Effect of wave exposure on growth and mortality rates of the mussel Perna perna: bottom up regulation of intertidal populations
- McQuaid, Christopher D, Lindsay, Tracy L
- Authors: McQuaid, Christopher D , Lindsay, Tracy L
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6955 , http://hdl.handle.net/10962/d1011994
- Description: The effect of wave exposure on the growth of low-shore populations of Perna perna (Linnaeus) was determined using 3 independent approaches at 6 sites on the south coast of South Africa: (1) Individual marking; notches were filed on the growing edges of mussels in situ. After 111 d, growth from the mark to the new growing edge was measured. (2) Internal shell-growth bands; mussels from the mark recapture experiment were used to establish that growth bands are laid down tidally. Unmarked individuals were then used to measure growth over the last 60 tides. (3) Shepherd¹s length-composition analysis (SLCA); growth rates were determined from length-frequency distributions in 11 samples collected at 6 wk intervals over 15 mo. All 3 approaches showed that growth rate was approximately twice as fast on exposed as on sheltered shores (ANCOVA, p < 0.05 in all cases). Mean length for the first year of growth (averaged for the 3 methods) was 47 and 22 mm, respectively. There were, however, considerable differences among methods. Marking provided the lowest estimates of growth rates, and SLCA the highest. The mean mortality index (Z yr-1) was significantly higher and annual survival rate lower for exposed shores, indicating faster turnover under exposed conditions. Mean longevity on exposed shores (2.6 yr) was only one-third of estimated longevity on sheltered shores (6.7 yr). These findings show that degree of exposure has important interactions with growth and mortality of mussels on the low shore, and that these effects are independent of the effects of exposure on density. The findings also indicate strong bottom up regulation of mussel populations.
- Full Text:
- Date Issued: 2000
- Authors: McQuaid, Christopher D , Lindsay, Tracy L
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6955 , http://hdl.handle.net/10962/d1011994
- Description: The effect of wave exposure on the growth of low-shore populations of Perna perna (Linnaeus) was determined using 3 independent approaches at 6 sites on the south coast of South Africa: (1) Individual marking; notches were filed on the growing edges of mussels in situ. After 111 d, growth from the mark to the new growing edge was measured. (2) Internal shell-growth bands; mussels from the mark recapture experiment were used to establish that growth bands are laid down tidally. Unmarked individuals were then used to measure growth over the last 60 tides. (3) Shepherd¹s length-composition analysis (SLCA); growth rates were determined from length-frequency distributions in 11 samples collected at 6 wk intervals over 15 mo. All 3 approaches showed that growth rate was approximately twice as fast on exposed as on sheltered shores (ANCOVA, p < 0.05 in all cases). Mean length for the first year of growth (averaged for the 3 methods) was 47 and 22 mm, respectively. There were, however, considerable differences among methods. Marking provided the lowest estimates of growth rates, and SLCA the highest. The mean mortality index (Z yr-1) was significantly higher and annual survival rate lower for exposed shores, indicating faster turnover under exposed conditions. Mean longevity on exposed shores (2.6 yr) was only one-third of estimated longevity on sheltered shores (6.7 yr). These findings show that degree of exposure has important interactions with growth and mortality of mussels on the low shore, and that these effects are independent of the effects of exposure on density. The findings also indicate strong bottom up regulation of mussel populations.
- Full Text:
- Date Issued: 2000
δ13C and δ15N biogeographic trends in rocky intertidal communities along the coast of South Africa: evidence of strong environmental signatures
- Hill, Jaclyn M, McQuaid, Christopher D
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2000
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444664 , vital:74258 , https://doi.org/10.1016/j.ecss.2008.08.005
- Description: Ecosystem dynamics driven by top-down controls have been well documented in rocky intertidal communities, while the effects of bottom-up influences are comparatively poorly understood. We hypothesized that large-scale signatures of the physical environment may be identifiable along the South African coastline as it is subject to two very different current systems (Benguela and Agulhas Currents) that profoundly influence primary production and thus both food type and availability. Through stable isotope analysis, we examined biogeographic patterns in multiple trophic levels at four sites along a 1400-km stretch of South African coastline and investigated the dietary role of macroalgal-derived organic carbon in rocky intertidal communities. The general positioning of trophic groups was comparable across all sites, with animals from the same trophic levels grouping together and with a δ15N fractionation of 1–2‰ between levels.
- Full Text:
- Date Issued: 2000
- Authors: Hill, Jaclyn M , McQuaid, Christopher D
- Date: 2000
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444664 , vital:74258 , https://doi.org/10.1016/j.ecss.2008.08.005
- Description: Ecosystem dynamics driven by top-down controls have been well documented in rocky intertidal communities, while the effects of bottom-up influences are comparatively poorly understood. We hypothesized that large-scale signatures of the physical environment may be identifiable along the South African coastline as it is subject to two very different current systems (Benguela and Agulhas Currents) that profoundly influence primary production and thus both food type and availability. Through stable isotope analysis, we examined biogeographic patterns in multiple trophic levels at four sites along a 1400-km stretch of South African coastline and investigated the dietary role of macroalgal-derived organic carbon in rocky intertidal communities. The general positioning of trophic groups was comparable across all sites, with animals from the same trophic levels grouping together and with a δ15N fractionation of 1–2‰ between levels.
