No abstract

The effect of gamma radiation (0, 1, 3, and 5 kGy) on the shelf life of farmed rainbow trout (Oncorhynchus mykiss) fillets that were treated with sodium acetate and vacuum packaged and subsequently stored under refrigeration was studied by measuring microbiological, chemical, and organoleptic changes. Radiation affected populations of bacteria, namely, H2S-producing bacteria and Enterobacteriaceae (P < 0.05). Initial total viable counts of the control samples were ca. 4.41 log CFU/g, whereas the respective counts in samples irradiated at 1, 3, and 5 kGy were 3.08, 1.46, and < or = 1 log CFU/g at day 1 of refrigerated storage. The maximum count of Enterobacteriaceae reached 2.29 and 1.45 log CFU/g at the end of storage for 1 and 3 kGy, respectively, but at a 5-kGy dose no growth of Enterobacteriaceae was observed. Of the biochemical indicators, thiobarbituric acid values for irradiated trout were higher than for nonirradiated fish (P < 0.05). Sensory evaluation (taste) showed a reasonable and good correlation with bacterial populations with storage time. The results revealed that radiation at a high dose (5 kGy) might induce lipid and protein oxidation, although the growth of microorganisms was inhibited. Therefore, radiation at a low dose (3 kGy) could be used to control the microbial and safety biochemical indices of O. mykiss for up to 4 weeks at refrigerator temperature without adverse effects on quality and acceptability.

The main aim of this investigation was to determine the impact of a total dietary fish oil (FO) replacement by vegetable oils (soybean [SO] and canola [CO] oil) on the growth and fatty acid (FA) composition of juvenile Beluga sturgeon, Huso huso. Three practical‐type diets with equal protein and lipid content were formulated using FO, SO, and CO. Each of the diets was fed to apparent satiation five times daily to H. huso (initial weight 206 ± 7.3 g) for 120 d. All groups grew equally well. Fish weight gain, condition factor, daily growth, feed intake, feed conversion, feed efficiency, protein efficiency, and survival were not affected by diet treatment. Fish lipid composition reflected the inclusion of vegetable oils and their respective FA compositions. Monounsaturated FA and polyunsaturated FA significantly increased in fish fed the CO and SO diets, respectively, but the ratio n− 3/n− 6 were significantly reduced by the inclusion of dietary vegetable oils (P < 0.05). This study suggests that FO can be replaced by SO and CO in H. huso diets under our test conditions with no significant effect on growth. However, longer assessments of these substitutions are warranted to ensure that these treatments do not have an adverse effect on fish health.

No abstract

Microplastics (MPs) are environmental contaminants that are of increasing global concern. This study investigated presence of MPs in four varieties of marine derived commercial fish meal, followed by identification of their polymer composition using Fourier-Transform Infrared (FTIR) spectroscopy. Exposure experiments were conducted on cultured common carp (Cyprinus carpio) by feeding four varieties of commercially available fish meal to determine relationships between abundance and properties of MPs found both in meal and those transferred to cultured common carp. Mean particle sizes were 452±161 μm (±SD). Fragments were the predominant shape of MP found in fish meal (67%) and C. carpio gastrointestinal tract and gills (65%), and polypropylene and polystyrene were the most present plastic polymers found in fish meal (45% and 24%, respectively) and C. carpio (37% and 33%, respectively). Positive relationships were found between MP levels in fish meal and C. carpio. This study highlights that marine derived fish meal may be a source of MPs which can be transferred to cultured fish, thus posing a concern for aquaculture.