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An integrated closed system for fish-plankton aquaculture in Amazonian fresh water
- S. Gilles, R. Ismiño, H. Sánchez, F. David, J. Núñez, R. Dugué, M. J. Darias, U. Römer
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A prototype of an integrated closed system for fish-plankton aquaculture was developed in Iquitos (Peruvian Amazonia) in order to cultivate the Tiger Catfish, Pseudoplatystoma punctifer (Castelnau, 1855). This freshwater recirculating system consisted of two linked sewage tanks with an intensive rearing unit (a cage) for P. punctifer placed in the first, and with a fish-plankton trophic chain replacing the filters commonly used in clear water closed systems. Detritivorous and zooplanktivorous fishes (Loricariidae and Cichlidae), maintained without external feeding in the sewage volume, mineralized organic matter and permitted the stabilization of the phytoplankton biomass. Water exchange and organic waste discharge were not necessary. In this paper we describe the processes undertaken to equilibrate this ecosystem: first the elimination of an un-adapted spiny alga, Golenkinia sp., whose proliferation was favored by the presence of a small rotifer, Trichocerca sp., and second the control of this rotifer proliferation via the introduction of two cichlid species, Acaronia nassa Heckel, 1840 and Satanoperca jurupari Heckel, 1840, in the sewage part. This favored some development of the green algae Nannochloris sp. and Chlorella sp. At that time we took the opportunity to begin a 3-month rearing test of P. punctifer. The mean specific growth rate and feed conversion ratio (FCR) of P. punctifer were 1.43 and 1.27, respectively, and the global FCR, including fish in the sewage part, was 1.08. This system has proven to be suitable for growing P. punctifer juveniles out to adult, and provides several practical advantages compared with traditional recirculating clear water systems, which use a combination of mechanical and biological filters and require periodic waste removal, leading to water and organic matter losses.
13 - Sensory Systems in Old Age
- Edited by Paul B. Baltes, Max-Planck-Institut für Bildungsforschung, Berlin, Karl Ulrich Mayer, Max-Planck-Institut für Bildungsforschung, Berlin
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- Book:
- The Berlin Aging Study
- Published online:
- 06 December 2010
- Print publication:
- 28 November 1998, pp 360-383
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Summary
In this chapter, three sensory systems (hearing, vision, and balance/gait) are examined. We begin with a descriptive overview of individual differences and age difference patterns in sensory functioning. The pattern of how individual differences in sensory acuity might be related to performance in other psychological and behavioral domains is examined. We reveal a strong, negative pattern of age differences in all three senses studied. These negative age trends have implications for the classification of sensory impairment rates: Although participants in their 70s have levels of sensory acuity that might be classified, on average, as slightly or mildly impaired, by their 90s most participants evince levels that might be classified as moderately to severely impaired, not only in one but in multiple modalities. We also report prevalence rates for the use of commonly occurring compensatory devices and procedures (e.g., hearing aids, glasses, cataract operations). We report the following findings with regard to the relationship of sensory functioning to other domains of psychological and behavioral performance (e.g., intellectual functioning, basic and expanded everyday competence, personality characteristics, well-being, social network size):
(1) Relationships exist between all three sensory domains and the selected outcome domains. The relationships with intellectual functioning and everyday competence are particularly strong.
(2) In all domains studied, the sensory variables can explain or mediate virtually all of the age-related variance in those domains; that is, after statistically controlling for sensory performance, there is essentially no unique effect of chronological age.
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