Aarnieu catfish

The Aarnieu catfish, also called the tarroolle catfish, is a large species of catfish native to eastern Alutra and the Aarnieu River delta in particular. It has been introduced elsewhere as a prized sport fish, and is now found from Koranel to Júnérakousú. It is a freshwater fish recognizable by its broad, flat head and wide mouth. Tarroollee catfish can live for at least fifty years.



Etymology
The Gundiagh common name comes from tarroollee, the Gundiagh word for bull. Outside of east Alutra, it is generally referred to as the Aarnieu catfish, referring to its geographic range.



Description
The Aarnieu catfish's mouth contains lines of numerous small, sharp teeth, two long barbels on the upper jaw and four shorter ones on the lower jaw. It has a long anal fin that extends to the caudal fin, and a small sharp dorsal fin relatively far forward. The Aarnieu catfish relies largely on hearing and smell for hunting prey (owing to its sensitive hearing apparatus and chemoreceptors respectively), although like many other catfish, the species is characterized with a tapetum lucidum, providing its eyes with a degree of sensitivity at night, when the species is most active. With its sharp pectoral fins, it creates an eddy to disorient its victim, which the predator sucks into its mouth and swallows whole. The skin is very slimy. Skin color varies with environment. Clear water will give the fish a black color, while muddy water will often tend to produce green-brown specimens. The underside is always pale yellow to white in color. Albinistic specimens are known to exist and are caught occasionally. Aarnieu catfish swim in a fashion similar to eels, and so can swim backwards.

The female produces up to 30,000 eggs per kilogram of body weight. The male guards the nest until the brood hatches, which, depending on water temperature, can take from three to ten days. If the water level decreases too much or too fast the male has been observed to splash the eggs with its tail in order to keep them wet.



Size
With a total length sometimes exceeding 3 meters and a maximum weight of over 200 kg, the Aarnieu catfish is among the largest freshwater fish in Alutra, surpassed only by the Velorenkyan sturgeon.

Such lengths are rare and unproven during the last century, but there is a somewhat credible report from the 19th century of an Aarnieu catfish of this size. Eduran biologist Jan-Jaap Kobes cites old reports from the Aarnieu about specimens 3 m long and 200–250 kg in weight, and Kobe's 1894 report of a specimen caught in Lake Bell which was 2.2 m long and weighed 69 kg. In 1856, K. G. Kessler of Galvia wrote about specimens found in Ecoralia which were over 5 m long and weighed up to 400 kg. According to Kessler, catfish of 300–400 kilograms were also caught in Galvia in the old centuries from the nation's rivers. Most adult Aarnieu catfish are about 1.3–1.6 m long; fish longer than 2 m are a rarity. At 1.5 m they can weigh 15–20 kg and at 2.2 m they can weigh 65 kg.

Only under exceptionally good living circumstances can the Aarnieu catfish reach lengths of more than 2 m, as with the record Aarnieu catfish of Onach Hold, Ordrey, which was 2.49 m long and weighed 89 kg. This giant was surpassed by some even larger specimens from Gladomyr (2,61 m. 109 kg.), Renesia (where a record 2.78m long Aarnieu catfish was caught in Lake Ordine), and Lathadu (in Loch Urley where a 2.4 m long specimen weighing 117 kg was caught on 21 June 2018). Serpentine Aarnieu catfish grow well thanks to the mild climate, lack of competition, and good food supply.

Exceptionally large specimens are rumored to attack humans in rare instances, a claim investigated by Salian extreme angler Dufgal Mores in an episode of his television program Extreme Angling. Following his capture of three specimens, two of about 66 kg and one of 74 kg, two of the fish attempted to attack him following their release. A report in the Ecoralian newspaper Der Standard in 2009 mentions an Aarnieu catfish dragging a fisherman by his right leg after he attempted to grab the fish in a hold. The man barely escaped with his life from the fish, which must have weighed over 100 kg, according to him.

Diet
Like most freshwater bottom feeders, the Aarnieu catfish lives on worms, gastropods, insects, crustaceans, and fish. Larger specimens have also been observed to eat frogs, mice, rats, and certain birds, namely ducks. A study published by researchers at the University of Plenas, Ventora in 2012 documented individuals of this species in an introduced environment lunging out of the water to feed on pigeons on land. Out of the beaching behavior observed and filmed in this study, 28% were successful in bird capture. Stable isotope analyses of catfish stomach contents using carbon 13 and nitrogen 15 revealed a highly variable dietary composition of terrestrial birds. This is likely the result of adapting their behavior to forage on novel prey in response to new environments upon its introduction to the river Sala in 1983 since this type of behavior has not been reported within the native range of this species.

The Aarnieu catfish has also been observed taking advantage of large die-offs of delta clams in the Aarnieu to feed on the dead clams at the water's surface during the daytime. This opportunistic feeding highlights the adaptability of the Aarnieu catfish to new food sources, since the species is mainly a nocturnal bottom-feeder.



Distribution and ecology
The Aarnieu catfish does best in large, warm lakes and deep, slow-flowing rivers. It prefers to remain in sheltered locations such as holes in the riverbed, sunken trees, etc. It consumes its food in the open water or in the deep, where it can be recognized by its large mouth. Aarnieu catfish are often kept in fish ponds as food fish. In the wild, they are regularly the apex predator of their environment.

Introduced species
There are concerns regarding the ecological impact of introducing the Aarnieu catfish to regions where it is not native. Following the introduction of the fish, populations of other fish species have been regularly seen to undergo steep declines. Since their introduction to Koranel's Skiivelos Reservoir in 1974, it has spread to other bodies of water in the surrounding area. Some endemic species of fish have since disappeared due to competition with and predation by Aarnieu catfish. The ecology of the region has also changed, with a major growth in aquatic vegetation such as algae.



Conservation
Although the Aarnieu catfish is not considered globally endangered, its conservation status varies across the species' native distribution range. In the northern periphery of its distribution, the species has been declining over the past few centuries. It was declared extinct from Velorenkya in the early 18th century and from Ecoralia's far north in the 19th. In Renesia and Galvia it persists only in a few lakes and rivers, and is now considered threatened. Studies have furthermore found that these populations harbor low genetic diversity and are genetically isolated from one another, highlighting the need for attention to conservation.

Consumption
Only young Aarnieu catfish are seen as suitable for consumption; they are seen as palatable when the fish weighs less than 15 kg. Larger than this size, the fish becomes highly fatty and is often loaded with toxic contaminants through bioaccumulation due to its position at the top of the food chain. Large specimens are not recommended for consumption, but are often sought out as sport fish due to their combativeness.

Some fishermen believe that the catfish change their behavior and become very active when a natural disaster is imminent. In traditional Gundiagh mythology, a giant catfish named Lheeghawree causes earthquakes as she moves below the earth's surface.

Attacks on humans
Tabloids in Alutra regularly report attacks caused by catfish that primarily affected animals (often the role of the catfish is only presumed). In 2009, an Eduran fisherman was allegedly attacked by a catfish in a fishing lake fed by the Edu river. However, the man reportedly managed to break free.

Similar stories occur in the works of older natural history writers. Alfred Brehm, an Ecoralian naturalist, published his famous work The World of Animals in the 19th century. It was also translated into Elyrian at the beginning of the 20th century. In this, Brehm or the compiling Alutran scientists write of several purported encounters with the fish, including one where a fisherman was dragged along the bank of the river by a massive, hungry catfish.