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1

Digitale Medien

Perception of shape from shading in chimpanzees (Pan troglodytes) and humans (Homo sapiens) (1998)

Tomonaga, Masaki

Springer

Animal cognition 1 (1998), S. 25-35

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ISSN: 1435-9456

Schlagwort(e): Key words Shape from shading ; Visual search ; Texture segregation ; Chimpanzees ; Humans

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The perception of shape from shading was tested in two chimpanzees (Pan troglodytes) and five humans (Homo sapiens), using visual search tasks. Subjects were required to select and touch an odd item (target) from among uniform distractors. Humans found the target faster when shading was vertical than when it was horizontal, consistent with results of previous research. Both chimpanzees showed the opposite pattern: they found the target faster when shading was horizontal. The same difference in response was found in texture segregation tasks. This difference between the species could not be explained by head rotation or head shift parallel to the surface of the monitor. Furthermore, when the shaded shape was changed from a circle to a square, or the shading type was changed from gradual to stepwise, the difference in performance between vertical and horizontal shading disappeared in chimpanzees, but persisted in humans. These results suggest that chimpanzees process shading information in a different way from humans.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s100710050004

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2

Digitale Medien

Impact of water control projects on fisheries resources in Bangladesh (1996)

Mirza, Monirul Qader ; Ericksen, Neil J.

Springer

Environmental management 20 (1996), S. 523-539

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ISSN: 1432-1009

Schlagwort(e): Water control ; Floodplain ; Fisheries ; Bangladesh ; Chandpur

Quelle: Springer Online Journal Archives 1860-2000

Thema: Energietechnik

Notizen: Abstract Bangladesh is a very flat delta built up by the Ganges—Brahmaputra—Meghna/Barak river systems. Because of its geographical location, floods cause huge destruction of lives and properties almost every year. Water control programs have been undertaken to enhance development through mitigating the threat of disasters. This structural approach to flood hazard has severely affected floodplain fisheries that supply the major share of protein to rural Bangladesh, as exemplified by the Chandpur Irrigation Project. Although the regulated environment of the Chandpur project has become favorable for closed-water cultured fish farming, the natural open-water fishery loss has been substantial. Results from research show that fish yields were better under preproject conditions. Under project conditions per capita fish consumption has dropped significantly, and the price of fish has risen beyond the means of the poor people, so that fish protein in the diet of poor people is gradually declining. Bangladesh is planning to expand water control facilities to the remaining flood-prone areas in the next 15–20 years. This will cause further loss of floodplain fisheries. If prices for closed-water fish remain beyond the buying power of the poor, alternative sources of cheap protein will be required.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01474653

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3

Digitale Medien

Fish communities in the African Great Lakes (1996)

Lowe-McConnell, Rosemary

Springer

Environmental biology of fishes 45 (1996), S. 219-235

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ISSN: 1573-5133

Schlagwort(e): Ecology ; Behaviour ; Evolution ; Cichlids ; Fisheries ; Conservation

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Synopsis Ecological conditions in tropical lacustrine systems are considered by focusing on the evolution, maintenance, exploitation and vulnerability of fish communities in the African Great Lakes. The exceptionally high biodiversities in the littoral/sublittoral zones of the very ancient, deep, clear, permanently stratified rift lakes Tanganyika and Malawi, are contrasted with the simpler systems in their pelagic zones, also with biodiversity in the much younger, shallower Victoria, the world's largest tropical lake.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00003090

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4

Digitale Medien

Effects on fisheries and waterbirds of raising water levels at Kerkini Reservoir, a Ramsar site in northern greece (1995)

Crivelli, A. J. ; Grillas, P. ; Jerrentrup, H. ; [weitere]

Springer

Environmental management 19 (1995), S. 431-443

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ISSN: 1432-1009

Schlagwort(e): Reservoir ; Fisheries ; Breeding and wintering waterbirds ; Raising water levels ; Habitat change

Quelle: Springer Online Journal Archives 1860-2000

Thema: Energietechnik

Notizen: Abstract A new, higher dam was installed at Kerkini Reservoir in 1982, causing habitat and landscape disruption. A decrease in the area of grassland and shallow water areas, the rapid disappearance of reedbeds, the appearance of beds ofNymphaea, and the disappearance of half the forest area were all observed between 1982 and 1991. With the new hydrological regime, a lacustrine system was created, with an extensive, rather deep (4–8 m), pelagic zone favorable for the development of coarse fish species throughout the year. After 1982, an increase in fishing effort and a change in the relative abundance of fish species in the catch, including the disappearance of eels and wels, were observed. The impact of the rise in the water level of breeding aquatic birds led to a general decline in species typical of marshy habitats in favor of species preferring deeper open water habitats. A decrease was recorded in bird species that feed largely on invertebrates and to a lesser extent fish (e.g., glossy ibis) and that require extensive shallow feeding areas. There was a decline in geese, whose nests were regularly flooded, and a major increase in piscivorous birds, particularly diving birds (e.g., cormorants), which prefer deeper open water and benefitted directly from the large increase in coarse fish biomass. The disappearance of birds breeding in flooded meadows (e.g., black-winged stilts) and of those restricted to reedbeds (e.g., marsh harrier) occurred from 1983. Over the same period, the changes in populations of wintering birds at Kerkini were different from those occurring in other wetlands in northern Greece. The changes recorded in the populations of wintering birds at Kerkini did not therefore result from overall regional trends but from the major habitat modifications that occurred to this wetland. As for breeding birds, strictly piscivorous species increased greatly as a result of the increased availability of fish, but also due to the appearance of many suitable night roosting sites (flooded trees) and to the great increase in the area of open water greater than 2 m deep. Today, Kerkini has become the most important breeding site in Greece for a majority of colonial waterbirds. In contrast, wintering shorebirds practically disappeared. The many changes recorded in the status of breeding and wintering birds at Kerkini can mostly be explained by the changes that occurred in the functioning of the ecosystem and in the habitat structure following the inauguration of the new hydrological regime. These changes did not all occur at the same time: some were immediate and others required a delay before they could be detected.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02471984

