© 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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Bight Redfish / Red Snapper / Golden Snapper / Rosy Nannygai

Family Name:	Berycidae
Scientific Name:	Centroberyx gerrardi (Günther, 1887)
Recommended Status	South Australia and Western Australia: possibly Near Threatened; Commonwealth Waters: Near Threatened
Rationale:  Although Bight Redfish has a broad geographic distribution across southern Australia, and is an abundant species, it is included here because (i) it is a long-lived (65 - 70+ years) species with high variability in size at age, probably with low natural mortality rate and delayed maturity / high age at first spawning; it is commonly accepted that populations of such species cannot tolerate high and sustained catches over space and time; (ii) it is an aggregating / schooling species that is highly vulnerable to capture, and heavily targeted by numerous commercial and recreational fisheries across the range, with a recent age estimate of commercially caught specimens ranging from 9 to more than 60 years; (iii) year class strength may be highly variable, and environmentally-driven; (iv) despite poor knowledge of the population dynamics, and biomass (for which figures regularly and significantly fluctuate), and inadequate regulation of catches from all fisheries combined, the Commonwealth-managed commercial catches (Great Australian Bight - GAB) and commercial catches in W.A. have increased significantly during the past decade, and this species is also an increasingly popular recreational target in S.A. and W.A., particularly charter boat catches; (v) given the size range of commercially caught fish (e.g. in the GAB), compared with the reported size at maturity, it is possible that a significant proportion of the commercial catch is reproductively immature, and has not had opportunity to spawn before being caught; (vi) there are indications that the size (and age) structure of the population is being adversely affected by commercial fishing, with a decrease in the modal size of fish observed over 5 years, few larger (older) fish in the catches, and a decrease in the age range of caught fish over nearly two decades (from predominately 20-40 year old fish in the late 1980s, to mainly 14-24 year old fish in the following decade); (vii) despite annual abundance surveys using trawls in the Great Australian Bight, there is little information about this species across the range, including reliable measures of relative abundance and biomass over space and time; distribution and connectivity between populations; habitat preferences of adults and juveniles; reproduction; larval movement; population dynamics and ecology.

Page Contents

Current Conservation Status

There are no formal conservation listings for this species. Population abundance is poorly known, despite regular trawl surveys, but it is noted during the early mid-2000s, C. gerrardi was considered to be fully fished in the Great Australian Bight Trawl Fishery (see AFMA, 2003i). By the late 2000s, when catches had increased, the assessment was changed to not over-fished and current catches do not constitute over-fishing (Larcombe and Begg, 2008; Wilson et al., 2009).

Distribution

Southern Australia

The Bight Redfish is reportedly found from southern Victoria / Bass Strait, through to southern Western Australia (approximately as far north as Lancelin), with the Great Australian Bight being the centre of distribution (Hutchins and Swainston, 1986; Kuiter, in Gomon et al., 1994). The species is found in greatest numbers in the Great Australian Bight, where it is commercially fished (see Brown and Knuckey, 2002; AFFA, 2004b).

South Australia

The species is found in various parts of S.A., including the western and central Great Australian Bight (GAB); eastern GAB / western Eyre Peninsula (e.g. off headlands and islands); the Investigator Group islands / eastern Great Australian Bight; southern Spencer Gulf (including around islands in Thorny Passage), southern Eyre Peninsula (e.g. Memory Cove), and waters south of Spencer Gulf (including Gambier Islands and Neptune Islands); southern Yorke Peninsula (Investigator Strait waters, and around islands, including the Althorpe group); southern Gulf St Vincent; Backstairs Passage; northern and southern Kangaroo I., and the upper South-East, and lower South-East (Glover, 1979; Branden et al., 1986; Capel, 1994; Sweeney, 1996a, 1996b; Wilson, 2001a; Brown and Knuckey, 2002; Shepherd and Brook, unpubl. data, 2002; J. Brook, unpubl. data, 2004; Mensforth, undated; Fishnet, 2002, 2003, 2004; charter boat fishing reports, 2002, 2003; Baker, 2004, and references cited therein; Australian Museum records; Museum of Victoria records, cited in OZCAM database, 2009).

Habitat

The species is found on rocky reefs, and silty / muddy substrates, on the continental shelf and upper slope. Daley et al. (1998) and CSIRO et al. (2001) reported the depth range to be 10m – 300m. May and Maxwell (1986) reported a lower depth limit of 500m. In fished areas, the species is typically recorded in waters 80m – 210m (Daley et al., 1998) or 150m – 250m (CSIRO et al., 2001).

In some coastal locations in South Australia, there are records as shallow as 3-8m (e.g. Knob Point on Kangaroo Island: Australian Museum record).

Kuiter (1996a) reported the species to occur on rocky reefs, from shallow waters, to deep offshore (at least 300m). During surveys of fish habitats in south-western Australia, C. gerrardi have been recorded mainly on reefs of various type and cover (e.g. Harvey et al., 2004; Hutchins, 2005), but small numbers were also recorded over vegetated sand (Harvey et al., 2004).

It has been reported that Bight Redfish usually occur singly or in pairs, within caves and beneath ledges (Kuiter, in Gomon et al., 1994). Kuiter (1996a) also reported the species to be solitary. This conflicts with the nature (and large quantities) of catches in the Great Australian Bight Trawl Fishery, which more likely comprise aggregations / schools. It is also noted that Bight Redfish aggregations are taken by charter boat operators in some parts of South Australia; hence the species is not always solitary. The Bight Redfish is also found in and around shipwrecks, which provide shelter (Kuiter, 1996a), and, in some areas, around long jetties in deeper waters (e.g. Tanker Jetty, Esperance).

Notes on Biology

Age and Growth

Maximum size is around 66cm TL (Hutchins and Swainston, 1986). During a study of the Great Australian Bight Trawl Fishery in 2000-01, the size range of Bight Redfish recorded was 25cm to 51cm LCF, with the larger fish (40+cm) being recorded mainly in the Western Zone (Brown and Knuckey, 2002). Most fish were within the size range 27cm – 40cm (Brown and Knuckey, 2002). During a survey in 2004-05, the size range was 22cm – 59cm, with most fish in the size range 29-43cm (Stokie and Krusic-Golub, 2005). During a scientific monitoring program of the Great Australian Bight Trawl Fishery, in which 2,297 Bight Redfish were measured, the majority were in the size range 28-38cm (Talman et al. 2005).

