© 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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Globefish / Porcupine Fish

Family Name:	Diodontidae
Scientific Name:	Diodon nicthemerus Cuvier, 1818
Recommended Status in S.A:	Data Deficient (requiring fisheries impact assessment)
Rationale:  Although the Globefish has a broad geographic range across southern Australia, it is included here because the species (i) aggregates in coastal waters, which can increase its vulnerability to threatening processes; (ii) is highly vulnerable to capture in trawls (and other nets) in both State and Commonwealth waters across southern Australia, and is caught in some fisheries (such as the South East Trawl Fishery) in seemingly very large numbers; (iii) suffers barotrauma when caught in trawls, and therefore survival rate of discarded specimens is likely to be low, and trawling bycatch studies have reported that the Globefish is vulnerable to population impacts from trawl capture; and (iv) there is inadequate information on the relative abundance and population dynamics (including annual recruitment strength) of this species, including populations in South Australian waters, hence it is not possible to determine to what extent capture in Commonwealth- and State-managed fisheries may impact populations.

Page Contents

Current Conservation Status

No listings known

Distribution

Southern Australia

The Globefish ranges across southern Australia, from Seal Rocks (near Forster) in New South Wales (Gomon, in Gomon et al., 1994; Edgar, 2000) through to Dongara in W.A. (Hutchins and Swainston, 1986), and the distribution includes Tasmania (Jordan et al., 1998) and the Kent Group (Edgar, 1984, cited by RPDC Marine, 2002).

South Australia

The species has been recorded across South Australia, from the Great Australian Bight (GAB) through to the South East.
Examples of locations in S.A. in which the species has been recorded include the western, central and eastern parts of the GAB (from where there are many trawl records of specimens reported to be this species); southern Eyre Peninsula, northern Spencer Gulf; north-eastern and eastern Spencer Gulf (e.g. Port Pirie, Port Hughes, Moonta Bay, Wallaroo, Cape Elizabeth); southern Spencer Gulf (e.g. Corney Point); northern Gulf St Vincent (GSV) (e.g. Port Gawler); metropolitan GSV (e.g. Grange, Glenelg, Brighton); southern Fleurieu Peninsula (e.g. Haycock Point); western GSV / Yorke Peninsula (e.g. Wool Bay; Edithburgh); Althorpe Is.; southern Kangaroo I. (e.g. Vivonne Bay); Investigator Strait; Encounter Bay, and the upper South-East (Kuiter, 1983; MLSSA, 1997; Carrick, 1997; photograph by J. Lewis, 2004; Shepherd et al., 2005; Edgar et al., 2006; photograph by A. Braund, 2006; Australian Museum records; Museum of Victoria record; South Australian Museum records, cited in OZCAM database, 2007; CSIRO Marine Research data, cited by CSIRO, 2007).

Habitat

Globefish commonly occur in small aggregations in shallow coastal bays (Kuiter, 1993, 2000).
The species is found over sheltered and moderately exposed reefs with macroalgae (Hutchins and Swainston, 1986; Edgar, 2000; Harvey et al., 2004; Parks Victoria, 2006), and in sand habitats (Edgar, 2000), and also in coastal seagrass beds (O’Hara et al., 2002).
In Tasmania, the species has been recorded from Heterozostera tasmanica seagrass beds in various bays (Jordan et al., 1998).
In Victoria, the Globefish Diodon nicthemerus has also been recorded in intertidal mangroves and unvegetated mudflat habitats (Hindell and Jenkins, 2004).
The usual depth range is from very shallow subtidal (less than 1m) to about 50m (Kuiter, 2000); however it is noted that the CSIRO houses more than 20 records (purported to be this species) from 60m depth or more, with isolated records from as deep as 120m and 150m (CSIRO Marine Research data, cited in CSIRO, 2007).

Notes on the Biology and Behaviour

Growth

The species grows to between 31cm (Hutchins and Swainston, 1986) and 40cm total length (May and Maxwell, 1986, cited in Froese and Pauly, 2007).
The maximum weight recorded is around 1.45kg (Hutchins and Swainston, 1986; Australian Anglers Association, 2004), being a specimen caught in GSV in S.A., in 1986.

Diet

Globefish feed on small molluscs, which are crushed with the plate-like teeth (Parks Victoria, 2006). It is noted that the introduced screw shell Maoricolpus roseus is part of the diet of Globefish in southern Australia (Bax et al., 2003).

Other Notes on the Biology

Eggs and juvenile globefish in the Diodontidae family are pelagic, but the adults are benthic (Kuiter, 1993, 2000; Nelson, 1994).
The species is active at night, and also on overcast days (Kuiter, 1993, 2000).

