I & I NSW WILD FISHERIES RESEARCH PROGRAM Silver Trevally (Pseudocaranx georgianus) EXPLOITATION STATUS GROWTH OVERFISHED Minimum legal length (MLL) of 30 cm total length was implemented in September 2007 but recent size composition data indicate silver trevally should still be considered ‘growth overfished’. Status should be reviewed after the impact of the MLL implementation has been fully assessed. SCIENTIFIC NAME STANDARD NAME COMMENT Pseudocaranx georgianus silver trevally Was recently known as P. dentex. Pseudocaranx georgianus Image © Bernard Yau Background samples from Botany Bay between December and August, however the life history of juvenile Recent research determined that the silver trevally is poorly known. trevally in south-eastern Australian and northern New Zealand waters is distinct from Silver trevally is a relatively long lived, slow the larger tropical form (Pseudocaranx dentex) growing species, attaining a maximum age and the old name (P. georgianus) has been in excess of 25 years. In NSW coastal waters restored. Silver trevally occur in estuarine and trevally reach a maximum size of about coastal waters of southern Australian states 65 cm FL and weight of about 4 kg. Since the ranging from about Coffs Harbour in NSW 1980s, the average size of silver trevally in to about Perth in WA. Most of the Australian catches has declined considerably and in recent commercial catch is taken in NSW and eastern years fish greater than about 35 cm in length Victoria. Silver trevally is a schooling species, (or 0.75 kg in weight) have been very poorly inhabiting mainly sandy substrates and feeding represented in catches. Commercial catches are on benthic invertebrates, including worms and dominated by young fish, less than about five molluscs, and also on benthic and planktonic years of age. crustaceans. Commercial landings of silver trevally increased Silver trevally mature between 18 and 24 cm significantly to more than 1000 t per annum fork length (FL), at 2 - 4 years of age. Females during the early 1980s. Annual landings then have moderate fecundity (50,000–200,000 steadily declined to less than 500 t in the eggs) and spawn during an extended period late 1990s. Commercial landings have been from spring to autumn. Larvae occur in coastal around 200 to 300 t for the past decade. The waters throughout this period, and may enter bulk of the commercial catch of silver trevally estuaries before settling out as juveniles. is taken in ocean waters by otter trawling. Fish less than 10 cm in length were found in Smaller quantities are taken by fish trapping. STATUS OF FISHERIES RESOURCES IN NSW, 2008/09 SilvER TREvallY | P 291 WILD FISHERIES RESEARCH PROGRAM Commercial catches of silver trevally from Catch estuarine waters have declined significantly following the declaration of a Recreational Recreational Catch of Silver Trevally Fishing Haven in Botany Bay in 2002. In recent The annual recreational harvest of silver trevally years, buy-outs of trawling licences associated in NSW is likely to lie between 100 and 210 t. with the implementation of Marine Parks have This estimate is based upon the results of the resulted in a further decline in landings of offsite National Recreational and Indigenous silver trevally. Most trevally are sold fresh at the Fishing Survey (Henry and Lyle, 2003) and Sydney and Melbourne fish markets where the onsite surveys undertaken by I & I NSW. species receives moderate prices depending on the size grade and quality of handling after Historical Landings of Silver Trevally capture. Significant catches of silver trevally are taken by 1500 recreational fishers in both estuarine and ocean waters. In the mid 1990s the annual catch of silver trevally from ocean waters by recreational 1000 fishers was estimated to be between 150 and 210 t; however it is thought that recent catches have been lower. Landings (t) 500 Additional Notes • A minimum legal length (MLL) of 30 cm total 0 length was implemented in September 2007, 48/49 58/59 68/69 78/79 88/89 98/99 08/09 however this regulation does not apply to fish Financial Year Commercial landings (including available historical caught under Commonwealth jurisdiction. records) of silver trevally for NSW from 1944/45 to • The implementation of the zoning plan 2008/09 for all fishing methods. Note that the decline in reported catch during the late 1990s was due to changes for the Batemans Marine Park off the NSW in catch recording requirements for fishers with both south coast in 2007 resulted in the closure NSW and Commonwealth licences. to trawling of significant areas where silver trevally were previously targeted. A number Landings by Commercial Fishery of Silver Trevally of trawl licences were also bought out during the implementation of this Marine Park. Ocean Trap and Line (Primary Species) Fish Trawl (Primary Species) • NSW landings in 2007/08 were 133 t, and Estuary General size composition monitoring