Hardhead catfish

Hardhead catfish are found mostly in the near-shore waters of the Western Atlantic Ocean, around the southeast coast of the United States, around the Florida Keys and the coast of the Gulf of Mexico. but only occasionally enter freshwater. These barbels help the catfish find crabs, fish, and shrimp in the muddy or sandy bays where they live. The head is slightly flattened and conceals a hard plate between the eyes and dorsal fin. The dorsal and pectoral fins each are supported by a sharp, slime-covered, barbed spine. The dorsal spine is normally erect when the fish is excited and a tennis shoe or even a leather-soled shoe offers little protection. The gafftopsail catfish looks similar to the hardhead catfish, but its dorsal and pectoral spines have a distinctive fleshy extension (like the fore-and-aft topsail of a ship). ==Feeding behavior==

A. felis consumes a wide range of food. It is an opportunistic consumer that uses mud and sand flats as hunting grounds. ==Locomotion==

Significant evidence suggests correlation between the fish's activity patterns and seasonal changes. Under controlled conditions of photoperiod, temperature, and water quality, hardhead catfish display nonrandom oscillations in angular orientation of locomotive activity. There appears to be annual, bimodal cycles for all three of these variables. The cycles match with the seasonal inshore-offshore migrations of hardhead catfish. Photoperiod appears to be the exogenous cue that triggers the cyclic changes in behavior. The presence of this seasonal behavior indicates that a circadian neural mechanism may exist in hardhead catfish. ==Communication==

Chemical Hardhead catfish respond to chemicals released by injured individuals with increased activity, illustrating communication among catfish. Their activity level was highest right after the onset of the chemical stimulus. They also respond to chemical cues from injured sailfin mollies, but this response was weaker than that of the response from their own species. After examining the epidermis of the hardhead catfish, the alarm substance cells apparently were similar to those of freshwater catfish. These chemical responses had only been seen in freshwater ostariophysans. Hardhead catfish are the first marine ostariophysans found to elicit this type of alarm reaction. Echolocation Furthermore, hardhead catfish are the first indicator that Osteichthyes possibly could use directional hearing to detect obstacles. Emissions of low-frequency sounds were related to the detection and avoidance of close obstacles. Individuals within the group that produced sound avoided obstacles, whereas silent individuals crashed into obstacles frequently. Many fish have been associated with sound production for alarm, territorial, and courtship purposes, but sound probing of surroundings seems to be only be seen in hardhead catfish. So far, no evidence exists for far-field echolocation, such as seen in bats or toothed whales. The signal parameters have low frequency and amplitude, so far-field reverberations are unlikely to be useful. If echolocation exists, it is likely only useful in the near field by the catfish. Sound production Some evidence indicates sound production in hardhead catfish is differentiated both mechanistically and contextually. Mechanistically, sound can be produced in different ways. Thin bones by the swim bladder can be vibrated by specialized sonic muscles. Also, grinding of the pharyngeal teeth and rubbing of the pectoral spines against the pectoral girdle can produce sound. These two mechanisms appear to be evolved fright responses by the hardhead catfish. Some argue that hardhead catfish use an unrefined form of sonar as a means of echolocation, which also implies some directional hearing ability. It is possible, but is so far unproven, that sound is used in courtship and spawning. ==Lifecycle and reproduction==

The hardhead catfish has a reproductive season from around May to September. Males and females reach sexual maturity before age 2. ==Parental care==

Mouthbrooding Like other members of the Ariidae, hardhead catfish are paternal mouthbrooders. After spawning, the male carries the eggs in his mouth until they hatch. Several nonfunctioning eggs within the brood attach to the larger, viable eggs. These nonfunctioning eggs may be used as food for the male mouthbrooder, since mouthbrooders do not feed while they are taking care of the brood. At absorption of the yolk sac, juveniles begin to show adult characteristics. Advantages Many advantages to mouthbrooding exist as opposed to other forms of parental care, such as bubble nesting. Mouthbrooders are able to freely move with the eggs in their mouths, thus can move as necessary to protect both themselves and the broods. Though mouthbrooding requires more energy by the male, the chance of his young surviving to adulthood is greater, thus reproducing and continuing his genes; the eggs are not defenseless while in their father's mouth. ==Fishing==

Hardhead catfish are voracious feeders and will bite on almost any natural bait. Hardhead catfish are also known to steal bait. Shrimp is a particularly effective bait to use. When fishing for this species in fresh water, assorted meats tend to work best as bait. For example: bacon, chicken, cuts of steak, and smaller fish. Hardhead catfish are generally regarded as an undesirable catch by most anglers, largely due to the risk associated with handling the venomous fish, as well as its 'fishy' taste as opposed to desirable game fish. Hardhead catfish are edible, but like all catfish, require some effort to clean. It is one of the 30 most recreationally harvested species in the five-county area (Volusia, Brevard, Indian River, St. Lucie, Martin) encompassing the Indian River Lagoon in central Florida. From 1997 to 2001, 361,022 hardhead catfish were harvested within 200 miles of the shore in the IRL region. Hardheads are also harvested for industrial purposes in commercial bottom-trawling operations. Annual harvests vary greatly, but from 1987 to 2001, 1.04 million pounds of marine catfishes (including both the hardhead catfish and the gafftopsail catfish) were harvested in the IRL region. The harvest was valued at $777,497. ==Weight and length==

Hardhead catfish weigh around and measure long. As hardhead catfish grow longer, they increase in weight. The relationship between length and weight is not linear. The relationship between total length (L, in inches) and total weight (W, in pounds) for nearly all species of fish can be expressed by an equation of the form: :W = cL^b\!\, Invariably, b is close to 3.0 for all species, and c is a constant that varies among species. The relationship described in this section suggests that a hardhead catfish will weigh about , while a hardhead catfish will likely weigh at least . ==References==