I & I NSW Wild Fisheries research Program Dusky Flathead ( fuscus)

Exploitation Status Fully Fished

Commercial landings and catch rates are steady, but the species is primarily harvested by recreational fishers. Better catch information is required for the recreational fishery.

Scientific name Standard name comment Platycephalus fuscus dusky flathead

Platycephalus fuscus Image © Bernard Yau

Background same habitats as the adults. Dusky flathead grow quickly, reaching 40 cm total length (TL) The dusky flathead Platycephalus( fuscus) is after 3 years in NSW. They mature at around endemic to Australia occurring from Cairns 20 cm TL (males) and 55 cm (females). They are in Queensland to SA. In NSW waters, dusky reported to reach 120 cm in length, and about flathead are found primarily within estuaries, 10 kg in weight, but the majority of caught but also occur in inshore ocean waters. They are 40 to 50 cm in length and 0.5 to 1 kg. The are a bottom dwelling fish and are normally oldest fish in a recent NSW study was aged found on soft substrates, including mud, sand 16 years, but the majority of fish in catches are and seagrass. Dusky flathead eat small fish and aged 2 to 5 years. a variety of invertebrates including prawns, crabs and squid. They are essentially ambush The recreational catch of dusky flathead greatly predators that lie and wait (often partly buried) exceeds the commercial catch. The commercial for passing prey. catch of dusky flathead is mostly taken by the Estuary General Fishery. The highest levels of Spawning appears to occur both in the lower commercial catches occur during the winter reaches of estuaries and in the sea, typically months when overnight setting of mesh nets is during summer. The larvae enter estuaries and permitted. the small juveniles subsequently live in the

status of fisheries resources in nsw, 2008/09 Dusky Flathead | p 99 wild fisheries research program

Additional Notes Landings by Commercial Fishery of Dusky Flathead

• Results of studies of growth and reproductive Estuary General (Primary Species) biology have recently been published (Gray

and Barnes, 2008) 250 • The commercial catch declined after 2000 because of licence buy-outs during the 200 creation of Recreational Fishing Havens and 150 Marine Parks but landings have increased Landings (t)

again since 2004/05. 100 • Assessments for this species need to 50 acknowledge the variability between

estuaries. 0 97/98 99/00 01/02 03/04 05/06 07/08 • There is a minimum legal length of 36 cm Financial Year total length (TL) and a recreational bag limit Reported landings of dusky flathead by NSW commercial of 10 dusky flathead (with only one fish fisheries from 1997/98. Fisheries which contribute less greater than 70 cm TL). than 2.5% of the landings are excluded for clarity and privacy.

Catch Recreational Catch of Dusky Flathead Catch Per Unit Effort Information of Dusky Flathead The annual recreational harvest of Dusky Harvested by Mesh-Netting in NSW Flathead in NSW is likely to lie between 570 and 830 t. This estimate is based upon the 1.0 results of the offsite National Recreational and

Indigenous Fishing Survey (Henry and Lyle, 0.8 2003) and onsite surveys undertaken by

I & I NSW. 0.6

Historical Landings of Dusky Flathead 0.4 Relative Catch Rate 0.2 250 0.0 200 98/99 00/01 02/03 04/05 06/07 08/09 Financial Year 150 Catch rates of dusky flathead harvested using mesh- netting for NSW. Two indicators are provided: (1) median Landings (t) 100 catch rate (lower solid line); and (2) 90th percentile of the catch rate (upper dashed line). Note that catch rates are not a robust indicator of abundance in many cases. 50 Caution should be applied when interpreting these results. 0

58/59 68/69 78/79 88/89 98/99 08/09 Financial Year

Commercial landings (including available historical records) of dusky flathead for NSW from 1952/53 to 2008/09 for all fishing methods. Note the decrease after 1999/00 with the introduction of Recreational Fishing Havens.

p 100 | Dusky Flathead status of fisheries resources in nsw, 20008/09

Growth Curve of Dusky Flathead - Males Length Frequency of Dusky Flathead

● ● ●

● ● ● 1969/70−1989/90 ● ● ● ●

● ● 0.10

50 ● n = 25 670 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.08 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

40 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

● ● ● 0.06 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

● ● ● Proportion ● ● ● ● ● ● ● ● ● 0.04 TL (cm) 30 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.02 ● ● ● ● ● ●

20 ● ● ● ● ● ●

● 0.00 ● ● ● ● ● ● ● ● ● ● ● ● ● 30 40 50 60 70 80 90 100 ● ● ●

10 ●

0 1 2 3 4 5 6 7 Age (years) 1995/96−1996/97

0.10 n = 25 284 Age-length data with fitted growth curve for male dusky flathead (Gray and Barnes, 2008). Lengths are presented 0.08 as total length (TL). 0.06 Proportion 0.04 0.02 Growth Curve of Dusky Flathead - Females 0.00

● 100 ● 30 40 50 60 70 80 90 100 ● ● ● ● ● ● ● ●

● ● 80 ● ● ● ● ● ● ● ● ● ● ● ● ● 2007/08−2008/09 ● ● ● ● ● ● ● 0.10 n = 6588 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

60 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.08 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● TL (cm) ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 0.06 ● ● ● ● ● ● ● ● ● ● ● 40 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Proportion ● ● ● ●

● ● ● 0.04 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 20 ● ● ● ● ● 0.02 ● ● ● ● ● ● ● ● ● ● ● ● 0.00

0 5 10 15 30 40 50 60 70 80 90 100 Age (years) TL (cm) Age-length data with fitted growth curve for female The length distribution of dusky flathead in NSW dusky flathead (Gray and Barnes, 2008). Lengths are commercial landings was relatively stable from the presented as total length (TL). 1970s to the 1990s. There was an increase in the relative proportion of larger fish (>40 cm total length (TL)) in catches during the period 1995 to 1997. The minimum legal length for dusky flathead was increased from 33 cm to 36 cm TL in July 2001.

