Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?

The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knynsa seaho...

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Main Authors: Teske, P R, Lockyear, J F, Hecht, T, Kaiser, Horst
Format: Others
Language:English
Published: 2007
Online Access:http://hdl.handle.net/10962/d1011616
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spelling ndltd-netd.ac.za-oai-union.ndltd.org-rhodes-vital-68712018-03-06T03:55:28ZDoes the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?Teske, P RLockyear, J FHecht, TKaiser, HorstThe Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knynsa seahorses are associated with specific regions within the estuaries, on which conservation efforts could concentrate. The relationship of Knysna seahorses with aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine systems inhabited by H. capensis) to determine whether this species shows a preference for a particular plant species, vegetation density or vegetation height. Seahorses were associated with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum, Halophila ovalis and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects with which seahorses were associated. The relative abundance of plant species changed along the estuary, but seahorses were present throughout the system, except at the estuary mouth, which was characterized by low plant densities and strong currents. No significant difference was found between the proportion of plant species present in a particular region of the estuary and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast. Adult seahorse density (individuals/m²) was significantly correlated with percentage vegetation cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly more adult and juvenile seahorses were found at sites characterized by high vegetation cover (>75%) than at sites with lower cover. Our results indicate that although there is some evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be encountered anywhere in the estuary where aquatic plants are present. Conservation efforts in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise approximately 11% of the total submerged surface area.2007Article8 pagespdfvital:6871http://hdl.handle.net/10962/d1011616English
collection NDLTD
language English
format Others
sources NDLTD
description The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knynsa seahorses are associated with specific regions within the estuaries, on which conservation efforts could concentrate. The relationship of Knysna seahorses with aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine systems inhabited by H. capensis) to determine whether this species shows a preference for a particular plant species, vegetation density or vegetation height. Seahorses were associated with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum, Halophila ovalis and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects with which seahorses were associated. The relative abundance of plant species changed along the estuary, but seahorses were present throughout the system, except at the estuary mouth, which was characterized by low plant densities and strong currents. No significant difference was found between the proportion of plant species present in a particular region of the estuary and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast. Adult seahorse density (individuals/m²) was significantly correlated with percentage vegetation cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly more adult and juvenile seahorses were found at sites characterized by high vegetation cover (>75%) than at sites with lower cover. Our results indicate that although there is some evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be encountered anywhere in the estuary where aquatic plants are present. Conservation efforts in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise approximately 11% of the total submerged surface area.
author Teske, P R
Lockyear, J F
Hecht, T
Kaiser, Horst
spellingShingle Teske, P R
Lockyear, J F
Hecht, T
Kaiser, Horst
Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
author_facet Teske, P R
Lockyear, J F
Hecht, T
Kaiser, Horst
author_sort Teske, P R
title Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
title_short Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
title_full Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
title_fullStr Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
title_full_unstemmed Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
title_sort does the endangered knysna seahorse, hippocampus capensis, have a preference for aquatic vegetation type, cover or height?
publishDate 2007
url http://hdl.handle.net/10962/d1011616
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AT hechtt doestheendangeredknysnaseahorsehippocampuscapensishaveapreferenceforaquaticvegetationtypecoverorheight
AT kaiserhorst doestheendangeredknysnaseahorsehippocampuscapensishaveapreferenceforaquaticvegetationtypecoverorheight
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