is continuing * Ocean Hauling (Target Species) at the Sydney Fish Market following the implementation of the MLL. 500 • There was a large reduction in the Commonwealth Total Allowable Catch (TAC) 400 for silver trevally from 270 t in 2006 to 146 t in 2007, but only 67 t was landed in 2007. For 300 2008 the TAC was increased again to 296 t Landings (t) and landings were 112 t. 200 • The Commonwealth status of ‘not overfished’ 100 was based on an analysis of catch rate data 0 - that the stock may be considered ‘growth 97/98 99/00 01/02 03/04 05/06 07/08 overfished’ is not considered relevant to the Financial Year assessment (Wilson et al. 2009). Reported landings of silver trevally by NSW commercial • There is a minimum legal length of fisheries from 1997/98. * Fisheries which contribute less 30 cm total length for silver trevally and a than 2.5% of the landings are excluded for clarity and privacy. recreational bag limit of 20 for all trevallies. P 292 | SilvER TREvallY STATUS OF FISHERIES RESOURCES IN NSW, 2008/09 Catch Per Unit Effort Information of Silver Trevally Length Frequency of Silver Trevally Harvested by Fish Trawling in NSW 1980/81−1998/99 n = 20 568 0.20 1.0 0.15 0.8 0.10 0.6 Proportion 0.05 0.4 Relative Catch Rate 0.00 0.2 10 20 30 40 50 60 0.0 98/99 00/01 02/03 04/05 06/07 08/09 2000/01−2006/07 Financial Year n = 12 254 0.20 Catch rates of silver trevally harvested using fish trawling for NSW. Two indicators are provided: (1) median catch 0.15 rate (lower solid line); and (2) 90th percentile of the catch rate (upper dashed line). Note that catch rates are not a 0.10 robust indicator of abundance in many cases. Caution Proportion should be applied when interpreting these results. 0.05 0.00 10 20 30 40 50 60 Growth Curve of Silver Trevally 2007/08−2008/09 n = 3573 0.20 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.15 50 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.10 ● ● ● ● ● ● Proportion ● ● 40 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.05 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● FL (cm) ● ● ● ● ● ● ● ● ● ● ● 30 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.00 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 10 20 30 40 50 60 ● ● ● ● ● ● ● ● ● ● ● ● ● 20 ● ● ● ● ● ● ● ● FL (cm) ● ● ● ● ● ● ● ● ● ● ● The proportion of larger (> 30 cm fork length (FL)) ● ● ● silver trevally landed by NSW commercial fishers has 10 declined between 1980 and 2000, and recent catches 0 5 10 15 20 have comprised mainly fish between 20 and 30 cm FL. In Ring Count (years) September 2007 a minimum legal length of 30 cm total Age-length data with fitted growth curve for silver length (equivalent to 25 cm FL) was introduced for silver trevally (Rowling & Raines, 2000). Lengths are presented trevally in NSW. as fork length (FL). SilvER TREvallY | P 293 WILD FISHERIES RESEARCH PROGRAM Further Reading Broadhurst, M.K., C.A. Gray, D.D. Reid, M.E.L. Wooden, Stewart, J. and J. M. Hughes (2008). Determining D.J. Young, J.A. Haddy and C. Damiano (2005). appropriate sizes at harvest for species shared Mortality of key fish species released by recreational by the commercial trap and recreational fisheries anglers in an Australian estuary, Journal of in New South Wales. FRDC Project No. 2004/035. Experimental Marine Biology and Ecology 321: 171- Fisheries Final Report Series No.97 Cronulla, NSW 179. Department of Primary Industries: 282pp. Henry, G.W. and J.M. Lyle (2003). The National Wilson, D., R. Curtotti, G. Begg and K. Phillips, Eds. Recreational and Indigenous Fishing Survey. Final (2009). Fishery Status Reports 2008: status of fish Report to the Fisheries Research & Development stocks and fisheries managed by the Australian Corporation and the Fisheries Action Program Government. Canberra, Bureau of Rural Sciences Project FRDC 1999/158. NSW Fisheries Final Report & Australian Bureau of Agricultural and Resource Series No. 48. 188. Cronulla, NSW Fisheries. Economics. Rowling, K.R. and L.P. Raines (2000). Description of the biology and an assessment of the fishery for silver Please visit the CSIRO website, trevally Pseudocaranx dentex off New South Wales. http://www.marine.csiro.au/caab/ and search for the Final Report to Fisheries Research and Development species code (CAAB) 37 337062, common name or Corporation. Project 97/125. NSW Fisheries Final Report Series No. 24. Cronulla, NSW Fisheries: 69pp. scientific name to find further information. Smith-Vaniz, W.F. and H.L. Jelks (2006). Australian trevallies of the genus Pseudocaranx (Teleostei: Carangidae), with description of a new species from Western Australia. Memoirs of Museum Victoria 63 (1): 97-106. Steffe, S., J. Murphy, D. Chapman, B.E. Tarlington, G.N.G. Gordon and A. Grinberg (1996). An assessment of the impact of offshore recreational fishing in New South Wales on the management of commercial fisheries. Project 94/053. Sydney, NSW Fisheries Research Institute: 139 pp. Stewart, J.