Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8604
Title: Effects of plant-based lipid feeds on hepatic and gastrointestinal histology and the gastrointestinal microbiome of sablefish (Anoplopoma fimbria)
Author: Linda D. Rhodes, Ronald B. Johnson, Mark S. Myers
Publication Year: 2016
Journal: Aquaculture
Volume: 464
Pages: 683-691
Keywords: alternative feeds,sablefish,histopathology,microbiome

Sablefish (Anoplopoma fimbria) is a highly desired seafood product, which encourages development of sustain- able aquaculture methods for this marine fish. Conventional marine fish-based feeds provide essential nutrients including long chain fatty acids for piscivorous species such as sablefish. Alternative terrestrial ingredients could reduce fishing pressures on pelagic species that are the source of fish meal and fish oil, and improve source sus- tainability. Using juvenile sablefish, we compared the effects of a standard fish-based diet to two diets that contained primarily terrestrial plant ingredients with flaxseed or corn oil replacing the added fish oil. After an 8-week trial feeding period, there were striking differences attributable to diet. Fish receiving the alternative feeds had lower weight gain and shorter length than fish receiving the fish-based feed, suggesting sablefish ob- tained lower nutrients from the alternative feeds. Among the histological differences, the intestinal mucosa was significantly less vacuolated and the frequency of intestinal mucous cells was reduced in alternative feed fish. The most dramatic lesions were observed in the liver, where severe bile duct hyperplasia (53%, flaxseed oil diet; 33%, corn oil diet), and hepatocellular lesions (nuclear pleomorphism/megalocytosis, regeneration, hypertrophy, clear cell foci) occurred in only alternative feed fish. The hepatic and biliary lesions indicate the alternative diets may be deficient or possibly harmful to sablefish. The bacterial community structures from corn oil fish showed much less diversity than those for the other diets, and the microbiome structures from the three diets were distinctly different from each other. The intestinal microbiome for the fish-based diet included the largest number of fam- ilies (68), and these fish also had the largest number of unique bacterial families (11) compared to those for corn oil (two) or flaxseed oil (one) fish. Regardless of diet, the stomach and intestinal microbiomes differed signifi- cantly from each other, and the feed microbiome differed from all gastrointestinal communities, suggesting that feed is not a significant source of gut bacterial diversity. Similar to other teleosts, the sablefish gastrointesti- nal microbiome is dominated by Bacteroidetes, Firmicutes, and Proteobacteria. These results suggest that diet- induced shifts in microbiome can occur relatively quickly in sablefish, but the shifts may not be sufficiently adap- tive or cannot overcome nutrient deficiencies. This multidisciplinary study demonstrates the utility of histology and microbiology in characterizing dietary effects for novel aquaculture species.

Statement of relevance: Physiological assessments such as gastrointestinal microbiomes and histopathology can provide a near-term evaluation of the nutritional adequacy of alternative feeds, such as plant-based lipid diets for marine carnivorous finfish. This is the first examination of the microbiome of sablefish, a marine species under development for sustainable aquaculture. 

Theme: Sustainable, safe and secure seafood for healthy populations and vibrant communities
Foci: Develop research and technology to foster innovative and sustainable approaches to aquaculture.