© 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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Swallowtail

Family Name:	Berycidae
Scientific Name:	Centroberyx lineatus Cuvier, 1829
Recommended Status	South Australia - Data Deficient; Commonwealth waters - Data Deficient, possibly Near Threatened
Rationale:  Although the Swallowtail has a broad geographic distribution across southern Australia, and a broad depth range, it is included here because (i) it is a site-associated reef fish species, and can also form large schools, and therefore the population in some parts of the range may be vulnerable to fishing-induced declines or other impacts; (ii) the commercial catches (largely by-product and discards) from various fisheries may collectively amount to several dozen tonnes per annum (mainly from the GABTF); such catches are inadequately regulated and documented, and the sustainability of such catches is not known, because there are no population size estimates; (iii) there are inadequate measures to restrict the capture of this species, because the major catches result when a target species (Bight Redfish) is taken in waters less than 200m, and quotas of Redfish have increased in recent years; (iv) research on the related species Centroberyx gerrardi has shown that it lives for more than 70 years; preliminary work in South Australia has aged C. lineatus to at least 32 years, indicating that it is also a relatively long-lived species, which would increase its vulnerability to population impacts from fishing; (iv) there is very little information about this species across the range, including relative abundance, distribution and connectivity between populations, growth, longevity, reproduction, population dynamics and ecology.

Page Contents

Current Conservation Status

No listings known

Distribution

General

Swallowtail has a broad geographic range across southern Australia, from New South Wales, through to W.A. (Hutchins and Swainston, 1986; Kuiter, in Gomon et al., 1994). There are records purporting to be Centroberyx lineatus from Japan (Paxton et al., 1989); Hong Kong waters (Ni and Kwok, 1999), Viet Nam (Nguyen and Nguyen, 1994, cited in Froese and Pauly, 2009), and islands off Africa (Fricke, 1999). The validity of these records as C. lineatus (rather than a related species) is not known for this report.

South Australia

Examples of locations across S.A. where the species has been recorded include the western, central and eastern Great Australian Bight (GAB) (the latter including Nuyts Archipelago, and the Investigator Group islands); southern Spencer Gulf; Gambier Islands; Neptune Islands; Althorpe Islands (in Investigator Strait); Kangaroo Island (including the north-western coast), Gulf St Vincent, and the South-East region of S.A. (Kuiter, 1982; May and Maxwell, 1986; California Academy of Sciences records, cited by Anonymous, 1993; BRS commercial fishing data, 2001-02; Baker, 2004; Brock et al., 2004; Hutchins, 2005; Shepherd et al., 2005; Australian Museum records, Museum of Victoria records, South Australian Museum records, cited in OZCAM database, 2009; Baker et al., in prep.). There are hundreds of records from right across the Great Australian Bight (including waters off western Eyre Peninsula), of specimens reported to be C. lineatus taken by trawl during the 1960s and 1970s (BRS records; CSIRO Marine Research records, unverified, cited in CSIRO, 2009).

Habitat

The species is commonly found on deeper reefs along the south coast, but also occurs over shallow reefs adjacent to deep water (Hutchins and Swainston, 1986). In south-eastern Australia, this species is reported to have a strong association with reef habitat (Williams and Bax, 2001). In some areas, divers have recorded the species swimming in schools, close to reef structures of high vertical relief. At Cape Forbin on north-eastern Kangaroo Island, the species has been recorded near a high relief cliff-edge reef that is densely covered with Scytothalia, Ecklonia, Acrocarpia, Sargassum and other large macroalgae (data by A. Brown, 2008). During a survey at the Investigator Group islands in the eastern GAB, Swallowtail were recorded in schools at a number of islands, at depths ranging from the shallow subtidal to 20m, mainly in the vicinity of reefs (Kuiter, 1982). The species is abundant around reefs at the Recherche Archipelago, and frequently seen over reefs in bays of south-western Australia (Hutchins, 2005). During another survey in south-western Australia, Swallowtail were recorded on reefs with dense and medium cover of macroalgae (Ecklonia, and other macroalgae); also over deeper reefs (not vegetated), and low numbers were recorded in the vicinity of seagrass beds (Harvey et al., 2004). The species is reported to be recorded mainly on the continental shelf, within the depth range 100m – 200m, although there are records from as shallow as 10m, and as deep as 300m (CSIRO et al., 2001).