Fisheries Information

Commercial – South-eastern Australia

The Globefish is part of the discarded bycatch in a number of fisheries in southern Australia, such as the Commonwealth-managed SESSF (Southern and Eastern Scalefish and Shark Fisheries), which includes the South East Trawl Fishery (SETF) (AFMA, 2002a).
In the otter trawl sub-fishery of the South East Trawl Fishery, an Integrated Scientific Monitoring Program (ISMP) reported that in 245 trawl shots, about 2 tonnes of D. nicthemerus specimens were discarded (Wayte et al., 2004), which is an average of 8kg per trawl shot. In the Danish seine sub-fishery of the SETF, the ISMP reported that in 184 shots, about 1.9 tonnes of D. nicthemerus specimens were discarded (Wayte et al., 2004), which is an average of 10kg per shot.
The species is vulnerable to capture in small mesh gill nets (e.g. Walker et al., 2003).
Globefish is a minor bycatch species in the Bass Strait Scallop Fishery (Haddon and Semmens, 2001, 2002; Haddon et al., 2004).
In New South Wales, fishery-independent surveys to assess bycatch composition in the N.S.W. Ocean Fish Trawl Fishery showed that the percentage frequency of occurrence of Globefish across all trawls, was around 42% in the Wreck Bay and Tathra inshore grounds of the “ocean fish trawl shelf sector” (New South Wales Department of Primary Industries, 2004).
D. nicthemerus is collected in Tasmania for the aquarium industry. The permitted annual catch limit is 300 individuals, with a fishing block limit (6 x 6 nautical miles) of 50 individuals (DPIWE Tasmania, 2005b; Australian Government DEH, 2005b). In 2005, the export price was US$30 – 35 per fish (Ryan and Clarke, 2005). During the mid-late 2000s, specimens were being advertised for sale through a Tasmanian aquarium supply company.

Commercial – South Australia

Globefish is a minor component of the bycatch in the prawn trawl fishery in Spencer Gulf, South Australia. For example, 54 D. nicthemerus specimens were recorded from 32 trawl tows, in a sampling program during the mid 1990s, which represented 0.4% of the total number of scalefish in the bycatch of those tows (Carrick, 1997). During a more recent bycatch program (Dixon et al., 2005), the species was not included in a list of significant bycatch species, and is likely to have been grouped in the “miscellaneous fish” category, for which species’ identity of catches were not provided.
Observers have reported Globefish as part of the bycatch in the Gulf St Vincent prawn fishery (Richardson, 1999).
In S.A., during bycatch sampling in the Blue Crab fishery (2002-2005), no individuals were caught in Gulf St Vincent during those years. Only 1 Globefish specimen was caught in a pot in Spencer Gulf, in each of 2003 and 2004 (Svane and Hooper, 2004; Currie and Hooper, 2006).

Recreational

The National Recreational and Indigenous Fishing Survey (Henry and Lyle, 2003) reported that approximately 223 and 90 Porcupine Fish were caught and kept by recreational fishers in South Australia and Tasmania respectively during the survey time period (May 2000 to April 2001).
Although the species is not usually targeted, some recreational fishing clubs and associations keep records of the maximum sizes of specimens caught (e.g. Australian Anglers Association, 2004).

Vulnerable Characteristics of the Species

The species commonly occurs in a variety of habitats in continental shelf waters, and its distribution overlaps with some of the trawl (and other net) fisheries in southern Australia. Due to its spiny, inflatable body, Globefish can easily get entangled in fishing nets.
Diodontid fish often aggregate, which increases their vulnerability to capture (e.g. by trawls).
There is some evidence that the species might be vulnerable to impacts from pollutants. For example, liver damage due to extensive visceral haemosiderosis and fatty infiltration has been reported in D. nicthemerus populations in Port Phillip Bay, Lakes Entrance, Bass Strait, and the Derwent River in Tasmania. The species is considered normally to have low levels of visceral haemosiderin. These populations were therefore considered to be of sub-optimum health, and it was suggested that toxic or pollution-related causes were likely (Langdon, 1986).

Threatening Processes

A study of the susceptibility of trawl-caught fishes to population impacts (Stobutski et al., 2001) ranked fish bycatch species according to two overriding characteristics (based upon biological and ecological criteria): (i) the susceptibility to capture and mortality due to prawn trawling, and (ii) the population's capacity to recover after depletion. The rank of each species on these two characteristics determined its relative capacity to sustain trawling, and therefore its priority for research and management. Species that were the least likely to be sustainable included those in the Diodontidae. These species are highly susceptible to capture by trawls, they are benthic or demersal, their primary habitat is soft sediments, and their diet may include prawns, or other species found in prawn grounds. The recovery capacity of these species is also low, with the estimated removal rate by trawling (Stobutski et al., 2001).
Globefish was listed as one of the bycatch species in the N.S.W. Ocean Trawl Fishery that has a “high” fishery impact profile (New South Wales Department of Primary Industries, 2004). The species is reported to suffer barotrauma when hauled in trawls, and D. nicthemerus was classified overall as a species of “low to moderate” resilience, and a “high risk” species in terms of population impacts from trawl fishing (see N.S.W. Department of Primary Industries, 2004). In contrast, in a draft ecological risk assessment of the South East Trawl and Danish Seine Fishery (Wayte et al., 2004), 4 “productivity attributes” and 6 “attributes of susceptibility” for D. nicthemerus were used to categorise it as a “low risk” species in terms of susceptibility to population impacts from trawling, but it is noted that the species almost qualified for the “medium risk” category in that assessment.

Research and Management Requirements

More information is required on the distribution and relative abundance (particularly in South Australia).
There is little information on reproduction, and the population dynamics of this species, including annual recruitment strength.
If possible, an assessment of survival rate of trawl-caught, discarded specimens is required, particularly in the Commonwealth-managed fisheries in which this species is caught in large numbers. Even if this research is not undertaken, measures to reduce the large bycatch of Globefish are certainly required.
In Tasmania, an assessment is required of the sustainability and potential population impact of the annual take for the aquarium industry.

Other Information

The species is found in many of the marine parks and sanctuaries in Victoria, such as Yaringa, French Island, Churchill, Corner Inlet, Jawbone, Marengo Reef, Beware Reef, Ricketts Point, and Ninety Mile Beach (Plummer et al., 2003; Parks Victoria, 2006).