The record size for a specimen of C. gerrardi is 4.593kg (a spearfishing record from Hamelin Bay in W.A.) (Hutchins and Swainston, 1986; Australian Underwater Federation Inc., 2003). The Australian Anglers Association (W.A. Division), has also recorded a large specimen (4.26kg) of C. gerrardi, taken from Rockingham in W.A. in 1995. Wilson (2001a) reported Bight Redfish larger than 3kg from off Cape Radstock in South Australia. Daley et al. (1998) reported that C. gerrardi usually grows to nearly 2.5kg in weight, which might indicate that the size of Bight Redfish in commercially fished areas is now smaller than in other parts of the range.

In an ageing study in 2003-04, using otoliths from 628 specimens of Bight Redfish, the age estimates of the samples ranged between 8 and 64 years (Stokie, 2004). In 2004-05, age estimates were obtained from 571 Bight Redfish otoliths, and calculated ages ranged from 7 to 71 years overall (= 7 - 62 years for females, and 10 – 71 years for males, in that sample) (Stokie and Krusic-Golub, 2005). There is considerable variability in age among Bight Redfish of similar size, such that commercial catches consist of animals between 9 and more than 60 years old (Caton and McLoughlin, 2005; AFFA, 2005a). During another study, in which Bight Redfish otoliths were sampled from other parts of South Australia (e.g. Investigator strait, and some from Pearson Island in the eastern GAB), most fish were aged from 8 to 25 years, with a few older fish to 41 years (Saunders et al., 2009).

A study in South Australia, in which an age-length key was produced, supported the findings of Stokie, indicating that there is considerable variation in size at age. The South Australian study suggested that males grow faster than females (Saunders et al., 2009).

Migration and/or Aggregation

Bight Redfish school by sex (Knuckey and Brown, cited by FRDC, 2003b).

Waters shallower than 100m are probably a nursery area for the Bight Redfish (AFFA, 2004b).

Diet and Feeding Behaviour

Redfish are bentho-pelagic feeders, mainly feeding on bentho-pelagic fish and pelagic crustaceans (Coleman and Mobley, 1984, and Bulman et al., 2001, cited by Bruce et al., 2002).

Reproduction

Male Bight Redfish appear to mature at 35.2cm and female Bight Redfish at 32.4cm, but this needs to be confirmed using additional data (Knuckey and Brown, cited by FRDC, 2003b).

This species may have a high age at maturity (Department of Fisheries, WA, 2004d) but more work is required to ascertain reproductive parameters.

Bight Redfish are multiple batch spawners, with asynchronous development of eggs (Brown and Sivakumaran, 2007). In the GAB, spawning occurs in summer (Brown and Sivakumaran, 2007) to early autumn (Knuckey and Brown, cited by FRDC, 2003b).

Fisheries Information

Commercial - Commonwealth

The species Centroberyx gerrardi is marketed as Bight Redfish (Seafood Services Australia, 2003). Various processors in Australia and New Zealand sell this species.

Bight Redfish is a target species in the Great Australian Bight trawl fishery component of the SESSF (Southern and Eastern Scalefish and Shark Fisheries). It is reported to be a bycatch in the Gillnet, Hook and Trap fishery and South East Trawl fishery components of the SESSF, and also in the Western Deepwater Trawl fishery (Bromhead and Bolton, 2005). It is noted that two other fisheries in which this species is listed as bycatch (Norfolk Island Offshore Demersal Finfish Fishery and East Coast Deepwater trawl fishery – Bromhead and Bolton, 2005), are not within the published geographic range of this species, and catches in those fisheries might refer to the related species C. affinis. Bight Redfish is also listed as a bycatch in the so-called “High Seas Non-Trawl Fishery”, which describes high seas non-trawl (i.e. demersal long-line, drop-line and gillnet) operations outside the permit conditions of the formal Commonwealth fisheries (Bromhead and Bolton, 2005).

A single stock of Bight Redfish is assumed for fishery management purposes in the Commonwealth fisheries. Two other Centroberyx species form part of the catch in the west of the Great Australian Bight Trawl fishery (AFMA, 2002h).

The main commercial fishery for the species is the Great Australian Bight Trawl fishery (GABTF) component of the SESSF. The GABTF extends from Cape Leeuwin, Western Australia, to Cape Jervis near Kangaroo Island, South Australia. The Fishery excludes State (SA and WA) fishery shelf waters to the extreme east and west, which have traditionally been fished by State based fishers (AFMA, 2003i). The GABTF is primarily a demersal (bottom) otter trawl and mid-water trawl fishery, based on regular trawling of inshore species and periodic trawling for the deeper dwelling species. Bight Redfish are taken from the shelf / upper slope region (Brown and Knuckey, 2002; Caton and McLoughlin, 2005), and this part of the fishery extends approximately out to the 400 metre isobath; however the majority of the catch is taken from depths of 100-200 metres (with much targeting at 120m – 160m) at the 'head' of the Bight, where trawling is permitted in water less than 200 metres in depth. The two predominant shelf species taken are Deepwater Flathead Platycephalus conatus and Bight Redfish (Brown and Knuckey, 2002; AFMA, 2003i). Bight Redfish are taken year-round, with a peak in catches from February to April (Caton and McLoughlin, 2005).

