Courtney et al., 2007: 

"Non-technical Summary

OUTCOMES ACHIEVED TO DATE:

• All stakeholders, including the Queensland Fishery Managers, conservation agencies, industry, recreational fishing groups, the public, the Great Barrier Reef Marine Park Authority (GBRMPA) and DEH, are in a much more informed position to comment on how well the fishery management initiatives are reducing bycatch, and perhaps what more needs to be done.

• Greatly improved understanding of the catch rates and composition of bycatch in each of the major trawl fishery sectors.

• More fishers are using highly effective square mesh codends in the scallop and eastern king prawn fisheries as a result of the project.

• The project demonstrated that bycatch rates in the scallop fishery can be reduced by 77% if square mesh codend BRDs are made mandatory in this sector with TEDs. This large reduction can be achieved with no loss of marketable scallops and with 63% fewer undersized scallops being caught.

• Improved understanding of the impacts of trawling on species of high conservation or recreational value.

• The project showed fishers and managers how to reduce the incidental catch rate of stout whiting caught in prawn trawl nets by 57%.

• Greatly improved understanding of the elasmobranch bycatch in the trawl fishery, and the effects of TEDs and BRDs upon them.

• Stakeholders are in a more informed position to determine whether the bycatch composition in each of the major sectors is likely change as a result of TEDs and BRDs.

• The accuracy of standardised catch rates and stock assessments for prawns, scallops and bugs has improved because the project quantified the effects of TEDs and BRDs on them.

• Queensland fishery managers are in a stronger position to discuss the value of bycatch monitoring programs, to decide upon their implementation and to provide input to their design.

• Through the project staff involvement with the Technical Working Group, the design and specifications of BRDs has been improved.

• Through project staff interaction with the Boating and Fisheries Patrol, patrol officers are more informed about TED and BRD design specifications and functions. The Patrol are in a stronger position to police and enforce the devices.

• The yield and value of three spot crabs Portunus sanguinolentus has improved and the likelihood of overfishing this stock is reduced as a result of the project.

• Managers have an improved understanding of the distribution and composition of Balmain bug (Ibacus spp.) and mantis shrimp landings in Queensland.

• Reduced likelihood of overfishing Balmain bugs, as a result of the minimum legal size advice as a direct result of the project.

• Information obtained on the distribution of the pipehorse (Solegnathus cf. hardwickii), which is listed as vulnerable on the IUCN Red List, can be used to conserve populations of this species.

The project provided quantitative biological and technical information on two issues relating to the Queensland trawl fishery:

1) the assessment of TEDs and BRDs on the catch rates of bycatch, target species and bycatch community structure in the main trawl sectors, and

2) the biology, population dynamics and management of several species that are caught incidentally in the fishery that can now be retained and marketed.

These species are listed in the Trawl Fishery Management Plan [Fisheries (East Coast Trawl) Management Plan 1999] as the permitted species and include barking crayfish (Linuparus trigonus), Balmain bugs (Ibacus spp.), three spot crabs (Portunus sanguinolentus), mantis shrimps, (Stomatopoda), cuttlefish (Sepia spp.), octopus (Octopus spp.), pipehorses (Solegnathus spp.) and Pinkies (Nemipterus spp.).

Evaluating the performance of TEDs and BRDs

The project obtained 1619 measurements and sub-samples of bycatch during a) dedicated research charters that were designed to test TEDs and BRDs, and b) opportunistic sampling on board commercial vessels during their normal fishing activities. A total of 49.1 tonnes of bycatch was weighed at sea, of which 9.8 tonnes was sub-sampled and processed to species level in the laboratory. Over 1300 taxa were recorded in the bycatch, including records of new species occurrences in Queensland, and new information on the extent of species’ distributions.

Information is provided on the a) bycatch species composition in each major sector of the fishery and their catch rates, b) effects of TEDs and BRDs on the catch rates of prawns, scallops, byproduct species (i.e., Moreton Bay bugs and Balmain bugs), total bycatch and individual bycatch species, including the elasmobranchs (sharks and rays), and c) bycatch community assemblages and how they vary with latitude, depth and BRD type.

Research charters

The most promising finding from the project was obtained from one of the research charters which demonstrated that bycatch rates in the saucer scallop fishery could be reduced by a mean of 77% by using nets with both TEDs and square mesh codend BRDs, compared to standard nets. Importantly, this reduction was achieved with no reduction in the catch rate of legal size scallops, and with 63% fewer undersized scallops being caught. For these reasons we recommend that square mesh codend BRDs be made compulsory in the scallop fishery. (TEDs are already compulsory in all trawl sectors, but fishers can use less effective BRDs). If all scallop fishers used these devices, it would equate to a reduction in bycatch of over 10,000 tonnes annually compared to pre-2000 levels (i.e., before TEDs and BRDs were introduced). Use of the square mesh codend BRDs is likely to lower the incidental fishing mortality on undersized scallops, and possibly increase the available exploitable biomass.

The project also demonstrated high potential for square mesh codend BRDs with TEDs in the deep water eastern king prawn fishery, where the mean bycatch rate was reduced by 29%, with no loss of targeted prawn catch. For this reason, we also recommend the mandatory use of square mesh codend BRDs in this sector.