Notes on the Biology and Behaviour

Growth and Age

Maximum size is around 43cm (Hutchins and Swainston, 1986) or 46cm (May and Maxwell, 1986, cited in Froese and Pauly, 2006). One of the maximum weights recorded is 0.930kg, being a specimen taken at Rottnest Island in 1992 (Australian Anglers Association Inc., W.A. Division, 2005). Another large weight recorded was 0.87kg (Hutchins and Swainston, 1986).
During a South Australian study, otoliths were collected from 59 Swallowtail individuals, and preliminary results indicate that, of the readable otoliths (25 of the 59), most were aged from 8 to 20 years, and the oldest fish was aged to 32 years (Saunders et al., 2009). During that study, the growth curve indicated that most growth occurs before age 20, after which time subsequent growth is very slow (Saunders et al., 2009).

Diet

There is little information on the diet, but small bony fishes (such as pilchards) are part of the diet of C. lineatus (Masuda and Allen, cited in Froese and Pauly, 2009; Caines, 2005).

Behaviour

The species often forms large schools (Hutchins and Swainston, 1986).

Other Information

Swallowtail is a part of the diet of New Zealand Fur Seals Arctocephalus forsteri and Australian Fur Seal A. pusillus doriferus (Page et al., 2005; Caines, 2005). In one study, Swallowtail represented up to 5% biomass in some seasons, with frequencies of occurrence as high as 12% and 15%, according to seal species, gender and season sampled (Page et al., 2005).

Fisheries Information

Commercial - Commonwealth

When taken outside of 3 nautical miles (NM) from the coast, catches of Swallowtail are managed by the Commonwealth (and when taken inside 3 NM, are managed by the States) (AFMA, 2002a). In the Commonwealth-managed South East fisheries, Swallowtail 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 (e.g. in the Gillnet, Hook and Trap Fishery), and there are no Commonwealth catch limits (AFMA, 2005b).

Commonwealth-licensed commercial fishers catch Swallowtail around rocky reefs on the continental shelf and upper slope (Daley et al., 1998), and the official marketing name is “Swallowtail” (Seafood Services Australia, 2003). Swallowtail is reported to be a bycatch species in the following Commonwealth-managed fisheries: (i) the gill-net sub-fishery of the Southern Shark fishery (= a component of the GHAT: Gillnet-Hook and Trap Fishery) (Walker et al., 2003; Webb et al., 2004), and although it is considered to have no market value, it is often retained for bait (AFMA, 2001d); (ii) the South East Non-Trawl fishery component of the southern and Eastern Scalefish and Shark Fisheries (SESSF) (Knuckey et al., 2001; AFMA, 2002a); (iii) the South East Trawl fishery (SETF) component of the SESSF, in which the quantities caught and retained appear to be minor (e.g. Wayte et al., 2004); (iv) the Great Australian Bight Trawl fishery (see Threatening Processes, below) (Brown and Knuckey, 2002), (v) the Small Pelagic Fishery (Milton et al., 2004), and (vi) the High Seas Non-Trawl Fishery (Bromhead and Bolton, 2005). In the gillnet sub-fishery of the Southern Shark fishery (GHAT), a fixed station survey showed that Swallowtail caught as bycatch in the south-east of South Australia (e.g. out of Robe port) are returned dead to the water (Prince et al. 1999, cited by Webb et al., 2004).

