margin of the last two joints of the swimming legs. A few days before shedding, the peeler crab's narrow white lines give way to a red line, and fine white wrinkles appear on the blue skin between the wrist and upper arm. The actual molting lasts for only a few minutes as the crab pushes out the rear of the old shell.
 
The resulting soft crab, which is limp and wrinkled, will swell to normal shape and usually increase in size by 25 to 35 percent. If disturbed, the vulnerable soft shell crab can swim and walk but prefers seclusion. After a few hours, the crab's shell becomes parchment-like and is fully hardened within two or three days. During the spring, usually early April, there is a "run" of peeler crabs that lasts for about two weeks. At this time fishermen will target the female crabs that are molting into mature crabs after the winter dormancy. These crabs can be caught in "peeler pots" which are crab traps in which one or two large males are used as bait to attract the females which are ready to mate. The peeler crabs are held for a short time in shedding tanks until the molt. After molting, the soft shell crabs are removed from the water and refrigerated for sale.


Abundance and PredatorsFactors controlling year-to-year variation in blue crab stocks exert their influence early in the life cycle. Water circulation patterns controlled by prevailing winds, can either carry the larvae shoreward or sweep them away. Thus, recruitment (addition of new individuals) of megalopae and small crabs may be largely controlled by the coastal water currents and the weather. Young crabs within the estuaries are vulnerable to drought, flood, or unseasonable temperatures. A relationship seems to exist between river discharge and survival of small crabs. Small crabs survive best during years of relatively high fresh water runoff which increases nutrient input and decreases salinity.

However, too much rainfall can also flush the small crabs from the marsh. Predators claim large numbers of young crabs, and crab populations may vary from year to year according to the abundance of predators. Blue crabs are subject to predation throughout their life cycle and are particularly susceptible when they are soft during the molting process. As larvae, they are vulnerable to fishes, jellyfish and other planktivores. The megalopae and juvenile crabs are consumed by various fishes and birds, as well as other blue crabs.


Eating Habits
Blue crabs eat a variety of foods, including fishes, oysters, clams, snails, shrimp, worms and other crabs. At high tide, crabs may swim into the salt marsh to pluck snails from the tall grass. At times, they burrow into the bottom with only their eye stalks visible, lying in wait for an unsuspecting fish. Crabbers typically bait their pots with oily fishes which seem to work better than other baits. Presumably, the crabs home in on the oil or odor being released. Studies have shown that blue crabs can follow a current upstream by cris-crossing the stream bed. Crabs are opportunistic feeders, meaning they will eat what is most available regardless of their size, the season or the area they inhabit.


Fishing GearsThe most common type of commercial fishing gear is the crab pot which is a cubical wire trap with two or four entrance funnels. The pot has two chambers, a lower chamber which has the entrance funnels and the bait well and an upper chamber that is separated from the lower chamber by a wire partition that has two holes. The blue crab's natural reaction to confinement is to swim upward. In doing so, they move into the upper chamber, thereby reducing their chances for escape. The crab pot was first introduced in Chesapeake Bay in about 1936, but was not widely used in South Carolina until the late 1950's.

Blue Crabs are also caught and sold as part of the bycatch of shrimp trawlers and after the shrimp trawling season is closed, usually in January, trawling for crabs with large mesh trawls is permitted until March 31. Recreational blue crab fishermen employ several fishing gears and methods. South Carolina law allows individuals to fish two crab pots without a license if they are properly marked with floats bearing the owner's name. Fishing more than two pots requires a commercial crabbing license. Whether fishing from a dock or boat, recreational crab pots should have a marked float and enough line to prevent the float from being submerged at high tide. 

Recreational crabbers should also be careful not to leave a pot in an area that would expose the pot and crabs at low tide. Pots should be checked daily and catches can often be doubled if the pots are checked twice per day. To remove crabs, pull the wire apart and shake the crabs into a tub or bucket. Some stubborn crabs may have to be dislodged with a stick. Remember that crabs can pinch, so be very careful about putting your hand in a pot. Drop nets and collapsible traps, usually baited with herring, can be fished from docks and bridges. Another effective recreational method called "dipping" requires a long-handled dip net, several yards of string and bait.

The bait, usually a chicken neck or fish head, is tied to the string and thrown into the water away from the bank. Once a tug is felt, the crabber pulls the bait and crab close enough to be quickly dipped from the water and placed into a waiting bucket. The beginner should be cautious when handling a blue crab since the pinch of the powerful claws can be extremely painful. (The inexperienced crabber should probably wear thick gloves). Always approach from the rear when picking up a crab. An experienced crabber can quickly grab the base of one of its swimming legs while holding the claws down with some object. Should a crab get a hold on a finger, it is usually best not to pull it off. First, try letting it hang; many times the crab will release and drop. 

