EFFECTS OF ACCLIMATION ON THE TEMPERATURE 



AND SALINITY TOLERANCE OF THE YOLK-SAC LARVAE 



OF BAIRDIELLA ICISTIA (PISCES: SCIAENIDAE)i 



Robert C. May' 



ABSTRACT 



Eggs of the bairdiella, Bairdiella icistia, were fertilized and incubated in various combinations of 

 temperature and salinity, and the salinity and upper thermal tolerances of the yolk-sac larvae were 

 determined. The upper thermal tolerance was enhanced by acclimation to high temperatures and low 

 salinities. Acclimation to low salinities enhanced the lower salinity tolerance of larvae at 24 h after 

 exposure to test conditions, but an acclimation effect on the upper salinity tolerance was not apparent 

 until 48 h after exposure. Yolk-sac bairdiella larvae are more tolerant than the embryonic stages and 

 less tolerant than adults to extremes of temperature and salinity. 



Techniques for inducing gonadal maturation and 

 spawning under laboratory conditions are well 

 developed for the bairdiella, Bairdiella icistia 

 (Jordan and Gilbert), a sciaenid fish native to the 

 Gulf of California and now present in the Salton 

 Sea (Haydock 1971; May 1975). Hence bairdiella 

 eggs and larvae are extremely favorable material 

 for studying various facets of early development 

 in a marine fish, and detailed information on the 

 effects of temperature and salinity on fertiliza- 

 tion, embryonic development, and hatching in this 

 species has already been presented (May 1975). 

 The present paper is concerned with the effects of 

 acclimation on the tolerance of yolk-sac bairdiella 

 larvae to temperature and salinity. 



Acclimation has been defined as "the process of 

 bringing the animal to a steady state by setting 

 one or more of the conditions to which it is exposed 

 for an appropriate time before a given test (Fry 

 1971:14)." In the case of yolk-sac larvae of tropical 

 fish species which develop very rapidly, the term 

 acclimation has a somewhat special meaning, since 

 it necessarily refers to the conditions obtaining 

 during embryonic development. Virtually no 

 studies of acclimation in this context have here- 

 tofore been published. Although salinity has been 

 shown to affect the upper thermal tolerance of 



'Based on a portion of a dissertation submitted in partial sat- 

 isfaction of the requirements for the Ph.D. degree at the 

 University of California at San Diego, Scripps Institution of 

 Oceanography. 



^Hawaii Institute of Marine Biology, P.O. Box 1346, Kaneohe, 

 HI 96744. 



adult fish (e.g., Garside and Jordan 1968), no com- 

 parable work has been reported for fish larvae. 

 This paper investigates the upper thermal 

 tolerance of newly hatched bairdiella larvae and 

 the modifying influence of acclimation, i.e., the 

 influence of temperature and salinity during 

 embryonic development. Since there is little 

 likelihood that bairdiella larvae would encounter 

 lower lethal temperatures in nature (May 1975), 

 their lower thermal tolerance is not considered 

 here. In addition to upper thermal tolerance, the 

 upper and lower salinity tolerance of larval bair- 

 diella and the effect of the acclimation salinity are 

 also considered in this paper. This information, 

 together with results on embryonic tolerances 

 described earlier (May 1975) and available infor- 

 mation concerning adult tolerances, should lead to 

 a conclusion as to which stage in the life history of 

 bairdiella is the most sensitive to temperature and 

 salinity. 



METHODS 

 General 



Bairdiella eggs were obtained from fish which 

 had been held in normal seawater i^2t^/oo) and 

 induced to mature and spawn in the laboratory, as 

 described previously (May 1975). Eggs were ar- 

 tifically fertilized at specified temperatures 

 (within ±0.2°C) and salinities (±0.5''/oo) and 

 maintained under the same conditions until 

 hatching in specially designed incubators (May 



Manuscript accepted June 1974 



FISHERY BULLETIN: VOL. 73, NO. 2, 1975. 



249 