Another 10-night charter undertaken in the shallow water eastern king prawn fishery demonstrated a significant reduction in mean bycatch rate of 24% by using a radial escape section BRD and TED, compared to a standard net. This combination of devices was particularly effective at reducing catch rates of bentho-pelagic species with fusiform body shape, such as stout whiting Sillago robusta (57% reduction) and yellowtail scad Trachyurus novaezelandiae (32% reduction). Unfortunately, the mean catch rate of marketable size eastern king prawns was also reduced by a mean 20% during the charter, mainly via the TED. The charter showed high potential application for the radial escape section BRD in the shallow water eastern king prawn fishery. We believe the prawn loss could be largely mitigated by adjusting the angle of the TED.

The radial escape section BRD and TED were also evaluated in the north Queensland tiger/endeavour prawn fishery during an eight-night charter. While a significant 20% reduction in mean bycatch rate was demonstrated, it was concluded that the radial escape section BRD was less effective in this sector because a) the bycatch fish species were generally smaller than those of the eastern king prawn fishery and therefore less capable of swimming to, and escaping out of, the device, and b) trawl speed is higher and codends are longer in the tiger/endeavour prawn fishery, thus making it more difficult for small fish species to swim forward and out of the device. The results show that one BRD type is not suitable for all sectors of the fishery, that each sector has its own unique bycatch properties and that effective BRD usage needs to be tailored to each sector.

Opportunistic measures on board commercial vessels

Analysis of the opportunistic sampling obtained on board commercial vessels during their normal fishing activities indicated that, across the major prawn trawl sectors (i.e., north Queensland tiger/endeavour prawn, and shallow- and deepwater eastern king prawns sectors) there was no statistically significant reduction in total mean bycatch rate (i.e., all bycatch including large sharks, large rays and large sponges known collectively as “monsters”) due to TEDs and BRDs, compared to standard nets. When an analysis was undertaken excluding large fauna, the mean bycatch rate (i.e., excluding monsters) was significantly reduced by 25%, when both TEDs and BRDs were installed. The reduction in bycatch rate due to the TEDs and BRDs that were used by commercial fishers was low compared to those obtained during the research charters. Reductions in bycatch rates were greater in the tiger/endeavour prawn fishery, while no significant reductions were detected for devices being used in the shallow- and deepwater eastern king prawn sectors. No significant effects on marketable prawn catch rates were detected for the devices being used by industry. In the saucer scallop fishery, the TEDs and BRDs that were being used by fishers resulted in a reduction in total mean bycatch rate (i.e., includes monsters) of 68%. This reduction was due mainly to TEDs excluding large sponges which dominate the bycatch weight in this sector. A significant reduction in scallop catch rate of 11% was detected and mainly attributed to BRDs.

Bycatch reduction could be improved in the Queensland trawl fishery by a) promoting regular meetings of the Technical Working Group which was formed to evaluate BRDs and improve upon their technical specifications, b) further research and testing of BRDs, c) workshops with fishers that demonstrate and promote the more effective devices, d) educational programs for the Boating and Fisheries Patrol to enhance enforcement of the devices, and e) incentives for fishers to reduce their bycatch.

Biology and management of the permitted species

The project provided information on the biology, distribution and management of the permitted species. New information is provided on the species composition of Balmain bug landings in Queensland; the garlic bug Ibacus chacei constitutes the majority of Balmain bug landings, followed by the honey bug Ibacus brucei and the velvet bug Ibacus alticrenatus. The project provided a clearer understanding of the distribution and fishery for these species, as well as an improved understanding of the growth rates of I. chacei and the size, age and location at which it reproduces. Minimum legal sizes for Balmain bugs were developed and recommended to the fishery managers. The first detailed description of the reproductive biology, distribution and fishery for the little-known barking crayfish Linuparus trigonus is provided. We also recommended a minimum legal size of 80 mm CL for barking crayfish. The reproductive biology and growth of three spot crabs Portunus sanguinolentus were described and a minimum legal size of 100 mm CW was recommended and adopted, based on yield-per-recruit analysis. The project provided new information on the distribution and reproductive biology of mantis shrimps in Moreton Bay, where the majority of mantis shrimp reported catch is taken. New information on the catch rates, distribution, sizes and faunal community associations for the pipehorse, Solegnathus cf hardwickii, which is considered vulnerable and listed on the International Union for the Conservation of Nature Red List, is also provided. Information obtained on pinkies (Nemipterus theodorei and N. aurifilum) is preliminary and includes the first published accounts of the reproductive biology, distribution and growth for N. theodorei, which is the main species being retained and marketed. Collectively, the permitted species are valued at $1–2 million annually in Queensland and while the study has made a significant contribution to understanding their biology and improving management, further effort and funding are required to reduce the risk of overfishing these resources."

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Citation and/or URL

Courtney, A.J., Haddy, J.A., Campbell, M.J., Roy, D.P., Tonks, M.L., Gaddes, S.W., Chilcott, K.E., O.Neil, M.F., Brown, I.W., McLennan, M., Jebeen, E.J., van der Geest, C., Rose, C., Kistle, S., Turnbull, C.T., Kyne, P.M., Bennett, M.B. & Taylor, J. 2007, Bycatch weight, composition and preliminary estimates of the impact of bycatch reduction devices (BRDs): report to the Fisheries Research and Development Corporation. no. 2000/170, Queensland Department of Primary Industries and Fisheries, Brisbane, Australia

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Spatial Coverage

Queensland

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Temporal Coverage

Post 2000

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Update Frequency

Not applicable 

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Other Information

None