If the crab will not release, use the free hand to immobilize the other claw and slowly bend the offending claw backward until the crab releases it. Crabs can be caught during all twelve months, but become inactive in winter when water temperature falls below 50-55 degrees F. As temperatures rise in March and April, catch rates increase rapidly. The best time of year to harvest large, heavy crabs is usually from October to December. Mature females are typically near the ocean, but large males are most common in the rivers and creeks.

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Swimming Crabs Types Crab

Swimming crabs have certain unique characteristics that set them apart from walking crabs. Almost all crabs have five matched pairs of limbs: four pairs of “legs” and two claws. The last pair of legs (those furthest from the claws) on swimming crabs is flattened out into paddles. These legs are called swimmerets and allow the crabs to swim quite rapidly. They are also used to dig into the sand or mud. Most swimming crabs have flatter bodies and more pronounced spikes than their walking crab relatives.

Blue Crab

The Blue Crab has an olive green to brown body with points on each side. The underside of the blue crab is white. The crab gets its name from the brilliantblue colored claws and legs. The tips of the claws are red or orange and can be used to determine the sex of the crab. Males have red or orange coloration only at the very tips, while the red or orange in females covers more of the claw.

Lady Crab

 The Lady Crab is a small, rounded crab with a collection of red and purple calico spots. The markings serve as a camouflage both to defend against predators and to help them ambush their primary prey, small fish. Found on the sandy shoals just offshore, the Lady Crab often buries itself, leaving just its eyes and antennae exposed.

Speckled Crab

This crab is identified by the large number of white dots on its brown to olive shell. The Speckled Crab has a flat shell with points on both sides, similar to the Blue Crab. Like most swimming crabs, their body design works just as well for digging as it does for swimming. Their coloration helps them blend in with the sandy sediments. Speckled Crabs are often found in tide pools.

Walking Crabs

Walking crabs get their name because all of their legs end in points. Because these crabs can not swim, they navigate the ocean and river bottom using their 4 matching pairs of legs. Walking crabs shells are generally more dome-shaped than those of swimming crabs.

Ghost Crab

These land-dwelling crabs can be seen scurrying quickly (up to 10 mph) along the beach between dusk and dawn. Ghost Crabs have 1.5- to 2-inch square, beige colored bodies that allow them to “disappear” into the sand. Mainly a land crab that burrows in the dry sand, Ghost Crabs wet their gills at the water's edge and the females enter the ocean to lay eggs in the salt water. While not very large, Ghost Crabs can prey on sea turtle hatchlings. They also eat coquina clams and flying insects that they catch in mid-air.

Spider Crab

This crab looks like a large spider with a bumpy brown, pear-shaped body and long legs. Spider Crabs are often found on mud bottoms, clinging to marsh grasses, or riding along on Cannonball Jellyfish. A Spider Crabs rough shell collects bacteria and plankton. This coating encourages the growth of other plants and animals on the shell surface. Nicknamed the “decorator crab,” Spider Crabs use this coating to disguise themselves. The shell decorations also are a source of food for the crab.


Stone Crab

Growing to over 5 inches across with massive claws, the Stone Crab is prized for its meat. Care must be taken, however, because the massive claw of an adult Stone Crab can easily crush the finger of an inattentive crabber. Because of their slow growth rate, only the larger of the two claws is taken at harvest. The crab is returned to the water where the missing claw will regenerate. Stone Crabs are purplish-tan in color with a thick oval body and black “finger tips” on the claws.

Hermit Crab

Hermit Crabs are unusual in that their hard outer shell covers just their head and claws, not their entire bodies like other crabs. To protect their fragile bodies, Hermit Crabs find and move into empty snail and whelk shells. Their bodies are specially designed so that their two back pairs of legs hook into the protective shells. They cannot be removed without destroying the animal. Hermit Crabs found on Kiawah are not the same as those sold in pet stores. Our local Hermit Crabs live in salt water and cannot survive out of the water for a prolonged period.

Marsh Crabs 

Two types of marsh crabs are found on Kiawah. The first species, the Wharf Crab (also known as the Grey Marsh Crab, Square-Back Marsh Crab, or Friendly Crab) is found in the higher marsh areas and bordering regions. When you are out for a stroll, these small, dark-colored crabs with square, flattened shells often surprise you by darting across the bike path or beach access. The other species is the Marsh Crab, or Purple Marsh Crab, which prefers the lower areas of the marsh where it constructs a burrow with a mud “chimney.” It has a square body like its relative the Wharf Crab, but has a thicker body. As the name implies, the coloration of the Marsh Crab is typically purple and they are often mistaken for young Stone Crabs. However the tips of the Marsh Crabs claws are light-colored and their legs are “fuzzy."


