ADDITION OF A RED MACROALGAE TO ALTERNATIVE PLANT BASED FEEDS FOR JUVENILE SABLEFISH Anoplopoma fimbria

Ronald B. Johnson*, Peter M. Nicklason, Lisa C. Armbruster, Frank C. Sommers, Junghoon JEE, David Marancik, Brad A. Gadberry, John E. Colt
 
NOAA Fisheries
Northwest Fisheries Science Center
2725 Montlake Blvd E.
Seattle, WA 98112
*email: ronald.b.johnson@noaa.gov
 

Sablefish is a cold-water marine fish of the Eastern Pacific Ocean with good economic potential for aquaculture. Previous research at our laboratory has demonstrated that sablefish have a dietary requirement for taurine when fed alternative, plant based feeds.  Terrestrial plant ingredients are void of taurine, but taurine is present in considerable amounts in some red macroalgae, including Turkish Towel Chondracanthus exasperates.  Macroalgae also contains many essential nutrients that may be limiting in terrestrial plant ingredients, including trace minerals, omega-3 fatty acids, and essential amino acids.  In addition, there appears to be health benefits associated with the use of macroalgae in aquaculture feeds for some fish species.  Turkish Towel, cultured intensively in land based tanks at NOAA's Manchester, WA laboratory, averages 24% protein and 0.8% taurine, on a dry weight basis.  The current research study aimed to assess the potential benefits of incrementally replacing wheat flour with Turkish Towel in a typical plant based diet for juvenile sablefish, with or without synthetic taurine supplementation.  The substitution of wheat flour with Turkish Towel resulted in slight increases in feed taurine concentrations.  

Fish growth significantly increased with the addition of taurine (p<0.001), and to a lesser extent, Turkish Towel (p=0.058) to the experimental feeds (Figure 1).  Feed efficiency and protein retention were significantly improved with the addition of taurine, but were not affected by Turkish Towel addition.  Liver histomorphology was generally normal; however evidence of cellular alteration was present in some fish by the end of the experiment.   The number of fish affected was lower among fish receiving feeds containing Turkish Towel.  In particular, fish with hepatocellular nuclear pleomorphism and clear cell foci were significantly fewer (p<0.05) among algae fish.  The addition of taurine to experimental feeds had no effect on liver histomorphology.  Overall, results from this study reaffirm taurine supplementation is beneficial to sablefish receiving plant based feeds, and indicate Turkish Towel may be a promising alternative feed ingredient for cold water marine fish.