has allowed both temporal and spatial variability in 

 daily growth rates to be investigated (Graham and 

 Townsend 1985; Thomas 1986; Leak and Houde 

 1987). 



Although temperate clupeid species have been the 

 focus of considerable scientific attention (Blaxter 

 and Hunter 1982), the diverse assemblage of heavily 

 exploited clupeids of the tropical Indo-Pacific remain 

 poorly understood (Longhurst 1971; Whitehead 

 1985). There is a limited selection of literature avaU- 

 able on the Indian oil sardines {Sardinella aurita 

 and S. longiceps (e.g., Nair 1959; Raja 1970)), but 

 these species are not a conspicuous component of 

 nearshore fish communities in tropical Australia 

 (Whitehead 1985). Williams and Clarke (1983) have 

 examined growth in juvenile and adult Herklot- 

 sichthys quadrimaculatus from Hawaii using the 

 otolith increment technique. A. I. Robertson (MS in 

 prep.) has used length-frequency data to estimate 

 growth in juvenile Herklotsichthys castelnaui and 

 Sardinella albella from mangrove nursery areas in 

 tropical northeastern Australia. Dayaratne and 

 Gjosaeter (1986) analyzed age structure of juveniles 

 and adults in four species of Sardinella from Sri 

 Lanka using daily growth increments on otoliths. 

 Relatively few studies have measured larval age 

 and growth in field situations; these parameters 

 have not been reported for any tropical clupeid 

 species. 



In this paper, I examine daily increments in oto- 

 liths to determine some early life history parameters 

 of a common clupeid of tropical northeastern Aus- 

 tralia. Herklotsichthys castelnaui (Harengula abbre- 

 viata of many authors) is a coastal pelagic clupeid 

 found along the eastern seaboard of Australia from 

 Bloomfield (lat. 15°56'S) to Pambula (lat. 36°57'S; 

 Whitehead 1985). Although little is known of the 

 biology of H. castelnaui, it inhabits estuaries and 

 inlets (Robertson and Duke 1987), spawning in simi- 

 mer (January-March) in the southern parts of its 

 range (Blackburn 1941), but probably earlier in the 

 year in more northern areas (Robertson, MS in 

 prep.). There is no information available on larval 

 biology. 



The specific aims of this project were to 



1) validate daily growth increments in the otoliths 

 of larval H. castelnaui, 



2) obtain estimates of daily growth for larvae in 

 the field, 



3) investigate relationships between otolith size, 

 standard length, and age, and 



4) determine the frequency distribution of larval 

 birthdates during the spawning season. 



FISHERY BULLETIN: VOL. 87, NO. 1 



METHODS 



Collection of Larvae 



Larvae were collected weekly from Breakwater 

 Marina, Townsville, Australia (Fig. 1) during August 

 to November 1987. The marina is some 5.2 hectares 

 in area, with an average water depth of 5 m (mhw), 

 and is connected to Cleveland Bay by a 30 m wide 

 entrance. Water is flushed in and out of the marina 

 during the normal tidal cycle. Cleveland Bay is 

 shallow, approximately 25 km wide, and bounded 

 by Magnetic Island on its eastern side (Fig. 1). 

 Physical oceanographic parameters of the bay have 

 been described by Walker (1981a, b). 



Sampling was conducted at night using three flu- 

 orescent lamps sealed within a clear perspex tube 

 and a 1 m X 250 /im mesh size plankton net. The 

 lamps were switched on and the tube lowered into 

 the water from a jetty to a depth of 1.5 m. The 

 plankton net was then lowered approximately 3 m 

 below the tube. The lamps were left on for 15 min- 

 utes, then the plankton net was hauled rapidly up 

 over the perspex tube to the surface. This sequence 

 was repeated 4 times during a sampling night at 

 hourly intervals commencing at 20:00. 



Almost all larvae were alive upon net retrieval and 

 were transferred immediately into 98% ethanol for 

 subsequent sorting and analysis. Handling speci- 

 mens in this way minimized shrinkage (Theilacker 

 1980) and physical damage due to net capture 

 (McGurk 1985). 



Two species of clupeid larvae were collected from 

 samples taken in the Breakwater Marina. These 

 species were identified as H. castelnaui and Escua- 

 losa thoracata in a size series of specimens collected 

 during the sampling period. Details of the number 

 ofH. castelnaui larvae collected and numbers ana- 

 lyzed for age and growth are given in Table 1. 



Table 1.— Summary of sampling dates in 1987, number 

 of Herklotsichthys castelnaui collected and numbers sub- 

 sequently used for otolith examination. 



74 



