© Baker, J.L. (2009) Marine Species of Conservation Concern in South Australia Full citation Baker, J.L. (2009) Marine Species of Conservation Concern in South Australia: Volume 1 - Bony and Cartilaginous Fishes. Report for the South Australian Working Group for Marine Species of Conservation Concern. J. Baker (consultant); Science and Conservation Division, and Coast and Marine Conservation branches of S.A. Department for Environment and Heritage (DEH); Marine and Coastal Community Network of S.A. (MCCN), and Threatened Species Network (TSN). Web version published by Reef Watch, South Australia.

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Knifejaw / Conway

Family Name:	Oplegnathidae
Scientific Name:	Oplegnathus woodwardi (Waite, 1900)
Recommended Status in S.A:	Data Deficient, possibly Near Threatened
Rationale:  Knifejaw is included here because (i) it is a southern Australian endemic species, and the single representative of the Oplegnathidae found in Australian waters; (ii) members of the genus Oplegnathus are usually strongly associated with habitat structures, such as reefs, which increases their vulnerability to capture; (iii) the species is becoming an increasingly popular food fish taken by various Commonwealth-managed and State-managed fisheries in southern Australia, with larger quantities being taken in some fisheries in recent years; (iv) Knifejaw has been classified as being at risk to population impacts from trawl fishing, long-line fishing, and gillnet fishing; (v) the species is taken in at least 10 different commercial fisheries across the range, and also by anglers (including S.A.), and there are inadequate regulations over the numbers taken in both commercial and recreational fisheries; (vi) very little is known of the biology or population dynamics of Knifejaw; and (vii) despite the increased fishing mortality during the past decade, no assessments have been undertaken to determine the size of Knifejaw populations, or the sustainability of fishing them in the current quantities.

Page Contents

Current Conservation Status

No listings known

Distribution

Southern Australia

Knifejaw are found across southern Australia, from about Shark Bay in W.A., to at least Terrigal in N.S.W. (Glover, in Gomon et al., 1994), and the distribution includes Tasmania (Last et al., 1983).
The species is more commonly found in the Great Australian Bight than in other localities (Glover, in Gomon et al., 1994; Australian Museum, 2003y).
Knifejaw are reported to be rare in New South Wales (Hutchins and Swainston, 2001).

South Australia

 In South Australia, the species is known from deeper waters across the entire S.A. portion of the Great Australian Bight; as well as deeper waters out of Coffin Bay, and also south of the tip of Eyre Peninsula; deeper waters south and south-east of Kangaroo Island; Investigator Strait; Backstairs Passage; deeper waters south of Encounter Bay; upper South East (e.g. deeper waters seaward of the lower Coorong / Lacepede Bay area, and also the Robe area); and deeper waters of the lower South-East (e.g. off Southend, Carpenters Rocks, Blackfellows Caves, and Port MacDonnell, extending into Victoria (Anonymous, 2001a; S.A. commercial and recreational fishing data, cited in Baker, 2004; CSIRO Marine Research records, cited in CSIRO, 2007; Australian Museum records, South Australian Museum record, cited in OZCAM database, 2007).

Habitat

Knifejaw occur in waters of the continental shelf and upper slope, generally between about 50m and 400m (May and Maxwell, 1986; Glover, in Gomon et al., 1994; Australian Museum, 2003y). Most specimens are known from the depth range 50m – 200m (CSIRO et al., 2001).
There is a CSIRO Marine Research record of O. woodwardi reportedly taken at 1030m deep, off Cape Banks (Commonwealth waters, seaward of Cape Banks, off south-eastern S.A.).
There appears to be little specific information recorded about habitat; however it is noted that almost all other members of the genus Oplegnathus are associated with reefs (Froese and Pauly, 2007). In south-western W.A., during a survey of fishes, O. woodwardi was reported to be found on vegetated sand (Harvey et al., 2004).
Juveniles are occasionally found in shallow inshore waters (Glover, in Gomon et al., 1994; Australian Museum, 2003y).

