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Effectiveness of passive acoustic telemetry on coral reefs depends on deployment strategy and benthic substrate characteristics
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Acoustic telemetry can be an effective technology for investigating movement and behaviour ofaquatic species. While some scientific studies have evaluated the performance of acoustic receivers infreshwater and estuarine habitats, few studies have been carried out in coastal coral reef environments.This study investigated the effects of receiver deployment strategy and abiotic and biotic factors(benthic habitat characteristics, background noise, and depth) on detection rates and detection range incoral reef habitats. These effects were examined using stationary acoustic transmitters deployed in thewater column or surgically inserted in free-swimming fish of two species of herbivorous rabbitfish(Siganidae). Deployment strategy had the largest effect on detection rates and detection range withinthe acoustic array. Acoustic receivers deployed high in the water column were far more efficient thanthose deployed close to the bottom, with approximately 45% more detections registered andsignificantly increased detection ranges. This was consistent with the results from tagged rabbitfish, asacoustic receivers deployed high in the water column recorded more than twice as many detections than receivers deployed close to the bottom for fish displaying natural behaviour. Benthic substrate interms of hard substrate, rubble, and sand had an impact on detection rates and there was a clear dielpattern in detection rates between day and night. To conclude, deployment strategy and habitat characteristics have a large impact on detection rates and detection ranges in passive acoustic arrays incoral reef habitats. This finding emphasises the importance of using permanent transmitters as controlsto evaluate effectiveness of acoustic receivers throughout acoustic telemetry studies.

National Category
Biological Sciences
Research subject
Marine Ecotoxicology
Identifiers
URN: urn:nbn:se:su:diva-125594OAI: oai:DiVA.org:su-125594DiVA: diva2:894218
Available from: 2016-01-14 Created: 2016-01-14 Last updated: 2016-01-29Bibliographically approved
In thesis
1. Coral Reef Habitats and Fish Connectivity: Implications for coastal management and fishery
Open this publication in new window or tab >>Coral Reef Habitats and Fish Connectivity: Implications for coastal management and fishery
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coral reefs have one of the highest levels of biodiversity of all ecosystems in the world and are important for both human livelihood and food security throughout many tropical countries. However, due to increased anthropogenic pressure on marine ecosystems, especially during the last couple of decades, coral reefs have become critically over-fished, and many reefs are now in a degraded state and are facing additional future threats due to further over-exploitation, chemical pollution, sedimentation, and effects of climate change.

The main aim of this PhD thesis was to understand effects of anthropogenic disturbances on tropical coastal ecosystems and fish connectivity for coastal management purposes. Therefore, linkages between anthropogenic disturbance and corals were investigated (Paper I), as well as interactions between coral reef habitat and associated fish assemblage (Paper II). Furthermore, connectivity between coral reefs and other tropical coastal ecosystems was explored (Paper III), as well as fish migration to reproduction sites (Paper IV), and evaluations of spatial ecology methods (Paper V).

The result showed that coral reefs that are already exposed to disturbances, such as freshwater and nutrient run-offs, may be more sensitive to climate change, in terms of increased sea surface temperatures (Paper I). In addition, there were also clear linkages between coral reef quality, in terms of coral coverage, and fish assemblages, which displayed high spatial variability and suggesting patchy recovery after the 1997/1998 bleaching and subsequent coral mass mortality event (Paper II). This highlights the importance of understanding effects of disturbances on corals, especially in terms of synergistic effects between increased water temperatures and other coastal stressors such as decreased salinity and increased nutrients; and the indirect effects of habitat degradation on the fish community.

Linkages between fish and different coastal habitats were further explored. The results showed that coral reefs were strongly connected with mangrove and seagrass beds, through ontogenetic migration of fish (Paper III). Migrations to spawning sites of groupers were related to lunar activities when thousands of fish gather for reproduction purposes during new moon, which increases the risk of over-exploitation (Paper IV). The results emphasises the importance of protecting key areas such as nursing grounds and reproduction sites. Furthermore, acoustic telemetry has become an increasingly common method in studies of fish movement, and the results showed that efficiency of acoustic arrays may increase depending on deployment strategies and habitat characteristics (Paper V).

In conclusion, the results from this PhD thesis emphasises the importance of protecting coral reef habitats, as well as identifying related susceptible tropical coastal areas, such as nursing grounds and reproduction sites. Indeed, a better scientific understanding of coral reef ecology and indirect and direct effects on fish assemblages are needed for efficient and accurate coastal management decisions.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2016. 80 p.
Keyword
anthropogenic disturbance, coral reef habitat, fish community, coastal ecosystems, conservation management, spatial ecology, seascape perspective, holistic approach
National Category
Biological Sciences
Research subject
Marine Ecotoxicology
Identifiers
urn:nbn:se:su:diva-125595 (URN)978-91-7649-337-3 (ISBN)
Public defence
2016-03-11, Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.

Available from: 2016-02-17 Created: 2016-01-14 Last updated: 2016-03-01Bibliographically approved

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Jörgensen, Tove Lund
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