Fin condition and growth among rainbow trout reared at different sizes, densities and feeding frequencies in high-temperature re-circulated water

Abstract

Rainbow trout were studied at different rearing densities, fish sizes and feeding frequencies so that we could evaluate the effect of these parameters on fin condition, growth and feed utilisation. In one study, two sizes of rainbow trout (18-70 g or 48-125 g), fed to near satiation at 17.7°C, were examined at two rearing densities (11-41 kg m -3 or 21-92 kg m -3 ). This study showed that the anal fin was healthier (P < 0.05) at low densities. In the second study rainbow trout were again fed to near satiation and grown from 50 g to 125 g in 16.4°C water, and they were fed either once daily or three times daily at two densities (18-45 kg m -3 or 54-124 kg m -3 ). Rainbow trout growth and feed utilisation were slightly but significantly (P < 0.05) reduced at high densities, while dorsal fin condition, surprisingly, was better (P < 0.0001) at the high densities. Possible explanations to these findings are discussed. Condition of the left pectoral fin was improved at once daily feeding (P < 0.05) compared with three feedings per day, at which fights for feed possibly are more frequent.

Factors Affecting Fin Damage of Farmed Rainbow Trout

“…In our study, SD was the only factor that did not have an effect on the level of fin damage. This finding conforms to other research that there is no relationship between SD and the level of fin damage (3,6,7,9,32). The normal recommended SD for rainbow trout is 2 -80 kg/m 3 (26).…”

“…When feeding rainbow trout to satiety from self-feeders, reducing the daily number of meals from 3 to 1 significantly reduces the recovery from historical dorsal fin erosion (19). However, when rainbow trout receive a fixed satiation ration, increasing the daily number of meals from 1 to 3 increases the damage of the left pectoral fin (7). Fish should have the opportunity to feed without undue competition (5) and the contemporary Fin damage of farmed rainbow trout Unauthenticated Download Date | 5/10/18 12:09 PM feeding strategies promote self-feeding or ondemand feeding regimes than fixed feeding regimes (19,20,21,22,23,24).…”

“…There is a significant body of experimental research which identified that the main factors affecting fin damage are feeding practices, water quality, stocking density and routine handling, not excluding the bacterial infections (3,6,7,8,9). However, despite the experimental approach, there are few research reports that determine the important factors having effect on fin damage and fish welfare under different commercial production systems (5,10).…”

A Simple and Effective Recirculating Hatchery for Salmonids

“…The data obtained from water quality monitoring confirmed adequate biofilter function indicated by increase in non-toxic nitrates, low levels of ammonia and nitrite, stable pH, and low level of organic load (Table 1) [28,31]. Manual feeding at short intervals and pathogen free fresh water intake provided rearing conditions with no negative impact on fish health and welfare [30]. Conditions resulted in rapid growth and low FCR, not only with Production cycle 79.6 ± 4.7 ___ 21.1 ± 2.8 11 Table 2: The average duration of each period of production cycle (days, %), average losses during each period (%), and the number of observed production cycles (n).…”

“…This parameter must be associated with a satisfactory feed conversion ratio and fish welfare [29,30]. The data obtained from water quality monitoring confirmed adequate biofilter function indicated by increase in non-toxic nitrates, low levels of ammonia and nitrite, stable pH, and low level of organic load (Table 1) [28,31].…”