Fiddler Crabs

Fiddler crabs occur in both sandy and muddy environments and are very common along creeks and mud flats around Kiawah. The male Fiddler Crabs large, white claw is unmistakable. Males are typically seen waving this claw back and forth in a territorial display. Females in habit the same areas as males, but are often harder to spot since they lack a large, bright-colored claw. The male uses his single smaller claw (and the female uses her two small claws) to scrape up mud and sediment for food. They are excellent burrowers and their holes can sometimes extend down more than 2 feet. These burrows have an added benefit of aerating the marshes and preventing the “rotten egg” smell associated with some saltwater marshes.


Crabbing
Crabbing is a popular activity on Kiawah Island. A simple crabbing set-up consists of string, a chicken neck for bait, and a long-handled net for scooping the crabs up. Remember, blue crabs must be more than 5 inches across the back, tip to tip, to keep. One of the best places to crab on the island is the Kiawah River Bridge.

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Emperor Red Snapper

The Emperor Red Snapper family Lutjanidae contains more than 100 species of tropical and sub-tropical fish known as snappers. Most species of interest in the inshore fisheries of Pacific Islands belong to the genus Lutjanus, which contains about 60 species. One of the most widely distributed of the snappers in the Pacific Ocean is the common blue stripe snapper, Lutjanus kasmira, which reaches lengths of about 30 cm. The species is found in many Pacific Islands and was introduced into Hawaii in the 1950s.

Although most Emperor Red snappers live near coral reefs, some species are found in areas of less salty water in the mouths of rivers. The young of some species school on sea grass beds and sandy areas, while larger fish may be more solitary and live on coral reefs. Many species gather in large feeding schools around coral formations during daylight hours. Snappers feed on smaller fi sh, crabs, shrimps, and sea snails. They are eaten by a number of larger fish. In some locations, species such as the two-spot red snapper, Lutjanus bohar, are responsible for ciguatera fish poisoning (see the glossary in the Guide to Information Sheets).


Emperor Red Snappers have separate sexes. Smaller species have a maximum lifespan of about 4 years and larger species live for more than 15 years. Many common species grow to sizes of 25 to 35 cm and reach reproductive maturity at about 45 per cent of their maximum size (that is, 11 to 16 cm in the most common species).

Emperor Red Snappers generally spawn throughout the year in warmer waters but during the warmer months in cooler waters. Many snappers travel long distances to particular areas along outer reefs and channels to breed (in spawning aggregations), often around the time of the new moon and full moon. During breeding, females (~) release eggs (often more than 1 million) and these are fertilised by sperm released by males (|). In most reef associated snappers, fertilised eggs hatch within a day or two into small forms (larval stages) that drift with currents for about 1 month. Less than one in every thousand of these small floating forms survives to settle on a reef as a young fish (juvenile). And less than one in every hundred juveniles survives the period of 3 to 8 years that it takes to become a mature adult capable of reproducing. Emperor Red Snappers are most often taken by using baited hooks and hand lines but are also caught by using spears, traps and gill nets.

Many snappers are caught as they gather in large groups to breed (in spawning aggregations). Fishing in this way is destructive as these breeding fi sh are responsible for producing small fi sh, many of which will grow and be available to be caught in future years.


Minimum size limits for snappers have been applied in some countries (e.g., 30 cm length from the tip of the mouth to the middle of the tail). However, the particular species of snapper is not usually stated. Taking into account the wide variation between Emperor Red Snapper species, this size limit would be of little use in protecting larger species. Size limits should be applied to individual species. Some countries have restricted fishing methods to the use of hook and line only. Catch (bag) limits have also been applied but such a measure is usually inappropriate in community-based fisheries. Locally managed fi sh reserves (no-take areas) could be established but, for species that travel long distances to spawning sites, these will not protect reproducing fi sh. However, if spawning times and areas are known by local fishers, the following management actions are possible:



- A ban on fishing during the times that fi sh form spawning aggregations, which may require a number of short closures (say for 3 to 4 days) around the periods of new moon and full moon, depending on the particular species.

- A ban on fi shing at known spawning areas or sites; such sites may include particular areas along outer reefs and channels where snappers are known to gather to breed. Additional community actions could include:
 
support for local national minimum size limits or (if not available) set community based minimum size limits at about 50 per cent of the maximum size of the species; A ban on the use of gear such as gill nets which catch too many fish, a restriction on small-mesh gill nets, enforcing a minimum mesh size may allow smaller fish to escape and grow to a size when they can reproduce.

