Year

2017

Degree Name

Doctor of Philosophy

Department

School of Biological Sciences

Abstract

Seascape ecology is an emerging sub-discipline of marine ecology, which examines the effect of spatial heterogeneity in marine ecosystems on ecological processes and species distributions. The opportunity to study seascape ecology in many coastal regions has been greatly assisted by advances in remote sensing technologies, which can acquire detailed habitat data over a range of spatial scales. This now allows quantification of spatial patterns in seascapes and the scientific examination of the ecological consequences of such patterns. Current research applying this approach has begun to demonstrate the importance of seascape connectivity and structural complexity in driving spatial variability of marine fish assemblages. Much of this research however, has focussed on tropical regions and as a result the effect of seascape patterning on temperate fishes remains poorly resolved. The aim of this thesis was to examine the seascape ecology of temperate fishes in two Marine Protected Areas (MPAs) in south-east Australian waters and also examine how this approach can aid in the design and assessment of MPAs. I achieved this by investigating spatial variability in temperate fish assemblages over three scales to examine the effect of i) three-dimensional reef structural complexity, ii) differences among habitat types (seagrass, rocky reef and unvegetated sediment) and iii) the seascape connectivity of habitats. I used baited remote underwater video systems (BRUVs) to survey demersal and mid-water fish assemblages in conjunction with existing habitat mapping to examine the relationship between fish and their habitats. In the Lord Howe Island Marine Park (LHIMP), reef structural complexity strongly influenced the abundance of yellowtail kingfish; Seriola lalandi. Despite being heavily targeted by fishers, a ‘conventional’ (GLM) assessment on the LHIMP revealed no difference in the abundance of S. lalandi between fished and unfished zones. However, on accounting for reef structural complexity in the assessment, I revealed substantially higher abundances of S. lalandi in unfished zones. This positive effect was only observed in their optimal habitat, reefs of high structural complexity. In the Jervis Bay Marine Park (JBMP), habitat type (seagrass, rocky reef and unvegetated sediment) was a strong and consistent predictor of the demersal fish assemblage but did not influence fishes in the mid-water environment. Although habitat influenced the abundance of many demersal fishes, some taxa from the demersal assemblage displayed no affinity to underlying habitat type. Seascape composition and connectivity also appeared to strongly influence temperate fish assemblages. The abundance and diversity of temperate fishes was correlated with the area of rocky reef and seagrass within the surrounding seascape. The apparent importance of seascape connectivity was also noted in the LHIMP, where adult black rockcod (Epinephelus daemelii) were only recorded in areas adjacent to their nursery grounds. Finally, I sought to compare the effectiveness of attractants other than bait (sight and sound stimuli) to entice pelagic fishes to video systems positioned in the mid-water environment. I found the combination of sight, sound and scent attractants on mid-water remote underwater videos (RUVs) recorded a substantially higher abundance and shorter time of first arrival of pelagic fishes compared to RUVs with one or no attractant. I suggest future studies using this sampling method to survey pelagic fishes employ multiple attractants. My findings demonstrate that temperate fishes are influenced by patterns in seascapes and habitats at a number of spatial scales. They also have important implications for spatial conservation strategies such as MPAs, particularly in terms of their design, assessment and adaptive management. Representation of seascape variability over a number of spatial scales in MPA planning is likely to better represent temperate fish assemblages. Furthermore, I demonstrate that habitat classes and measures of structural complexity are appropriate surrogates for certain fishes, which is useful in MPA planning. Finally, I demonstrate that accounting for seascape variability in MPA evaluation is likely to provide a better assessment and clearer understanding of ecological change associated with this management action. In conclusion, integrating seascape ecology into MPA science will increase the usefulness of this conservation strategy to combat growing declines in global marine biodiversity.

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