In the Great Australian Bight Trawl Fishery (GABTF), this species is a bycatch in the targeting of Bight Redfish (AFMA, 2008c). Between 1991 and 1993, the reported quantities of Swallowtail discarded in the GAB were in the order of 100kg to 0.5t per annum, but the species was not reported in bycatch records during the mid to late 1990s (AFMA, 2001c). Sampling of the GABTF during 2000 and 2001, showed that during the survey period, Centroberyx lineatus was recorded in 49 of the 209 trawl shots, none was retained, and the average quantity discarded was 24.2kg per shot (Brown and Knuckey, 2002). During the monitoring period in 2000 and 2001, about 1.9 tonnes were caught, 98% of which was discarded, but only a fraction of the total catch (155kg) was recorded in logbooks (see AFMA, 2002a). According to AFMA (2008c) an Integrated Scientific Monitoring Program (ISMP) during the early 2000s estimated that 38t per annum is caught in the GABTF, with 95% discarded. All specimens are caught shallower than 200m. It is noted that Bromhead and Bolton (2005) reported that Swallowtail is a retained by-product, not a discarded species, in the GAB Trawl Fishery.

AFMA (2002a) and Wayte et al. (2004) reported that in the otter trawl sub-fishery of the SETF, an Integrated Scientific Monitoring Program (ISMP) recorded, in 1 trawl shot: 1kg of Swallowtail (which was retained), and none discarded. Similarly in the Southern Shark fishery, during a bycatch survey in 1998-2001, Walker et al. (2003) recorded very low numbers of Swallowtail in the catch of 6-inch nets, and no specimens in nets of other sizes. In the Southern Shark Fishery, Swallowtail catches are often retained for bait, and the numbers caught vary with depth and area being fished (AFMA, 2000f).

Commercial - States

There are no species-specific statistics in W.A. for Swallowtail. The two main Centroberyx species reported to be taken in W.A. fisheries are C. gerrardi and C. australis (previously incorrectly reported as C. affinis, but reported as “Centroberyx spp.” from 2003/04 onwards). The proportion of the Centroberyx catch in W.A. that is C. lineatus is not known for this report. Reported catches of Redfish species such as C. gerrardi and C. australis in W.A. might also comprise a small proportion of C. lineatus (M. Cliff, W.A. Fisheries Research Centre, pers comm., 2006).

Recorded catches in the Western Australian temperate demersal gillnet and demersal long-line fisheries appear to be very low (e.g. several specimens per year in each of several zones, according to a bycatch study between 1994 and 1999 – see McAuley and Simpfendorfer, 2003).

It is noted that the species is not specifically targeted by South Australian fishers, and available data (from the mid to late 1990s) show that the catches of Swallowtail recorded at State level are minor, being in the order of less than 1t per annum for all areas combined (e.g. southern and northern Kangaroo Island; Investigator Strait; Backstairs Passage).

In the South Australian Rock Lobster fishery, bycatch of Swallowtail is retained for sale (Sloan, 2003a). During a bycatch survey (2001-2003) in the South Australian Rock Lobster Fishery (Brock et al., 2004), low numbers of Swallowtail were recorded in the fishers’ logbooks in the Southern Zone, possibly in the order of less than 15 specimens per year. For example, during 2001/02, 8 specimens were recorded in 545,886 pot lifts (= 60% of all pot lifts that year), and in 2002/03, 3 specimens were recorded in 486,155 pot lifts (= 57% of all pot lifts that year) (Brock et al., 2004).

Recreational

In all States in which Swallowtail occurs, it is recorded as being taken by recreational fishers, particularly in the shallower parts of the species depth range. Some clubs and associations keep records of the maximum sizes caught (e.g. Australian Anglers Association, W.A. Division; New South Wales Fishing Clubs Association).

In the South Coast region of W.A., Swallowtail is caught by recreational fishers, including charter boats. In the South Coast bioregion, the reported charter catches of Swallowtail in 2002, 2003, 2004 and 2005 were about 1t, 1t, 2t and 2t respectively (Department of Fisheries, Western Australia, 2005c; 2006c, 2007a).

