Talk:Giant guitarfish/Temp

The giant guitarfish (Rhynchobatus djiddensis) is a large species of guitarfish in the family Rhinidae. It is restricted to the Red Sea, Persian Gulf, and western Indian Ocean but was formerly considered more widespread due to confusion with its relatives. Because of this, relatively little information is available on this species across its range.

Taxonomy and Range The giant guitarfish was previously believed to range throughout a large part of the Indo-Pacific, but recent evidence has shown that it, as traditionally defined, actually was a species complex consisting of four different species. In addition to the giant guitarfish, this complex includes the white-spotted guitarfish, the broadnose wedgefish and possibly the smoothnose wedgefish. With these as separate species, the giant guitarfish has a relatively restricted range; it is found only in the Red Sea and Persian Gulf, and the western Indian Ocean as far south as South Africa. Ranging across the western Indian Ocean, it is common to misidentify the separate species of guitarfish within a similar range.

Wedgefishes There are ten species in the Rhinidae family from three different genera. The genera of the wedgefishes include Rhynchobatus, Rhynchorhina, and Rhina. Found in warm temperate to tropical coastal waters, only two of the ten species live in the eastern Atlantic Ocean while the other species inhabit the Pacific.

Description A large fish reaching up to 3.1 m (10 ft) long and weighing as much as 227 kg (500 lb), it is brownish or greyish above with a variable pattern of white spots. Juveniles have a black spot above each pectoral fin, but in adults it is a dusky ring or absent. There is a dark, bar-like pattern between the eyes (on top of the head), which separates it from the other Rhynchobatus species in its range. In addition to this, the guitarfish can also be characterized by the large black eyespots on the pectoral bases and a distinct pointed snout.

Misidentification Wedgefishes and giant guitarfishes are both shark-like rays that inhabit the tropical waters along the West Indo-Pacific. Because their distribution and ranges overlap with each other, misidentification is quite common in numerous species. As of today, there isn't much information when fully distinguishing the different species of wedgefishes and giant guitarfishes. This is due to the misidentification of species and the limited research on the different species. What makes the different species more difficult to interpret is their identical morphology and the similar experiences of fishing pressure.

In addition to the misidentification aspect, there are actually two species of "giant guitarfish." For the wedgefish species, it would be the whitespotted wedgefish. On the contrary, there's the giant guitarfish that is technically a guitarfish. The whitespotted wedgefish (Rhynchobatus djiddensis) belongs to the Rhinidae family, and most species in this family have white spots across their bodies. The giant guitarfish (Glaucostegus typus) belongs to the Glaucostegidae family, and most species don't possess the spots that the wedgefish do.

Behavior The giant guitarfish is considered ovoviviparous, where the embryos initially feed on the yolk and then receive more nourishment from uterine fluid enriched with mucus which is obtained by means of indirect absorption. Because of their lower fecundity, the giant guitarfish are known to only produce, on average, four pups per litter during the summer. When the pups are born, they're typically 43 to 60 centimeters in length. Initial tagging data indicate that the species also has a very slow growth rate.

The giant guitarfish feeds on bivalves, crabs, lobsters, squid, and small fish. Despite not having any cutting teeth, this species is a known predator of stingrays. One specimen from the Philippines had more than 20 stingray barbs stuck in its jaw, apparently unaffected by the stingray's venom.

Habitat It is a shy fish, found at depths of 2–50 m (6.6–164.0 ft), inhabiting areas with a sandy sea floor. These are generally around coastal reefs or reef flats, but they will sometimes venture into the brackish waters of estuaries. One of the prime habitats for the giant guitarfish also includes the mangrove forests of Southeast Asia. The mangrove forests are exceptionally biodiverse and provide various ecosystem opportunities that species of fish and even millions of people depend on. Mangroves are known to enhance fisheries and coastal protection for the numerous species inhabiting the area. However, the mangrove forests have experienced a drastic increase in deforestation owing to global demand for commodities, and studies have identified the expansion of aquaculture as one of the primary reasons why this is occurring.

Threats From a global perspective, wedgefishes and giant guitarfishes are subject to extreme fishing pressure in their coastal range due to no regulations in their various distributions. They are caught in different types of fisheries, including industrial, subsistence, and artisanal. From this, the wedgefishes and giant guitarfishes are caught using different fishing methods, including traditional hook and line, gillnetting, trawling, seine netting, and trapping. The cartilaginous fish are generally kept for their fins and meat due to their high trade value. The increase in expanding fisheries has ultimately led to higher fishing pressure and overexploitation of marine animals in major areas of the Indo-West Pacific and the Eastern Atlantic.

Population The rhynchobatids, including the giant guitarfish, are among the most threatened families of chondrichthyans due to their restricted coastal habitat, slow life history traits, susceptibility to various fishing methods, and a continued increase in demand. Giant guitarfish have been exploited as incidental catch, and as a result, it has led to severe declines, reduced population size, and disappearances. Though the giant is labeled as critically endangered on the IUCN Red List, there is no specific data for the species that could be used to calculate the number of individuals in the decreasing population. Species-specific reporting and identification issues are the two major components as to why no accurate data is kept. Although there's an insufficient data record kept on the exact giant guitarfish population; the harvest rates infer that the species is substantially decreasing while the fishing rates remain stable or even increase. As the human population along the coastlines increase, fishing technology is improvised, and the expansion of the fish markets ultimately lead to an increase in fishing effort on a global scale. The highest increases in the fishing industry have occurred around the regions of Asia.

Regarding the catch databases of the giant guitarfish, a research survey from the Gulf of Thailand a ninety-three percent decline in the catch rates of Rhinobathidae, which includes the numerous species of wedgefishes and guitarfishes. From this respective data, the peak catch rate occurred in 1968 to a low in 1972. Additionally, the Indonesian Aru Islands wedgefish gillnet fishery had rapidly expanded their industry from the mid 1970s to its peak in 1987, operating with more than five hundred boats. Shortly afterward, the catch rate of the fish declined significantly and only a hundred boats remained in the area by 1996. By 1992, a wedgefish fishery in the Arafura Sea had been withdrawn because the area had been significantly overfished and the Indonesian investors only obtained limited returns from their investment.

Concerning the catch rates at varying levels of taxonomy, five contemporary datasets are available for accounted data ranging from Iran, Pakistan, India, and Indonesia. Though it's uncertain, these datasets most likely include various species of wedgefishes and giant guitarfishes, and each probable species is listed within the collected data. Raje and Zacharia 2009, an included dataset, doesn't include the count of giant guitarfish but rather represents the landing data of myliobatid rays including stingrays, butterfly rays, devil rays, and eagle rays. Although this dataset doesn't specifically account for the giant guitarfish population, the collected data can be utilized to infer the decline of giant guitarfishes considering they share the same distributions, habitat, and susceptibility to capture as the several species of myliobatid rays. Overall, the collected data is utilized to calculate proportional declines, annual change in population, and the reduction of the wedgefishes/giant guitarfishes over the three generations of complementary data.

From the studies compiled over three generations, fifteen out of the sixteen species of wedgefish and guitarfish are labeled as Critically Endangered under the IUCN Red List of Threatened Species. From this, it can be inferred that this family of fish is the most impacted by anthropogenic factors throughout their distribution.