Holohalaelurus regani (Gilchrist 1922)
(Fig. 5, Table 2)
Scylliorhinus regani Gilchrist, 1922 ZBK : 5.
Scylliorhinus regani ZBK : Barnard, 1925: 42.
Not Scyliorhinus regani Fowler, 1925 : 188; Fowler, 1926: 32; Barnard, 1927: 1013 (= Poroderma marleyi Fowler 1934 ZBK ).
Halaelurus (Holohalaelurus) regani : Fowler, 1934: 235; Fowler, 1941: 42.
Holohalaelurus regani reganisubsp. nov. : Human, 2003: 95.
Holohalaelurus regani typical subspecies : Compagno et al., 2005: 237.
Type Series and Locality. Neotype , designated herein, and type species for the genus Holohalaelurus ZBK , SAM 32448 , mature male 628mm TL, R.V. Africana Cruise 079, station A9830 082-3162 (erroneously recorded as 082-3160 on label) , 30°57’S16°46’E , from southeast of Hondeklip Bay, Northern Cape Province , South Africa , from 234m, 27th January, 1990 , in excellent condition.
Diagnosis. Holohalaelurus regani is the largest species of Holohalaelurus ZBK , and the following distinguishes H. regani from other Holohalaelurus ZBK sharks: denticles on dorsal midline from snout to second dorsal fin origin greatly enlarged; denticles on dorsal surface of pectoral fins greatly enlarged in adults; club-shaped papillae not present on the distal tip of the clasper; buccal papillae in mouth large and prominent on upper and lower surfaces; relatively high vertebral count, 126 total vertebrae in the neotype (mean 121.2); relatively high tooth counts, 71 upper teeth in total in the neotype (mean 64.5), 72 lower teeth in total in the neotype (mean 59.8). Adults with large horseshoe shaped markings, larger than eye diameter, on yellow-brown background; juveniles with large, irregularly shaped spots, ontogenetically fusing into the adult pattern; white spots never present.
Description. Morphometric and meristic data are given in Table 2. Neotype, mature male 628mm TL (mean of all specimens examined in Table 2, including the neotype, see Study material): body slender and elongate; head depressed, head width 2.33 (2.60) times its height at the posterior margin of the orbit, and head width 1.86 (2.14) times its height at the pectoral fin origin; trunk depressed, trunk width 1.46 (1.48) times its height; abdomen slightly depressed, abdomen width 1.08 (1.21) times its height; tail slightly compressed, tail width 0.86 (0.98) times its height; caudal peduncle compressed, caudal peduncle height 1.14 (1.44) times its width; ventral sensory pores conspicuously black; head moderately long, head length 0.22 (0.22) times the precaudal length; snout short, rounded and coming to a point, preoral length 0.22 (0.30) times the snout to first gill slit distance; mouth moderately long and relatively wide, moderately arched, buccal papillae in mouth large and prominent on upper and lower surfaces, mouth width 2.42 (2.85) times its length; eye slit like, eye length 2.07 (1.88) times its height, distance from snout to the anterior origin of the orbit 0.66 (0.68) times the snout to spiracle length; spiracle length 0.31 (0.19) times the eye length; area around gill slits naked, lacking denticles; distance from snout to first dorsal fin origin 0.69 (0.67) times the distance from the snout to the second dorsal fin origin; enlarged denticles on the dorsal midline from snout to second dorsal fin origin; first dorsal fin length 1.97 (2.18) times its height, length of the base of first dorsal fin 0.90 (0.73) times the length of the base of second dorsal fin; second dorsal fin length 2.44 (2.37) times its height; snout to pectoral origin length 0.46 (0.47) times the snout to pelvic fin origin length; pectoral fin large and winglike, enlarged denticles on the dorsal surface in adults, in the centre of the fin and towards the posterior margin of the fin, pectoral fin length 1.28 (1.34) times its height; height of the pectoral fin 3.03 (2.64) times the height of the pelvic fin; distance from pectoral insertion to pelvic origin 1.16 (1.09) times the distance between the insertion of the second dorsal fin and the caudal fin dorsal origin; pelvic fin long and low, pelvic fin length 3.73 (3.42) times its height, pelvic fin free rear tips variably fused, but never completely fused; claspers elongate without papillae on the distal tips, clasper inner margin length 9.0 (8.33) times their base; snout to anal origin length 4.85 (4.38) times the distance between the anal fin insertion and the origin of the ventral caudal fin; anal fin long and low, anal fin length 4.97 (4.87) times its height; length of anal fin base 1.88 (1.84) times the length of the second dorsal fin base; caudal dorsal margin length 1.52 (1.51) times the interdorsal space, caudal ventral lobe weakly developed. Vertebral counts: 30 (30.4) monospondylous, 58 (54.3) precaudal diplospondylous and 38 (36.5) caudal diplospondylous vertebrae. Dental formula: upper jaw (left) 32 (31.9), symphyseal 6 (2.0), (right) 33 (30.8); lower jaw (left) 33 (28.8), (symphyseal) 6 (2.7), (right) 33 (28.4).
