ADDITION OF LATE SEASON SUGAR KELP Saccharina latissima TO ALTERNATIVE PLANT BASED FEEDS FOR JUVENILE SABLEFISH Anoplopoma fimbria

The demand for fishmeal and fish oil in aquaculture feeds, has increased dramatically in recent years.  Alternative protein and oil sources are needed if further development of the aquaculture industry is to be sustained. Terrestrial plant ingredients can replace a portion of the fishmeal used in feeds for a number of species.  Complete replacement, however, is seldom achieved.  Macroalgae may prove a more appropriate feed ingredient than terrestrial plants products for marine fish feeds as macroalgae contains many essential nutrients from the marine environment that are limiting in terrestrial plants.  There additionally appears to be health benefits associated with the use of some macroalgae species for some marine fish sp

With the emergence of kelp aquaculture in the United States, there is an opportunity to use off-product plants in marine fish feeds.  Off-product kelp is generally mature plants which are approaching senescence and unsuitable for human consumption.  The product is of low value and is either discarded at sea or processed into fertilizer.  

In this study, we incrementally added off-product sugar kelp to alternate plant based feeds for juvenile sablefish to evaluate the effect of this ingredient on fish growth, feed intake, feed efficiency, whole body nutrient composition, and liver condition.  Four isonitrogenous feeds were prepared with 0, 2.5, 5, and 7.5% late season sugar kelp.  As kelp was added, soy, corn, and wheat ingredients were proportionately removed from the diets.  Kelp was sourced from Hood Head Mariculture, Bainbridge Island, WA, USA in Spring 2018.

Fish grew well during the 8 week the study with 100% survival.   Feed intake increased with the addition of kelp to the feeds (P < 0.001, Figure).  Growth was similar among treatments (P = 0.186), but was numerically highest among 5% kelp fish.  Whole body lipid content was also affected by kelp addition (P = 0.060), with 5% kelp fish having the highest lipid content.  Feed efficiency and protein retention were inversely correlated with the addition of kelp to the feeds (P = 0.002 and P = 0.001, respectively), and we encountered physical limitations to extruding feeds containing higher than 7.5% kelp.  Future research activities directed at increasing kelp content in extruded feeds and improving feed efficiencies will be discussed.