Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

THE EFFECTS OF FOOD LEVEL AND STOCKING DENSITY ON GROWTH AND SURVIVAL OF YELLOWFIN TUNA Thunnus albacares AND PACIFIC BLUEFIN TUNA Thunnus orientalis LARVAE

Daniel Margulies *, Yole Buchalla, Susana Cusatti, Vernon Scholey , Aki Miyashima, Yasuo Agawa,  Tomoki Honryo, Yoshifumi Sawada

Inter-American Tropical Tuna Commission

 8901 La Jolla Shore Drive, La Jolla CA 92037

dmargulies@iattc.org

 



A comparative study  investigating the effects of food level and stocking density on growth and survival  of larvae  was conducted with yellowfin tuna (YFT) Thunnus albacares at  the  Achotines Laboratory, Inter-American Tropical Tuna Commission (IATTC), Republic of Panama , and Pacific bluefin tuna (PBF) Thunnus orientalis at Oshima Station, Kindai University, Japan, in May and July of 2023.

Larvae of each species were  tested  during the first 10 days of feeding  (DOF)  under  replicated combination  treatments of low and high  food levels (500 rotifers/L and 5000 rotifers/L), and low and high  initial stocking densities (5 larvae/L and 15 larvae/L) .  The  replicated  treatments were:  High F ood: Low Density (HF:LD ); Low F ood: Low D ensity (LF:LD); High F ood: High D ensity (HF:HD); and Low F ood: High Density (LF:HD).

 Larvae were sampled on  1  DOF, 6 DOF and 11 DOF, and measurements of standard length (SL), and dry weight (WT) were obtained . On the last day of  the experiment ,  all individual larvae from each tank were manually counted and an estimation of  expected  survival rate and standardized biomass of  each treatment  cohort were made.

With YFT larvae , both food level and density  significantly affected growth in SL and WT (ANOVA, P < 0.01) . With PBF larvae , however, only food level  significantly affected final SL and WT (ANOVA, P < 0.01), and density only affected  growth  significantly when interacting with food level (P = 0.016) .  At all treatment levels except the LF:HD level, specific growth rate (SGR)  in dry weight  was higher for YFT  compared to PBF  and ranged from 28-33%/d, while SGR for PBF ranged from  27-30%/d. In the LF:HD treatment, SGR  in dry weight  was nearly the same for both species (23-24%/d).  Survival rates  on DOF 11  were  higher for YFT compared to PBF over all treatments ,  and ranged from 5 -22%, including a surprisingly-high level of 20% at the LF:LD treatment. For YFT, there were statistically significant differences in final survival among treatments (ANOVA, P< 0.05), and stocking density significantly affected final survival .   Over all treatments, mean survival at DOF 11 for PBF ranged from 4-14% , and  no  significant differences in survival  were detected  among food treatment s, although food  level had a stronger e ffect than density on survival . With both species, only food level had a significant effect on standardized biomass of the cohort ( ANOVA, P < 0.05) .

Food level strongly affects growth of both species , with stocking  density exhibiting a pronounced effect on YFT survival.  YFT exhibit surprisingly strong survival and growth under low density conditions. Both species  show high potential as candidate species for marine aquaculture.