Size and Sexual Maturity. Holohalaelurus regani is the largest of the Holohalaelurus ZBK sharks. The largest total length recorded here was 631mm and the largest weight recorded was 691.3g, for males (Fig. 1 and Table 2). In the current study, males were found to be juvenile at 232mm to 420mm TL, and mature at 598mm to 631mm TL. Females were found to be juvenile at 140mm to 254mm TL, adolescent at 224mm to 351mm TL, and mature at 425mm to 515mm TL. The heaviest female examined in this study weighed 320g.
Colouration. The colour pattern of adult H. regani is very striking and unique amongst Holohalaelurus ZBK , dorsal background colouration pale yellow to pale yellow brown, also pale yellow grey, yellow brown to mustard, pale brown, but these may be preservation artefacts. Ontogenetic progression of dorsal patterning is as follows: juveniles (Fig. 6B) with moderately large irregularly shaped solid dark brown spots that increase in size and begin to fuse in larger individuals to form small bars, blotches and reticulations, several indistinct saddles may be variably present or absent; in adolescent and mature animals (Figs. 5 & 6A), the patterning is a maze of large bold reticulations and horseshoe shaped markings, with spots virtually absent, when present, found only on the caudal peduncle or on fin webs, saddles absent; pattern on pectoral and pelvic fins identical to that of the dorsal patterning corresponding to the stage of maturity; white spots never present, no white spot above pectoral base or white spots at dorsal fin origins. Ventral colouration uniformly white, or off white in fresh or well preserved specimens, ranging to dull grey or brown in preserved specimens; with sensory pores conspicuously black on underside of head, trunk, pectoral and pelvic fins.
Comparison with other species. Holohalaelurus regani has greatly enlarged denticles on the dorsal midline, equivalent to H. favus and more so than other Holohalaelurus ZBK species. Adult H. regani have enlarged denticles on the dorsal surface of the pectoral fins, as do adult H. favus . The buccal papillae are large and conspicuous, but less so than in H. punctatus . Adults of H. regani have a unique dorsal patterning of large bold reticulations and horseshoe shaped markings, with spots few or absent, and no white spots. The dorsal patterning of juveniles is similar to that found in H. favus , H. grennian and H. punctatus , but distinguishable from these in the absence of white spots, absence of a white spot above the pectoral fin bases, and the absence of a honeycomb pattern. Holohalaelurus regani grows to a larger size than any other shark in this genus. Holohalaelurus regani is closest to H. favus and H. melanostigma in overall morphology, with adult colouration closest to H. melanostigma , and juvenile colouration closest to H. favus .
Remarks. Two forms of H. regani have been described (Bass et al., 1975) and generally recognised prior to this study. These forms include the “Cape” or “typical” form, and the “Natal” or “northeastern” form. The “Natal” form was diagnosed as a taxon warranting the rank of species, here described as H. favussp. nov. , whereas the “Cape” or “typical” form represents the true H. regani as originally described by Gilchrist (1922).
There are two juvenile female specimens in the SAIAB collection (RUSI 952) that are currently recognised as the syntypes for H. regani . Both of these animals are at the minimum extreme of total length for free swimming animals of this species. Gilchrist (1922) lists locality stations without reference to any specimens, and there is no reference to these localities anywhere within the species description. The only specimen referred to by Gilchrist in his description of H. regani was of a male 50cm long, clearly not referable to either of the female RUSI 952 specimens, which were measured by the author as being 205mm TL and 254mm TL. Gilchrist (1922) also describes “horseshoe-shaped bands”, which are absent on both of the syntypes because the horseshoe patterning only develops in H. regani at a much larger size than the RUSI 952 specimens. The catalogue for the SAIAB collection does not contain any details of who deposited these specimens or how they came to be syntypes, and Recommendation 72D states that labelling accompanying a type should unmistakably denote their status (ICZN, 1999).