In terms of biomass, Bight Redfish is the 3rd most important species taken in the GABTF (e.g. Lynch and Garvey, 2003). Based on studies of otoliths, Bight Redfish are considered to be fully recruited to the fishery by 15-18 years for males, and 17-22 years for females (Stokie, 2004; Stokie and Krusic-Golub, 2005). Based on samples of fish collected in 2003/04 and 2004/05, the sex ratio of the commercial catch is considered to be close to even (Stokie, 2004; Stokie and Krusic-Golub, 2005). In the GABTF, overall annual fishing effort increased markedly from 1994 to 1997, then fell from 1997 to 2000, but has since risen again in recent years (AFFA, 2004b; Larcombe and Begg, 2008). Throughout the 1990s, the tonnage of Bight Redfish taken in the GABTF fluctuated in relation to the catch of other species. For example, for years in which the catches of Deepwater Flathead are relatively low, the catches of Bight Redfish and Orange Roughy are higher, and vice versa. Since the fishery began, Deepwater Flathead and Bight Redfish have been the two main species taken in the Central Zone of the GAB Trawl Fishery, and Bight Redfish is also taken, previously in smaller quantities, in the Western Zone (Lynch and Garvey, 2003). Size ranges of Bight Redfish caught in the fishery are discussed above, in Notes on Biology. Juvenile Bight Redfish are rarely discarded; however they are purportedly not often caught due to the depth range worked by the fishery (AFFA, 2004b). ISMP reports showed that the discard rates in 2004 and 2005 were low (0.6t, or 0.1% of the catch in 2004, and 0.01%, or 0.09t in 2005) (Talman et al., 2005; Koopman et al., 2006). From 1990-1994, the tonnage of Bight Redfish taken in the GABTF ranged from 121 to 271t, equivalent to less than 12% of the total catch (Lynch and Garvey, 2003). Between 1990 and 2002, the highest catch of Bight Redfish over that period was taken in 1999 (= 415t, according to Lynch and Garvey, 2003), but after 2002, annual catches continued to rise over 800t, to 1000t or more during the late 2000s. Sampling of the GAB Trawl Fishery during 2000 and 2001 showed that during the survey period, Bight Redfish was recorded in 134 of the 209 trawl shots, and the average quantity retained was 119kg per shot, with only 400g per shot discarded (Brown and Knuckey, 2002). In 2004, in the central and western fishing zone of the GABTF, an estimated 28t was taken in 94 shots, and in 2005, the same quantity was estimated to have been taken from that region in 185 shots (Koopman et al., 2006). In 2004, the total catch for the GAB was estimated to be 838 tonnes retained (Talman et al., 2005). The 2004 catch was more than 60% higher than the 2003 catch (Caton and McLoughlin, 2006). One estimate of the total catch of Bight Redfish in the GAB Trawl Fishery between 1990 and 2007 is shown below. Generally, catches were in the low hundreds of tonnes from the mid 1990s to early 2000s, then increased over 900t from 2003 to 2005, with the highest catch date of about 1,024t in 2006/07. In 2008, there was discrepancy between sources in the reported catch. AFMA reported the total SESSF catch of Bight Redfish (of which the majority was taken in the GABTF) to be 656 tonnes (AFMA, 2009a), but Wilson et al. (2009) reported that the GAB catch alone was 721t in 2008. The numbers on the catch line show the number of vessels operating in each year. Catch rates over the history of the fishery are not shown here, but are discussed in the sections on Vulnerable Characteristics of the Species, and Threatening Processes.

Reported Catches of Bight Redfish in the GAB Trawl Fishery, 1988 – 2007

(adapted from Klaer, 2008)

Prior to the development of the GABTF, between 1977 and 1979, a fish processing company from Western Australia and a British trawling company, jointly undertook 20 trawl fishing trips to the Great Australian Bight, using 3 large stern trawlers. Catch rates of fish per vessel ranged from 2,301 kg per day to 7,279 kg per day. Bight Redfish Centroberyx gerrardi, Chinaman leatherjacket Nelusetta ayraudi, Jackass Morwong Nemadactylus macropterus, and Jack Mackerel Trachurus declivis were found to be the most economically important species, with a value exceeding 50 per cent of the total catch. Greatest catch rates occurred in March and April, with catch rates exceeding 500 kg per hour in some grid areas (Walker and Clarke, 1990). During the 1970s, large catches of Bight Redfish, including an annual Australian commercial total of 83 tonnes of Bight Redfish in 1975-76, 82 tonnes in 1976-77, and 332 tonnes in 1977-78 (BRR, 1991), would have included the Great Australian Bight exploratory trawl catch (see above). Other large catches included 60 tonnes in 1985/86 (BRR, 1991).

C. gerrardi appears to be a minor part of the bycatch in the otter trawl sub-fishery of the South East Trawl fishery of the SESSF. According to Wayte et al. (2004), in an Integrated Scientific Monitoring Program, the species was recorded in only 2 shots (with 9kg retained, and none discarded).

In the Commonwealth-managed Gillnet, Hook and Trap fishery (which comprises the previously named South East Non-Trawl and Southern Shark fisheries), Bight Redfish is one of the bony fish species taken as by-product (Ward et al., 2003). A study by Walker et al. (2003) of the bycatch from South Australia in the Southern Shark fishery during a 1998-2001 survey period, showed that an average of 10 (S.E. = 10) and 43 (S.E. = 20) Bight Redfish C. gerrardi were caught per 100,000 hook-hours (= 1,000km hours), using 6 inch and 6 ½ inch mesh nets, respectively. It is also vulnerable to capture on shark hooks. The total catch during sampling over the 1998-2001 period was reported to be 64 animals, with 98% of the catch being retained. It is not known for this report how representative the survey catches were of the numbers currently taken in that fishery. During that bycatch survey in the shark fishery, C. gerrardi was more commonly caught in waters off South Australia than from waters in Bass Strait or Tasmania, and it was one of the top 4 scalefish species caught as bycatch, in terms of numbers (Walker et al., 2003). According to maps by BRS (2004), less than 2t per annum of Bight Redfish were taken from south-eastern South Australia and western Victoria in 2001 and 2002.

Redfish is one of the scalefish species taken in Western Australia’s Joint Authority Southern Demersal Gillnet and Demersal Longline Fishery (JASDGDLF), a fishery that extends from Bunbury in southern W.A., across to the S.A. / W.A. border, and is managed by the Commonwealth Government and W.A. Fisheries. The fishery mainly targets several shark species; however a number of scalefish are also caught as by-product. Redfish is also a lesser catch in the West Coast Demersal Gillnet and Demersal Longline Fishery (WCDGDLF) (McCauley and Simpfendorfer, 2003), but generally taken in higher numbers than in the JASDGDLF. During surveys of the catch composition of these two fisheries between 1994 and 1999, the mean annual catch of Redfish was 5.4t, taken with gillnets, mainly from regions 1, 2 and 3 (i.e. western GAB, to southern end of W.A.). Redfish caught during that period were within the range 31cm to 71cm fork length, average 53cm (McCauley and Simpfendorfer, 2003). In 1999/2000, Redfish constituted 5.5% of the scalefish catch (and scalefish comprised 13% of the total catch) in Zone 2 of the JASDGDLF (Fisheries Research Division, 2001). In 2001/02, in the JASDGDLMF, about 4.5t of Redfish were reported to be taken, almost all in zone 2 (i.e. eastern zone, located east of 116° 30' E to the SA border (129° 00' E) (Borg and McAuley, 2004). In 2002/03, the West Coast Demersal (WCDGDLF) scalefish catch of Bight Redfish was reported to be 52t (Department of Fisheries, Western Australia, 2005c).

