Table 1: Stock status determination for Balmain Bug
Jurisdiction |
New South Wales, Queensland |
Stock |
East coast
(ECOTF, OTF-PS, OTF-FS) |
Stock status |
|
Sustainable |
Indicators |
Catch rates, size structure |
ECOTF = East Coast Otter Trawl Fishery (Queensland); OTF-FS = Ocean Trawl Fishery – Fish Sector (New South Wales); OTF-PS = Ocean Trawl Fishery – Prawn Sector (New South Wales)
The common name ‘Balmain Bug’ refers to four similar species of fan lobster: Ibacus alticrenatus, I. brucei, I. chacei and I. peronii1. These species overlap in their distributions on the east coast of Australia and have evolved different life-history strategies. They are treated as a single biological stock in this report because they are rarely distinguished by fishers or fish marketers.
The true Balmain Bug (I. peronii) is widely distributed around the southern half of the continent, from around the Queensland–New South Wales border (latitude 28°S) to central Western Australia (latitude 29°S), including the east coast of Tasmania and Bass Strait. The true Balmain Bug is mainly found close to shore, in waters less than 80 m deep. Given the prevailing influence of the East Australian Current and a protracted (~80 days) pelagic larval life, I. peronii along the east coast is thought to be a single biological stock1.
The Smooth Bug (I. chacei) is distributed between northern Queensland (latitude 17°S) and southern New South Wales (latitude 36°S), although it is rarely caught south of Sydney (latitude 34°S). It is most abundant on the mid-continental shelf in depths of 50–150 m. Given the prevailing influence of the East Australian Current in these depths, a pelagic larval phase and a northerly migration through life, Smooth Bugs are thought to be a single biological stock1.
The Honey Bug (I. brucei) is distributed between central Queensland and northern New South Wales. It is most abundant on the outer continental shelf and upper slope in waters between 120 m and 300 m deep. Given the prevailing influence of the East Australian Current in these depths and a pelagic larval phase, Honey Bugs are thought to be a single biological stock1.
The Deepwater Bug (I. alticrenatus) is distributed about southern Australia and in New Zealand waters. It is most abundant at depths of 200–400 m on the upper continental slope1.
East Coast biological stock
This cross-jurisdictional multispecies biological stock has components in New South Wales and Queensland. Each jurisdiction assesses the part of the biological stock that occurs in its waters. The status presented here for the entire biological stock has been established using evidence from both jurisdictions.
In New South Wales, Balmain Bugs (true Balmain Bugs and Smooth Bugs) are assessed separately in terms of their commercial catch rates and length compositions in landings. Increasing catch rates and stable length compositions during the past 15 years indicate sustainable levels of fishing mortality and have resulted in both species being assessed as fully fished in New South Wales2.
The Queensland assessment for Balmain Bugs (Smooth, Honey and Deepwater Bugs) considers that the risk of overfishing is low in waters south of the Great Barrier Reef Marine Park, where the majority of these species are taken, due to limited fishing effort and minimum legal sizes that protect juveniles3.
The above evidence indicates that the biomass of the east coast biological stock of Balmain Bugs is not recruitment overfished and that the current level of fishing mortality is unlikely to cause the biological stock to become recruitment overfished.
On the basis of the evidence provided above, the east coast biological stock is classified as a sustainable stock.
Table 2: Balmain Bug biology1,4,6–9
Longevity and maximum size |
Balmain Bug: 15 years; 8.6 cm CL
Smooth Bug: 5–7 years; 8 cm CL
Honey Bug: longevity largely unknown; maximum CL in Queensland samples is 7.2 cm for females and 6.6 cm for males
Deepwater Bug: longevity largely unknown; maximum CL in Queensland samples is 5.5 cm for both females and males
|
Maturity (50%) |
Balmain Bug: 2 years; 5 cm CL
Smooth Bug: 2 years; 5.5 cm CL
Honey Bug: 4.7 cm CL
Deepwater Bug: 4.5 cm CL |
CL = carapace length (Not to be confused with carapace width. Carapace width is generally used for size limits in Balmain Bugs as it is a simple and rapid measure for use by commercial and recreational fishers5.
Figure 1: Distribution of reported commercial catch of Balmain Bug in Australia waters, 2010
- Balmain Bugs are landed as byproduct in the trawl fisheries that target Eastern King Prawn (Penaeus plebejus) and fish in New South Wales and Queensland.
- As a byproduct, few specific management regulations apply to Balmain Bugs:
- A minimum legal size of 10 cm carapace width applies in New South Wales for Balmain and Smooth Bugs.
- A minimum legal size applies in Queensland of 10.5 cm carapace width for Smooth Bugs and 7.5 cm carapace width for Honey and Deepwater Bugs.
- Landing egg-bearing Balmain Bugs is prohibited in New South Wales and Queensland.
- In 2010, 102 vessels in New South Wales and 171 vessels in Queensland caught Balmain Bugs.
- The total quantity of Balmain Bugs caught commercially in Australia in 2010 was 133 tonnes (t), comprising 37 t in both sectors of the Ocean Trawl Fishery (New South Wales) and 96 t in the East Coast Otter Trawl Fishery (Queensland). These species are not targeted by either recreational or Indigenous fishers.
a)
b)
Figure 2: a) Commercial catch of Balmain Bugs in Australian waters, 2001–10 (calendar year);
b) mean catch rates of Balmain Bugs in Australian waters, 2001–10 (calendar year)
Total landings have fluctuated between about 100 t and 200 t per year since 2001. Most of the catch (~80 per cent) in Queensland waters is Smooth Bugs; in New South Wales, about equal quantities of Smooth and Balmain Bugs are landed. Catches of Deepwater Bugs in Queensland appear to be limited to a few tonnes (<20 t) annually from boats operating in deeper water (>100 m). Catch rates (kg/day) have been increasing or stable in both New South Wales and Queensland over the past decade, with catch rates being lower in New South Wales in comparison to Queensland. In Queensland, total landings and nominal catch rates of Balmain Bugs (Smooth Bugs) are strongly influenced by effort targeting deepwater Eastern King Prawns.
- Bycatch reduction devices and turtle excluder devices are employed by all boats to minimise the amount of bycatch.
- The East Coast Otter Trawl Fishery (Queensland) interacts with a number of protected species, including turtles, sea snakes and sawfish. These interactions are monitored through mandatory ‘Species of Conservation Interest’ logbooks.
- The major environmental factor influencing the Balmain Bug biological stock is likely to be the southerly flow of the East Australian Current. The impact of changes in the East Australian Current on recruitment of these species is currently unknown1,8.
a Department of Primary Industries, New South Wales
b Department of Agriculture, Fisheries and Forestry, Queensland