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Humpback Grouper Indonesian Fish

Humpback Grouper

Humpback Grouper is a serranidae family with widespread population in tropical and sub tropical water territory and product for seafood that is very favourite in world. As one of non oil export commodity, this species is the most popular among fish species living in rock and becomes important economic commodity of fishery in Asia Pacific region. Furthermore, it explained that one of constraint in Humpback grouper (C. altivelis) cultured in Indonesia is limitation of supply of seed caused by pathogen infection causing mortality more than 80%, even till 100%. Therefore, the problem needs an attention seriously and prevention because of loss resulted stress and corrupt in industrial cultured.


One of cause of industrial loss in grouper cultured is VNN attack. VNN causes retinopathy and encephalopathy which having wide host range. It is included one of epidemic disease almost in the world and inscribed in OIE (Office International des Epizooties). VNN is reported to attack some fish species as Japanese parrot fish (Oplegnathus fasciatus), redspotted grouper (Epinephelus akaara), striped jack (Pseudocaranxdentex), Japanese flounder (Paralichthys olivaeeus), tiger puffer (Takifugu rubripes), kelp grouper (Epinephelus moara) and barfin flounder (Verasper moseri), barramundi (Lates calcarifer), turbot (Scophthalmus maximus) and sea bass (Dicentrarchus labrax).


Humpback Grouper In Indonesia, it is reported that VNN has attacked most of grouper cultured with mortality of 100%. In East Java, seeding industry also get a loss as result of VNN attack in seed stadium and even in adult (data is not publicized). The symptom is fish whirling, happened sleeping dead or fish resides in base like death and existence of unnatural fish behavior symptom.

Important role of defense system of grouper to VNN is receptor protein expressed at part of grouper body. VNN target on grouper are eye, brain, kidney, flesh, liver and also gill. In this research, it will be seen VNN infection in grouper brain as agent that is very endangers because VNN can weaken fish nervous system so that fish will loss nervous control, happened weakness of motion, and finally death. The role of nervous cells to VNN agent is target of protein receptor which is important to neutralize VNN besides other organ as heart and kidney that functions for circulation and osmoregulation of blood in body fish.


Something that causes the mechanism of this viral infection is the bonding between VNN adhesin and its receptor molecule in grouper organs. Viral adhesin can be in the form of viral basic component namely coat protein and nucleic acid. Coat protein of VNN is primary factor in mechanism of virus infect the host (humpback grouper) where the protein have a role in attachment of viral to host receptor. It has been known that one of adhesin of VNN is haemaglutinin. Further development both adhesin and its receptor can be exploited to produce a protein material for a diagnostic tools to virus infection and so its prevention for fish cultured industry. For this purpose, the research objective is to identify how a role and expression of receptor protein from grouper brain, heart and kidney mediated by nervous, heart and nephrose cells in infection mechanism of VNN.

Characteristics of the humpback grouper, Cromileptes altivelis Common names: Humpback grouper, panther grouper, mouse grouper, highfin grouper. Size and age: Max size 70.0 cm TL. Environment: Reef-associated; marine; depth range 2–40 m. Climate: Tropical; 32°N - 23°S, 88°E - 168°E Importance: Juveniles are commonly caught for the aquarium trade while adults are utilized as a food fish. Very high value in China Hong Kong SAR live fish markets. Resilience: Low, minimum population doubling time 4.5–14 years. Biology and ecology: Generally inhabits lagoon and seaward reefs and are typically found in dead or silty areas. Also found around coral reefs and in tide pools. Growth is very slow. Feed on small fishes and crustaceans.

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Grouper and Groupers

Groupers (class Actinopterygii, order Perciformes, family Serranidae, sub-family Epinephelinae) comprise 14 genera and 449 species of the subfamily Epinephelinae, or roughly half of all species in the family Serranidae (groupers and sea basses). There are 16 major grouper species that are cultured; the dominant species vary somewhat regionally. The most consistently abundant species that are captured for culture purposes and also reared in hatcheries are Epinephelus coioides and E. malabaricus.

Other important species are E. bleekeri, E. akaara, E. awoara and E. areolatus. E. amblycephalus, E. fuscoguttatus, E. lanceolatus, E. sexfasciatus, E. trimaculatus, E. quoyanus, E. bruneus, Cromileptes altivelis, Plectropomus leopardus and P. maculatus are cultured in small amounts. In the southeastern United States of America and the Caribbean, E. striatus, E. itajara, Mycteroperca microlepis and M. bonaci seem to have good farming potential. However, CBA for groupers in the western hemisphere has not been developed to any large extent, unlike in Southeast Asia.

