75 



Abstract — The population biology 

 and status of the painted sweeplips 

 iDiagramma pictum) and spangled 

 emperor (Lethrinus ncbiilosus) in the 

 southern Arabian Gulf were estab- 

 lished by using a combination of 

 size-frequency, biological, and size- 

 at-age data. Transverse sections of 

 sagittal otoliths were characterized 

 by alternating translucent and opaque 

 bands that were validated as annuli. 

 Comparisons of growth characteris- 

 tics showed that there were no sig- 

 nificant differences (P>0.05) between 

 sexes. There were well defined peaks 

 in the reproductive cycle, spawning 

 occurred from April to May for both 

 species, and the mean size at which 

 females attained sexual maturity was 

 31.8 cm fork length (Lp) for D. pictum 

 and 27.6 cm (Lp) for L. nebulosus. The 

 mean sizes at first capture (21.1 cm 

 Lp for D. pictum and 26.4 cm Lp for 

 L. nebulosus) were smaller than the 

 sizes for both at first sexual maturity 

 and those at which yield per recruit 

 would be maximized. The range of 

 fishing-induced mortality rates for 

 D. pictum (0.37-0.62/yr) was sub- 

 stantially greater than the target 

 (F„p, = 0.07/yr) and limit lF,,^„ = 0.09/ 

 yr) estimates. The range of fishing- 

 induced mortality rates for L. nebu- 

 losus (0.15/yr to 0.57/yr) was also in 

 excess of biological reference points 

 (F„p^ = 0.10/yr and F,,^„ = 0.13/yr). In 

 addition to growth overfishing, the 

 stocks were considered to be recruit- 

 ment overfished because the biomass 

 per recruit was less than 20'^* of the 

 unexploited levels for both species. 

 The results of the study are important 

 to fisheries management authorities in 

 the region because they indicate that 

 both a reduction in fishing effort and 

 mesh-size regulations are required 

 for the demersal trap fishery. 



Biology and assessment of the painted sweetlips 

 iDiagramma pictum (Thunberg, 1792)) and the 

 spangled emperor (Lethrinus nebulosus 

 (Forsskal, 1775)) in the southern Arabian Gulf 



Edwin M. Grandcourt 



Thabit Z. Al Abdessalaam 



Ahmed T. Al Shamsi 



Franklin Francis 



Marine Environment Research Centre 



Environmental Research and Wildlife Development Agency 



Corniche Road 



P O Box 45553 



Khalidlya 



Abu Dhabi, United Arab Emirates 



E-mail address (for E M Grandcourt) egrandcourtS'erwdagovae 



Manuscript submitted 29 December 

 2003 to the Scientific Editors Office. 



Manuscript approved for publication 

 11 July 2005 by the Scientific Editor. 



Fish. Bull. 104:75-88 (2006). 



The painted sweetlips iDiagramma 

 pictum (Thunberg, 1792)). is a member 

 of the family Haemuli(iae and is 

 widely distributed throughout the 

 Indo-West Pacific, from the Red Sea 

 and East Africa to Japan and New 

 Caledonia (Randall et al., 1997). 

 Adults are found in shallow coastal 

 waters and coral reefs down to a depth 

 of 80 m, and juveniles are often found 

 in weedy areas (Smith and McKay, 

 1986). The diet of this species consists 

 of benthic invertebrates and fishes 

 (Sommer et al., 1996). It is a rela- 

 tively large tropical species attaining 

 100 cm fork length and 6 kg in total 

 weight (Torres, 1991); consequently it 

 is exploited throughout its range with 

 a variety of gears, including hand- 

 lines, traps, and nets (Fischer and 

 Bianchi, 1984). Diagramma. pictum 

 has a gonochoristic reproductive mode 

 and spawning occurs annually with 

 one clear seasonal peak (Breder and 

 Rosen, 1966). 



Fishes of the family Lethrinidae 

 are abundant in the coastal tropical 

 and subtropical Indo-Pacific (Young 

 and Martin, 1982). The spangled em- 

 peror (Lethrinus nebulosus (Forsskal, 

 1775)), is distributed throughout the 

 Indo-West Pacific from the Red Sea 

 and East Africa to southern Japan 

 and Samoa. It is found in a variety 

 of habitats including coral reefs, sea 

 grass beds and mangroves from near 

 shore to a depth of 75 m (Randall, 



1995). Adults are either solitary or 

 are found in small schools, and ju- 

 veniles form large schools in shal- 

 low, sheltered sandy areas. The diet 

 of this species is mainly composed 

 of moUusks, crustaceans, polychaete 

 worms, and echinoderms (Fischer and 

 Bianchi, 1984). 



As with other representatives of 

 the family Lethrinidae, L. nebulosus 

 is a protogynous hermaphrodite, and 

 sexual transformation from female to 

 male occurs over a wide range of sizes 

 (Young and Martin, 1982; Ebisawa, 

 1990). Lethrinids are considered to 

 have long spawning seasons, running 

 from spring to at least early fall, with 

 spring and fall peaks. Spawning oc- 

 curs after dark for most species in 

 aggregations along the inner or outer 

 edge of the fringing reef (Johannes, 

 1981). Lethrinus nebulosus is a large 

 tropical species reaching 80.0 cm total 

 length and 8.4 kg total weight (Ran- 

 dall, 1995) and is exploited through- 

 out its range with a variety of gears 

 (Fischer and Bianchi, 1984). 



Both species form an important part 

 of fisheries landings in the southern 

 Arabian Gulf, where they are mainly 

 caught with dome-shaped wire traps 

 that have a hexagonal mesh of ap- 

 proximately 3.5 cm in diameter. 

 Traps are either set individually or 

 in strings from traditional wooden 

 dhows, sets are made to a maximum 

 depth of 40 m, and vessels fish an 