The species is taken in the South Australian charter boat fishery. 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 567 Swallowtail (reported to be approximately 302kg) were caught and retained during Period 1, and 1,198 (reportedly 540kg) 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 55 and 74 respectively. The numbers of undersized specimens caught and released were 50 and 292 respectively. Examples of locations in South Australia where Swallowtail is taken by recreational fishers (including charter boats) include southern Spencer Gulf; southern Eyre Peninsula; Neptune Islands (mainly charter boat fishing); Gambier Islands (caught by charter boat fishers, but not usually targeted); waters west and north-west of Kangaroo Island; Investigator Strait; southern Yorke Peninsula / south-western Gulf St Vincent (Baker, 2004, and recreational fishing references cited therein; charter boat fishing promotional materials, 2005-2009).

The species is also taken by spear-fishers. Swallowtail (specimens over 0.4kg) was listed as a target species in the 54th Australian Spearfishing Titles 2006, held on northern Kangaroo Island (Australian Underwater Federation Inc., 2006). Centroberyx species are amongst the most common fish species taken by some angling clubs in Western Australia. Centroberyx species are significant for recreational boat fishers in southern W.A. (Fisheries Research Division, W.A. Fisheries, 2002). 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).

Vulnerable Characteristics of the Species

Although the biology and population dynamics of this species have not been studied in detail, it is probable that Swallowtail is similar to related Centroberyx species in southern Australia, which are long-lived, schooling species associated with particular habitat features / structures, and may have a high age at maturity, and a low rate of natural mortality (see synopsis on C. gerrardi). These characteristics make populations susceptible to over-exploitation. This species is also easy to find, easy to catch, and there are few controls over catches.

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, 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. For these reasons, Category 1 fish are considered to have a high risk of overexploitation, and require a high degree of protection (Harrison, 2001; W.A. Department of Fisheries, 2004a).

Based upon age and growth data, C. lineatus is reported to have a low resilience to exploitation, in terms of population doubling time, and high vulnerability to fishing-induced population decline (Cheung et al., 2005, cited in Froese and Pauly, 2009).

Threatening Processes

Fishing may be the major threatening process for populations of this species, particularly the uncertain level of fishing pressure from Commonwealth-managed GAB fishery (in which Swallowtail is caught when Redfish is targetted; there are no fishery-based catch data, and also, there are very few fishery-independent estimates of annual catch). Additionally, all shelf-dwelling Centroberyx species 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 of Centroberyx species over several years result from a particularly successful year class (or series of year classes) moving through the fishery, and if catch quotas are not set conservatively or responsively as those year abundant 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.

In the GAB, the increasing catches of the related species Bight Redfish C. gerrardi (see synopsis), coupled with increased activity of the fishing industry in that region, may affect the abundance of Swallowtail over time, particularly if the current level of quota remains high, yet C. lineatus may not be as abundant as C. gerrardi in that region, but still be caught due to overlap in distribution and habitat.

The relative proportion of the related species Bight Redfish in continental shelf landings of the GAB Trawl Fishery has varied over time, and 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 Swallowtail would increase the vulnerability of this species to over-exploitation.

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).

In 2006, an Ecological Risk Assessment (ERA) for species in the Great Australian Bight Trawl Fishery (Daley et al., 2006), ranked Centroberyx lineatus as a potential “high risk” species, in terms of population impacts from capture in the GAB Trawl Fishery. The assessment noted that the species also occurs outside Australian waters, and that Swallowtail within Australian waters is likely to be a separate stock, which increases the risk rating (Daley et al., 2006). In a “Level 2 Residual risk assessment” for species in the GABTF, this species was again ranked as being at “high risk”, with the assessment noting that: “ISMP estimates 38t annual catch with 95% discarded, all shallower than 200m. FIS may provide information over time. Unlikely to be separately targetable to Bight Redfish, therefore Bight Redfish TAC may provide some control. ....the species has a higher productivity risk than the target species (Bight Redfish). The inshore boundary may provide some protection for this species but it is unclear how effective this will be” (AFMA, 2008c). 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 (2008d), 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 or uneven area of occupancy, rather than even distribution throughout space (the latter of which is unrealistic, for site-associated benthic 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 lineatus was ranked as being at low risk of population impacts from trawl fishing in the South East Trawl Fishery (Wayte et al., 2004) and in the Gillnet, Hook and Trap fishery (i.e. the South East Non-trawl Fishery and Southern Shark Fishery combined) (Webb et al., 2004).

