Titre :	An altered carrying capacity of the benguela upwelling ecosystem for African penguins (Spheniscus demersus)
Type de document :	texte imprimé
Auteurs :	Crawford, Robert J. M., Auteur
Importance :	pp. 570-576
Langues :	Anglais (eng)
Index. décimale :	508 Voyages et relevés scientifiques. Histoire naturelle
Résumé :	The carrying capacity of an ecosystem for a species is an input parameter that is required for some models that assess population viability. It may be changed by an altered structure or functioning of the ecosystem, e.g. as a consequence of changes brought about by fishing or environmental change. Hence, it cannot necessarily be assumed that the pristine level of abundance of a species reflects the present-day carrying capacity of the ecosystem for that species. Historical and modern information on abundance and density-dependent responses is used to investigate changes in the carrying capacity of the Benguela upwelling ecosystem for African penguins (Spheniscus demersus), a species categorized as vulnerable. The carrying capacity was estimated to decrease from 1.5-3.0 million adult birds in the 1920s to just 10-20% of this value from 1978 to 2006, as a result inter alia of increased competition for food with purse-seine fisheries and fur seals (Arctocephalus pusillus pusillus). From 1988/1989 to 2005/2006, the per capita recruitment of young penguins to a colony where nesting space was not limiting was inversely related to the size of that colony, suggestive of a density-dependent response perhaps related to food availability.

An altered carrying capacity of the benguela upwelling ecosystem for African penguins (Spheniscus demersus) [texte imprimé] / Crawford, Robert J. M., Auteur . - [s.d.] . - pp. 570-576.
Langues : Anglais (eng)

Index. décimale :

508 Voyages et relevés scientifiques. Histoire naturelle

Résumé :

The carrying capacity of an ecosystem for a species is an input parameter that is required for some models that assess population viability. It may be changed by an altered structure or functioning of the ecosystem, e.g. as a consequence of changes brought about by fishing or environmental change. Hence, it cannot necessarily be assumed that the pristine level of abundance of a species reflects the present-day carrying capacity of the ecosystem for that species. Historical and modern information on abundance and density-dependent responses is used to investigate changes in the carrying capacity of the Benguela upwelling ecosystem for African penguins (Spheniscus demersus), a species categorized as vulnerable. The carrying capacity was estimated to decrease from 1.5-3.0 million adult birds in the 1920s to just 10-20% of this value from 1978 to 2006, as a result inter alia of increased competition for food with purse-seine fisheries and fur seals (Arctocephalus pusillus pusillus). From 1988/1989 to 2005/2006, the per capita recruitment of young penguins to a colony where nesting space was not limiting was inversely related to the size of that colony, suggestive of a density-dependent response perhaps related to food availability.