Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa)
As the biomass of jellyfish (medusae of the Scyphozoa and Hydrozoa) has risen in numerous locations worldwide, awareness of their potential to exert a controlling influence on marine ecosystems and hinder the recruitment of fish stocks has increased. Medusae are capable of intensive, size–selective,...
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Format: | Doctoral or Postdoctoral Thesis |
Language: | English |
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University of St Andrews
2008
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Online Access: | http://hdl.handle.net/10023/466 |
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ftstandrewserep:oai:research-repository.st-andrews.ac.uk:10023/466 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
University of St Andrews: Digital Research Repository |
op_collection_id |
ftstandrewserep |
language |
English |
topic |
Jellyfish Zooplankton Acoustics Fish QL377.S4L8 Jellyfishes--Ecology Marine invertebrate populations--Estimates Animal population density--Measurement Echo sounding Underwater acoustics--Analysis |
spellingShingle |
Jellyfish Zooplankton Acoustics Fish QL377.S4L8 Jellyfishes--Ecology Marine invertebrate populations--Estimates Animal population density--Measurement Echo sounding Underwater acoustics--Analysis Lynam, Christopher Philip Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa) |
topic_facet |
Jellyfish Zooplankton Acoustics Fish QL377.S4L8 Jellyfishes--Ecology Marine invertebrate populations--Estimates Animal population density--Measurement Echo sounding Underwater acoustics--Analysis |
description |
As the biomass of jellyfish (medusae of the Scyphozoa and Hydrozoa) has risen in numerous locations worldwide, awareness of their potential to exert a controlling influence on marine ecosystems and hinder the recruitment of fish stocks has increased. Medusae are capable of intensive, size–selective, predation on zooplankton, which may alter the composition of the plankton community. Jellyfish are often found in dense layers, up to hundreds of metres thick, which can extend horizontally for hundreds of kilometres. Such aggregations may benefit specialist feeders, such as turtles, that rely upon jellyfish for food and those fish that are able to find refuge under the jellyfish umbrellas. Nonetheless, the predominance of jellyfish in pelagic ecosystems is not generally viewed as desirable; in fact, this situation has been portrayed as the result of pollution and overexploitation of otherwise productive seas. However, jellyfish are sensitive indicators of environmental change, and their populations appear to respond to climatic fluctuations, so jellyfish warrant study for their intrinsic ecosystem role particularly given present concerns over climate change. With growing acceptance that fishery management should take an holistic ‘ecosystem approach’, knowledge of the interactions between jellyfish, fisheries and climate may be vital in progression towards the goal of ecosystem–based sustainable management of fisheries. Unfortunately, due to their gelatinous nature, medusae are difficult to sample using conventional netting techniques and data on changes in distribution and abundance are consequently sparse. Recent studies have demonstrated that medusae can be detected acoustically and that this technique could provide a rapid and cost–effective estimate of their biomass and distribution. This thesis reports my endeavour to demonstrate the ecosystem role of medusae and to develop acoustic techniques to monitor their biomass. Through regession analyses, I link the abundance of medusae (Aurelia aurita, Cyanea lamarckii, and Cyanea capillata) in regions of the North Sea to climatic fluctuations, as quantified by the North Atlantic Oscillation Index, and show that medusae may be important indicators of regional ecosystem change. The mechanisms linking climatic fluctuations to ecosystem changes are explored via a correlative modelling approach using General Additive Models; I show that the mechanisms are location dependent and explainable in terms of direct, rapidly responding (intra–annual) influences (surface warming, river run–off, and wind–driven mixing and advection) and longer–term (interannual) oceanographic responses (changes in circulation currents i.e. the northward extent of the gulf stream and relative strength of inflow into the North Sea of the North Atlantic current, Continental Shelf Jet and Arctic waters). I present correlative evidence for a detrimental impact by Aurelia aurita on herring 0–group recruitment, once the influence of interannual change in herring spewing stock biomass on recruitment is