Commercial - South Australia

Bight Redfish is one of the 8 main seafood products sold by one of Australia’s largest seafood supply companies, based in South Australia.

In the South Australian Marine Scalefish Fishery, the annual catches of “Redfish” (likely to comprise mainly C. gerrardi) are shown in the figure below. The commercial catches in S.A. have decreased during the past decade, and are currently an order of magnitude less than those in Western Australia. Effort data in the S.A. fishery from 1998 to the present are not available for this report. In South Australia, there are State-based records of Redfish being taken in deeper waters south of Kangaroo Island (e.g. 6t in 1995/96 and 3t in 1996/97), and also in the area west of Kangaroo Island and south of Spencer Gulf (e.g. 1.7t in 1995/96) and in the deeper waters west of Anxious Bay, on the west coast of S.A. (e.g. 2t in 1996/97). Minor catches (e.g. less than 1t per annum during the mid to late 1990s) have been recorded from a number of other areas in the State, such as southern Spencer Gulf; southern Eyre Peninsula; western and south-western Eyre Peninsula (i.e. eastern and south-eastern Great Australian Bight); Investigator Strait; and deeper waters west of the Coorong (SARDI Aquatic Sciences data, 1995 – 1997, unpublished).

Annual Catch of “Redfish” in the S.A. Marine Scalefish Fishery, 1989 – 2008

(Catch = solid black line. Effort = grey dashed line. Effort data from 1998/99 onwards not available for this report)

In the South Australian Rock Lobster fishery, bycatch of Redfish is retained for sale (Sloan, 2003a), or used as bait (Ward et al., 2003). Bight Redfish is caught, reportedly in small numbers, in the Northern Zone of the S.A. Rock Lobster Fishery (Ward et al., 2003). During a bycatch survey (2001 - 2003) in the South Australian Rock Lobster Fishery (Brock et al., 2004), low numbers of Bight Redfish were recorded in the fishers’ logbooks in the Northern Zone, possibly in the order of less than 15 specimens per year. For example, a sample of 60% of the total number of pot lifts in 2001/02 showed that 7 specimens were caught over the period; in a sample of 57% of the total number of pot lifts the following year, only one specimen was caught (Brock et al., 2004). Only one specimen was recorded in logbooks in the Southern Zone during that period (i.e. 1 caught in 2002/03; none in 2001/02). In a bycatch sampling program in 2002/03, during which 1% of the total number of pot lifts was sampled, 1 specimen of Bight Redfish was recorded in the Northern Zone (Brock et al., 2004). If the 1% sample is representative, than that may indicate that slightly higher numbers might be caught per annum, compared with those recorded in logbooks.

Commercial – Western Australia

Previously, combined catches of Bight Redfish from all commercial fisheries in W.A., according to fishers’ statutory monthly returns, underestimated the total catch, because additional data (such as those from research logbooks and processors) were not included (W.A. State of the Fisheries report, 2002-2003). BRR (1991) reported occasional large but sporadic catches from WA during the 1970s and 1980s, such as 331 tonnes in 1997/78, and 60t in 1985/86. The proportion of these early catches that was taken by exploratory trawling in the GAB was not specified. Redfish is one of the top 10 species taken in the West Coast region and the South Coast region of W.A.’s “wetline” fishery, with catches of over 20t per annum in each of these regions in some years of the 1990s and early 2000s, and higher catches in the late 2000s. In the South Coast bioregion, the catch in 2002/03 of “Centroberyx sp.” was about 34t, and most of this was probably C. gerrardi (Department of Fisheries, W.A., 2005c). In the West Coast Demersal Fishery (WCDF), about 52t of Bight Redfish were taken in 2002/03 by line fishing (Department of Fisheries, W.A., 2005c). W.A. fisheries in State waters collectively caught 114t of Bight Redfish in 2005 (36t from South Coast and 78t from West Coast bioregion), and there has been a 7-fold increase in west coast catches since 1998 (research by M. Mackie, cited in AFMA, 2006h). Catch statistics provided in the annual W.A. State of the Fisheries Report show that annual catches of Bight Redfish tripled from the early 2000s to late 2000s. Prior to 2000, catches of C. gerrardi were not reported by species, and may have been confused with other Centroberyx taxa. Reported catches of other Redfish species (e.g. C. australis, often incorrectly reported as “Nannygai”) in W.A. might also comprise a proportion of C. gerrardi (M. Cliff, W.A. Fisheries Research Centre, pers. comm., 2006).

Reported Catches of C. gerrardi from W.A. waters 2000 to 2007 (may also include quantities of C. australis and possibly C. lineatus)
Year	Live Weight (kg)
2000/01	14,422
2001/02	22,355
2002/03	18,501
2003/04	35,356
2004/05	41,868
2005/06	68,257
2006/07	54,723
(W.A. State of the Fisheries reports, 2000/01 – 2007/08).

In the Western Deepwater Trawl Fishery (WDTF), which operates between 300m and 600m deep in waters south of 260S (AFMA, 2004f), reported “catch volumes” of C. gerrardi are low (e.g. AFMA, 2004f), likely because the upper limit of the fishing area (300m) is the lower limit of the depth range for this species.

Recreational

Previously, Wilson (2001a) reported that few anglers specifically target Redfish; however anglers fishing for snapper over offshore reefs frequently catch Redfish. Game fishers specifically target Redfish, including those seeking tuna and other game fishes. In recent years, increasing accessibility of offshore reefs to charter boat fishing has resulted in Redfish being a target species in some areas.