Notes on the Biology

The species grows to a size of at least 48cm (Glover, in Gomon et al., 1994; Hutchins and Swainston, 2001). Knifejaw in the size range 17cm to 45cm are caught in the GAB Trawl Fishery (Brown and Knuckey, 2002). It is noted that in Western Australia, McAuley and Simpfendorfer (2003) reported Knifejaw specimens as large as 94cm, in the bycatch of the Joint Authority Southern Demersal Gillnet and Demersal Longline Fishery. Most specimens caught during the survey period of 1994 to 1999 were in the range 36cm – 50cm, with few outliers (e.g. specimens of approximately 58cm, 72cm, and 94cm were recorded) (McAuley and Simpfendorfer, 2003).
The maximum size is not recorded; however one record size of a captured specimen was 4.16kg, being a specimen taken from south-western W.A. in 1986. Another large specimen was 2.977kg, taken from Rottnest Island, in 1967 (Australian Anglers Association (AAA), 2005; AAA WA Division Inc., 2005).
Oplegnathid fish feed on barnacles and molluscs (Nelson, 1994, cited in Froese and Pauly, 2007), and sea urchins (Grove and Lavenberg, 1997, cited by G. Edgar, pers. comm., 2006).

Fisheries Information

Commercial – Commonwealth

The species is mainly trawled in deep, offshore waters, between 50m and 400m, particularly in the Great Australian Bight (Glover, in Gomon et al., 1994). Knifejaw is described as being frequently caught in deeper offshore waters of southern Australia (Hutchins and Swainston, 2001).
Total catches of Knifejaw in Australian waters during the 1990s and early 2000s are listed below, according to statistics from BRS’s National Fisheries Production Database (NFPD), and ABARE and FRDC (2003 - 2006). In 2004/05, the catch was about 92 tonnes (ABARE and FRDC, 2006). The majority of the catch comes from Commonwealth-managed waters (i.e. the Great Australian Bight Trawl Fishery, as discussed below). Small amounts, such as 1t to several tonnes per year, have also been taken from Victoria and Western Australia (Table 22) (BRS, 2004).

Table 22 Knifejaw: Total Reported Catch from Australian Waters
Year	Catch (t)
1990/91	33
1991/92	33
1992/93	1
1993/94	3
1994/95	43
1995/96	40
1996/97	60
1997/98	54
1998/99	48
1999/00	31
2000/01	32
2001/02	34
2002/03	41
2003/04	67
2004/05	92

* = date not available for this report (Catches for 1990/91 - 1998/99 from BRS, 2004; catches for 1999/00 - 2003/04 from ABARE and FRDC, 2003, 2004, 2005, 2006)

The species is a retained by-product in the Gillnet, Hook and Trap (GHAT) fishery (which includes the Southern Shark Fishery, and 5 other sub-fisheries) (Ward et al., 2003; Webb et al., 2004; Bromhead and Bolton, 2005); the Great Australian Bight Trawl Fishery (GABTF); the South East Trawl Fishery (SETF); South East Non-Trawl Fishery (SENTF), and the Western Deepwater Trawl Fishery (WDTF) (AFMA, 2004e; Bromhead and Bolton, 2005). For Commonwealth licence holders with Scalefish Hook, Shark Hook, Gillnet Sectors and Coastal Waters permits, Knifejaw may be caught in Commonwealth waters (outside 3 NM) but not in coastal waters (inside 3NM), with a concession that allows methods other than trawl, and there are no catch restrictions (AFMA, 2004e).
Knifejaw is one of the 8 main seafood products sold by one of Australia’s largest seafood supply companies, based in South Australia. The species is also sold in the south-eastern States, and was previously marketed as “Conway” (AFFA, 2004d); however the marketing name “Knifejaw” is now used officially (Seafood Services Australia, 2005). Variable, but often small, quantities per month are sold at the Sydney Fish Market (e.g. 922kg in December 1998; 14kg in July 2001). Larger quantities are sold in Melbourne. Maximum and minimum monthly quantities of Knifejaw sold at the Melbourne Wholesale Fish Market during recent years are shown (Table 23).

Table 23 Annual quantities of Knifejaw sold, and maximum and minimum quantities sold per month at Melbourne wholesale fish market, 1993-2001
Year	Minimum monthly quantity sold	Maximum monthly quantity sold (kg)	Total quantity sold per annum (tonnes)
1993	0kg (Jan, Feb, Mar, Apr, May)	2,130kg (Oct)	6.09t
1994	0kg (Jun, Jul, Aug)	4,860kg (Mar)	12.69t
1995	0kg (Jan – Mar; May – Nov)	2,850kg (Apr)	4.92t
1996	0kg (Feb, Oct)	6,330kg (Dec)	20.07t
1997	240kg (May)	4,500kg (Feb)	22.2t
1998	0kg (Apr)	1,980kg (Dec)	7.77t
1999	0kg (Sep)	4,380kg (Feb)	12.24t
2000	90kg (Jul)	1,800kg (Nov)	10.95t
2001	30kg (Jul)	3,690kg (Jan)	10.89t*
*N.B. data in 2001 for January - July only (Adapted from C.H. Smith Marine, 2004)