- Full Text:
- Date Issued: 2000
Regionalism in marine biology: the convergence of ecology, economics and politics in South Africa
- McQuaid, Christopher D, Payne, A I L
- Authors: McQuaid, Christopher D , Payne, A I L
- Date: 1998
- Language: English
- Type: Article
- Identifier: vital:6938 , http://hdl.handle.net/10962/d1011960
- Description: The South African coast includes biogeographic provinces which are quite distinct in their abilities to sustain exploitation and in the types of exploitation they experience. As a result, no single region can act as a model for the management of living resources around the entire coast. Instead, appropriate management must rest on regionally based research. Past research in marine biology focused on the west coast with much less attention being given to the east and south coasts, where non-commercial, subsistence-level fisheries predominate. A partial decentralisation of research focus is essential. This requires commitment from national-level research bodies and some certainty about at least medium-term funding. This paper addresses the convergence of ecology, economics and politics in South Africa and illustrates the direct relevance that fundamental or basic research can have to socioeconomic problems. Recruitment of the resource; Geographical variation in biological processes; State of research policy; Promise of regulations.
- Full Text: false
- Date Issued: 1998
- Authors: McQuaid, Christopher D , Payne, A I L
- Date: 1998
- Language: English
- Type: Article
- Identifier: vital:6938 , http://hdl.handle.net/10962/d1011960
- Description: The South African coast includes biogeographic provinces which are quite distinct in their abilities to sustain exploitation and in the types of exploitation they experience. As a result, no single region can act as a model for the management of living resources around the entire coast. Instead, appropriate management must rest on regionally based research. Past research in marine biology focused on the west coast with much less attention being given to the east and south coasts, where non-commercial, subsistence-level fisheries predominate. A partial decentralisation of research focus is essential. This requires commitment from national-level research bodies and some certainty about at least medium-term funding. This paper addresses the convergence of ecology, economics and politics in South Africa and illustrates the direct relevance that fundamental or basic research can have to socioeconomic problems. Recruitment of the resource; Geographical variation in biological processes; State of research policy; Promise of regulations.
- Full Text: false
- Date Issued: 1998
Spatial and temporal variability in recruitment of intertidal mussels around the coast of southern Africa
- Harris, Jean M, Branch, George M, Elliot, Bridget L, Currie, Bronwen, Dye, Arthur H, McQuaid, Christopher D, Tomalin, Bruce J, Velasquez, Claudio
- Authors: Harris, Jean M , Branch, George M , Elliot, Bridget L , Currie, Bronwen , Dye, Arthur H , McQuaid, Christopher D , Tomalin, Bruce J , Velasquez, Claudio
- Date: 1998
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447579 , vital:74658 , https://www.ajol.info/index.php/az/article/view/154717
- Description: Intensity of intertidal mussel recruitment was compared across a range of different spatial and temporal scales around the coast of southern Africa between June 1995 and October 1996. Comparison of the east and west coasts revealed significantly higher recruit densities on the west coast, corresponding to larger adult densities. This difference between the two coasts reflects biogeographic disparities in mussel species composition, growth rates and spawning intensities, oceanographic conditions and productivity. Significant spatial variations in recruitment were recorded between regions 100–1000 km apart and between localities 1–25 km apart. Results suggest that the influence of dispersal processes on recruitment patterns acts at a relatively small scale, and may affect the distribution and abundance of adults among shores only a few kilometres apart.
- Full Text:
- Date Issued: 1998
- Authors: Harris, Jean M , Branch, George M , Elliot, Bridget L , Currie, Bronwen , Dye, Arthur H , McQuaid, Christopher D , Tomalin, Bruce J , Velasquez, Claudio
- Date: 1998
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447579 , vital:74658 , https://www.ajol.info/index.php/az/article/view/154717
- Description: Intensity of intertidal mussel recruitment was compared across a range of different spatial and temporal scales around the coast of southern Africa between June 1995 and October 1996. Comparison of the east and west coasts revealed significantly higher recruit densities on the west coast, corresponding to larger adult densities. This difference between the two coasts reflects biogeographic disparities in mussel species composition, growth rates and spawning intensities, oceanographic conditions and productivity. Significant spatial variations in recruitment were recorded between regions 100–1000 km apart and between localities 1–25 km apart. Results suggest that the influence of dispersal processes on recruitment patterns acts at a relatively small scale, and may affect the distribution and abundance of adults among shores only a few kilometres apart.
- Full Text:
- Date Issued: 1998