The reported recreational catch from South Australia is comparatively large. The National Recreational and Indigenous Fishing Survey (Henry and Lyle, 2003) estimated that 45,189 Red Snapper (= Bight Redfish) were caught and kept by recreational fishers during the survey time period (May 2000 to April 2001), comprising 41,551 fish from South Australia, and 3,638 from W.A. (Henry and Lyle, 2003). Additional catches from W.A. in the combined “Red Snapper / Redfish / Scarlet Perch” category amounted to 1,959 specimens, and might have included a proportion of Bight Redfish. Similarly, the category “Nannygai”, which included a catch of 331 specimens from W.A., is also likely to mean Bight Redfish, when caught in shallow W.A. waters. Catches from W.A. in any of these three categories might also have included a proportion of Yellow-eyed Red Snapper Centroberyx australis, if caught in deeper waters.

Some of the national sports fishing and angling organisations (and their State divisions) keep records of the maximum sizes caught (e.g. Australian Anglers Association; Australian National Sportsfishing Association). The species is taken mainly in W.A. and S.A., but there are also recreational fishing records from Victoria, reported to be this species (e.g. AAA – Victorian Division, 2003).

The species is taken by spear fishers. The national record sized specimen was taken by spear, in W.A. (Hutchins and Swainston, 1986; Australian Underwater Federation Inc., 2003). Specimens of “Nannygai” (most likely to be Bight Redfish) over 30cm length and 0.5kg weight were listed as target species in the 54th Australian Spearfishing Titles 2006, held on northern Kangaroo Island (Australian Underwater Federation Inc., 2006).

A Western Australian Fisheries Department survey conducted in 1996-1997 in the West Coast Bioregion (between Augusta and Kalbarri), reported that 1,293 (SE = 262) C. gerrardi were kept by recreational boat fishers during that period (Sumner and Williamson, 1999).

Centroberyx species are significant for recreational boat fishers in southern W.A. (Fisheries Research Division, W.A. Fisheries, 2002). Recreational fishing participation between Augusta and the W.A. / S.A. border is estimated at around 20% of recreational anglers in W.A., or some 120,000 anglers per year, generating 2 million fishing days. Charter activity is also important, with 20 fishing tour licences and 2 eco-tour licences issued for the south coast bioregion during the mid 2000s. Boat fishing is concentrated near major population centres, with Centroberyx species being amongst approximately 6 major target species taken by recreational fishers in the South Coast Bioregion (Fisheries Research Division, W.A. Fisheries, 2002). In the South Coast region of W.A., Bight Redfish are caught by recreational fishers, including charter boats. Tour operators reported catches of about 4t, 6t, 8t and 5t of Bight Redfish, in 2002, 2003, 2004 and 2005 respectively (Department of Fisheries, Western Australia, 2005c, 2007a).

Centroberyx species are amongst the most common fish species taken by some angling clubs in W.A. (e.g. Victoria Park Angling Club, W.A.).

In South Australia, this is one of the major target species of offshore fishing charters. Examples of locations in South Australia where the species is taken by recreational fishers and/or charter boat fishers include the headlands of western Eyre Peninsula / eastern GAB (e.g. deeper waters off Cape Radstock, Cape Bauer and other headlands); islands of the eastern Great Australian Bight (e.g. Nuyts Archipelago, Olive Islands, and Flinders Reef, amongst others); south-western Spencer Gulf; southern Eyre Peninsula; Neptune Islands (e.g. targeted by charter boats on reefs south of South Neptune Island); waters south of Spencer Gulf (such as the area between Wedge Island and Thistle Island, where reef aggregations of Red Snapper are targeted by charter boats); Gambier Islands; Althorpe Islands (another area where aggregations of Redfish are targeted by charter boat fishers); lower Yorke Peninsula (e.g. in Investigator Strait, off Marion Bay); northern Kangaroo Island / Investigator Strait area (promoted by charter boat operators as a location for catching Redfish); the upper South-East, and lower South-East (including the Port MacDonnell area, where Redfish is one of several major species targeted by recreational fishers) (Capel, 1994; Sweeney, 1996a, 1996b; Wilson, 2001a; Mensforth, undated; Fishnet, 2002, 2003, 2004; McLeay et al., 2003; Baker, 2004; charter boat fishing reports, 2002 - 2009). During two monitoring periods in the South Australian Charter Boat fishery (Period 1 = September 2005 to June 2006, and Period 2 = July 2006 to June 2007) a total of 5,613 “Red Snapper / Nannygai” (= approx. 8,391kg) were caught and retained during Period 1, and 9,477 (= approx. 14,263kg) were caught and retained during Period 2. During Period 1 and Period 2, the numbers of legal sized specimens that were caught and released were 239 and 1,015 respectively. The numbers of undersized specimens caught and released were 351 and 845 respectively. Recorded catches were highest during the summer and early autumn, particularly during the second sampling period, when more than half of the catch was taken during this December to April period (Knight et al., 2007). The proportion of the “Red Snapper / Nannygai” catches that constituted C. gerrardi is not known for this report, but it is noted that Bight Redfish is commonly called “Red Snapper” by fishers in South Australia.

Small Redfish are used as bait for tuna and other game fish, because small Redfish remain alive for long periods of time and do not become active until a predator arrives (Wilson, 2001a).

Vulnerable Characteristics of the Species

Stokie (2004) and Stokie and Krusic-Golub (2005) recorded maximum ages of 64 and 71 years respectively in studies of the otoliths of Bight Redfish. Due to the considerable variability in age among Bight Redfish of similar size, commercial catches consist of animals between 9 and more than 60 years old (Caton and McLoughlin, 2005; AFFA, 2005a). Bight Redfish is a site-associated, long-lived (> 70 years), schooling species, and may have a high age at maturity, and a low rate of natural mortality (Department of Fisheries, WA, 2004d; uncited reference, in Caton and McLoughlin, 2006). These characteristics make populations susceptible to over-exploitation. This species is also easy to find, easy to catch, and catches during the late 2000s were increasing significantly in both W.A. State fisheries, and the Commonwealth-managed GAB trawl fishery.

Ageing studies have indicated that the catch of Bight Redfish in 1988-1990 was dominated by 20-40 year old fish, and in the following decade was dominated by 14-24 year old fish (AFFA, 2005a). Although “fish-downs” of age structure are “expected” in the early years of a fishery, and are considered acceptable management practice (AFFA, 2005a, Larcombe and Begg, 2008), the implications for long-term sustainability of the resource need to be considered, particularly in terms of reproductive capacity, which is poorly known for this species. A cautious management strategy has not been adopted, in light of insufficient information on the reproductive capacity and population dynamics of this species over space and time.

