Effect of dietary fat on adipocyte size in farmed age‐2 white sturgeon ( Acipenser transmontanus , Richardson, 1836)

Abstract

Summary Determining the age at which farmed sturgeon begin storing ovarian fat will potentially enable sturgeon farmers to adjust husbandry practices, such as feeding different dietary fat levels at an early age. We investigated the influence of dietary fat on the size of ovarian adipocytes in farmed age‐2 white sturgeon Acipenser transmontanus. At age 1 month, all fish were fed a commercial high fat (HF; 17% fat) diet. At age 6 months, half were transitioned to an experimental low fat (LF; 9% fat) diet. Fish at this time averaged 160 g (±30 g), and individual tank density was 4.1 kg/m3. Tanks were 3.7 m in diameter, 1.3 m deep, each with a volume of 13.7 m3. Each tank maintained a flow rate of 150 L/min using groundwater with water temperatures ranging from 19 to 21°C and dissolved oxygen ranging from 6.5 to 12.0 ppm. All fish were fed the diet assigned to their tank for an additional 18 months prior to sampling. At age 25 months (now referred to as “age 2”), tissue was collected from fish and processed histologically. Adipocytes were measured along the ovarian fold (anterior), furthest from the ovarian fold (posterior), and randomly in between the anterior and posterior sections. Randomly chosen adipocytes from each location were measured histologically. Mean adipocyte size did not statistically differ among sample locations in fish fed the same diet. Once pooled by sampling location, average adipocyte size was 5,491.18 μm (±98.97) in fish fed the HF diet and 3,348.62 μm (±40.85) in fish fed the LF diet. Fish fed the HF diet had larger adipocytes than fish fed the LF diets (t = 20.01, df = 78.54, p < .01). The results demonstrate that diet can influence the size of adipocytes found in juvenile white sturgeon ovaries. Additional research is needed to determine whether the accumulation of large adipocytes as a juvenile confers to adulthood and influences reproductive ability and caviar yield and quality.

A microwave energy meter to estimate energetic reserves in juvenile sturgeon

“…Fatmeter measurements detected muscular, not visceral lipid content (Davidson & Marshall, 2010). In Acipenseriformes, lipid stores tend to be higher in gonads (Treanor et al, 2017), liver, and peritoneum (Singer & Ballantyne, 2004) for estimating whole-body energetic reserves in fish smaller than 320 mm, Fatmeter measurements together with size and condition metrics were effective at explaining 40 to 45% of variation in wholebody energetic reserves of larger fish, a modest improvement upon models including only size and relative condition as predictors. These results were notably lower compared to previous studies on fishes with musculature-oriented fat reserves (Tables 1 and 4).…”

Accuracy of histology, endoscopy, ultrasonography, and plasma sex steroids in describing the population reproductive structure of hatchery‐origin and wild white sturgeon

“…In both those studies, accuracy was influenced by a portion of samples that did not contain germ cells, stressing the importance of recognizing gonadal tissue during sample collection which can be challenging in the field without adequate training. Lastly, while a biopsy collected in the field may be successful in collecting gonadal tissue, the tissue can also contain adipocytes (Treanor et al, 2018) and somatic cells and may not always contain germ cells, thus influencing the accuracy when assigning sex or stage of maturity.…”

Histological Evaluation of Gonad Impairments in Russian Sturgeon (Acipenser gueldenstaedtii) Reared in Recirculating Aquatic System (RAS)

“…Under RAS conditions, an energetic surplus can be easily achieved, which can result in increased visceral fat deposition and subsequently lead to an imbalance of sex hormones and disturbed gonadal development in sturgeons. A reduction in the ovarian adipocyte size can be achieved by lowering dietary fat at the pre-pubertal stage of sturgeon development [ 43 ]. Nevertheless, the mutual interaction between ovarian adipogenesis and oocyte loss should be urgently researched in the future, as increased degeneration of germinal cells in the early stages of gonadal development will have a detrimental effect on fish fecundity.…”