Eschmeyer (1998) lists these specimens as the type series for H. regani based on Compagno (1984b), Bass (1986) and Compagno et al. (1991), however, Compagno (1984b) lists them as “probable syntypes”, Bass (1986) makes no mention of any type series, and Compagno et al. (1991) only list the S.S. Pickle stations from Gilchrist (1922) without reference to the RUSI specimens. Article 72.4.7 (ICZN, 1999) states that the recognition of putative type material in publications other than in the original description, labels accompanying the putative type series, or museum catalogue entries, are not necessarily evidence that a putative type series is legitimate, as is the case with the RUSI 952 specimens. Although these specimens are currently recognised as syntypes (Eschmeyer, 1998), scrutiny reveals that these specimens are invalid type material for H. regani due to the lack of reference to these specimens in the original species description and lack of corroborating evidence. Barnard (1925) refers to a type specimen for H. regani in the Collection of the Government Marine Survey, with no further details. If indeed a H. regani type existed in this collection, it has since been lost.
This issue was referred to the ICZN (case 3364) - BZN 62(4), 16 December 2005 . New Applications. CASE 3364: Scylliorhinus regani Gilchrist, 1922 ZBK (currently Holohalaelurus regani ; Chondrichthyes, Carcharhiniformes SCYLIORHINIDAE ): proposed conservation of current usage by designation of a neotype. B.A. Human. Their conclusion was “…when no name-bearing type specimen is believed to be extant [since there is no evidence to support the validity of the RUSI 952 specimens as type material], no ruling of the Commission is needed to designate a neotype of Scylliorhinus regani Gilchrist, 1922 ZBK … following the provisions of the Code (Article 75)… Therefore, the Secretariat is prepared to close the case” (S. Nikolaeva, pers. comm.).
Given the state of the type series for Holohalaelurus ZBK sharks, and to promote the stability of nomenclature for species within this genus, the designation of a neotype for H. regani would be warranted in accordance with Articles 75.1 and 75.3 (ICZN, 1999). The designation of a neotype (SAM 32448) from southeast of Hondeklip Bay, Northern Cape, results in the type locality changing to southeast of Hondeklip Bay, Northern Cape, in accordance with Article 76.3 (ICZN, 1999).
The type locality for H. regani given in Gilchrists’ original description, was “Cape Seas… in 95 to 175 fathoms”, and not 95-131 fathoms as listed by Eschmeyer (1998). The type locality data that accompanies the syntypes of H. regani , listed four possible S.S. Pickle stations from off of Table Bay, Western Cape (stations 234, 235, 241, or 243), with the possibility that the specimens may have also come from stations 324 or 359, presumable S.S. Pickle stations (exact location unknown). In any event, these localities are sufficiently ambiguous that the proposed type locality does not violate the requirement that the neotype be collected from the type locality (Article 75.3.6, ICZN, 1999), and furthermore, the proposed neotype type locality still falls into the type locality defined by Gilchrist, i.e. “Cape Seas”.
A source of taxonomic confusion in this genus is that there is marked ontogenetic allometry (as noted by Bass, 1973) and patterning in this species. In juveniles, the caudal peduncle is extremely elongated and the body and head are very short compared to adults (Fig. 6B). Also, although the colour observed in the juveniles is similar to that of immature and adult H. regani , albeit somewhat duller (possible preservation artefact), the patterning in juveniles is of large diffuse spots and short bars, with no signs of reticulations. The reticulations that are characteristic of the adults, take form in late juveniles and immature specimens. This ontogenetic shift may be present in other members of the genus and caution must be used when attempting to identify juveniles.
Fowler (1934) states that he erroneously described Poroderma marleyi ZBK (= P. pantherinum ) under the name Scyliorhinus regani in Fowler (1925, 1926), which was followed by Barnard (1927). In both publications, Fowler illustrates specimens that are readily recognisable as P. pantherinum (Human, 2006).
Morphometric proportions given by Bass et al. (1975) are a combination of H. favussp. nov. and H. regani , and although their proportions are similar to those given here, they should be used with caution. Strong sexual dimorphism is present in H. regani , with males growing much larger than females, and has been noted by many authors (Bass, 1973; Bass et al., 1975; Springer, 1979; Richardson et al., 2000; Human, 2003). Meristics and dentition given by Bass et al. (1975) are referable to H. favus and should not be used for comparison to H. regani as defined here and by Gilchrist (1922). Compagno (1988) defines Holohalaelurus ZBK as having seven turns in the spiral valve. In this study, spiral valve counts for H. regani ranged from three to six in specimens not in the type series.