Given the size range of fish taken in commercial fisheries, particularly in the Great Australian Bight (see Notes on the Biology, above), and the reported size at maturity (of 35.2cm for males and 32.4 cm for females), it is highly likely that a significant portion of the stock that is being caught, is reproductively immature.

In the Great Australian Bight, the size structure of the population has decreased over a 5 year period of intense fishing, from a modal length of 35cm in the 2005, to ~31 cm in 2009. There is also some evidence of a reduced proportion of larger (>45cm) fish in the survey (Knuckey et al., 2009). Given the large increases in catches per annum in recent years, coupled with the decline in the modal size of the fish being caught, a situation of growth-overfishing may be likely in future, which may further threaten sustainability of Bight Redfish populations.

Although reproduction in this species is poorly known, it is possible that spawning output from WA replenishes stocks in the Great Australian Bight.

Based upon age and growth data, the Bight Redfish is reported to have a very low resilience to exploitation, in terms of population doubling time (Froese and Pauly, 2009), and high vulnerability to fishing-induced population decline (Cheung et al., 2005). Due to high maximum age and probable slow growth rate, the high index of vulnerability was also reported in a study of age and growth of this species in South Australia (Saunders et al., 2009, following the methods of Cheung et al., 2005).

Threatening Processes

Fishing is the major threatening process for populations of this species, and there is high fishing pressure on the population, from the Commonwealth-managed GAB fishery, and increasingly also from commercial fishing in W.A. (Department of Fisheries, WA, 2004d). Additionally, Redfish are increasingly being targeted by recreational fishers (especially charter boats) in both S.A. and W.A., as capacity to fish deeper waters continues to improve. It is possible that large commercial catches over several years result from a particularly successful year class (or series of year classes) moving through the fishery, and if quota is not set conservatively or responsively as those abundant year classes are exhausted, population structure and biomass may be adversely affected if weak year classes (resulting in lower total abundance and biomass) are targetted at the same high levels over time.

For assessment periods between 1992 and 2005, the Bight Redfish stock was considered to be of uncertain status (AFFA, 2004b; Caton and McLoughlin, 2005, 2006). By the late 2000s, when catches increased to over 1,000t per annum, the unfished biomass was estimated to be at least 18,000 tonnes, and it was estimated in 2007 that current biomass may be around 80% of that level (research by Knuckey et al., cited in Larcombe and Begg, 2008). The relative biomass estimate of Bight Redfish for 2009 was 23,410t, 60% higher than the 2008 estimate and 12% higher than the 2005 estimate. Estimates of relative biomass of Bight Redfish were about 21,000t in 2005; about 25,000t in 2006 and 2007, and about 14.5t in 2008 (Knuckey et al., 2009). It is noted that for schooling species of uneven distribution, biomass estimates may be unreliable (particularly older estimates based on log-book data), and have ranged from as low as 9,000t (Wise and Tilzey, 2000) to as high as 52,000t, depending on method and year of analysis. Annual estimates of biomass during the mid-late 2000s were approximately double that estimated during the 1990s. Recommended catches per annum (under a new TAC, introduced in 2006) have been increased, in light of the recent optimistic biomass estimates, and possibly also due to requests from industry, due to the greater number of boats (10) now catching this species (e.g. AFMA, 2005d). The current recommended catches per annum (Larcombe and Begg, 2008; AFMA, 2009a) are more than double the sustainable yields estimated during the 1990s (e.g. AFFA, 2005a). According to AFFA (2004b), although assessment models indicate that annual catches of Bight Redfish are sustainable, there is potential for catches to reach unsustainable levels, particularly due to latent effort in the fishery (AFFA, 2004b). During the mid-late 2000s, there were 10 operators in the fishery, with 4 to 6 of those working consistently. During the mid 2000s, it was considered unlikely that the Bight Redfish stock could be sustained over the long-term if simultaneous fishing by all 10 operators occurred (AFFA, 2004b), yet that is occurring, and catches predictably have increased over the short term, supported by results of several years of stock biomass estimate surveys. Over the long-term, despite the current succession of increased catches, further development of shelf water trawling along the south and south-west coast of W.A., and across the Great Australian Bight, may adversely affect populations of this species, particularly if large aggregations or schools of this long-lived species are being caught, and the age and size structure continue to be eroded.

It is noted that the catch per unit effort (CPUE) fell below the “trigger value” (i.e. the level requiring additional management action to protect the fishery) in several years during the past 15 years, such as 1995, 1996 and 2002. Catch rates for this species have fluctuated significantly throughout the history of the GAB fishery, but the very high catch rates of the early fishery in 1990 have not been repeated (graphs in Caton and McLoughlin, 2006), despite obvious peaks and troughs during the past 20 years. Environmental drivers of abundance of both Bight Redfish and Deepwater Flathead have been suggested to influence catch rate (Caton and McLoughlin, 2006). However, it is noted that CPUE is an unreliable indicator for aggregating species, particularly if scaled up over the entire range of the species, and the erroneous assumption of even distribution of the fish over space is made.

The relative proportion of Bight Redfish and Deepwater Flathead in continental shelf landings of the GAB Trawl Fishery has varied over time, and currently the apparently inverse relationship between catch rates of these two species is considered likely to be environmentally-driven (Caton and McLoughlin, 2005). Similar variation in catch rates between cold and warm periods has been observed in eastern Australia, for the related species C. affinis (Rowling, 2001, cited by Bruce et al., 2002). If so, then environmentally-driven variations over time in availability of Bight Redfish would increase the vulnerability of this species to over-exploitation.

In 2006, a draft Ecological Risk Assessment (ERA) for species in the Great Australian Bight Trawl Fishery (Daley et al., 2006), ranked Centroberyx gerrardi as a “high risk” species, in terms of population impacts from capture in the GAB Trawl Fishery, noting also the “endemic” nature of the stock in the GAB. In a Residual Risk Assessment of the Level 2 Ecological Risk Assessment, this species was considered at lower risk than when initially assessed, due to the introduction of a catch quota in 2006 (but see information above, on annual increases in quota since that time). However, in a “rapid quantitative Level 3 assessment, or Sustainability Assessment of Fishing Effects (SAFE) assessment” undertaken by AFMA, a supplement to the ecological risk assessment (by CSIRO) for the GABTF, this species was ranked as “low risk” of impact from operation of the fishery. According to AFMA (2008c), the Level 3 assessment process considers the mitigating effects of management arrangements that were not explicitly included in the ERAs, or introduced after the process commenced. It is noted that the level 3 assessment is made proportional to the spatial area in which the fishery operates, compared with the spatial area of distribution of the species, but this does not account for aggregation, rather than even distribution throughout space (the latter of which is unrealistic, for reef-associated species in a heterogeneous benthic environment).

