Abstract
The aim of this study was to document the composition and distribution of deep-water fishes associated with a submarine canyon-valley feature. A work-class Remotely Operated Vehicle (ROV) fitted with stereo-video cameras was used to record fish abundance and assemblage composition along transects at water depths between 300 and 900 metres. Three areas (A, B, C) were sampled along a submarine canyon-valley feature on the continental slope of tropical north-western Australia. Water conductivity/salinity, temperature, and depth were also collected using an ROV mounted Conductivity Temperature and Depth (CTD) instrument. Multivariate analyses were used to investigate fish assemblage composition, and species distribution models were fitted using boosted regression trees. These models were used to generate predictive maps of the occurrence of four abundant taxa over the survey areas. CTD data identified three water masses, tropical surface water, South Indian Central Water (centred ∼200 m depth), and a lower salinity Antarctic Intermediate Water (AAIW) ∼550 m depth. Distinct fish assemblages were found among areas and between canyon-valley and non-canyon habitats. The canyon-valley habitats supported more fish and taxa than non-canyon habitats. The fish assemblages of the deeper location (∼700–900 m, Area A) were different to that of the shallower locations (∼400–700 m, Areas B and C). Deep-water habitats were characterised by a Paraliparis (snail fish) species, while shallower habitats were characterised by the family Macrouridae (rat tails). Species distribution models highlighted the fine-scale environmental niche associations of the four most abundant taxa. The survey area had a high diversity of fish taxa and was dominated by the family Macrouridae. The deepest habitat had a different fish fauna to the shallower areas. This faunal break can be attributed to the influence of AAIW. ROVs provide a platform on which multiple instruments can be mounted and complementary streams of data collected simultaneously. By surveying fish in situ along transects of defined dimensions it is possible to produce species distribution models that will facilitate a greater insight into the ecology of deep-water marine systems.
Highlights
The deep sea is the largest environment on earth (Levin et al, 2001) and plays a pivotal role in cycling nutrients and water at global scales
Macrouridae sp4 was predicted to be most likely to occur at depths between 500 and 600 m (Figure 7)
Higher probability of occurrence of Macrouridae sp2 and Macrouridae sp4 was predicted on the seabed surrounding the canyon-valley slopes, whereas Macrouridae sp5 was predicted to be deeper and associated with both flat areas of low structural complexity, and within the feature on canyon-valley slopes and the canyon floor (Figures 7, 8)
Summary
The deep sea is the largest environment on earth (Levin et al, 2001) and plays a pivotal role in cycling nutrients and water at global scales. Conducting research in deep-sea environments is challenging due to a lack of natural light, high water pressure, low temperature, low oxygen levels and the need for large vessels and advanced technologies to reach these depths. Despite their remoteness, deep-water habitats are susceptible to numerous anthropogenic impacts on global and local scales, including climate change (Hoegh-Guldberg and Bruno, 2010; Rogers, 2015), overfishing (Clark, 2001), plastic pollution (Woodall et al, 2014), exploration and development activities such as drilling (Jones, 2009) or accidents such as oil spills (White et al, 2012). It is important that quantitative data on these ecosystems is obtained in order to assess their vulnerability and ability to recover from disturbance, and to mitigate anthropogenic impacts on these ecosystems
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