Research Recommendations

The relationship between Swallowtail populations within and outside of Australian waters should be determined.

There is little information on the biology (particularly age and growth, longevity and reproduction) and population dynamics of this species.

More information is required about the habitat of this species in deeper continental shelf waters, given that Swallowtail in shallow waters are normally associated with reefs. The relationship between populations in deep and shallow waters needs to be ascertained.

There is a possibility of ontogenetic patterns of movement in this and other related Centroberyx, which should be investigated. The potential impacts of trawling on Swallowtail habitat in the GAB (where the species is commonly taken by trawl) should be investigated.

Ecological models of food web dynamics should consider the significance of pilchards in the diet of this species, and the significance of Swallowtail in the diet of fur seals. Potential impacts of any increases in commercial take of baitfish and Swallowtail should be determined if possible.

Management Notes

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 Swallowtail (Department of Fisheries, W.A., 2006b, 2009a).

In South Australia, for recreational fishing of all Centroberyx species (including Swallowtail), 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 Swallowtail (for charters up to 3 people) or 5 Swallowtail (for charters up to 6 people), equivalent to a charter boat limit of 30 Swallowtail (Presser and Mavrakis, 2005; PIRSA, 2005b).

Management Recommendations

All catches of Centroberyx species, including discards, in the Commonwealth-managed fisheries, should be recorded. According to AFMA (2008c) an Integrated Scientific Monitoring Program (ISMP) during the early 2000s estimated that 38t per annum is caught in the GABTF, with 95% discarded. All specimens are caught shallower than 200m. According to figures provided by AFMA (2002a), the bycatch sampling program in 2000 – 01 in the Great Australian Bight Trawl fishery showed that only 155kg of the total catch of nearly 2 tonnes of Swallowtail was recorded in logbooks, and such practice can significantly underestimate the total catch.

It is possible, and undesirable, that catches in the GAB will continue to increase unchecked, given the increase in recent years in Bight Redfish quota (and the distribution and habitat of Swallowtail overlap with that species). Monitoring of catches of Centroberyx lineatus over space and time is required, particularly in the Commonwealth-managed fisheries of southern Australia. Stock assessment of Centroberyx lineatus should be undertaken, given this species’ possible high susceptibility to depletion in the Great Australian Bight.

Based on CSIRO records, it is possible that this species was taken in high numbers during the 1960s and 1970s in the GAB. Given that Swallowtail catches are commonly discarded, catches are not correctly recorded, and there was no knowledge of population size prior to fishing, it would be difficult to retrospectively determine whether impacts have already occurred in the population, particularly in the GAB. However, management of the fishery should consider the vulnerability of this species, and work accordingly to reduce future catches and discards.

Centroberyx species caught in State-based commercial fisheries should be identified to species level, and catches should be monitored over space and time if possible.

Data should be collected with a view to undertaking a population assessment in future, which would integrate data from both State-managed and Commonwealth-managed fisheries.

Although catches of Swallowtail are apparently low, measures to reduce bycatch of all Centroberyx species in rock lobster pots should be implemented where possible.

Measures (such as barotrauma reduction methods) should be undertaken to try to ensure the survival of hooked undersized specimens taken by charter boat fishers. Several hundred per year undersized specimens have been recorded in S.A., and an unknown number in W.A. and other States.

Where possible, compliance with recreational (including charter boat) catch limits for Centroberyx species should be checked.