Aquaculture America 2020

February 9 - 12, 2020

Honolulu, Hawaii

INVESTIGATIONS IN PRODUCING STERILE SUNSHINE BASS

David L. Straus*,  Anita M. Kelly, Herbert E. Quintero  and  Jason  W. Abernathy
 
USDA - A gricultural R esearch Service
 Harry K. Dupree - Stuttgart National Aquaculture Research Center
Stuttgart, AR  72160
Dave.Straus@usda.gov
 

Sunshine bass are an important food fish raised in US aquaculture.  Spawning of these hybrid striped bass is done by manual fertilization of female white bass eggs with male striped bass sperm.  The industry grows these fish to ~1.5 to 2 lbs  over ~1.5 to 2 years, during whi ch time the females can become fertile and produce eggs.  This is a major problem in the industry, as the majority of producers sell these fish whole and there is a considerable loss in weight (i.e., dollars) due to expulsion of eggs caused by handling stress;  eggs  prematurely released can also lead to considerable water quality issues.   Therefore, the industry needs a way to produce sterile fish.  

One way to produce sterile fish is  through the creation of triploids.  Triploidy can be induced through temperature  shock  applied  to the embryo shortly after fertilization ; so far, there has been only limited success.  We chose a range of temperatures and times post-fertilization to shock the eggs during initial trials .  L arvae  produced  were  then  checked for triploidy using a flow cytometer.  Based on these data, we chose the highest triploid rates from the cold- and warm-shocks  to continue trials.  A large-scale trial was performed and l arvae from both treatments  and a diploid control were spawned from a single batch of eggs .   Fish will be grown  for two years to examine growth and gross morphology.

From this large-scale trial, flow-cytometer results  on 2 -day old larvae indicated triploid production was 54% in the warm- and 52%  in the cold-shock treatment groups.   Fish  were transferred to a fertilized pond where the larvae ate zooplankton over 28 days and grew to about 2 cm .  There were few survivors in the cold-shock pond; none of these were triploid when checked with a Coulter Counter (CC).  T here were several thousand  fish in the warm-shock pond and a sample of 50 fish indicated  14% triploid (by CC) .   Diploid and  warm-shock triploid fish were then moved to separate growout ponds and fed commercial  hybrid striped bass diets for 5 months;  we then determined 7% success rate  (by CC)  of the  triploid survivors .  We will grow  these until spring spawning 2020 to verify maturation/ gamete production vs diploid fish from the same batch of eggs.