A comparison of retinol, retinal and retinyl ester concentrations in larvae of Atlantic halibut (Hippoglossus hippoglossus L.) fed Artemia or zooplankton

Atlantic halibut (Hippoglossus hippoglossus L.) larvae were fed enriched Artemia or zooplankton in duplicate tanks from 0 to 60 days after first‐feeding. Both diets and the larvae were analysed for vitamin A (VA) in order to confirm earlier findings, in which Artemia fed larvae had lower levels of VA compared with larvae fed zooplankton. Furthermore, we wanted to investigate the composition of the retinoids in the larvae. The results showed that Artemia and zooplankton contains low levels of VA, probably too low to sustain the assumed requirement. Nevertheless, larvae fed Artemia had the same level of retinal and retinol as larvae fed zooplankton. We found a significant lower level of retinyl esters in larvae fed Artemia. The total VA level was lower in larvae fed Artemia only at the end of the feeding trial after the onset of metamorphosis. Our conclusion is that feeding Artemia to Atlantic halibut larvae is not likely to cause VA deficiency.     

An evaluation of the duration of efficacy of emamectin benzoate in the control of Caligus curtus Müller infestations in Atlantic cod, Gadus morhua L

The duration of efficacy of emamectin benzoate in the control of Caligus curtus infestations in Atlantic cod, Gadus morhua L., was studied following an administration of 50 μg kg^?1 for seven consecutive days. No lice were found on medicated fish when challenged 1 week (challenge 1) or 5 weeks (challenge 2) following termination of medication, whereas the mean abundance of lice among the unmedicated fish was 17.9 and 19.3 lice per fish in challenge 1 and 2, respectively. Muscle concentrations of 19.5 ± 8.2 ng g^?1 and 3.4 ± 0.9 ng g^?1, respectively, and skin concentrations of 23.1 ± 10.8 and 4.2 ± 1.0 ng g^?1, respectively, were found 27 and 55 days following the termination of medication. Tissue concentrations and the duration of efficacy indicate a dosing regime for emamectin in cod, similar to the regime used for Atlantic salmon, Salmo salar L.     

Minimum requirement of vitamin E for Atlantic salmon, Salmo salar L., at first feeding

The minimum requirement of vitamin E for Atlantic salmon, Salmo salar L., at first feeding was found to be 60 mg dl-α-tocopheryl acetate per kg dry diet. The dry diet contained 5.6% polyunsaturated fatty acids, which is similar to that used in practical diets at first feeding. Preliminary results indicate that the optimal dietary vitamin E level is 120 mg dl-α-tocopheryl acetate per kg dry diet, or more. Further research is necessary to confirm this hypothesis.     

Tree plantations on farms: Evaluating growth and potential for success

Interest in native species is growing across the tropics as reforestation of degraded lands becomes more widespread. In this study four tree species native to Panama - Cedrela odorata, Pachira quinata, Samanea saman, and Tabebuia rosea - were grown on rural farms at two dry tropical sites in Panama for up to five years. Survivorship and growth data at these “on-farm” trials are compared to data recorded from nearby experimental or “species selection” trial sites and evaluated in terms of soil fertility and management. Participant farmers were also asked about their interest in planting trees in general as well as their interest in 61 species grown in the species selection trial.Although, on-farm survivorship was variable and generally lower than that found on the species selection trial, one species (S. saman) experienced high and consistent survivorship. High survivorship combined with growth data from farms at both sites for this species suggests it would be a good candidate for extension projects working with rural farmers. Survivorship of other species appears more sensitive to farmer management and/or local site conditions. Generally lower growth on the Los Santos farms as compared to the species-selection trial is attributed to the lower soil fertility (plant available P) at the on-farm sites compared to the species selection trial. In contrast, only one species - P. quinata - had a growth variable found to be significantly lower between the on-farm and species selection trial sites in Rio Hato. C. odorata, P. quinata T. rosea can all be used in on-farm conditions with consideration to specific site and management conditions.By 2009, approximately 80% of the farmers planting trees still wished to participate in tree planting activities. All of the farmers no longer wishing to continue with the project expressed slow growth rates of trees as a principal reason. All but one of these farmers had growth rates for his/her trees markedly below those of the species selection trial nearby. Some farmers wishing to continue had very high mortality rates (>70% for all species), suggesting non-tangible benefits for participating in project activities. Other species that were not tested on-farm but grew well in the species-selection trials and were of interest to local farmers are discussed.As long as specific site and management conditions are carefully considered, data from species selection trials can be useful in informing tree planting projects with rural farmers; however, care should be taken to manage expectations.     

30,000 years of hydrothermal activity at the lost city vent field

Strontium, carbon, and oxygen isotope data and radiocarbon ages document at least 30,000 years of hydrothermal activity driven by serpentinization reactions at Lost City. Serpentinization beneath this off-axis field is estimated to occur at a minimum rate of 1.2 x 10(-4) cubic kilometers per year. The access of seawater to relatively cool, fresh peridotite, coupled with faulting, volumetric expansion, and mass wasting processes, are crucial to sustain such systems. The amount of heat produced by serpentinization of peridotite massifs, typical of slow and ultraslow spreading environments, has the potential to drive Lost City-type systems for hundreds of thousands, possibly millions, of years.     

Systems of knowledge as systems of domination: The limitations of established meaning

The hegemony of Western science, inherent in international development projects, often increases the poverty and oppression of Third World women by pre-empting alternative realities. In African and Asian agrarian societies women grow from 60 to 90% of the food (World Bank, 1989); they hold incredible potential to increase food production. Their ability to operate under more marginal conditions than their male counterparts would seem to indicate that they have developed valuable knowledge— knowledge often generated in response to limited access to the more tangible resources offered by development assistance to male farmers. Recognizing the marginalization of women in the Third World, the Women in Development (WID) network was established during the 1970's to produce knowledge about women, fill in the gaps, and set the record straight. But knowledge creation for these purposes leaves underlying paradigms of Western science-based development unquestioned. Research from a feminist standpoint is used to challenge the objectivity and reliability of EuroAmerican development science. To date, WID has documented and analyzed the causes and consequences of Third World women's oppression with no substantial results to end them. Alternatively, feminist research validates women's perceptions of their reality, helping ordinary people to understand the connections between their experiences and broader social, economic, and political struggles. The paper emphasizes research pursued in order to act, closely linking knowing to doing to promote the emancipation of oppressed groups. A feminist standpoint is used to privilege the perspective of rural women in developing countries and ask: “What are the implications of the standard EuroAmerican approach to science for maximizing the potential contributions of rural women to agricultural development?” Some of these implications are illustrated with examples from on-farm research in Nigeria. To some extent, implications can be addressed by constructing meanings to structure a symbolic framework that includes female farmers and other disadvantaged groups.