Several indices were examined to assess the physical condition of wrasse stocked on Atlantic salmon, Salmo salar, farms as cleaner fish, and included examination of eye condition, snout erosion, skin hemorrhaging, and erosion and splitting of dorsal, pectoral, anal and caudal fins. Baseline values were determined for five wrasse species: goldsinny, Ctenolabrus rupestris; rock cook, Centrolabrus exoletus; corkwing, Crenilabrus melops; cuckoo, Labrus mixtus; and ballan, Labrus bergylta, held in a farm environment for 3 mo prior to transfer to salmon farms. The caudal fin was most affected by injury. The fin erosion index (FEI) was low in all species and below 0.6. The fin splitting index (FSI) was the most prominent index and was significantly higher in the caudal fin (FSI > 2) compared with other fins (FSI < 0.5), and also significantly higher in corkwing and rock cook compared with the other wrasse species. The FEI and FSI were also calculated for a group of ballan wrasse before stocking on a seawater farm, during the first winter and upon harvesting. There were no significant differences in the scores of fin erosion and fin splitting in any of the samples, although the indices were marginally poorer in winter.
Abstract. In the present study, the effects coelomic fluid removal method (rinsing with clear water versus siphoning) and de-adhesion substances (milk solution, starch suspension and urea-NaCl-tannic acid solutions) had on fertilization rates and hatching success and time of Siberian sturgeon, Acipenser baerii Brandt were compared. It was concluded that 1) rinsing Siberian sturgeon eggs prior to fertilization is recommended when there is abundant, viscous coelomic fluid; 2) de-adhesion with milk or urea-NaCl-tannic acid is less time-consuming and results in higher, although not significantly, hatching percentages than those obtained with starch, and 3) de-adhesion with milk ensures the shortest and most synchronous hatching of Siberian sturgeon larvae. All of these issues require further experimental investigations.
The effects of different weaning strategies on survival, cannibalism and growth were investigated in pikeperch (Sander lucioperca) larvae. Two weaning strategies were tested with 15 days post hatch (DPH) larvae: Co-feeding and Supplementary feeding. Co-feeding was performed with Artemia nauplii and dry feed by the gradual reduction of nauplii either @ 25% day-1 or 14% day-1 , whereas supplementary feeding was performed with sudden weaning to exclusively dry feed while Artemia nauplii was the last meal of the day. Each strategy was tested in two time durations, for 4 and 7 days. Co-feeding weaning strategy seems to be more beneficial compare to supplementary feeding weaning strategy in response of lower mortality (%), higher growth and finally maximum total yield. Even though higher cannibalism was found in the larvae weaned for 7 days from 15-22 DPH but higher growth and survival in this group make this weaning strategy better than larvae weaned for 4 days from 15-19 DPH. Therefore, it is concluded that the co-feeding weaning strategy for 7 days from 15 to 22 DPH should be followed for successful larviculture of pikeperch.
Larvae of the "European" (ARR) and "Siberian" (ARM) sterlets were fed initially with Tubifex, and further were gradually weaned to dry diet. Additionally two other feeding strategies were tested in ARM: feeding exclusively with dry diet, and sudden weaning from 10 day post-hatch (dph). Survival and yield at 30 dph of the ARM was significantly higher than that of ARR. Significant differences were found within ARM groups with different weaning strategies. We suppose that ARM has at least same potential for aquaculture than the ARR. Also we suggest that the initial use of live foods for ARM would be preferable
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