factored out through modelling with a Ricker stock–recruitment relationship. Similarly, a commensal relationship between whiting and Cyanea spp. medusae is shown to improve North Sea whiting survival to the 1–group. In progress towards the automated acoustic identification of species, I have developed an in situ discrimination tool that can distinguish between echoes from: Aequorea aequorea; Chrysaora hysoscella; clupeid fish (sardine, anchovy and round herring); and horse mackerel/Cape hake. The technique relies upon characteristic differences in echo strength between frequencies, which are determined for each jellyfish species and finfish group using combined multifrequency acoustic and pelagic trawl samples. This method has facilitated the world’s first acoustic–based estimate of jellyfish biomass in the Namibian Benguela Sea. The 12.2 million tonnes of biomass of medusae (Aequorea aequorea and Chrysaora hysoscella) in the Namibian Benguela Sea was found to be greater than the combined biomass, 3.6 million tonnes, of commercially important fish (horse mackerel, Cape hake, sardines, anchovy, and round herring) in the same area. These results suggest that medusae may have an important role in the Benguela ecosystem that has previously been overlooked and that their biomass should be monitored. |
author2 |
Brierley, Andrew |
format |
Doctoral or Postdoctoral Thesis |
author |
Lynam, Christopher Philip |
author_facet |
Lynam, Christopher Philip |
author_sort |
Lynam, Christopher Philip |
title |
Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa) |
title_short |
Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa) |
title_full |
Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa) |
title_fullStr |
Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa) |
title_full_unstemmed |
Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa) |
title_sort |
ecological and acoustic investigations of jellyfish (scyphozoa and hydrozoa) |
publisher |
University of St Andrews |
publishDate |
2008 |
url |
http://hdl.handle.net/10023/466 |
op_coverage |
264 p. |
long_lat |
ENVELOPE(15.612,15.612,66.797,66.797) ENVELOPE(162.000,162.000,-76.550,-76.550) |
geographic |
Arctic Hake Endeavour |
geographic_facet |
Arctic Hake Endeavour |
genre |
Arctic Climate change north atlantic current North Atlantic North Atlantic oscillation Zooplankton |
genre_facet |
Arctic Climate change north atlantic current North Atlantic North Atlantic oscillation Zooplankton |
op_relation |
Aebischer, N. J., J. C. Coulson, J. M. Colebrook (1990). Parallel Long-Term Trends across 4 Marine Trophic Levels and Weather. Nature 347(6295): 753-755. Alheit, J., E. Hagen (1997). Long-term climate forcing of European herring and sardine populations. Fisheries Oceanography 6(2): 130-139 Alldredge, A. L. (1983). The quantitative significance of gelatinous zooplankton as pelagic consumers, p. 407-433. In M. J. R. Fasham [ed.], Flow of Energy and Materials in Marine Ecosystems: Theory and Practice. Plenum Press. Aquascope (2000). Tjärnö Marine Biological Laboratory, Strömstad, Sweden. http://www.vattenkikaren.gu.se/defaulte.html. uk.bl.ethos.552115 http://hdl.handle.net/10023/466 |
op_rights |
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported http://creativecommons.org/licenses/by-nc-nd/3.0/ |
op_rightsnorm |
CC-BY-NC-ND |
_version_ |
1766350493161881600 |
spelling |
ftstandrewserep:oai:research-repository.st-andrews.ac.uk:10023/466 2023-05-15T15:20:15+02:00 Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa) Lynam, Christopher Philip Brierley, Andrew 264 p. 2008-04-17T14:31:59Z 14143367 bytes application/pdf http://hdl.handle.net/10023/466 en eng University of St Andrews The University of St Andrews Aebischer, N. J., J. C. Coulson, J. M. Colebrook (1990). Parallel Long-Term Trends across 4 Marine Trophic Levels and Weather. Nature 347(6295): 753-755. Alheit, J., E. Hagen (1997). Long-term climate forcing of European herring and sardine populations. Fisheries Oceanography 6(2): 130-139 Alldredge, A. L. (1983). The quantitative significance of gelatinous zooplankton as pelagic consumers, p. 407-433. In M. J. R. Fasham [ed.], Flow of Energy and Materials in Marine Ecosystems: Theory and Practice. Plenum Press. Aquascope (2000). Tjärnö Marine Biological Laboratory, Strömstad, Sweden. http://www.vattenkikaren.gu.se/defaulte.html. uk.bl.ethos.552115 http://hdl.handle.net/10023/466 Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported http://creativecommons.org/licenses/by-nc-nd/3.0/ CC-BY-NC-ND Jellyfish Zooplankton Acoustics Fish QL377.S4L8 Jellyfishes--Ecology Marine invertebrate populations--Estimates Animal population density--Measurement Echo sounding Underwater acoustics--Analysis Thesis