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Hermelink B.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Wuertz S.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Rennert B.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Kloas W.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | And 3 more authors.

After temperature-induced puberty at 12. °C for 12. weeks, the progression of gametogenesis in maturing pikeperch (S. ander lucioperca) was studied at 12. °C, 14. °C, 16. °C, and 18. °C, compared with a control group reared at 23. °C. The plasma concentration of the sex steroids estradiol (E2), testosterone (T), 11-ketotestosterone (11-KT), and 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P) as well as the histology of the gonad confirmed the successful induction of puberty in all treatment groups and an advanced gonadal maturation until the end of the experiment in both. After 16. weeks at 14. °C, 80% of the female pikeperch examined were in mid vitellogenesis compared with a slower progression at 12. °C, 16. °C, and 18. °C. After 20. weeks, all fish reared at 14. °C accomplished mid vitellogenesis accompanied by a significant up-regulation of E2, which was also detected in the conspecifics reared at 12. °C and 16. °C, although not as advanced. In females reared at 18. °C, only a small percentage reached mid vitellogenesis accompanied by decreasing E2 concentrations, succeeding the induction of puberty at week 12. After 20. weeks, the level of T as well as 11-KT peaked in fish of both sexes kept between 12. °C and 16. °C. As in females, temperature influenced postpubertal maturation in males, which was indicated by significant temperature dependent changes of the sex steroids. E2 plasma concentrations in males exhibited a bimodal pattern with two maxima, first after 12. weeks at the onset of puberty and the second after week 26, coinciding with the end of spermatogenesis as indicated by milt production. In conclusion, postpubertal temperatures around 14. °C promoted a complete ripening in pikeperch of both sexes within 8. weeks, whereas higher temperatures constrained full gonadal maturation. Furthermore, with reference to the optimal temperature for the induction of puberty previously discussed, slightly higher temperatures around 14. °C are optimal for postpubertal maturation. This clearly indicates the existence of a dynamic temperature influence for optimal maturation due to postpubertal inhibition of maturation at temperatures higher than 18. °C. Consequently, in addition to the role of low temperatures in the induction of puberty, this is the first evidence that emphasizes the need for a closely controlled temperature range to be maintained during the ongoing maturation, which should be considered in year round production of pikeperch. © 2013. Source

Velasquez Y.C.,University of Magdalena | Kijora C.,Humboldt University of Berlin | Wuertz S.,GMA Gesellschaft fur Marine Aquakultur mbH | Wuertz S.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | And 2 more authors.
Livestock Research for Rural Development

An 8-week feeding experiment was conducted to evaluate the growth performance, feed efficiency, digestibility, carcass composition and, liver and intestine histology of juvenile Nile Tilapia (3.18 ± 0.02 g) fed on a control diet and four experimental diets (35% CP). The experiment aimed to assess the utilization of local macrophytes; namely fermented duckweeds at 15% (DW15) and 25% (DW25) as well as fermented water fern at 15% (WF15) and 25% (WF25). The growth performance comprising of weight gain (WG), specific growth ratio (SGR) and protein efficiency ratio (PER) was assessed in triplicates and no significant differences between diets were observed. Feed conversion ratio (FCR) and ash content of the carcass were similar in all the treatments except for WF25 where significantly higher FCR and ash content were recorded compared to the control diet. However, lipid and protein content of the carcass was comparable between diets. Results showed that the inclusion of fermented duckweeds up to 25% and fermented water fern up to 15% in diets for Nile Tilapia was feasible without any negative effect compared to the control group. © 2015 Fundacion CIPAV. All rights reserved. Source

Tusche K.,University of Kiel | Arning S.,University of Rostock | Wuertz S.,GMA Gesellschaft fur Marine Aquakultur mbH | Wuertz S.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | And 2 more authors.

In contrast to potato and other plant proteins, wheat gluten does not require complex and costly purification and may thus be utilized in aquaculture diets according to aquaculture guideline EC 710/2009. Therefore, a feeding trial was conducted to evaluate the effect of various combinations of wheat gluten (WG) and potato protein concentrate (PPC) in nutrition of rainbow trout (Oncorhynchus mykiss). Seven isonitrogenous (459±6g CP kg -1) and isoenergetic (21.4±0.1MJkg -1) diets were formulated to contain varying levels of wheat gluten and potato protein concentrate (6/27; 9/24; 11/21; 14/19; 17/16; 19/13 as proportion of WG/PPC in % of the diet) at constant fishmeal replacement level of 56% on protein level and one fish meal diet served as control. Experimental diets were fed over a period of 56days to triplicate experimental groups until apparent satiation.Growth performance showed no significant differences between all feeding groups at the end of the experimental period. No influences on health and nutritional status were documented between the treatments in the body composition and blood parameter. The wheat gluten and PPC as fish meal replacement in organic diets for rainbow trout revealed positive and equal results for use in the inclusion level of the presented trial. © 2012 Elsevier B.V.. Source

