Depth and medium-scale spatial processes influence fish assemblage structure of unconsolidated habitats in a subtropical marine park.

Arthur L Schultz,Michelle Linklater,Stephen D A Smith,Hamish A Malcolm,Daniel J Bucher,Dennis M Higgs

doi:10.1371/journal.pone.0096798

Arthur L Schultz, Michelle Linklater + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0096798

Copy DOI

Abstract

Where biological datasets are spatially limited, abiotic surrogates have been advocated to inform objective planning for Marine Protected Areas. However, this approach assumes close correlation between abiotic and biotic patterns. The Solitary Islands Marine Park, northern NSW, Australia, currently uses a habitat classification system (HCS) to assist with planning, but this is based only on data for reefs. We used Baited Remote Underwater Videos (BRUVs) to survey fish assemblages of unconsolidated substrata at different depths, distances from shore, and across an along-shore spatial scale of 10 s of km (2 transects) to examine how well the HCS works for this dominant habitat. We used multivariate regression modelling to examine the importance of these, and other environmental factors (backscatter intensity, fine-scale bathymetric variation and rugosity), in structuring fish assemblages. There were significant differences in fish assemblages across depths, distance from shore, and over the medium spatial scale of the study: together, these factors generated the optimum model in multivariate regression. However, marginal tests suggested that backscatter intensity, which itself is a surrogate for sediment type and hardness, might also influence fish assemblages and needs further investigation. Species richness was significantly different across all factors: however, total MaxN only differed significantly between locations. This study demonstrates that the pre-existing abiotic HCS only partially represents the range of fish assemblages of unconsolidated habitats in the region.

Highlights

To adequately represent the entire range of biota present, conservation planning for sub-tidal marine ecosystems should be based on comprehensive understanding of species, habitats, ecosystems and associated ecological processes [1,2]
As data on the broad composition of unconsolidated habitats has recently been generated using swath acoustic multi-beam sidescan sonar [40], we explored the relationship between fish assemblages and physical habitat characteristics
Sixty-five Baited Remote Underwater Video (BRUV) deployments were completed within the Solitary Islands Marine Park (SIMP) during the Austral winter of 2011 (Fig. 1, Table 1)

Summary

Introduction

To adequately represent the entire range of biota present, conservation planning for sub-tidal marine ecosystems should be based on comprehensive understanding of species, habitats, ecosystems and associated ecological processes [1,2]. In most cases, these data are not available, and much of the decision-making for planning and management of Marine Protected Areas (MPAs) relies on incomplete species inventories and distributions [1,3,4,5]. New approaches that better integrate abiotic data into overall planning have been advocated [1,4,6,7]. Physical and biophysical surrogates for biotic communities are commonly used in planning of MPAs as they are more measured, categorised and geo-referenced [8,9]. The use of abiotic characteristics in planning carries the assumption that biotic patterns, which are the end-points of conservation management, consistently correlate with abiotic variables. Testing needs to be on a scale relevant to MPA planning [8,16,17], and better information on biotic distributions is required for integration into existing planning and management of MPAs [4,16]

Methods

Results

Discussion

Conclusion