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Black Rockcod - Epinephelus daemelii
By John Pogonoski
Threatened Fish Profile – In Newsletter 30_2, December 2000
(Drawing by Jack Hannan, NSW Fisheries)
Conservation Status:
Protected species in NSW State waters and Commonwealth waters; Listed as a Vulnerable species in NSW under the Fisheries Management Act 1994; ASFB – Potentially threatened; No Commonwealth or IUCN listings.
Description:
The black rockcod is a large, reef-dwelling grouper species belonging to the family Serranidae. Its appearance varies between the juvenile and adult phases; juveniles have a distinct black caudal peduncle (or ‘saddle’ just forward of the tail), that may fade as the fish grows but is still faintly visible in adults. Similarly, there are five irregular oblique grey to black bars (including the stripe from the nape to the eye, but excluding the bar or saddle on the caudal peduncle) which originate at the dorsal margin and sometimes fade as they approach the ventral margin of the fish. These bars are also more distinct in juveniles and sub-adults and fade as the fish grows, and are more distinct in live fish as opposed to dead or preserved specimens. Large specimens (over 50cm) have distinct canine teeth on both sides of the upper and lower jaws. The black rockcod has a rounded caudal fin and small black spots are also present on the body and/or fins of some specimens, as are occasional whitish blotches. All groupers of the genus Epinephelus have 11 dorsal spines (Heemstra and Randall, 1993). In Australian waters, the black rockcod attains at least 1.5m total length (Hutchins and Swainston, 1986; Leadbitter, 1992) and a weight of 81kg (Hutchins and Swainston, 1986). At the Kermadec Islands, north of New Zealand, E. daemelii may reach 2m in length. In New Zealand waters, the recorded maximum size is 1.8m, but they are usually 40-80cm in length (Paulin and Roberts, 1992).
Distribution and abundance:
The black rockcod occurs in warm temperate and subtropical waters of the south-western Pacific. Their distribution includes south-eastern Australia (southern Qld to northern Victoria), Norfolk Island, Elizabeth and Middleton Reefs, Lord Howe Island, Kermadec Islands and New Zealand (North Island and Poor Knights Islands). Rarely, expatriates have been found westwards to Kangaroo Island off South Australia (Heemstra and Randall, 1993; Gill and Reader, 1992). Like many large groupers that govern a home territory, the black rockcod is likely to have a low abundance, especially as adults, and large males are considered to be rare.
Habitat and feeding:
The black rockcod occurs in reef caves, gutters and beneath bommies (Gill and Reader, 1992) on rocky reefs from near shore to depths of at least 50m (Heemstra and Randall, 1993). This species is generally found on coastal reefs, estuaries and deeper offshore waters, often not seen except when diving with a torch at night (Kuiter, 1996). Recently settled juveniles can be common in coastal rock pools along the NSW coastline (Hutchins and Swainston, 1986). The black rockcod is an opportunistic carnivore (Leadbitter, 1992), preying on fishes and crustaceans (McCulloch, 1922). Juveniles feed on crabs and fishes (Heemstra and Randall, 1993).
Life History:
The black rockcod is an aggressive territorial species that may occupy a particular cave for life (Heemstra and Randall, 1993). Observations by fishermen and divers suggest that this species is slow growing and also slow moving (Leadbitter, 1992). Ayling and Cox (1982) noted that individual fish could change their colour depending on their mood and the colour of the background. The black rockcod, like many groupers are protogynous hermaphrodites (Heemstra and Randall, 1993). Small fish are females and change sex to become males at around 100-110cm length (Paulin and Roberts, 1992).
Threats:
The territorial and sometimes curious nature of the black rockcod makes it extremely vulnerable to spearfishing. The total fishing ban in NSW was enforced following a noticeable decline in numbers, mainly attributed to the rise in the popularity of spearfishing in the early 1970’s (Leadbitter, 1992). Lincoln-Smith et al. (1989) noted that in NSW 137 black rockcod averaging 2.4kg per fish were speared in NSW spearfishing competitions in 1976 alone. Divers at the Kermadec Islands record very large E. daemelii to be extremely curious and easily approached, being almost tame. This behaviour makes them easy to spear, and stocks have been quickly reduced by recreational as well as commercial fishing. Recent protection at the Kermadec Islands may help to alleviate this problem (Stewart, 1999). Roughley (1916) reported of E. daemelii “at one time it was fairly plentiful in the vicinity of Port Jackson, but has become very scarce in recent years, owing to the havoc wrought by fishermen…”. The black rockcod does not form breeding populations in the North Island waters of NZ, but individuals may grow to a large size and so appear to be capable of surviving for a number of years (Stewart, 1999). Their status in NZ mainland waters is not secure, as they do not form breeding populations (C. Roberts, pers. comm.). McCulloch (1922) reported that E. daemelii was a valuable food fish in NSW, indicating that this species was once quite common in that state.
Conservation/management:
Continued protection in NSW waters and Commonwealth waters will assist the survival of the black rockcod. The implementation of Marine Protected Areas or no take fishing zones in known habitats may be necessary to provide further protection. The main threat to this species appears to be that of illegal fishing activities. Additionally, the black rockcod is likely to be taken in small numbers as a bycatch of commercial and recreational fishing activities in rocky shore and island habitats along the southern Qld, NSW and northern Victorian coastlines.
References:
Ayling, T and Cox, G.C. (1982) Collins Guide to the Sea Fishes of New Zealand. Collins, Auckland, New Zealand, 343pp.
Gill, A.C. and Reader, S.E. (1992) Fishes In: Reef Biology. A Survey of Elizabeth and Middleton Reefs, South Pacific, by The Australian Museum. Kowari 3: 90-92. ANPWS, Canberra.
Heemstra, P.C. and Randall, J.E. (1993). FAO Species Catalogue Volume 16 Groupers of the World (Family Serranidae, Subfamily Epinephelinae). Food and Agriculture Organisation of the United Nations, Rome, pp. 382.
Hutchins, B and Swainston, R. (1986). Sea Fishes of Southern Australia - Complete Field Guide for Divers and Anglers. Swainston, Perth, Western Australia, 180pp.
Leadbitter, D. (1992) Special Fauna (B) Black Cod Survey (in) Reef Biology. A Survey of Elizabeth and Middleton Reefs, South Pacific, by The Australian Museum. Kowari 3:103-106. ANPWS, Canberra.
Lincoln-Smith, M.P., Bell, J.D., Pollard, D.A. and Russell, B.C. (1989). Catch and effort of competition spearfishermen in Southeastern Australia. Fisheries Research 8: 45-61.
McCulloch, A.R. (1922). Checklist of the Fishes and Fish-like Animals of New South Wales. Royal Zoological Society of New South Wales, Sydney, Australia.
Paulin, C.D. and Roberts, C. (1992) Rockpool Fishes of New Zealand. National Library of New Zealand, Wellington, 177pp.
Clive Roberts, Museum of New Zealand, Wellington, pers. comm. April 2000.
Stewart, A. (1999). Summer Visitors ’99. Seafood New Zealand. pp.78-79.
Further information:
Mr John Pogonoski,
Australian Museum,
6 College St, Sydney, NSW, 2010.
Ph: (02) 9320 6139
Email: johnpog@austmus.gov.au