Haas S.,GMA Gesellschaft fur Marine Aquakultur mbH | Haas S.,University of Kiel | Bauer J.L.,University of Kiel | Adakli A.,Cukurova University | And 5 more authors.
Journal of Applied Phycology

In the present study, the potential of the microalga Pavlova viridis (=Diacronema viridis) as an n-3 polyunsaturated fatty acid (PUFA) source was evaluated and compared to Nannochloropsis sp. in diets for juvenile European sea bass (Dicentrarchus labrax L.) (initial weight ~12.8 ± 1.7 g) in an 8-week feeding trial. Six different isoenergetic and isonitrogenous test diets were used: (1) fish oil diet (FO), major lipid source fish oil (100 %), (2) basal diet, 40 % fish oil and 60 % plant oil (in equal parts rapeseed, sunflower, and linseed oil), (3) Pavlova 50 % (P50), 50 % of the fish oil of the basal diet was substituted by lipid content of P. viridis meal, (4) Pavlova 100 % (P100), 100 % of the fish oil of the basal diet was substituted by lipid content of P. viridis meal, (5) Nannochloropsis 50 % (N50), 50 % of the fish oil of the basal diet was substituted by lipid content of Nannochloropsis sp. meal, and (6) Nannochloropsis 100 % (N100), 100 % of the fish oil of the basal diet was substituted by lipid content of Nannochloropsis sp. meal. The specific growth rate was highest and feed conversion ratio was lowest in the P100 group (SGR 1.77 ± 0.10 % day−1; FCR 1.17 ± 0.01), although not significantly different to the results for the FO and the other algae-groups. Furthermore, the sum of PUFA was also highest in the P100 group, followed by the P50, N100, N50, and B group (mainly due to the high content of linoleic and linolenic acids coming from plant oils and microalgal products) with the lowest levels in the FO group. The highest amounts of docosahexaenoic acid (DHA) of total fatty acids were found in the FO and B group, although not significantly higher than in groups P50 and P100. The significantly highest amount of eicosapentaenoic acid (EPA, % of total fatty acids) was in the P100 samples and the lowest amount was in samples of the basal group. The histological analyses of liver and intestine samples did not reveal any negative effects caused by the experimental treatments. Based on the basal diet, a 50 % fish oil replacement by Nannochloropsis sp. meal and a total replacement by P. viridis meal were possible without negative effects on the growth performance and nutrient utilization of juvenile sea bass. © 2015 Springer Science+Business Media Dordrecht Source

Rehberg-Haas S.,GMA Gesellschaft fur Marine Aquakultur mbH | Rehberg-Haas S.,University of Kiel | Meyer S.,GMA Gesellschaft fur Marine Aquakultur mbH | Lippemeier S.,BlueBioTech GmbH | And 2 more authors.

In the present study the potential of different products of the marine microalga Pavlova sp. for the cultivation of rotifers (Brachionus plicatilis) was tested. Two growth performance trials were conducted: In a first laboratory scale experiment rotifers were cultivated for 14days with Pavlova viridis concentrate, P. viridis fresh culture, Pavlova sp. fresh culture, baker's yeast and Nannochloropsis sp. concentrate. The P. viridis fresh culture fed groups resulted in significantly the highest rotifer density (109.2rotifersmL-1) and instantaneous growth rate (G=0.14±0.02d-1). There were no significant differences found of the G between the P. viridis concentrate group and the Pavlova sp. fresh culture group. The baker's yeast fed group showed significantly the lowest rotifer numbers and growth rate. Based on the high growth rate of the P. viridis fresh culture group in the first experiment, different P. viridis products (concentrate, fresh culture, frozen concentrate, and freeze-dried powder) were examined in the second (larger scale) experiment and compared to Nannochloropsis sp. concentrate. The highest rotifer growth rate G in experiment 2 was determined for the frozen P. viridis group (G=0.09±0.03 d-1), although it was not significantly different in comparison to the G of the rotifers fed with Nannochloropsis sp. and the Pavlova concentrate and fresh culture. The frozen Pavlova product seems the most suitable Pavlova product for the cultivation of live feed and it provides advantages of storability and application. © 2014 Elsevier B.V. Source

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