Distribution. Holohalaelurus regani is a near endemic of South Africa and endemic to southern Africa (Fig. 7). This species prefers temperate to cool temperate waters, although it is also found in the subtropical waters of kwaZulu-Natal (Bass et al., 1975; Compagno et al., 1991; Richardson et al., 2000; present study). Holohalaelurus regani occurs in the Indian Ocean from about Durban, kwaZulu-Natal, South Africa, southwards and westwards to Cape Agulhas, continuing westwards into the Atlantic Ocean, and then northwards to southeast of Lüderitz , Namibia (Compagno et al., 1991; Richardson et al., 2000; present study).
Holohalaelurus regani is common to abundant on the continental shelf and upper slope down to at least 1075m (the deepest record yet published for this species), although it is more common between around 150 to 300m, and rare above 100m (Compagno et al., 1991; Richardson et al., 2000; present study). Holohalaelurus regani appears to prefer depths between 200m and 300m on the west coast, and depths between 100m and 200m on the south coast (Richardson et al., 2000). This species is a common bycatch of demersal trawlers (Compagno & Smale, 1989; Richardson et al., 2000) and was the most frequently encountered cartilaginous fish in the study by Compagno et al. (1991).
Compagno et al. (1991) also report this animal as far north in the Atlantic Ocean as southeast of Lüderitz , Namibia, and reasoned that this is the northern most limit of this sharks range in the Atlantic Ocean, as H. regani was not caught in Spanish research cruises that trawled the entire length of the Namibian coastline. It appears that Galeus polli ZBK replaces H. regani (and Scyliorhinus capensis ), north of the Atlantic limit of H. regani , possibly occupying the same niche that H. regani occupies in southern Africa (Compagno et al., 1991; L. Compagno, pers. comm.).
Bass et al. (1975) give the distribution of H. regani as from South Africa, Zanzibar and Somalia. Their records of H. regani in Zanzibar are based on H. grenniansp. nov. and H. melanostigma , and the source of their Somalian record is Fraser-Brunner (1952 in Bass et al., 1975). It is highly unlikely that H. regani occurs this far north, and it is more likely that the Somalian record is based on H. grennian or possibly H. melanostigma . The occurrence of Holohalaelurus ZBK north of Kenya needs further investigation.
Etymology. This catshark is “[n]amed after Mr Regan, who has described many South African fish” (Gilchrist, 1922).
Common name. Izak or Izak catshark have been used as common names for H. regani . Gilchrist (1922) called it a “Mottled Dog-fish”.
Study material. BAH 20020110.01 , mature male 630mm TL, R.V. Africana Cruise 165, A20476 3403-015 , 35°36'S19°36'E ; BAH 20020414.06 , mature male 598mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.07 , mature female 460mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.08 , mature female 483mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.09 , gravid female 455mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.10 , mature female 428mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.11 , gravid female 431mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020414.12 , mature male 598mm TL, R.V. Africana Cruise 167, A20804 3028-001 ; BAH 20020419.02 , mature male 600mm TL, R.V. Africana Cruise 167, A20814 4053-010 ; BAH 20020419.03 , mature female 515mm TL, R.V. Africana Cruise 167, A20814 4053- 010 ; BAH 20020419.04 , gravid female 466mm TL, R.V. Africana Cruise 167, A20815 3270-011 ; LJVC 860111 , juvenile female 140mm TL, R.V. Africana Cruise 39, A3340 3404-017 , 35°57'S19°42.4'E ; RUSI 952 , invalid syntypes , 2 specimens, both juvenile females, 254mm TL and 205mm TL, off Table Bay?Western Cape , South Africa , S.S. Pickle sta. 234?, 235?, 241?, or 243? ; RUSI 2800 , juvenile female 349mm TL, off Knysna , Eastern Cape , South Africa , 34°02'S23°02'E ; RUSI 25726 , mature male 598mm TL, R.V. Africana Cruise 39, A3337 2662-014 , 35°42'18"S19°44'24"E ; RUSI 38280 , adolescent female 351mm TL, [[ off Durban ]] 29°57'05"S31°14'30"E ; RUSI 48813 , immature female 224mm TL, Namibia , 29°56'00”S16°23'18"E ; RUSI 53725 , mature male 604mm TL, Namibia , R.V. Africana Cruise 59, A6949 0219-88 , 27°27'24"S14°25'00"E ; SAM 12986 , adolescent