169 



Abstract — Age estimates for striped 

 trumpeter (Latris lineata) from Tas- 

 manian waters were produced by 

 counting annuli on the transverse 

 section of sagittal otoliths and were 

 validated by comparison of growth 

 with known-age individuals and 

 modal progression of a strong recruit- 

 ment pulse. Estimated ages ranged 

 from one to 43 years; fast growth 

 rates were observed for the first five 

 years. Minimal sexual dimorphism 

 was shown to exist between length, 

 weight, and growth characteristics of 

 striped trumpeter. Seasonal growth 

 variability was strong in individuals 

 up to at least age four, and growth 

 rates peaked approximately one month 

 after the observed peak in sea surface 

 temperature. A modified two-phase 

 von Bertalanffy growth function was 

 fitted to the length-at-age data, and 

 the transition between growth phases 

 was linked to apparent changes in 

 physiological and life history traits, 

 including offshore movement as fish 

 approach maturity. The two-phase 

 curve was found to represent the 

 mean length at age in the data better 

 than the standard von Bertalanffy 

 growth function. Total mortality 

 was estimated by using catch curve 

 analysis based on the standard and 

 two-phase von Bertalanffy growth 

 functions, and estimates of natural 

 mortality were calculated by using 

 two empirical models, one based on 

 longevity and the other based on the 

 parameters L, and k from both growth 

 functions. The interactions between 

 an inshore gillnet fishery targeting 

 predominately juveniles and an off- 

 shore hook fishery targeting predomi- 

 nately adults highlight the need to 

 use a precautionary approach when 

 developing harvest strategies. 



Age validation, growth modeling, 

 and mortality estimates for striped trumpeter 

 (Latris lineata) from southeastern Australia: 

 making the most of patchy data 



Sean R. Tracey 



Jeremy M. Lyle 



Marine Research Laboratories 



Tasmanian Aquaculture and Fisheries Institute 



Private Bag 49 



Hobart 7001, Tasmania, Australia 



E-mail address (for S R Tracey): straceyigutas edu au 



Manuscript submitted 20 December 2003 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



7 September 2004 by the Scientific Editor. 



Fish. Bull. 103:169-182 (2005). 



Striped trumpeter (Latris lineata) are 

 widely distributed around the tem- 

 perate latitudes of southern Austra- 

 lia, New Zealand (Last et al., 1983), 

 the Gough and Tristan Da Cunha 

 Island groups in the southern Atlan- 

 tic Ocean (Andrew et al, 1995), and 

 the Amsterdam and St. Paul Island 

 groups in the southern Indian Ocean 

 (Duhamel, 1989). They are opportu- 

 nistic carnivores associated with epi- 

 benthic communities over rocky reefs 

 at moderate depths from 5 to 300 m 

 along the continental shelf. The spe- 

 cies can grow to a relatively large 

 size, 1200 mm in total length and 25 

 kg in weight (Gomon et al., 1994). 

 Spawning apparently occurs offshore, 

 and females are highly fecund mul- 

 tiple-spawners (Furlani and Ruwald, 

 1999). Although there have been a 

 number of ichthyoplankton surveys in 

 Tasmanian waters, only a few striped 

 trumpeter larvae have been collected, 

 caught during the late austral winter 

 through early spring months at near- 

 shore (30-50 m) and shelf edge sites 

 (-200 m) (Furlani and Ruwald, 1999). 

 Larval rearing trials have shown that 

 the presettlement phase is complex 

 and extended; individuals can remain 

 in this neritic-pelagic phase for up 

 to 9 months after hatching before 

 metamorphosis into the juvenile stage 

 takes place (Morehead 1 ). As juveniles 

 striped trumpeter settle on shallow 

 rocky reefs. 



In Tasmania striped trumpeter 

 are taken commercially over inshore 

 reefs (5 to 50 m), generally as a by- 



catch of gillnetting, and are targeted 

 with hook methods (handline, drop- 

 line, longline, and trotline) on deeper 

 reefs (80 to 300 m). Small, subadult 

 individuals dominate inshore catches, 

 whereas larger individuals are taken 

 from offshore reefs. In recent years 

 the combined annual commercial 

 catch has been typically less than 100 

 metric tons (Lyle 2 ). Striped trumpeter 

 also attract significant interest from 

 recreational fishermen, who use both 

 hooks and gill nets. Furthermore, 

 the aquaculture potential for this 

 species is currently being assessed 

 in Tasmania (Furlani and Ruwald, 

 1999; Cobcroft et al., 2001). Despite 

 wide interest in this species, there is 

 a general paucity of information on 

 age, growth, and stock structure of 

 wild populations. 



Assessing the growth of a species is 

 a fundamental part of fisheries popu- 

 lation dynamics. Ever since Beverton 

 and Holt (1957) introduced the von 

 Bertalanffy growth model to fisheries 

 research it has become ubiquitous in 

 descriptions of the increase in size 



1 Morehead. D. 2003. Personal commun. 

 Tasmanian Aquaculture and Fisheries 

 Institute, Univ. Tasmania. GPO Private 

 Bag 49, Hobart, Tasmania, Australia 

 7001. 



2 Lyle. J. M. 2003. Tasmanian scale- 

 fish fishery — 2002. Fishery assessment 

 report of the Marine Research Laborato- 

 ries, Tasmanian Aquaculture and Fish- 

 eries Institute, Tasmania. [Available 

 from TAFI GPO Private Bag 49, Hobart, 

 Tasmania, Australia 7001.] 