In contrast to the ranking for this species in the GAB Trawl Fishery, it is noted that in 2004, Centroberyx gerrardi was ranked as being at “medium risk” of population impacts from trawl fishing in the South East Trawl fishery (Wayte et al., 2004), a fishery in which much lower catches are taken.

In W.A., Centroberyx species are defined for fisheries management purposes as a “Category 1” species. Fish in this category are generally long-lived, slow-growing, mature at four years-plus (i.e. generally have a high age at maturity), form semi-resident populations, are vulnerable to localised depletion due to their life history, and are of low abundance and/or highly targeted. Category 1 fish have low catch rates, and are highly valued for their fishing and eating qualities, and there is usually significant pressure on stocks. For these reasons, Category 1 fish in W.A. are considered to have a high risk of over-exploitation, and require a high degree of protection (Harrison, 2001; W.A. Department of Fisheries, 2004a, 2004d).

According to D. Mackie (W.A. Department of Fisheries), all commercial and recreational fisheries targeting Bight Redfish are likely to impact each other, either directly through fishing similar areas or indirectly if spatially discrete stocks are linked by larval drift/post-settlement movement.

In W.A., this species is considered by the Department of Fisheries to be a key indicator of ecosystem health. The increasing catches, high vulnerability to over-exploitation, limited information on biology and population dynamics, and disparate management (by multiple sectors and jurisdictions) raises considerable concern for the future sustainability of Bight Redfish (research application by M. Mackie, W.A. Department of Fisheries, cited by AFMA, 200gh).

Research Notes

Between 1988 and 1990, a logbook program was used for the regular collection of biological information on Bight Redfish. During that time, there was periodic port-based sampling of the Bight Redfish catches to determine sex, size and age. This program resumed between mid-1993 and 2001 (AFFA, 2005a). Fisheries Research and Development Corporation funding was obtained for an onboard catch-sampling program during 2000–01, to assess bycatch and discarding practices, collect specific biological information, and calibrate the catch sampling in ports. Industry agreed to fund the continuation of the program, which is now a main source of catch-composition data (AFFA, 2005a).

During the mid to late 2000s, fishery independent research trawl surveys (I. Knuckey and associates) were being undertaken in the GAB to determine the biomass of the Bight Redfish stock, in conjunction with the GAB Industry Association (GABIA) and Australian Fisheries Management Authority (AFMA). These surveys aimed to obtain an annual relative abundance index for Bight Redfish in the current region of the main GABTF shelf fishery, and to provide a density estimate of Bight Redfish inshore of the current fishery. The indices are used in the GAB trawl fishery stock assessment model, and to assist the setting of Total Allowable Catches. The surveys also aimed to collect biological and population data on this species (AFMA, 2006c; Knuckey et al., 2009).

During the mid 2000s, a structured method for setting Total Allowable Catches was developed, utilising clear decision rules in a 4-tiered system, depending on the amount and type of information available to assess stock status (Day and Klaer, 2006). Bight Redfish is one of the species for which this system is used to determine appropriate catch levels.

During the 1990s - 2000s, various stock assessments were undertaken for C. gerrardi in the GABTF, utilising historical data, logbook catches and CPUE (kg/km2), observer data and biological data.

During the late 2000s, one of the major research projects that was initiated in relation to this species, was a project titled Bight Redfish: towards integrated management of a vulnerable, cross-jurisdictional and multi-sectorial resource (by M. Mackie and associates, W.A. Department of Fisheries). Objectives of the W.A.-based project included (i) an understanding of stock linkages across the species range, including significance of W.A. stocks maintaining broader population levels; (ii) development of a cohesive management plan within W.A. waters, incorporating resource allocation across all sectors (particularly in relation to the catch by “wet-line” fishers in W.A.), including collaboration with the GAB Resource Assessment Group; (iii) an assessment of acoustic methods as an economical, reliable and non-destructive means of ongoing monitoring of stocks; and (iv) demonstration of the utility of new commercial and recreational logbooks in provision of State fishery data. In the project, it was planned that information about stock linkages, ontogenetic changes in habitat, and relative spawning output would be obtained from comparative studies of otolith microchemistry and biological parameters. Additional use of improved genetic techniques (based on mitochondrial DNA) is also being investigated. Management decisions will be based on a stock assessment, comprising a biological study undertaken by Murdoch University (see below), in conjunction with WA Department of Fisheries. In the project, description of commercial and recreational fisheries is planned, using catch and effort statistics, fisher interviews and logbooks. Another phase of the project will include the building of an ecological model (incorporating spatial and temporal patterns in distribution and abundance, connectivity between stocks, and fisheries models, including an age-structured model to estimate biomass (research proposal by M. Mackie, W.A. Department of Fisheries, cited in AFMA, 2006h).

During the late 2000s, there was a Fisheries Research and Development Corporation (FRDC)-funded research project (J. Chaplin, Murdoch University) investigating the stock structure of Bight Redfish (Centroberyx gerrardi) in southern Western Australia.

In W.A., previously there has been considerable confusion in catch reports of Centroberyx species received from commercial fishers. Previously, the Department of Fisheries did not have on-board sampling programs to verify species identifications (M. Cliff, W.A. Fisheries Research Centre, pers. comm., 2006). Therefore, a research program was planned from 2007 onwards, in an effort to better understand the Bight Redfish stocks off the south coast of W.A. (M. Cliff, pers. comm., 2006).

Research Recommendations

More information is required on the habitat requirements and location of juvenile Bight Redfish, particularly the location of “nursery areas”.

The relation between inshore “solitary” Bight Redfish (Kuiter, in Gomon et al., 1994) and aggregating and schooling offshore Bight Redfish needs to be determined. It is noted that Bight Redfish in the GAB are highly likely to school and aggregate, similar to the eastern Redfish C. affinis (see Tilzey, 1994; Bruce et al., 2002), and as evidenced by the operation and catches of the GAB Trawl Fishery.

