HOUDE and LUBBERS: SURVIVAL AND GROWTH OF STRIPED BASS 



striped bass from the Patuxent River. Sperm from 

 Patuxent River male striped bass were used to fer- 

 tilize eggs. The hybrids resulted from fertilization 

 by Tennessee white bass males and Patuxent River 

 white perch males. 



Larvae were held in hatchery troughs and fed 

 Artemia nauplii from 6 to 8 d after hatching. A total 

 of 2,500 9-d-old larvae were stocked in each en- 

 closure on 12 May 1983. Larvae were sampled by 

 dipnet and preserved in 5% Formalin at 13, 17, 20, 

 23, and 27 d after hatching. At 30 d all survivors 

 from each enclosure were counted and samples pre- 

 served. Temperatures in the pond ranged from 

 18.5° to 22.0°C during the course of the experiment. 



Pond Zooplankton 



The kinds and abundances of potentially edible 

 zooplankton were sampled on each day that larvae 

 were collected, using a 15 cm diameter, 72 pm mesh 

 plankton net that was lifted vertically in each 

 enclosure. For comparison, zooplankton also was 

 collected in three vertical lifts of the net outside the 

 enclosures. 



Analysis 



Survival, lengths and weights at age, growth 

 rates, and weight-length relationships were cal- 

 culated as for the laboratory experiments. Variance, 

 covariance, and regression analyses were used to 

 test for differences in means among the striped bass 

 and two types of hybrid larvae. 



RESULTS 



Laboratory Experiments 



Survival 



Survival at 30 d after hatching ranged from 45.8 

 to 85.4% (Table 1). Mean percentage survivals were 

 striped bass, 84.7%; white bass hybrid, 60.4%; and 

 white perch hybrid, 73.1%. The mean expected 

 number of survivors differed significantly among 

 types of larvae (ANOVA, P < 0.05). Mean survival 

 of striped bass was significantly higher than that 

 of the white bass hybrids (SNK multiple comparison 

 procedure, P < 0.05). There were no detectable dif- 

 ferences in mean survival between the two Artemia 

 nauplii feeding levels (ANOVA, P > 0.05). 



Size-at-Age 



The white perch hybrid larvae were significantly 

 shorter and weighed less than either striped bass 

 or white bass hybrid larvae when the experiments 

 began at 6 d after hatching, before larvae had been 

 fed (Table 2; ANOVA, P < 0.05). 



At 30 d after hatching there were some statistical- 

 ly significant differences in mean lengths and 

 weights among the three types of larvae, and be- 

 tween the two food levels, but no clear result was 

 obtained (Table 2). No significant differences among 

 mean lengths or weights of the white bass hybrid 

 larvae were detected between the 100 L _1 and 500 

 L _1 food levels. But, the striped bass and white 



Table 1.— Survival at 30 d after hatching of striped bass (SB), striped bass x white bass (WBX), 

 and striped bass x white perch (WPX) larvae in laboratory experiments at two food levels. 



Larvae 



and 



experiment 



numbers 



Artemia 

 concentration 

 (number L" 1 ) 



Number 

 preserved 



Number 



of 

 survivors 



Expected 

 number 1 



of 

 survivors 



Expected 

 instantaneous 

 daily mortality 



rates (Z) 



Expected 



percentage 



survival 



SB-1 

 SB-2 

 SB-3 



SB mean 



WBX-1 

 WBX-2 

 WBX-3 



WBX mean 



WPX-1 

 WPX-2 

 WPX-3 



WPX mean 



500 

 500 

 100 



500 

 500 

 100 



500 

 500 

 100 



91.3 



105.3 



0.0130 



73.1 



'Expected number of survivors is the adjusted number, accounting for samples of larvae that were preserved dur- 

 ing the experiment (see Methods). 



2 The SB mean differed significantly from the WBX and WPX means (Analysis of variance followed by SNK multiple 

 comparison procedure, P < 0.05). 



907 