male; SAM 12987 , 3 specimens, juvenile males, 270mm TL and 420mm TL, immature male, 270mm TL, [[ S of Cape Town ]] 34°43'15"S18°30'00”E ; SAM 12988, previously PF 12684 , gravid female 425mm TL, NW½N 18mi off East London , Eastern Cape , South Africa , S.S. Pieter Faure , 33°15'S28°09.5'E ; SAM 12989 , juvenile male 270mm TL, NE½N 19mi off Cape Point , Western Cape , South Africa , S.S. Pieter Faure , 34°36'S18°18'E ; SAM 12990 , 5 specimens, 4 juvenile females, 176mm TL, 200mm TL, 230mm TL, and 254mm TL, and one juvenile male, 232mm TL, NE by E¾E 8mi off Cape Point , Western Cape , South Africa , S.S. Pieter Faure , 34°24.5'S18°23'E ; SAM 12991 , adolescent female ; SAM 24408 , 2 specimens, one adolescent female, one mature male ; SAM 27027 ; SAM 31695 ; SAM 32448, designated neotype of H. regani , see under Type Series and Locality for details; SAM 32619 , mature female, R.V. Africana Cruise 86, A10600 , 35°04'S20°44'E ; SAM 32995 , R.V. Africana Cruise 60, A7045 , 35°07'S19°28'E ; SAM 33287 , R.V. Africana Cruise 111, A14748 , 36°09'S20°7'E ; SAM 34500 , R.V. Africana Cruise 139, A18578 2606-083 , 35°06.5'S19°08.5'E ; SAM 34648 , R.V. Africana Cruise 109, A14673 , 33°19'S16°35.5'E .
- Brett A. Human (2006): A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species. Zootaxa 1315, 1-56: 18-27, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:D0E51C4E-FFF5-4BFF-9D16-5408E14AA741
Habitat and Ecology
Water temperature and chemistry ranges based on 1487 samples.
Depth range (m): 46 - 1075
Temperature range (°C): 3.145 - 17.304
Nitrate (umol/L): 8.004 - 32.269
Salinity (PPS): 34.402 - 35.352
Oxygen (ml/l): 3.111 - 5.220
Phosphate (umol/l): 0.692 - 2.394
Silicate (umol/l): 5.919 - 52.299
Depth range (m): 46 - 1075
Temperature range (°C): 3.145 - 17.304
Nitrate (umol/L): 8.004 - 32.269
Salinity (PPS): 34.402 - 35.352
Oxygen (ml/l): 3.111 - 5.220
Phosphate (umol/l): 0.692 - 2.394
Silicate (umol/l): 5.919 - 52.299
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
From 160 to 740 meters.
Life History and Behavior
Molecular Biology and Genetics
Barcode data: Holohalaelurus regani
No available public DNA sequences.
Download FASTA File
Statistics of barcoding coverage: Holohalaelurus regani
Public Records: 5
Specimens with Barcodes: 7
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
The Izak catshark (or simply Izak, Holohalaelurus regani) is a species of catshark, belonging to the family Scyliorhinidae, common off the coasts of South Africa and southern Namibia. It typically inhabits the outer continental shelf at depths of 100–300 m (330–980 ft), with the males found deeper than the females and juveniles. 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. This species reaches 69 cm (27 in) in length, with the males larger than females.
Bottom-dwelling and perhaps relatively active in nature, the Izak catshark feeds mainly on a diverse array of bony fishes, crustaceans, and cephalopods. A significant portion of its diet may be scavenged from offal discarded by fisheries. This species is oviparous, with females producing encapsulated eggs two at a time year-round. The Izak catshark is regularly caught incidentally by a South African bottom trawl commercial fishery, but is discarded rather than utilized. Despite the fishing pressure, its population has been increasing and thus the International Union for Conservation of Nature (IUCN) has assessed it as Least Concern.
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 (25 in) long male caught in Hondeklip Bay as the species neotype.
Historically, 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. Furthermore, 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.
The body of the Izak catshark is firm and stout, tapering dramatically towards the tail. 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; each has a rudimentary nictitating membrane and is followed by a spiracle. The nostrils are preceded by triangular flaps of skin that almost reach the long, angular mouth. The mouth contains prominent papillae on both the roof and the floor, and lacks furrows at the corners. The upper and lower jaws contain on average 65 and 60 tooth rows respectively; each tooth is relatively large, with a narrow central cusp flanked by 1–2 smaller cusplets. There are five pairs of gill slits.