There is insufficient information on reproduction (particularly size and age at maturity; fecundity at size and age; and also recruitment strength over space and time). Spawning dynamics should also be investigated, so that the fishery can avoid capturing adults during peak spawning periods, which could jeopardise the sustainability of the stock and the fishery if it continued to occur.

Given that Bight Redfish is a relatively long-lived species, and older age classes have been fished down since the 1980s, continued collection of information on the size- and age-composition of the stock in the GAB is considered essential for the proper management of the fishery (AFFA, 2005a).

The stock-recruitment relationship could be very important for this species, and requires further investigation (including modelling work).

More information is required on aggregation and migration over space and time, and the relation between Bight Redfish in S.A. and W.A., in terms of stock structure etc. Research to reduce the uncertainty of the stock structure (e.g. AFMA, 2005d) is a priority (see Research Notes, for example of project being undertaken in W.A.).

There is a possibility of ontogenetic patterns of movement in this and other related Centroberyx species, which should be investigated.

Research is required on the relation of Bight Redfish movements, aggregations, variations in relative abundance (and therefore variations in availability to the fishery) with environmental variables, such as the Southern Oscillation Index, the Leeuwin Current, and El Niño and La Niña cycles.

Management Notes

Prior to introduction of Bight Redfish quota in 2006, the Great Australian Bight Trawl fishery (in which Bight Redfish is a major target species) was managed through input controls, including limited entry of vessels, limited cod-end mesh size, and area restrictions for boats in excess of 40 m in length. There were 10 operators in the fishery in 2001-2002 (AFMA, 2003i), but some of these did not fish in every year of the previous decade. There has been increased participation in the fishery and significant increases in fishing effort and fishing efficiency of active vessels since 2003, and by the late 2000s, a larger number of boats was operating. One of the main objectives during the early 2000s was to maintain catch rates of Bight Redfish above 1988–94 minima (AFMA, 2003i). N.B. The issue of using catch rate as an indicator of stock status, for schooling and aggregating species in heterogeneous habitats, is discussed in the section on Threatening Processes.

Quotas were introduced from 2006 onwards. Quota is reported to be set in line with the Commonwealth Harvest Strategy Policy, and species assessment harvest control rules (AFMA, 2008c). During the early 2000s, prior to the quota introduction, there was a “voluntary trigger limit” of 950t, whereby management action would be triggered if this catch limit was reached. At the time, 6 of the 10 boats were working in the GAB. In 2006, when all 10 boats were fishing, the total allowable catch in the GABTF was increased to 1,400 tonnes, plus 20t research catch. The allowable catch was increased to more than 2,000 tonnes per annum in 2007 (AFMA, 2006b, AFMA, 2009b) and 2,000t in 2008 (AFMA, 2009a). It is noted that there is much uncertainty associated with the biomass estimates upon which quota is reportedly based (see Threatening Processes, above).

In April 1998, Environment Australia declared the Great Australian Bight Marine Park (Commonwealth waters) under the National Parks and Wildlife Conservation Act 1975. The Park was designated to ensure the long term protection and maintenance of biological diversity within the area. The Park is divided into a marine mammal protection area and a benthic protection strip. Seasonal closures have been implemented within the marine mammal protection area, and demersal trawling has been prohibited within the benthic protection strip area (AFMA, 2003i). The GAB fishing industry considers that the park has closed some “good Bight Redfish fishing grounds”, hence it is possible that a small portion of the stock is protected in the region of the GABMP. It is noted, however, that (i) at the depths at which Bight Redfish are fished, the GABMP benthic protection “strip” covers a very small proportion of the fishable area in the GAB; and (ii) total allowable catches in the Great Australian Bight have continued to increase since the declaration of this protected area.

In South Australia, for recreational fishing of all Centroberyx species (including Bight Redfish), there is a legal minimum length of 30cm, a bag limit of 10 fish, and a boat limit of 30 fish (PIRSA, 2006). In the charter boat fishery in S.A., there is a legal minimum size of 30cm, and a passenger limit of 10 Redfish (for charters up to 3 people) or 5 Redfish (for charters up to 6 people), equivalent to a charter boat limit of 30 Redfish (Presser and Mavrakis, 2005; PIRSA, 2005b).

In W.A., during the mid to late 2000s, the legal minimum size of any Centroberyx species taken in the West Coast Bioregion (between Augusta and Kalbarri) was 30cm (previously 23cm), and there was a daily bag limit of 4 fish, for all Centroberyx species combined (Department of Fisheries, W.A., 2004a, 2008c). In the South Coast Bioregion of W.A., there is a legal minimum size of 30cm, and a bag limit of 8 Centroberyx species (Department of Fisheries, W.A., 2006b, 2009a).

Management Recommendations

Measures to reduce the catch of sexually immature fish are required, so that those younger Bight Redfish have the opportunity to reproduce and help to perpetuate the stock of this long-lived, and probably late-maturing species. A closure to fishing during the spawning season should be considered, to enable a larger portion of the population to spawn before being caught. On a related note, given the reduction in size of fish now being caught (since at least the early 2000s), measures to prevent a situation of growth overfishing in the GAB fishery should be developed as a priority.

Commercial quotas in the GAB (and commercial catches in W.A. and S.A. State waters) should be reduced until more reliable and consistent estimates of biomass are obtained, and until relations between populations in W.A. and S.A. are ascertained (see Research Notes).

More information is required on aggregation and migration over space and time, and the relation between Bight Redfish in S.A. and W.A., in terms of stock structure etc. (see Research Notes).

Stocks assessments for this species in the GAB trawl fishery should also consider the State waters catches in S.A. and W.A., both commercial and recreational (e.g. charter boat). Stock assessments must include all major catches of this species, and all other relevant data (e.g. size structure and age structure), over space and time. Analyses by researchers working at Commonwealth and State levels must be compatible, and inclusive.

Measures (such as barotrauma reduction methods) should be undertaken to try to ensure the survival of hooked undersized specimens taken by charter boat fishers. Where possible, compliance with recreational (including charter boat) catch limits for Centroberyx species should be checked.

Measures to reduce Centroberyx bycatch in rock lobster pots should be implemented where possible.

Other Information

This species has been recorded in the Kingston Reef Sanctuary at Rottnest Island in W.A. (Kleczkowski et al., 2008).