Doctoral PhD Doctor of Philosophy 2008 ftstandrewserep 2021-08-08T10:16:52Z As the biomass of jellyfish (medusae of the Scyphozoa and Hydrozoa) has risen in numerous locations worldwide, awareness of their potential to exert a controlling influence on marine ecosystems and hinder the recruitment of fish stocks has increased. Medusae are capable of intensive, size–selective, predation on zooplankton, which may alter the composition of the plankton community. Jellyfish are often found in dense layers, up to hundreds of metres thick, which can extend horizontally for hundreds of kilometres. Such aggregations may benefit specialist feeders, such as turtles, that rely upon jellyfish for food and those fish that are able to find refuge under the jellyfish umbrellas. Nonetheless, the predominance of jellyfish in pelagic ecosystems is not generally viewed as desirable; in fact, this situation has been portrayed as the result of pollution and overexploitation of otherwise productive seas. However, jellyfish are sensitive indicators of environmental change, and their populations appear to respond to climatic fluctuations, so jellyfish warrant study for their intrinsic ecosystem role particularly given present concerns over climate change. With growing acceptance that fishery management should take an holistic ‘ecosystem approach’, knowledge of the interactions between jellyfish, fisheries and climate may be vital in progression towards the goal of ecosystem–based sustainable management of fisheries. Unfortunately, due to their gelatinous nature, medusae are difficult to sample using conventional netting techniques and data on changes in distribution and abundance are consequently sparse. Recent studies have demonstrated that medusae can be detected acoustically and that this technique could provide a rapid and cost–effective estimate of their biomass and distribution. This thesis reports my endeavour to demonstrate the ecosystem role of medusae and to develop acoustic techniques to monitor their biomass. Through regession analyses, I link the abundance of medusae (Aurelia aurita, Cyanea lamarckii, and Cyanea capillata) in regions of the North Sea to climatic fluctuations, as quantified by the North Atlantic Oscillation Index, and show that medusae may be important indicators of regional ecosystem change. The mechanisms linking climatic fluctuations to ecosystem changes are explored via a correlative modelling approach using General Additive Models; I show that the mechanisms are location dependent and explainable in terms of direct, rapidly responding (intra–annual) influences (surface warming, river run–off, and wind–driven mixing and advection) and longer–term (interannual) oceanographic responses (changes in circulation currents i.e. the northward extent of the gulf stream and relative strength of inflow into the North Sea of the North Atlantic current, Continental Shelf Jet and Arctic waters). I present correlative evidence for a detrimental impact by Aurelia aurita on herring 0–group recruitment, once the influence of interannual change in herring spewing stock biomass on recruitment is factored out through modelling with a Ricker stock–recruitment relationship. Similarly, a commensal relationship between whiting and Cyanea spp. medusae is shown to improve North Sea whiting survival to the 1–group. In progress towards the automated acoustic identification of species, I have developed an in situ discrimination tool that can distinguish between echoes from: Aequorea aequorea; Chrysaora hysoscella; clupeid fish (sardine, anchovy and round herring); and horse mackerel/Cape hake. The technique relies upon characteristic differences in echo strength between frequencies, which are determined for each jellyfish species and finfish group using combined multifrequency acoustic and pelagic trawl samples. This method has facilitated the world’s first acoustic–based estimate of jellyfish biomass in the Namibian Benguela Sea. The 12.2 million tonnes of biomass of medusae (Aequorea aequorea and Chrysaora hysoscella) in the Namibian Benguela Sea was found to be greater than the combined biomass, 3.6 million tonnes, of commercially important fish (horse mackerel, Cape hake, sardines, anchovy, and round herring) in the same area. These results suggest that medusae may have an important role in the Benguela ecosystem that has previously been overlooked and that their biomass should be monitored. Doctoral or Postdoctoral Thesis Arctic Climate change north atlantic current North Atlantic North Atlantic oscillation Zooplankton University of St Andrews: Digital Research Repository Arctic Hake ENVELOPE(15.612,15.612,66.797,66.797) Endeavour ENVELOPE(162.000,162.000,-76.550,-76.550) |