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5

Digitale Medien

Ecology and fish catches in natural lakes of Benin, West Africa (1995)

Adite, Alphonse ; Thielen, Rudi

Springer

Environmental biology of fishes 43 (1995), S. 381-391

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ISSN: 1573-5133

Schlagwort(e): Fisheries ; Irrigation ; Reproductive seasonality ; Sarotherodon galilaeus ; Species richness ; Water quality

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Synopsis A preliminary study of the ecology and commercial fish catches was carried out in the Toho-Todougba, Ahouangan and Dati lakes (1500 ha) in southern Benin (West Africa) over a period of 18 consecutive months. Water quality, species richness, and the reproductive biology of the dominant species, Sarotherodon galilaeus, were examined. Unlike Lagoon Toho-Todougba, lakes Ahouangan and Dati are less favourable for fish production because of their high total iron content and their relative low pH. The study revealed the existence of 19 species belonging to eleven (11) families: 16 species in Lagoon Toho-Todougba,12 in Lake Ahouangan, and 7 in Lake Dati. Lakes Ahouangan and Dati had a relatively high faunal similarity whereas Lagoon Toho-Todougba exhibited a relatively low faunal similarity with the former systems. In Lagoon Toho-Todougba, six cichlid species were the most important component of the fishery: Sarotherodon galilaeus, Tilapia guineensis, T. zillii, T. mariae, Chromidotilapia guntheri, Hemichromis fasciatus. Three catfish species Chrysichthys auratus, Clarias agboyiensis, and Clarias lazera were harvested in low abundances. Some other fish, such as Polypterus senegalus senegalus, Protopterus annectens and Heterotis niloticus were captured sporadically, with H. niloticus appearing more consistently in catches than the others. Although not abundant, Gymnarchus niloticus and the African pike, Hepsetus odoe, were almost always present in the catches. Ctenopoma kingsleyae appeared only in Ahouangan. Some predatory species, such as Notopterus afer and Xenomystus nigri, are encountered only in lakes Ahouangan and Dati. In Lagoon Toho-Todougba, Sarotherodon galilaeus had a sex ratio (♂: ♀) of 0.49:1, and size at maturation was estimated as 12.3 cm TL. The spawning period extended from May to September with the peak occurring in July. Fecundity was correlated to log-body length (r = 0.74) and log-body weight (r = 0.76). Fish catches were estimated at 389 kg ha−1 year−1; about 73% of which was Sarotherodon galilaeus. The overexploitation of juvenile fish and the use of this lagoon for the irrigation of palm tree plantations have reduced fish recruitment and mean size.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00001173

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6

Digitale Medien

Grass carp status in the United States: A review (1983)

Pierce, Barry A.

Springer

Environmental management 7 (1983), S. 151-160

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ISSN: 1432-1009

Schlagwort(e): Grass carp ; Biological control ; Nuisance aquatic weeds ; Fisheries ; Aquaculture ; Reproductive requirements ; Arkansas management plan ; Sterile hybrids

Quelle: Springer Online Journal Archives 1860-2000

Thema: Energietechnik

Notizen: Abstract Grass carp (Ctenopharyngodon idella Val.) were introduced into the United States in 1963 as potential biological control agents for nuisance aquatic weeds. Since that time an oftentimes bitter controversy has raged over its effects on sportfishing, and its possible natural reproduction and naturalization in North America. This review considers the history, ecology, and present status of grass carp in the United States in light of the voluminous scientific research conducted since its importation. Particular attention is given to the role of grass carp in the fisheries management plans of Arkansas. Recent development of a sterile, triploid grass carp hybrid may lead to widespread use of grass carp to control nuisance aquatic weeds in culturally eutrophicated waters of the United States.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01867276

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7

Digitale Medien

Thermoregulatory behavior and diel activity of yearling winter flounder, Pseudopleuronectes americanus (Walbaum) (1982)

Casterlin, Martha E. ; Reynolds, William W.

Springer

Environmental biology of fishes 7 (1982), S. 177-180

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ISSN: 1573-5133

Schlagwort(e): Temperature ; Behavior ; Ecology ; Fisheries ; Fish ; Marine juveniles

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Synopsis Sixteen yearling winter flounder, tested individually for 3-day periods in electronic shuttleboxes, voluntarily occupied an 8–27°C range of temperature, with a modal final thermal preferendum of 18.5°C (mean 18.7°C, median 19°C, midpoint 17.5°C, s.d. 1.9°C, S k + 0.33). The locomotor activity pattern of the yearling fish in the laboratory was markedly nocturnal, with mean hourly nocturnal activity exceeding mean hourly diurnal activity by a factor of 3.4. Maximum activity occurred at 0300 EST, minimum activity at 1400 EST. While activity generally increased with temperature, a local activity minimum occurred at 18.7°C, coinciding with the 24-hour mean final thermal preferendum. Comparison of these laboratory data with previously published field data suggest that behavioral responses to temperature and light play significant roles in determining age- and size-specific differences in seasonal depth stratification and onshore-offshore distributions in this species.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00001789

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