The pectoral fins are rather 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 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. The thick skin is covered by well-calcified dermal denticles, except around the gill slits. Enlarged, spike-like denticles are found on the upper surface of the pectoral fins and along the dorsal midline from the snout to the second dorsal fin origin. Juvenile Izak catsharks are boldly patterned with many irregularly shaped dark brown spots on a light yellow to yellowish brown background. The spots enlarge and fuse with age to form an intricate pattern of reticulations and U-shaped markings in adults. The underside is plain white, with obvious black sensory pores beneath the head, body, and paired fins. Like other Holohalaelurus species, but contrary to the pattern in most cartilaginous fishes, males attain a much greater maximum length than females: 69 cm (27 in) versus 52 cm (20 in).
Distribution and habitat
Endemic to the southern tip of Africa, the range of the Izak catshark extends from Lüderitz, Namibia in the west to Durban, South Africa in the east. Older records further north along the East African coast (e.g. Somalia) most likely refer to other Holohalaelurus species. This abundant, bottom-dwelling species inhabits the outer continental shelf and upper continental slope, from 40 m (130 ft) to at least 1,075 m (3,527 ft) deep. Off South Africa, it is most common in areas with a wider continental shelf, and at depths of 100–200 m (330–660 ft) off the south coast and 200–300 m (660–980 ft) 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.
Biology and ecology
Compared to other deep-sea sharks, the Izak catshark has a large heart suggestive of a relatively active lifestyle. It is a generalist that feeds on a wide variety of bony fishes, crustaceans, and cephalopods; larger sharks consume proportionately more crustaceans and fewer fishes. At least some part of its recorded diet probably represents scavenging from fishery discards, given the presence of fast-moving, pelagic species that the shark is unlikely to have captured live. Polychaete worms, hydrozoans, gastropods, and hagfish eggs may also be occasionally ingested. This species often has nematode and flatworm parasites in its stomach.
The Izak catshark is oviparous and reproduction proceeds throughout the year without seasonal patterns. Mature females have a single functional ovary and two functional oviducts; a single egg matures within each oviduct at a time. Each egg is contained within a purse-shaped capsule 3.6–4.3 cm (1.4–1.7 in) long and 1.2–1.5 cm (0.47–0.59 in) across. The capsule 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 bears lengthwise striations. The rate of egg laying is unknown but thought to be high, based on this shark's resilience to fishing pressure. The preponderance of females and juveniles at shallower depths may indicate that such waters serve as nursery areas. The young hatch at under 11 cm (4.3 in) long. Males and females mature sexually at 45–50 cm (18–20 in) and 40–45 cm (16–18 in) long respectively.
The Izak catshark is harmless and of no commercial value. It is regularly caught incidentally (and discarded) by a bottom trawl fishery targeting hake south of Cape Town. In contrast to most cartilaginous fishes, its numbers have been increasing in the presence of commercial fishing. The reasons for this may include its high reproductive rate, its breeding in less-fished shallower waters, its hardiness allowing for high post-capture survival, and its opportunistic diet. The International Union for Conservation of Nature (IUCN) has consequently listed the Izak catshark under Least Concern, while still noting that it merits continued population monitoring because of its highly restricted range.
- Human, B.A. (2007). "Holohalaelurus regani". IUCN Red List of Threatened Species. Version 2011.1. International Union for Conservation of Nature.
- Human, B.A. (2006). "A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species". Zootaxa 1315: 1–56.
- Gilchrist, J.D.F. (1922). "Deep-sea fishes procured by the S.S. "Pickle" (Part I)". Report of the Fisheries and Marine Biological Survey, Union of South Africa 2 (3): 41–79.
- Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization of the United Nations. pp. 338–339. ISBN 92-5-101384-5.
- Richardson, A.J.; Maharaj, G.; Compagno, L.J.V.; Leslie, R.W.; Ebert, D.A.; Gibbons, M.J. (March 2000). "Abundance, distribution, morphometrics, reproduction and diet of the Izak catshark". Journal of Fish Biology 56 (3): 552–576. doi:10.1111/j.1095-8649.2000.tb00755.x.
- Froese, R.; Pauly, D., eds. (2011). Holohalaelurus regani. FishBase. September 2011 version.