94 



Abstract— Sex-specific demography 

 and reproductive biology- of stripey bass 

 [Lutjanus carponotatus l I also known as 

 Spanish flag snapper. FAO ) were exam- 

 ined at the Palm and Lizard island 

 groups, Great Barrier Reef ( GBR). Total 

 mortality rates were similar between 

 the sexes. Males had larger L . at both 

 island groups and Lizard Island group 

 fish had larger overall L_,, Female:male 

 sex ratios were 1.3 and 1.1 at the Palm 

 and Lizard island groups, respectively. 

 The former is statistically different 

 from 1, but is unlikely significantly 

 different in a biological sense. Females 

 matured on average at 2 years of age 

 and 190 mm fork length at both loca- 

 tions. Female gonadal lipid body indices 

 peaked from August through October, 

 preceding peak gonadosomatic indices 

 in October, November, and December 

 that were twice as great as in any 

 other month. However, ovarian stag- 

 ing revealed 50^ or more ovaries were 

 ripe from September through February, 

 suggesting a more protracted spawning 

 season and highlighting the different 

 interpretations that can arise between 

 gonad weight and gonad staging meth- 

 ods. Gonadosomatic index increases 

 slightly with body size and larger fish 

 have a longer average spawning season, 

 which suggests that larger fish produce 

 greater relative reproductive output. 

 Lizard Island group females had 

 ovaries nearly twice as large as Palm 

 Island group females at a given body 

 size. However, it is unclear whether 

 this reflects spatial differences akin 

 to those observed in growth or effects 

 of sampling Lizard Island group fish 

 closer to their date of spawning. These 

 results support an existing 250 mm 

 minimum size limit for L. carponotatus 

 on the GBR, as well as the timing of a 

 proposed October through December 

 spawning closure for the fishery. The 

 results also caution against assessing 

 reef-fish stocks without reference to 

 sex-, size-, and location-specific biologi- 

 cal traits. 



Sex-specific growth and mortality, spawning 

 season, and female maturation of the stripey bass 

 {Lutjanus carponotatus) on the Great Barrier Reef 



Jacob P. Kritzer 



School of Marine Biology & Aquaculture 



and CRC Reef Research Centre-Effects of Line Fishing Project 



James Cook University 



Townsville. Queensland 4811, Australia 



Present address: Department of Biological Sciences 



University of Windsor 



401 Sunset Avenue 



Windsor, Ontario N9B 3P4, Canada 

 E-mail address kntzenSuwindsorca 



Manuscript approved for publication 

 22 July 2003 by Scientific Editor. 



Manuscript received 22 July 2003 at 

 NMFS Scientific Publications Office. 



Fish Bull. 102:94-107 (2004). 



Lutjanid snappers are among the 

 most prominent species comprising 

 the catch of hook-and-line fisheries 

 on tropical reefs worldwide (Dalzell, 

 1996). A notable exception is the line 

 fishery on Australia's Great Barrier 

 Reef (GBR). There, the finfish catch, 

 and therefore the majority of fisheries 

 research, is dominated by coral trouts 

 of the genus Plectropomus (Mapstone et 

 al. 1 ). However, the GBR finfish harvest 

 is diverse and the catch of many sec- 

 ondary species has risen steadily since 

 the early 1990s (Mapstone et al. 1 ). 

 Furthermore, over the past decade, 

 the GBR fishery has changed with the 

 advent of the lucrative Asian live reef- 

 fish market. At present, only a handful 

 of the many species harvested on the 

 GBR are exported to the live reef-fish 

 market. However, continued expansion 

 of the trade coupled with the depletion 

 of fish stocks in other source nations 

 (Bentley 2 ) has the potential to intro- 

 duce demand for a wider range of spe- 

 cies. Even in the absence of changes in 

 the species composition of live reef-fish 

 exports, increased demand for second- 

 ary species due to changes in either 

 domestic preferences or availability of 

 primary species has the potential to 

 elevate harvest of currently nontarget 

 species (Kritzer, 2003). 



Effective multispecies management 

 of the GBR fishery will ultimately re- 

 quire understanding the biology of more 

 than simply the primary target species. 

 For example, spawning closures of the 

 fishery have been proposed for nine-day 



periods around the new moon in Octo- 

 ber, November, and December on the 

 rationale that this will protect spawn- 

 ing activity of a wide range of harvested 

 species (Queensland Fisheries Manage- 

 ment Authority 3 ). Yet, spawning season 

 information for species beyond the com- 

 mon coral trout {P. leopardus ) ( Ferreira, 

 1995; Samoilys. 1997 ) is nearly nonexis- 

 tent. The GBR fishery is in a fortunate 

 position with respect to management 

 of many species for which exploitation 

 is still at relatively low levels because 

 baseline biological characteristics can 

 be estimated before stock structure is 

 drastically altered by fishing. These da- 

 ta can then be used in both formulating 

 management strategies and monitoring 

 effects of fishing. 



1 Mapstone. B. D.. J. P. MacKinlay, and C. R. 

 Davies. 1996. A description of the com- 

 mercial reef line fishery log book data held 

 by the Queensland Fisheries Management 

 Authority. Report to the Queensland 

 Fisheries Management Authority. 480 p. 

 Primary Industries Building, GPO Box 4(i. 

 Brisbane. Queensland 4001. Australia. 



2 Bentley. N. 1999. Fishing for solutions: 

 can the live trade in wild groupers and 

 wrasses from Southeast Asia be managed? 

 TRAFFIC Southeast Asia report. 143 p. 

 Unit 9-3A, 3rd Floor. Jalan SS23/11, 

 Taman SEA. 47400 Petaling Java, Selan- 

 gor, Malaysia. 



3 Queensland Fisheries Management Auth- 

 ority. 1999. Queensland coral reef fin 

 fish fishery. Draft management plan and 

 regulatory impact statement, 80 p. Pri- 

 mary Industries Building. GPO Box 46, 

 Brisbane, Queensland 4001, Australia. 



