28 



Fishery Bulletin 93(1), 1995 



tigate the larval ecology of commercially important 

 fishes of South Australian waters. An important pre- 

 requisite of any such program is the ability to make 

 an accurate identification of larvae to species. This 

 paper details the development of Sillaginodes 

 punctata, Sillago schomburgkii, and S. bassensis lar- 

 vae collected during this study. 



Materials and methods 



Specimens were obtained from plankton and beach 

 seine samples collected between March 1986 and 

 March 1991 aboard the research vessel MRV Ngerin 

 in coastal waters and at various inshore nursery ar- 

 eas off South Australia. Details of sampling locations 

 and procedures are described in Bruce (1989). Briefly, 

 larvae were obtained from stepped oblique tows with 

 70-cm-diameter bongo nets fitted with 500-micron 

 mesh. Postsettlement (refer to definition below) lar- 

 vae and juveniles were captured with a fine mesh 

 beach seine (7 m x 1.8 m, 2-mm mesh) as well as by 

 dipnetting and diving. The field-collected series of 

 Sillaginodes punctata was supplemented with lar- 

 vae reared in the laboratory at West Beach, Adelaide. 



All field-collected specimens used for description 

 were fixed in a 10% formalin-seawater solution buff- 

 ered with sodium tetraborate (borax) and were later 

 transferred to a 5% solution buffered with sodium 

 B-glycerophosphate (0.5 g per 1,000 mL). Reared lar- 

 vae were fixed immediately in the 5% solution. 

 Reared S. punctata were used for illustration when 

 possible because of their superior condition. Some 

 pigment differences were apparent between reared 

 and field-collected larvae largely as a result of ex- 

 pansion or contraction of melanophores. Melano- 

 phores of field-collected larvae were generally less 

 expanded than reared specimens. Reared larvae were 

 typically greater in length than similarly developed 

 field-collected material owing to increased shrink- 

 age in the latter. Similar shrinkage effects have been 

 previously reported for a variety of species (Theilacker, 

 1980; Hay, 1981; Bruce, 1988). Unless specified, devel- 

 opment at length refers to field-collected material. 



Representative series of S. punctata and Sillago 

 bassensis are deposited with the I.S.R. Munro Fish 

 Collection, CSIRO, Hobart Tasmania. Too few S. 

 schomburgkii larvae were collected to allow a com- 

 plete analysis and all are currently held in a collec- 

 tion maintained by the author at CSIRO Division of 

 Fisheries, Hobart, Tasmania. 



Developmental terminology and body measure- 

 ments follow Leis and Trnski (1989). The term 

 "postsettlement" is used to describe newly settled 

 individuals prior to the acquisition of scales and ju- 



venile colour patterns, after which they are referred 

 to as juveniles. Body length measurements (BL) are 

 measured as notochord length, NL (i.e. from the snout 

 tip to the end of the notochord), in preflexion and 

 flexion larvae, and standard length, SL (i.e. from the 

 snout tip to the posterior margin of the superior 

 hypural elements), in postflexion larvae and juve- 

 niles. Body depth is taken at two points. Body depth 

 at pectoral (BDp) is equivalent to "body depth" as 

 defined by Leis and Trnski ( 1989), that is, as "the 

 vertical distance between body margins (exclusive 

 of fins) through the anterior margin of the pectoral 

 fin base." Body depth at anus (BDa) is defined as the 

 vertical distance between body margins (exclusive 

 of fins and, initially, the gut) through the midpoint 

 of the anal opening. BDa includes the gut only after 

 overlying musculature has developed. Sillaginodes 

 punctata eggs were measured with a Zeiss photomi- 

 croscope III fitted with an ITC 510 video camera and 

 linked to an Apple Macintosh SE computer via an 

 HEI 582A video coordinate digitizer. Egg dimensions 

 are reported to the nearest micron. Larvae were 

 measured to the nearest 0.1 mm with a dissecting 

 microscope fitted with an ocular micrometer. 

 Postsettlement larvae and juveniles were measured 

 to the nearest 0.1 mm with vernier calipers. 



Meristic counts were made on S. punctata and 

 Sillago bassensis specimens cleared and stained with 

 alcian blue and alizarin red-S following Potthoff 

 (1984). Insufficient specimens of S. schomburgkii 

 were available for clearing and staining and therefore 

 all meristics were taken from unstained material. 



Descriptions are based primarily on the detailed 

 examination of a representative series of specimens; 

 however, comments on pigment and meristic vari- 

 ability stem from the routine examination of all lar- 

 vae collected. The number of specimens examined in 

 detail, the size range covered, and the museum ref- 

 erence numbers (for lodged material) are provided 

 under each species account. 



Results 



Identification 



Larvae were identified to family level from larval 

 sillaginid characters reported in the literature. Silla- 

 ginid larvae are elongate and have 30-^t4 myomeres 

 (Johnson, 1984; Miskiewicz, 1987; Leis and Trnski, 

 1989). The gut typically reaches to greater than 55% 

 body length in preflexion larvae. The anus is reported 

 to migrate anteriorly during development (often dur- 

 ing flexion) as a result of coiling of the anterior sec- 

 tion of the gut, thus shortening the preanal length 