Knifejaw is a significant by-product species in the Great Australian Bight Trawl Fishery. The species is ranked 11^th of the “top 40” fish and shark species taken, in terms of weight, and accounted for 2% of the catch composition in the GAB Trawl Fishery between 2000 and 2002 (Lynch and Garvey, 2003). According to AFFA (2004b, 2004c, 2005a), catches from the continental shelf component of the fishery in 2001, 2002 and 2003 were 44t, 45t and 66t respectively, being higher than in the previous few years. For 2001 and 2002, the discrepancy between the catches reported by Lynch and Garvey (2003) and AFFA (2004b, 2004c) may reflect the change in reporting arrangements from logbook data to landings data, with logbook data under-representing the catches (AFFA, 2004b). According to Ward et al. (2003), annual catches and catch per unit effort (CPUE) of Knifejaw increased as effort on the continental shelf of the GAB increased in the early 1990s. There was also a significant increase in effort in 2003, which resulted in higher catches of various continental shelf species, including the highest recorded catch of Knifejaw in the GAB Trawl Fishery during the past decade (Table 24) (AFFA, 2005a).

Table 24 Knifejaw: Reported commercial catch in the GABTF
Year	Catch (t)#
1995	36
1996	47
1997	44
1998	46
1999	40
2000	30
2001	33  (44)*
2002	33  (45) *
2003	66*
2004	73*

# from Lynch and Garvey, 2003 *from AFFA, 2004b, 2004c, 2005a, 2006

Bycatch sampling in the GABTF reported by Brown and Knuckey (2002) showed that Knifejaw were caught during the sampling periods in 2000 and 2001, and about 61% of the catch was retained. During that period, Oplegnathus woodwardi was observed in 160 of the 209 trawl shots; the average quantity retained was 11.2kg per trawl shot, and the average quantity discarded was 5.3kg per trawl shot (Brown and Knuckey, 2002). During that survey of the GAB Trawl Fishery bycatch, Knifejaw were caught in both the Western Zone (N = 407) and Central Zone (N = 35), and specimens ranged between 15cm and 45cm. During the survey period, all specimens caught in the Central Zone (26cm – 45cm) were retained, but in the Western Zone, a large proportion of the specimens in the size range 20cm – 30cm were discarded, although some specimens in the size range 20cm – 41cm were retained (Brown and Knuckey, 2002; Figure 17).
Knifejaw is a bycatch species in other Commonwealth fisheries, such as the South East Trawl Fishery (SETF) and the South East Non Trawl Fishery (SENTF). In 2000/2001, fishers’ logbooks in the SETF and SENTF respectively recorded by-catches of about 1.6t and 1.2t of Knifejaw, and a scientific monitoring program during the same period reported that almost all of the catch in the SETF was retained (AFMA, 2002a). It is noted that a bycatch monitoring program in the SENTF (Knuckey et al., 2001) recorded very low quantities of this species, compared with the amount reported by AFMA from fishers’ logbooks. The accuracy of the SENTF data is not known for this report.
Knifejaw is also part of the bycatch in the Southern Shark Fishery (SSF). In 2000/2001, fishers’ logbooks in the SSF recorded a bycatch of about 1.1t (AFMA, 2002a). It is noted that very minor quantities were recorded during a bycatch sampling program in 1998-2001 (see Walker et al., 2003), much lower than that reported by AFMA from fishers’ logbooks. The accuracy of the SSF data is not known for this report. In the SSF, Knifejaw is caught by gillnet and hooks on longlines (Webb et al., 2004).
Knifejaw is taken in the Western Deepwater Trawl Fishery (WDTF), which operates between 300m and 600m deep in waters south of 26oS (AFMA, 2004f). In the WDTF, fishing effort almost doubled between 1994/95 and 1996/97, when up to 514 trawlers worked the upper slope grounds for species such as Gemfish, Mirror Dory, Big-spine Boarfish, Deepwater Flathead and deepwater sharks. “Catch volumes” of Knifejaw fish in the WDTF, according to fishers’ logbooks, have included 91 in 1993/94; 680 in 196/97, 5 in 1997/98, 147 in 2001/02, and 161 in 2002/03, and 165 in 2002/04 (AFMA, 2004f). A total catch of 1,331 Knifejaw specimens was reported for the period 1992 – 2004 (AFMA, 2004f), but it is not known for this report whether the data from logbooks accurately reflects the total catch, or is underestimated.