Juveniles and adults of some grouper species live in coastal or lagoonal waters and estuaries, while others prefer the cleaner waters of offshore reefs. Their eggs are single, non-adhesive, and buoyant at normal salinities. The larvae of most species spend about 30–50 days as planktonic larvae. As they become juveniles, groupers settle in shallow waters where they seek shelter in seagrass beds, mangrove prop roots, coral rubble, branching coral or branching macroalgae. Some juvenile groupers are habitat generalists, settling in any available shelter, while other species have specific nursery habitats in which their growth and survival are enhanced. After hatching, wild grouper larvae eat copepods and other small zooplankton. They switch to larger crustaceans, such as amphipods and mysid shrimp, as they grow. Wild juveniles and adults eat fish, crabs, shrimp, lobsters and molluscs, although the genus Plectropomus tends to be predominantly piscivorous.

Groupers range in maximum size from only 12 cm (e.g. Paranthias colonus) to over 3 m (e.g. Epinephelus lanceolatus). Most groupers that have been studied are sexually mature within 2–6 years, but some of the larger species may take longer to mature, e.g. Epinephelus fuscoguttatus, which matures at about 9 years. Most serranids are protogynous hermaphrodites. As a rule, some change from female to male as they grow older; others may change only if there is a shortage of males. In nature, many species spawn in large aggregations (hundreds to thousands of fish) with a sex ratio nearing 1:1. In some cases, several grouper species may share the same aggregation site.

Groupers are some of the top predators on coral reefs, and tend to be K-strategists demonstrating slow growth, late reproduction, large size and long life-spans which make them vulnerable to overexploitation. Also contributing to their vulnerability is the fact that they are sex-changers with a low proportion of males in the smaller cohorts, which means that heavy fishing pressure often removes most of the males (or removes fish before they can become male). Additionally, many groupers form spawning aggregations that are predictable in space and time, making them extremely easy to harvest. These aggregations can represent the entire annual reproductive output for some species. Groupers are sedentary in character and strongly territorial, making them easy targets for spear fisheries.

Groupers are greatly valued for the quality of their flesh, and most species command high market prices. Groupers are the most intensively exploited group in the live fish trade, and the high prices paid by exporters to local fishermen mean that target species may be heavily over-fished. In order to alleviate the pressure on wild grouper stocks, many nations have promoted aquaculture in the hopes of producing a more sustainable grouper yield. However, full-cycle culture of most grouper species is not yet possible, although several important advances have been made in recent years. For this reason, about two-thirds of all grouper culture involves the capture and grow-out of wild seed. This is known as capture-based aquaculture (CBA).

There are at least 16 species of groupers that are cultured in many Southeast Asian countries, including Indonesia, Malaysia, Philippines, Taiwan Province of China, Thailand, China Hong Kong Special Administrative Region (SAR), the southeast of the China and Viet Nam (Sadovy, 2000). Grouper culture is also undertaken in India, Sri Lanka, Saudi Arabia, Republic of Korea, Australia, the Caribbean and in the southeastern United States of America. Despite the huge popularity of live fish in China and Southeast Asia, only 15–20 percent of the amount consumed each year comes from aquaculture, as culture is principally constrained by limited and unreliable supplies of wild seed and the difficulties of spawning in captivity.

Grouper seed is collected using a variety of methods. Capture methods are generally artisanal and the fishermen employ a variety of artificial habitats. Some grouper seed collection methods are more damaging than others. Clearly destructive methods include those that result in high mortality, involve high levels of bycatch, and/or cause damage to the fish habitat. A further problem is that some methods result in monopolization of the local fishery by a few individuals. Destructive methods include scissor nets and fyke nets, which are already banned in some areas. The mortality rates that follow capture and transport are not well documented; estimates for over the first 2 months after harvest are quite variable (30–70 percent), depending on the quality of fry, the level of transport stress, and the presence of disease and cannibalism.

Because full-cycle culture of most grouper species is not yet possible, approximately 66–80 percent of all grouper culture involves the capture and grow-out of wild seed and the volume of seed caught each year exceeds hundreds of millions of individuals. When seed catches are compared to the numbers of marketable fish produced, the results strongly suggest crude and wasteful culture practices. Sadovy (2000) estimated that about 60 million seed fish are needed to produce the regional total of 23 000 tonnes of table-size live fish from culture annually.

Trash fish is commonly used for feeding in grouper cage culture, but its increasing cost, shortage of supply, variable quality and poor feed conversion ratios indicate that this form of feed may not be the best from either a nutritional or an economic point of view. A dependable supply of cost-effective, non-marine, sources of alternative protein must be provided if grouper farming is to remain profitable. Millemena (2002) demonstrated that up to 80 percent of fishmeal protein can be replaced by processed meat meal and blood meal derived from terrestrial animals with no adverse effects on growth, survival, and food conversion ratio (FCR). From an economic standpoint, replacement of fishmeal with cheaper animal by-product meals in practical diets can alleviate the problem of low fishmeal availability and high costs.

