Journal of Fisheries

Quality and shelf life of vacuum- and nitrogen-packed dried barb fish (Puntius spp.)

2020-09-26T16:33:16+00:00

Vacuum and modified atmosphere packaging are widely used for preserving food items including fish. In this context, the quality and shelf life of air- (control), vacuum- and nitrogen-packed dried barb fish (Puntius spp.) stored at ambient temperature were evaluated through biochemical and microbial analyses for 90 days. In most of the storage days, significantly lower values of moisture, total volatile base-nitrogen (TVB-N) and peroxide value (PV) were observed in the vacuum pack sample compared to control. However, the TVB-N, PV, total coliforms and faecal coliforms counts were within the acceptable limit in all groups. The total plate count (TPC) increased gradually with time from an initial value of 4.29 log CFUg^–1. However, compared to control, significantly lower TPC were found on and after the 30^th day of storage in vacuum and nitrogen pack samples. Considering the TPC value of 5 log CFUg^–1, the shelf life was determined at approximately 15 days for control, 35 days for nitrogen pack and 45 days for vacuum pack samples. Therefore, the vacuum pack is considered the best packaging, which may be utilised by the processors to produce and retail the dried products with prolonged shelf life.

Relationship between cortisol and glucose as physiological stress indicators during growth season in juvenile Siberian sturgeon Acipenser baerii

2020-09-21T16:15:45+00:00

The relationship between cortisol and glucose was studied in two-year old farmed Siberian sturgeon Acipenser baerii with a body weight of 340±30 g (mean ± SD) and total length of 45±1 cm from August to November 2017. Thirty-six individuals were randomly selected and stocked in some 3×300 L fiberglass tanks. Blood samples were collected monthly from the tagged fish. The mean cortisol in August, September, October and November were 4.7±0.9, 23.5±3.0, 6.3±0.9 and 7.4±0.9 ng mL^–1 respectively whereas glucose concentrations were 44.6±0.4, 27.3±0.6, 49.2±0.7 and 48.5±0.7 mg dL^–1 respectively indicating a significant increase in cortisol and decrease in glucose in September, may be due to the exposure to prolonged high temperature (26–28.5°C). Although it was expected to happen naturally due to hyperglycemia of cortisol but no such phenomena was detected. Our results suggest that the consumption of glucose for maintenance of homeostasis and physiological status is a mechanism against the non-optimal thermal regime. This mechanism consumes glucose at a rate higher than that produced by cortisol, causing significant decrease of plasma glucose. In general, there was a reverse relationship between cortisol and glucose concentration during the experiment in Siberian sturgeons.

Effects of different background colors on adult spawning, egg hatchability, and larval survival of zebrafish (Danio rerio)

2020-09-21T16:15:45+00:00

Background color has significant effects on the reproductive and survival performance of fish species. While zebrafish (Danio rerio) is a popular species in laboratory and recreational aquaculture, very little has been known about its background color preference. Thus, this study evaluated the effects of different colors of aquaria on the spawning, hatching, and survival of this species. The study found that zebrafish do not have color preference for spawning. Though red and black backgrounds are statistically comparable, these colors showed significantly higher (P < 0.05) hatching and survival rates than other colors used in this study. Furthermore, performance of red was higher than black but it was not statistically significant. This study reveals that, among all colors evaluated, red is the most suitable for hatching of zebrafish eggs and survival of its larvae whereas, yellow and transparent should be avoided.

Meristic and morphometric characteristics of the Black Sea salmon, Salmo labrax Pallas, 1814 culture line: an endemic species for Eastern Black Sea

2020-09-21T16:15:46+00:00

The Black Sea salmon Salmo labrax Pallas, 1814 is an essential species for the Turkish aquaculture sector, given increasing trends of the annual productions. To date, there are few studies on meristic and morphometric characteristics of this species. In this study, the fifth filial generation of the species was specified and studied for meristic and morphometric characteristics. The results obtained in this study were compared with available literature and a similarity was found between the study specimens and wild individuals. The morphological characteristics of any cultured species is valuable especially when a new culture generation is formed and therefore this study outcomes may provide important information to the literature.

Feed intake, nutrient digestibility and nutrient retention in Atlantic salmon (Salmo salar L.) fed diets with different physical pellet quality

2020-08-04T14:53:10+00:00

Three feeds with different physical pellet quality but the same formulation were fed to Atlantic salmon for 97 days. Pellet quality was measured as bulk density, durability, fat leakage, hardness, water stability and porosity. The largest difference among the feeds was measured in hardness (201, 236 and 86 Newton for Diet 1, Diet 2 and Diet 3 respectively). The relative feed intake was highest in salmon fed Diet 2 and Diet 3 with no effects of pellet hardness. Growth and feed efficiency ratio were similar among all fish. The apparent digestibility of energy, dry matter, nitrogen and lipid was similar for all feeds, whereas the apparent digestibility of phosphorus and zinc was the lowest in Diet 3. Retention of energy, lipid and nitrogen was also similar for all feeds. Salmon fed Diet 1 and Diet 3 retained more phosphorus than those fed Diet 2. An increased retention of the digested zinc was found in salmon fed Diet 3. This study concludes that physical pellet quality affects feed intake and improve utilisation of feed in salmon if optimised properly. Moreover, pellet hardness can be optimised in commercial scale without compromising feed intake as it has no influence on feed intake.