Commercial – Western Australia

Knifejaw catches from W.A. waters are shown in the table below. Catches have varied from year to year by an order of magnitude in some cases, with the lowest and highest catches within a decade being taken in 1997/98 and 2000/01 respectively (Table 25).

Table 25 Reported catches of Knifejaw from W.A. waters, 1994-95 to 2004-05
Year	Live weight (kg)	Landed weight (kg)
1994/95	3,636	3,468
1995/96	1,321	1,162
1996/97	1,050	956
1997/98	864	826
1998/99	754	661
1999/00	1,321	1,162
2000/01	8,627	8,551
2001/02	4,926	4,823
2002/03	2,065	1,895
2003/04	2,154	2,108
2004/05	3,182	3,101

(W.A. Fisheries Research Services Division statistics 1994-2001, extracted from W.A. Fisheries web site, 2003, and W.A. State of the Fisheries reports, 2000/2001 - 2005/2006)

In W.A.’s JASDGDLF (Joint Authority Southern Demersal Gillnet and Demersal Longline Fishery) and the WCDGDLF (West Coast Demersal Gillnet and Demersal Longline Fishery), the annual catch of Knifejaw in gillnets is estimated to be in the range of about 1.4t to 2.7t, based on 5 years of observer data during the 1990s (McAuley and Simpfendorfer, 2003). This estimate accords with the catch figures reported to W.A. fisheries (see above). In the JASDGDLF, the highest catches of Knifejaw come from the south-western tip of W.A. (Region 3, between longitudes 116°E and 119°E; and Region 4, between longitude 116°E and latitude 33°S) (McAuley and Simpfendorfer, 2003).
The species is also taken in the Western Deepwater Trawl Fishery (see above, on Commonwealth Fisheries).

Commercial – South Australia

Under the Commonwealth’s Fisheries Management Amendment Regulations 2000 (No. 6) 2000 No. 339 - Schedule 1, there are restrictions to the number of Knifejaw that may be taken by Commonwealth fishers who have permits to fish in South Australian state waters. Primary Industries and Resources South Australia (PIRSA) manages catches of Knifejaw that are taken within 3 nautical miles (NM) of the coast, and the Commonwealth manages catches taken outside of 3 NM (AFMA, 2002a).
Knifejaw are taken in small incidental quantities in the Marine Scalefish Fishery, off the tip of southern Eyre Peninsula; deeper waters south of Kangaroo Island, and along the South-East coast of S.A., to the Victorian border. During the mid-late 1990s, less than 1t per annum were taken from these areas collectively.
Knifejaw is caught as bycatch in the South Australian Rock Lobster Fishery (Sloan, 2003a). Prescott and Xiao (2001) reported that 33 Knifejaw specimens were caught in 17 lobster pots, during sampling of 32,000 pots in the Northern Zone Rock Lobster fishery in S.A., in 1991 – 1992. For the Southern Zone (21,000 pots sampled), only 1 Knifejaw was reported to be caught during the 1991-92 season (Prescott and Xiao, 2001). During a more recent bycatch monitoring program in this fishery, several hundred Knifejaw specimens were recorded from both the Northern Zone and Southern Zone, in 20021/02 and 2001/03. Catches are shown in the table below (from Brock et al., 2004). By-catch from half of the total number of pot lifts per annum was recorded and therefore, the total catch (from all pots) could be in the vicinity of 600 specimens or more in each of the Northern Zone and Southern Zone. During this program, the bycatch was also sampled from 1% of the total number of pot lifts during the 2002/03 fishing season, and 14 specimens of O. woodwardi were recorded in the Northern Zone, and 17 in the Southern Zone. Based on bycatch sampling by observers, the annual catches of Knifejaw in the Northern Zone and Southern Zone may in the vicinity of 1,500 specimens in each zone, which is double that estimated from logbook data. Regardless of the differences in results according to sampling methods, the rock lobster bycatch survey program data indicate that hundreds of specimens per annum may be taken as bycatch in this fishery (Table 26).

