FISHERY BULLETIN: VOL. 85, NO. 2 



temperatures between 16° and 22° C and with a 

 minimum of 1,000-2,000 Artemia nauplii/L. The 

 optimum saUnity range was between 3.5 and 

 14.0"/oo (Bayless 1972). Davies (1973) studied larval 

 survival under combinations of temperature, pH, 

 and dissolved solids. Optimum temperature was 

 17.0°C; optimum pH, 7.5. Eldridge et al. (1981) 

 studied the growth of larvae under various feeding 

 regimes and found growth rates which approx- 

 imated field growth rates at concentrations of 5,000 

 ArtemialL. They found that the "point of no return" 

 was ill defined and starved larvae could live for as 

 long as 31 days. Dey (1981) has reported on growth 

 and survival of wild larvae, using length and 

 developmental stage to estimate growth. He found 

 growth was temperature dependent and tempera- 

 tures between 12° and 15°C resulted in massive 

 mortalities. 



The purpose of this study was to determine the 

 relationship between age, environmental condition, 

 and otolith increment depositional rates in labora- 

 tory-raised striped bass larvae. This was accom- 

 plished by studying the increments of known-age lar- 

 vae reared under both optimal laboratory conditions 

 and restricted feeding regimes (laboratory-simulated 

 suboptimal field conditions). Larvae were subjected 

 to various periods of food deprivation to determine 

 the potential dependence of increment depositional 

 rates on nutritional condition. Specifically, incre- 

 mental counts made with light microscopy and SEM 

 were compared to evaluate the reality of apparent 

 interruptions of daily deposition. 



METHODS 



Striped bass eggs were obtained from the Ver- 

 plank Hatchery, Verplank, NY, within 24 hours of 

 fertilization. Eggs were held in water obtained at 

 the hatchery (O'Vi,,, salinity) at 18°C, under a 14L: 

 lOD photoperiod. Light levels were 25-31 n Ein- 

 steins/m- per second. This light level is approx- 

 imately equal to light at a depth of 2-3 m in a coastal 

 stream or 1 m in a coastal estuary depending on tur- 

 bidity and season of the year. Eggs hatched within 

 24 hours of fertilization. Newly hatched larvae were 

 transferred to 4 L jars and stocked at densities of 

 50 per liter. Over the first 8 days, salinities were 

 gradually raised to 5°/oo by adding filtered seawater 

 with 0"/()(i water. Seventy-six days after hatching of 

 the larvae, salinities were gradually raised to lO'Voo 

 over a span of 8 days. Water was changed at least 

 every other day. 



Four feeding conditions were established. The 

 food for all conditions was newly hatched brine 



shrimp, Artemia. Larvae were fed ad libitum (con- 

 dition 1), other larvae were starved throughout the 

 experiment (condition 2), and other larvae were 

 starved for the first 15 days after hatching, then fed 

 ad libitum (condition 3). Condition 4 consisted of lar- 

 vae that were intermittently deprived of food. These 

 larvae were not fed between 39-43, 51-55, and 62-66 

 days after hatching, for a total of 15 days out of the 

 68 days they were reared. For the remaining time 

 they were fed ad libitum. 



Larvae were sampled according to the schedule 

 listed in Table 1. Larvae that were sampled were 

 anesthetized with Tricaine methanesulfonate (Cre- 

 sent Research Chemical) and sacrificed. Total 

 length was measured to the nearest 0.1 mm. Oto- 

 liths were teased from the otic capsules with fine 

 dissecting needles, cleared of tissue, washed in de- 

 ionized water and transferred with a micropipette 

 or with fine dissecting needles to a labeled micro- 

 scope slide. 



Small otoliths were mounted permanently in 

 Ewparol without grinding. Larger otoliths were 

 mounted in Flowtex (Lerner Laboratories), ground 

 with 600 grit sandpaper and read with the light 

 microscope. A subsample of ground otoliths was re- 

 moved from the Flowtex, mounted in Spurr's me- 

 dium, and ground to the core on Beuhler lapidary 

 wheels. Initial grinding on the wheels began at 180 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Table 1 .—Sample size at age of striped bass larvae reared 

 under four feeding regimes. N.T. = not taken. 



172 