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Paradise Fish Origan Taiwan Fish

Paradise Fish (Macropodus Opercularis) 

The Paradise Fish (Macropodus opercularis) is naturally distributed in western Taiwan, but is
rare now because of such factors as environment pollution and habitat loss. Conservation
of this animal in Taiwan is becoming more urgent. Some closely related species, such as
Chinese paradise fish (M. chinensis), are difficult to distinguish with morphological characters. We sequenced and compared the control region of mitochondrial DNA (mtDNA) to reveal the genetic distance and molecular phylogeny of paradise fish populations from different geographical regions: Taiwan, Singapore, and mainland China.

The interspecific distance between M. opercularis (Taiwan, Singapore) and M. chinensis (Zhejiang, Jilin) is 0.1341 ±0.0124, much more highly divergent than the distance between the Taiwanese and Singaporean populations, or within the Chinese populations. Five haplotypes from 11 specimens of the Taiwanese native population have been identified from a 1034-bp-length of mtDNA. However, the lower haplotypic diversity (H = 0.68) indicates a decreasing population in Taiwan, in contrast with the M. chinensis (H = 0.89). In addition, the unique genotype in Miaoli and Taichung may imply their subdivision because of exotic input of fish from a different geographic region. Thus conservation work should focus on avoiding the random release of paradise fishes into the wild.

Effects of temperature and floating materials on breeding by the paradise fish (Macropodus opercularis) in the non-reproductive season. Zoological Studies 45(4): 475-482. The paradise fish, Macropodus opercularis, is native to Taiwan, and its reproductive season spans from Mar. to Oct. This experiment was conducted to examine Paradise Fish breeding in winter, a non-reproductive season, using different treatments of water temperatures (23, 27, and 31C) and floating materials (floating ferns, green Styrofoam pieces, and no floating material). The fish built 1-3 bubble nests during the 20 d experimental period. A significant negative correlation was found between the temperature and the frequency of nest building, indicating that a high water temperature of 31 C was unfavorable for building nests.

In the treatments with floating ferns and green Styrofoam pieces, the paradise fish built more nests than in the treatment without floating materials. The sizes of the 1st bubble nests built were significantly larger at 27 and 31..C than at 23..C. Floating materials played an important role after the fish acclimated to the temperature. In the treatment with green Styrofoam pieces, the fish built smaller-sized 2nd nests than in the treatment without floating materials. One female in a tank treated at 27..C with green Styrofoam pieces laid 421 eggs during the 20 d experimental period. Two hundred and eighty larvae hatched the next day, for a hatching rate of 66.5%. In short, the paradise fish can breed at appropriate temperatures, such as 27..C, in winter, normally a non-reproductive season, and artificial floating materials are conducive to successful reproduction.


The Paradise Fish, Macropodus opercularis (Linnaeus), belongs to the family Anabantidae in which most of the members are..bubble-nest.. builders. This species is characterized by the presence of a labyrinthiform organ, which is derived from the 1st gill arch and enables the fish to breathe in the air. Floating plants are usually dominant in spawning areas of the fish. Plants or other substrates are necessary to hold the nest in place. The paradise fish sexually matures at approximately 6 mo, breeds well in aquaria, and reaches a maximum size of approximately 80-100 mm in standard length.


The paradise fish is native to China and nearby islands. It is widely distributed in eastern Asia from the Yangtze River basin to Hainan I. in China, as well as Taiwan and North Vietnam (Freyhof and Herder 2002). The range of the fish, is habitation is 20-30 N and 102-122 E, and its climatic temperature range of 16-26 C indicates that it is a subtropical and temperate fish. Indigenous to Taiwan, it is commonly known as the Formosan fighting fish, three-spot fish, and Chinese unicorn fish (Chen and Fang 1999, Shao and Chen 2003). Prior to the mid-1970s, the fish was widely distributed in lowland areas of Taiwan where it inhabited bodies of fresh water ranging in size from rice paddy fields to lakes.

Salvinia natans, Lemna minor, and Pistia stratiotes are floating plants to which the fish, is bubble nests are commonly found to be attached in Taiwan (Jan 1994, Huang et al. 1998). The reproductive season of the fish spans from Mar. to Oct. in Taiwan (Jan 1994), and is particularly concentrated from May to July (Chen and Fung 1999, Shao and Chen 2003). In the last few decades, this fish has become rare in Taiwan (Shen 1993, Chen and Fang 1999). The construction of farmland irrigation canals and ditches and the heavy use of pesticides and insecticides in agriculture may be the main reasons why its abundance has fallen (Tzeng 1990, Young 1995). For the protection of the fish, it was listed as a rare and valuable species in the Wildlife Conservation Law on 31 Aug. 1989 by the Taiwanese government in order to ban the catching, killing, and selling of the species (ESRI 1996). However, to the present, studies of the conservation and enhancement of this fish species are still rare in Taiwan.