Table 26 Proportional catch of Knifejaw in the S.A. Rock Lobster Fishery
Northern Zone	No. pot lifts (and percentage of total)	No. O. woodwardi specimens caught
2001/02	320,003 (51%)	566
2002/03	265,843 (47%)	163
Southern Zone	No. pot lifts (and percentage of total)	No. O. woodwardi specimens caught
2001/02	545,886 (60%)	385
2002/03	486,155 (57%)	313
from Log Book Monitoring 2001-2003 (Brock et al., 2004)

Commercial – Other States

The species is caught by trawls in deeper waters off the N.S.W. coast (NSW Fisheries data, 2001), although it is not common in that State (Hutchins and Swainston, 2001).
There are commercial fishing records from Bass Strait (Anonymous, 2002b).
Knifejaw is reported in the Tasmanian Scalefish fishery (Lyle and Jordan, 1999). Based on general Fishing Returns, the annual catch during 1990 to 2000 ranged between 0kg and 500kg, with around 100kg to 200kg per annum caught in six of those years (Lyle and Jordan, 1999; Jordan and Lyle, 2000; Lyle and Hodgson, 2001).

Recreational

The National Recreational and Indigenous Fishing Survey (Henry and Lyle, 2003) reported that 1,489 Knifejaw specimens were caught and kept by recreational fishers in South Australia during the survey time period (May 2000 to April 2001). During that survey, the species was not recorded in the recreational catch statistics for other States. During that survey, one of the locations at which Knifejaw was recorded in the recreational catch, was the deeper waters out of Coffin Bay.
Some recreational fishing clubs and associations keep records of the maximum sizes caught (e.g. Australian Anglers Association, WA Division Inc., 2005; Australian Anglers Association, 2005).    Knifejaw catches in the charter boat fishing in South Australia are now expected to be reported, using a catch code (PIRSA, 2004); however, catches of this species are not subject to catch limitations (see Presser and Mavrakis, 2005; PIRSA, 2005b).
O. woodwardi is also captured in southern Australian States by spear fishers. The Australian record size taken by a spear fisher is reported to be 1.9kg, being a specimen taken at Hamelin Bay in W.A., in 1995 (Australian Underwater Federation Inc., 2003).

Vulnerable Characteristics of the Species

Members of the genus Oplegnathus are usually strongly associated with habitat structures, such as reefs, which can increase their vulnerability to capture.
Members of the family feed on benthic organisms (e.g. barnacles and molluscs), and Knifejaw populations in some areas may thus be vulnerable to decline from physical impacts that damage benthic reef structure and composition; however more information is required.
Knifejaw is a southern Australian endemic species, and the single representative of the Oplegnathidae found in Australia waters.

Threatening Processes

The combined effects of commercial and recreational fishing are likely to be the main threatening process. As shown in the sections above, dozens of tonnes of Knifejaw are killed per annum, through the collective efforts of trawl fishing, hook and line fishing, gillnet fishing, rock lobster pot fishing, and recreational fishers, and no assessments have been undertaken to determine the sustainability of fishing this species at current levels. During the past decade, the increasing popularity and marketing of this species as a quality food fish are likely to further increase the fishing effort over time.
In a draft ecological risk assessment report for the South East Trawl Fishery (Wayte et al. 2004), 3 “productivity attributes” and 6 “susceptibility attributes” were used to classify O. woodwardi as being a “medium risk” species in terms of potential population impacts from trawling, although the calculated “overall risk value” was close to the upper limit for that category, hence the species almost qualified as “high risk” in that assessment.
Similarly in the Southern Shark Fishery, Webb et al. (2004) used productivity and susceptibility attributes to classify the species as being at “medium risk” of population impacts from capture in the demersal long-line sub-fishery, and the gillnet sub-fishery of the SSF.
Little is known of the habits, and critical habitat of Knifejaw; however Oplegnathus species in general are strongly associated with benthic habitats, and therefore trawl damage to the benthos in some parts of the range may be a threat to Knifejaw populations.
 

Research and Management Requirements

Despite the increased fishing mortality during the past decade, no assessments have been undertaken to determine the size of Knifejaw populations, or the sustainability of fishing them in the current quantities. As a matter of priority, stocks assessment should be undertaken in commercial fisheries that target this species, or retain it as by-product.
The relation between Knifejaw populations in the fished parts of the range needs to be determined, to assess whether co-management arrangements are required between Commonwealth and State fisheries, or between States (e.g. S.A. and W.A.), for Knifejaw populations and the fisheries that target them, or take the species as by-product.
In addition to data on abundance, more information is required on the geographic and depth distribution, habitat requirements, biology and ecology of this species.
In both Commonwealth- and State-managed fisheries, target catches and bycatch of Knifejaw should be monitored over space and time.
Measures to reduce the bycatch of this species in trawl fisheries and rock lobster pots are required.
Catch limitations should be introduced for recreational fishing (angling, spear fishing and charter boats), pending further information on the species, such as an assessment of population sizes.