No abstract

Solar dryers are used to preserve very perishable foods like fish for long period of time by lowering the moisture content in high temperature areas and contribute to fish postharvest loss reduction. Therefore this study was conducted to evaluate dryers on moisture loss, moisture contents, drying and sensory properties of salted tilapia fillets. The experiment consisted of a factorial design, two factors with two levels of treatment processes, that is dryers (raised rack tent, solar tent and family tent) and salting methods (dry salted and brined). Open air dryer was used as control. Results show that there was no significant (p˃0.05) difference in minimum temperature record between raised rack and solar tents but significantly (p˂0.05) different in maximum temperature values among dryers. The highest temperature record was observed in raised rack tent (50°C) while lowest was in open air (26°C). Dryers and salting methods had significant (p<0.05) effect on moisture loss, moisture content (oven dried) and sensory properties. Brined fish fillets dried in open air showed highest moisture loss (79.54%) followed by raised rack tent (79.39%). Significant lowest moisture content values were observed in the products dried in raised rack tent (10.17%) using dry salted method than other dryers. Sensory evaluation revealed that the most acceptable product was obtained from brining method dried in raised rack tent. The color, flavor, texture, taste and overall acceptability scores of this product were 4.60, 4.20, 4.37, 4.40 and 4.47 (5-point hedonic scale), respectively. Therefore, raised rack tent fish dryer technology was found to produce acceptable sensory dried products and need to be demonstrated and popularized in high temperature areas.

The study was done to examine some aspects of the reproductive biology of Nile tilapia (Oreochromis niloticus) in Tekeze Reservoir a newly man made hydropower reservoir. A total number of 1826 specimens of Nile Tilapia (O. niloticus) were collected from the reservoir from July 2015 to June 2016. Size at first maturity, sex ratio, gonado-somatic index (GSI), breeding season and fecundity were studied. The overall sex-ratio female: Male (F: M) was 1.6:1 which is deviated from the expected 1:1 sex ratio (χ2 = 10.13; p<0.05). Length at first maturity was 14 and 15 cm for females and males respectively. The breeding period of females extended from January to September. Two annual breeding seasons were noticed. A minor breeding season which extended from January to March and a major breeding season from July to September and monthly Condition Factor (CF) (mean ± SD) value of O. niloticus in the reservoir ranged from 1.73±0.03 in July to 2.05±0.02 in November for males and 1.61±0.02 in July to 1.99±0.05 in April for females. Fecundity ranged between 399 to 2129 g. Fecundity correlated well with total weight (r = 0.086), total length (r = 0.77) and ovary weight (r = 0.72) than with gonadal weight (r = 0.86). Nile tilapia at Tekeze Reservoir showed isometric growth pattern (b=2.92), indicating that the reservoir was favorable for the fish growth. For proper management of the fish species in the reservoir, it is better for the fishermen not to capture the fish during the breeding season of the year in the reservoir.