Finishing diet, genetics, and other culture conditions affect ovarian adiposity and caviar yield in cultured white sturgeon (Acipenser transmontanus)

Abstract

The on-going and precipitous decline in sturgeon abundance and increased demand for caviar have promoted the development of sustainable sturgeon aquaculture. One common problem that confounds caviar farming efficiency is highly variable roe yield associated with the proliferation of ovarian fat: sturgeon females with fatty ovaries tend to produce a smaller yield of inferior quality roe compared to those with lean ovaries. Here, we evaluated the effects of finishing diet, farm origin, age at maturity, tank, and genotype on ovarian adiposity and caviar yield in cultured white sturgeon (Acipenser transmontanus). We conducted a feeding trial in which fish aged 5+years at two different commercial farms were either maintained on a high fat production diet or received a low fat finishing diet for 19 and 33months before caviar harvest; at this time fish were aged 7 or 8years, respectively. Measurements of ovarian fattiness, caviar yield, and morphology were collected at the time of harvest. Microsatellite genotyping was performed to estimate relatedness among experimental fish and subsequent heritability of these traits. Mean caviar yield normalized by body weight increased from 7.6–8.6% to 8.0–9.2% and mean caviar yield scaled by ovary weight increased from 55.5–59.8% to 61.3–64.6% in white sturgeon fed the high and low fat diets, respectively. All females were classified post hoc according to degree of ovarian fattiness: low, medium, or high. Regardless of diet, farm, or age, females in the high ovarian adiposity group had larger body size, higher condition factor, but lower caviar yields than those in the low fattiness group because of the presence of large ovarian fat lobes and adipocytes surrounding individual oocytes. Furthermore, only 11.8–17.2% of female white sturgeon given the low fat finishing diet displayed a high degree of ovarian fattiness compared to 18.0–33.2% of those on the high fat diet. Robust negative correlations were found between measurements of ovarian adiposity and caviar yield further illustrating this inverse relationship observed by caviar farmers. The fixed effects of diet, farm, age, and tank all significantly influenced ovarian adiposity and caviar yield except farm origin did not significantly impact ovarian fat lobe weight. Heritability values for measurements of ovarian adiposity and caviar yield were moderate and ranged from 0.20–0.39, however heritability of ovarian tissue weight was slightly lower (h2=0.11). Our study demonstrates that finishing diet, farm origin, age at maturity, tank and genotype significantly affect and may be manipulated to increase caviar yield in cultured white sturgeon. Statement of relevanceStudy findings will increase sturgeon aquaculture profits.