Dusky Flathead | p 101 wild fisheries research program

Further Reading Anon. (1981). The ecology of fish in Botany Bay Gray, C.A., V.J. Gale, S.L. Stringfellow and L.P. - biology of commercially and recreationally Raines (2002). Variations in sex, length and important species, State Pollution Control age compositions of commercial catches of Commission of New South Wales. Platycephalus fuscus (Pisces: ) in New South Wales, Australia, Marine and Freshwater Broadhurst, M.K., C.A. Gray, D.D. Reid, M.E.L. Wooden, Research 53: 1019-1100. D.J. Young, J.A. Haddy and C. Damiano (2005). Mortality of key fish species released by recreational Henry, G.W. and J.M. Lyle (2003). The National anglers in an Australian estuary, Journal of Recreational and Indigenous Fishing Survey. Final Experimental Marine Biology and Ecology 321: 171- Report to the Fisheries Research & Development 179. Corporation and the Fisheries Action Program Project FRDC 1999/158. NSW Fisheries Final Report Broadhurst, M.K., C.A. Gray, D.J. Young and D.D. Series No. 48. 188 pp. Cronulla, NSW Fisheries. Johnson (2003). Relative efficiency and size selectivity of bottom-set gillnets for dusky flathead Potter, I.C. and G.A. Hyndes (1999). Characteristics Platycephalus fuscus, and other species in New of the ichthyofaunas of southwestern Australian South Wales, Australia, Archive of Fishery and Marine estuaries, including comparisons with holarctic Research 50 (3): 289-302. estuaries and estuaries elsewhere in temperate Australia: A review. Australian Journal of Ecology 24: Gray, C.A. (2002). Management implications of 395-421. discarding in an estuarine multi-species gill net fishery, Fisheries Research 56: 177-192. Queensland Fisheries. (2010). Stock status of Queensland’s fisheries resources 2009-10. Gray, C.A., B.C. Pease, S.L. Stringfellow, L.P. Raines, B.K. Queensland, Department of Employment, Economic Rankin and T.R. Walford (2000). Sampling estuarine Development and Innovation: 65 pp. fish species for stock assessment, FRDC Project 94/042. NSW Fisheries Final Report Series No. 18. Steffe, A.S. and D.J. Chapman (2003).A survey of Cronulla, NSW Fisheries: 196 pp. daytime recreational fishing during the annual period, March 1999 to February 2000, in Lake Gray, C.A., D.D. Johnson, D.J. Young and M.K. Macquarie, New South Wales. Final Report Series Broadhurst (2003). Bycatch assessment of the No. 52. Sydney, NSW Fisheries. 124 pp. Estuarine Commercial Gill Net Fishery in NSW. Final Report to Fisheries Research and Development Steffe, A.S., J.J. Murphy, D.J. Chapman and C.C. Gray Corporation. Project 2000/172. (2005). An assessment of changes in the daytime recreational fishery of Lake Macquarie following Gray, C.A., D.D. Johnson, D.J. Young and M.K. the establishment of a ‘Recreational Fishing Haven’. Broadhurst (2004). Discards from the commercial Final Report Series No. 79. Cronulla, NSW Fisheries. gillnet fishery for dusky flathead,Platycephalus 103 pp. fuscus, in New South Wales, Australia: spatial variability and initial effects of change in minimum Steffe, A.S., J.J. Murphy, D.J. Chapman, G.P. Barret and legal length of target species, Fisheries Management C.C. Gray (2005). An assessment of changes in the and Ecology 11: 323-333. daytime, boat-based, recreational fishery of the Tuross Lake estuary following the establishment of a Gray, C.A., D.D. Johnson, M.K. Broadhurst and D. Young ‘Recreational Fishing Haven’. Final Report Series (2005). Seasonal, spatial and gear-related influences No. 81 Cronulla, NSW Fisheries. 70 pp. on relationships between retained and discarded catches in a multi-species gillnet fishery, Fisheries Steffe, S., J. Murphy, D. Chapman, B.E. Tarlington, Research 75: 56-72. G.N.G. Gordon and A. Grinberg (1996). An assessment of the impact of offshore recreational Gray, C., A., and L. M. Barnes (2008). Reproduction and fishing in New South Wales on the management of growth of dusky flathead Platycephalus( fuscus) in commercial fisheries. Project no. 94/053. Sydney, NSW estuaries. Final Report Series No. 101. Cronulla, NSW Fisheries Research Institute: 139 pp. NSW Department of Primary Industries: 26 pp West, R.J. (1993). Estuarine fisheries resources of two Gray, C.A., M.K. Broadhurst, D.D. Johnson and D.J. south eastern Australian rivers. Sydney, University of Young (2005). Influences of hanging ratio, fishing NSW. PhD Thesis. height, twine diameter and material of bottom-set gillnets on catches of dusky flathead Platycephalus( fuscus) and non-target species in New South Wales, Please visit the CSIRO website, Australia, Fisheries Science 71: 1217-1228. http://www.marine.csiro.au/caab/ and search for the species code (CAAB) 37 296004, common name or scientific name to find further information.

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Disclaimer: The information contained in this publication is based on knowledge and understanding at the time of writing (April 2010). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of Industry and Investment NSW or the user’s independent adviser. p 102 | Dusky Flathead