Dominique Ombredane

The effects of Passive Integrated Transponder tags on survival and growth of juvenile brown trout (Salmo trutta L.) and their use for studying movement in a small river

From 1993 to 1995, more than 2000 of 0 + brown trout (Salmo trutta L.) were captured in a small brook in October and released after clipping the left pelvic fin. More than 1700 of them were also tagged with a small Passive Integrated Transponder (PIT) tag (11 mm long) implanted in the body cavity. Tagged juveniles were recaptured in May in the brook but also one year later in the river Oir, and continuously in a trap during spring downstream migration in the river Oir.

Spatial avoidance of invading pastoral cattle by wild ungulates: insights from using point process statistics

Traditional rangelands in many developing countries are currently being encroached by cultivation, driving some herders to illegally use protected areas for grazing their cattle. Since cattle are an exotic species in these ecosystems, they might have an impact on the local wild herbivore communities, notably through competition. We used point pattern statistics to characterise the spatial relationships between wild ungulate species and cattle herds within a protected area in west Africa undergoing seasonal intrusions by cattle. We predicted that the wild ungulate species that are ecologically and morphologically similar to cattle, in terms of body mass and diet, would be more sensitive to grass depletion by cattle and would be separated from cattle to a larger extent. The spatial distribution of browsing and mixed-feeding antelopes did not seem to be affected much by cattle presence, whereas most grazing species showed spatial separation from cattle. Interestingly, elephants also showed significant separation from cattle herds. We discuss the likely processes that may have contributed to the observed spatial patterns. The spatial displacement of certain wild species, including megaherbivores, affects the whole community structure and, thus, other components of the ecosystem.

Heterogeneity and typology of fish habitat in the main stream of a Breton coastal river (Elorn-Finistère, France)

To study the salmonids potential production of a coastal river main stream from simple characterization of the fish habitat, it was necessary to rate the hydrosystem’s spatial heterogeneity.

Sustainability of fish pond culture in rural farming systems of Central and Western Cameroon

In Sub-Saharan Africa, fish ponds are often an integral part of farming systems but have suffered from a lack of viability and sustainability. The present study aims to understand the strategies used by fish farmers to overcome economic and environmental constraints. In 2008 and 2009, fish farmers were surveyed in Central and Western Cameroon, and the fish production systems were classified by cluster analysis. Four broad types were identified according to the complexity of household operations. The development of extensive systems (large-scale and low-input) in rural areas of central Cameroon is induced mainly by abundant available land. For semi-intensive systems in both regions (small-scale and high-input in the Western Region, large-scale and high-input in peri-urban areas of the Central Region), horizontal integration is not sufficient to make fish production profitable and sustainable. More intensive fish farms tend towards vertical integration, in which farmers establish close links with input suppliers. Main causes of low productivity of semi-intensive systems (1–2 t/ha/yr) are both lack of knowledge of fish farming principles by farmers and lack of technical improvement by extension agents and researchers which need to consider the local complexity of farming systems to develop and intensify fish production. The adaptation of development strategies to socio-economic and environmental contexts is a necessity to hope for an increase in fish pond aquaculture production in Africa.

Prediction of biological form at the adult stage of brown trout Salmo trutta using morphological or colorimetric criteria in migrating juveniles

To assess the correlation between four visual morphological types based on body colour and shape (fario trout, FT; shiny fario, SFT; presmolt trout, PST; typical smolt ST) of juvenile brown trout Salmo trutta during downstream spring migration and the biological form at the adult stage (river or sea), mark-recapture experiments were carried out over a period of 23 years. Evidence is provided that the visual SFT type is not a relevant one, while objective colorimetric measurements using a black basin are the best way to determine the morphological type in migrating juveniles.