Temperature is one of the most potent environmental factors that influence the development and growth of fish. Food intake, catabolism, and conversion rates of the food consumed by fish vary with body temperature. The body temperatures of most fish are close to and do not exceed 1..C difference from the ambient water temperature, suggesting that water temperature plays an important role in the life of fish. In temperate regions, the timing of reproduction in annually spawning species is controlled by an endogenous cycle that in turn is entrained by environmental cues. Water temperature is one of the most important annual environmental cues.

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Guppy (Poecilia Reticulata) and Predators

Predators of Guppy are widely assumed to create selection that shapes the evolution of prey escape abilities. However, this assumption is difficult to test directly due to the challenge of recording both predation and its evolutionary consequences in the wild. We examined these events by studying natural and experimental populations of Trinidadian guppies, Poecilia reticulata, which occur in distinct high-predation and low-predation environments within streams.
 
Importantly, in the last two decades several populations of guppies have been experimentally introduced from one type of predatory environment into the other, allowing measurements of the consequences of change. We used this system to test two hypotheses: First, that changes in predatory environments create phenotypic selection favoring changes in escape ability of guppies, and second, that this selection can result in rapid evolution.

For the first test we compared escape ability of wild caught guppies from high- versus low-predation environments by measuring survival rates during staged encounters with a major predator, the pike cichlid Crenicichla alta. We used guppies from three streams, comparing two within-stream pairs of natural populations and three within-stream pairs of an introduced population versus its natural source population. In every comparison, guppy fish from the high-predation population showed higher survival. These multiple, parallel divergences in guppy survival phenotype suggest that predatory environment does create selection of escape ability.

We tested our second hypothesis by rearing guppies in common garden conditions in the laboratory, then repeating the earlier experiments using the F2 generation. As before, each comparison resulted in higher survival of guppies descended from the high-predation populations, demonstrating that population differences in escape ability have a genetic basis. These results also show that escape ability can evolve very rapidly in nature, that is, within 26–36 generations in the introduced populations. Interestingly, we found rapid evolutionary loss of escape ability in populations introduced into low-predation environments, suggesting that steep fitness trade-offs may influence the evolution of escape traits.

Sexual selection is thought to be opposed by natural selection such that ornamental traits express a balance between these two antagonistic influences. Phenotypic variation among populations may indicate local shifts in this balance, or that different stable ‘solutions’ are possible, but testing these alternatives presents a major challenge. In the guppy (Poecilia reticulata), a small freshwater fish with male-limited ornamental coloration, these issues can be addressed by transplanting fish among sites of varying predation pressure, thus effectively manipulating the strength and nature of natural selection. Here, we contrast the evolutionary outcome of two such introductions conducted in the Trinidadian El Cedro and Aripo Rivers. 

We use sophisticated colour appraisal methods that account for full spectrum colour variation
and which incorporate the very latest visual sensitivity data for guppies and their predators. Our data indicate that ornamentation evolved along different trajectories: whereas Aripo males evolved more numerous and/or larger orange, black and iridescent markings, El Cedro males only evolved more extensive and brighter iridescence. Examination of the El Cedro experiment also revealed little or no ornamental evolution at the control site over 29 years, which contrasts markedly with the rapid (approx. 2–3 years) changes reported for introduction populations.

Finally, whole colour-pattern analysis suggested that the greatest visual difference between El Cedro introduction and control fish would be perceived by the two most salient viewers: guppies and the putatively dangerous predator Crenicichla alta. We discuss whether and how these evolutionary trajectories may result from founder effects, population-specific mate preferences and/or sensory drive.

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Oscar Fish Population and Maintenance

Oscar Fish is not known to exist in the wild in the Northern Territory. However, it is a popular aquarium fish throughout Australia and is considered to have the potential to become a major pest of wet tropical regions of northern Australia. Typically, oscar grows to about 200-280 mm, Young Oscar fish have wavy white and orange markings on a black background; colouration of the body and fins of adults is usually very dark, with olive blue-green and mustard colours, highlighting large dark blotches. Some have orange or red markings.

