IZAK OR IZAK CATSHARK
One shark increasing in population
The Izak or Izak catshark (Holohalaelurus regani) is a species of catshark, belonging to the family Scyliorhinidae. They are common off the coasts of Namibia and South Africa. It typically inhabits the outer continental shelf at depths of 328-984 feet. The is segregation by age and sex. The Izak catshark has a short, wide, flattened head and a robust body tapering to a long, slender tail. It can be identified by its ornate color pattern of dark brown spots (in juveniles) or reticulations and blotches (in adults) on a light yellowish background, as well as by the enlarged dermal denticles over its pectoral fins and along its dorsal midline from the snout to the second dorsal fin.
Family: Scyliorhinidae – Catsharks
Common Name– Ground Sharks
Common Name– Catsharks
Average Size and Length: With the Cape typical subspecies, egg cases measure 3.5 x 1.5 cm. Hatchlings measure less than 11 cm/4.3 inches. Mature males measure between 45-69 cm/1.4-2.2 feet. Mature females measure between 40-52 cm/1.3-1.7 feet. The maximum recorded is 69 cm/2.2 feet. Males are larger than females.
With the northeastern subspecies (now the Honeycomb Izak), mature males measure between 52-55 cm/1.7-1.8 feet and mature females measure between 38-44 cm/1.2-1.4 feet.
Current Rare Mythical Sightings: The Izak catshark was originally described by South African ichthyologist John Gilchrist in a 1922 fisheries survey report. He assigned the new species to the genus Scylliorhinus, and gave it the specific epithet regani in honor of fellow ichthyologist Charles Tate Regan. In 1934, Henry Weed Fowler assigned this species to his newly created Holohalaelurus, a subgenus of Halaelurus. Holohalaelurus has since been elevated to the rank of full genus. As there do not appear to be any existing type specimens referable to Gilchrist’s account, in 2006 Brett Human designated a 63 cm/2.2 foot long male caught in Hondeklip Bay as the species neotype.
There has been much confusion in the scientific literature between H. regani, H. punctatus, and H. melanostigma, the last of which at various times had been considered a junior synonym of H. regani and was itself confounded with H. grennian. Two forms of H. regani were once recognized: the “Cape” or “typical” form and the “Natal” or “northeastern” form. The latter “northeastern” form was described as a separate species, H. favus, in 2006. On this page, the Natal or northeastern subspecies is described alongside the typical Cape species, but to read more about Holohalaelurus favus or the Honeycomb Izak, visit its page.
Teeth and Jaw: The mouth is long and angular and contains prominent papillae on both the roof and the floor, and does not have furrows at the corners. The upper and lower jaws contain on average 65 and 60 tooth rows. Each tooth is relatively large, with a narrow central cusp flanked by 1–2 smaller cusplets. The teeth differ in size by sex, with males having a longer central cusp than females do.
Head: The head is very short, wide, and flattened, with a blunt snout. The horizontally oval eyes are placed high on the head and have thick ridges beneath. They eyes are equipped with nictitating membranes and is followed by a spiracle. The nostrils are preceded by triangular flaps of skin that almost reach the mouth.
Denticles: There are enlarged rough dermal denticles on the middle of the back. The thick skin is covered by well-calcified dermal denticles, except around the gill slits.
Tail: The caudal peduncle is long and thin, particularly in younger sharks. The caudal fin makes up one-fourth to one-fifth of the total length and has a weak lower lobe and a ventral notch near the tip of the upper lobe.
Demographic, Distribution, Habitat, Environment and Range: The Izak or Izak catshark can be found in the southeast Atlantic and southwest Indian Ocean. The typical Cape subspecies can be found from Namibia to South Africa, possible KwaZulu-Natal. It extends from Lüderitz, Namibia in the west to Durban, South Africa in the east (4°S – 37°S). They can be found on continental shelves and upper slopes. The typical Cape subspecies can be found between 131-2,986 feet, but mainly between 328-984 feet. They are considered bathydemersal.
Off South Africa, it is most common in areas with a wider continental shelf, and at depths of 328-656 feet off the south coast and 656-3,215 feet off the west coast. Females and juveniles tend to be found in shallower water than males. For the most part, the number of sharks in a given area remains largely constant throughout the year. However, sharks at the southernmost point of the Agulhas Bank may perform a small autumn migration towards the shore.
The northeastern subspecies (now the Honeycomb Izak) can be found in South Africa in KwaZulu-Natal and Mozambique. The northeastern subspecies (now the Honeycomb Izak) can be found between 656- 2,428 feet.
Diet: They eat small bony fish, crustaceans, cephalopods, polychaetes, hydrozoans, and kelp has been found in stomach contents. A significant portion of its diet may be scavenged from offal discarded by fisheries.
Aesthetic Identification: The Izak or Izak catshark has scattered tiny black dots beneath the head. They are yellowish to yellowish brown and white ventrally. The upper surface is covered with dark brown reticulations, bars and blotches. There are more spots in young sharks. The body of the Izak catshark is firm and stout, tapering dramatically towards the tail. There are no horizontal stripes, white spots, tear marks, or highlighted dark marks on the dorsal fins. The dorsal fins are short and angular. The young are dark and slender with a line of white spots on the sides, and black bars on the tiny fins. There are 5 pairs of gill slits.
The pectoral fins are long and broad. The first dorsal fin originates over the rear of the pelvic fin bases; the second dorsal fin is slightly larger and originates over the rear of the anal fin base. The pelvic and anal fins are long and low, and larger than the dorsal fins. The free rear tips of the pelvic fins may be fused together to some degree, but never completely. Males have slender, pointed claspers.
The Natal subspecies (now the Honeycomb Izak) has smaller reticulations and are more spotted or checkerboard patterned.
Biology and Reproduction: They are oviparous. Pairs of eggs are laid year-round. Each egg case is light brown with long tendrils at the four corners that likely serve to anchor it to rocks. Its surface has a velvet-like texture and has lengthwise striations. The rate of egg laying is unknown but thought to be high.
Males and females mature sexually at 45–50 cm/1.4-1.6 feet and 40–45 cm/1.3-.14 feet long.
Compared to other deep-sea sharks, the Izak catshark has a large heart suggestive of a relatively active lifestyle.
This Izak often has nematode and flatworm parasites in its stomach.
Behavioral Traits, Sensing and Intelligence: It is known that at least part of the population migrates inshore in autumn.
The northeastern subspecies (now the Honeycomb Izak) juveniles occur in deeper water than adults do.
The typical Cape subspecies juveniles in shallower water than adults.
There is segregation by sex, with males found deeper than females in certain populations. The preponderance of females and juveniles at shallower depths may indicate that such waters serve as nursery areas.
They are more than likely active in nature.
Izak or Izak Catshark Future and Conservation: They are currently of least concern. They are commonly caught and discarded as bycatch. The typical subspecies population is increasing. Once cause may be a suggested high reproduction rate, but this is not confirmed.
Izak or Izak Catshark Recorded Attacks on Humans: Not a threat to humans.