The base of the caudal fin has a large spot or ocellus bordered with red. Fin colouration varies; usually it is very dark, occasionally there are ocelli present and eyes are red. This species does not tolerate cold waters. A lower lethal temperature of 12.9°C has been reported for specimens under experimental conditions. The natural diet of oscar includes fruit, snails, insects and small fish. Other items such as reptiles may be opportunistically eaten. It is an omnivore with carnivorous tendencies. Oscar Fish is renowned for its aggressiveness. It may have a significant impact on native fishes through direct predation and competition for breeding areas.

Oscars mature early (10 to 12 months), have relatively high fecundity and are territorial during the breeding season. Spawning normally takes place in still waters on flat, solid surfaces. The female typically lays about 3,000 eggs and both parents are occasionally seen guarding hundreds of young in shallow water along shorelines.

DISTRIBUTION

Oscar is a cichlid native to the Amazon basin and has worldwide commercial value as an ornamental species. Over its native range oscar is found in the Amazon, Orinoco and La Plata River systems in South America. Wild populations of oscar are not known to exist in the Northern Territory. However, populations of this exotic fish do exist along the Central Queensland coast and it is considered to have the potential to become a major aquatic pest of wet tropical regions of northern Australia.

Oscar In Aquarium

When selecting filtration for an oscar tank, you will need to keep a few things in mind. First and foremost, you will need to remember that Oscars are very big and very messy creatures, probably messier than any other fish you have kept. They eat a lot, and a lot of what they eat ends up coming out of their gills in a mashed-up mess. The rest comes out the back end as prodigious amounts of feces. Combine that with the relatively large amount of urine produced by Oscars, and you have substantial hurdles for both biological and mechanical filtration.

A second consideration is the size of the tank. If you need help selecting an apropriate sized tank, read this article, and this article. Larger tanks will need more filtration, both to provide adequate water movement, and to ensure that all water in the tank passes through the filtration with a reasonable frequency. A third consideration is your budget. Different types of filters cost varying amounts. However, as we will examine later in this article, the old axim “you get what you pay for” is quite true in fishkeeping.

When I talk about wet/dry filtration, I am talking about sumps that sit under the tank, not the “bio-wheel” filters produced by Marineland. Wet/dry filters are the kings of biological filtration.
They achive this superior biological filtration by running water across massive amounts of biological media in the presence of air. Different designs achieve this in different ways, but the principles involved remain the same. The only drawback of wet/dry filters is that they normally either lack, or are very weak in the area of mechanical filtration.

As mentioned above, mechanical filtration is quite important in an oscar tank. Therefore, if you use a wet/dry set-up, you will need to make sure that mechanical filtration is covered. This can be done by either modifying your wet/dry system to include mechanical filtration directly, or by adding supplemental filters to perform the mechanical filtration role.

Filters
Modern cannisters are the Jacks-of-all-trades of the filtration world. They do this by providing large amounts of space for media that can be customized to fit your specific needs. They can be optimized to provide mainly biological, mainly mechanical, or a good balance between the two. Cannisters are also excellent investments because of their ease of maintenance, and relatively inexpensive operating costs. Properly-sized cannisters can go anywhere from a month to as much as 4 months without any maintenance. Compare this to most other types of filtration, which needs to be serviced at least every couple of weeks, and you can see some substantial savings in bot time, and media costs.

Also called Hang-On-the-Back, or HOB filters, the power filters are by far the cheapest filters to buy. They are an excellent choice for smaller (55 gallons and under) tanks, or as supplemental and/or back-up filtration on a larger tank. While it is theoretically possible to put enough HOB filters on tanks up to about 125 gallons to provide adequate filtration, I do not recommend it. This is because in this size range, you are talking about at least three filtes that will most likely need to be maintained weekly. This is an aweful lot of work and recurring expense for filters that are only marginally adequate.

While it would be difficult to add enough to properly filter a tank with one or more full-grown
oscars, sponge filters do have some good uses in Oscar keeping. They are a cheap way to add
a little extra mechanical and biological filtration to a tank, and make nice back-up filters. Also, if you keep one running in a large tank, you have a pre-cycled filter ready if you need to set-up a hospital tank. Sponge filters are also cheap, effective filters for fry grow-out tanks.

Two factors essentially rule out undergravel filters (uGFs) for oscar tanks. First is the general messiness of Oscars, which is discussed above. The waste tends to clog up the gravel, and reduce the flow through your UGF. Second, Oscars love to dig, especially around spawning time. They dig so much that they will often dig all the way to the bottom of the gravel, and expose the UGF's plates. This will cause a short-circuit in the water flow, and virtually eliminate any filtration occuring in the UGF. When combining these two factors, it is generally best to avoid UGfs in an Oscar tank. While they might provide some benefit as supplemental filtration, the work involved in keeping the gravel clean and the UGF plates covered is simply not worth it.

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