BRUVS in Hamelin Pool - Part I: What are BRUVS?

By Kelly Campbell 
on 22 Nov 2016 
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Renowned for its natural beauty and scientific significance, the Shark Bay World Heritage Area is home to the Wooramel Bank, which is the largest seagrass bank (4,800 km2) in the world. It also has one of the largest and most stable populations of Dugongs, and the largest and most diverse assemblage of modern Stromatolites in Hamelin Pool.

Although research has been conducted throughout greater Shark Bay, minimal ecological research has been undertaken within the hyper-saline waters of Hamelin Pool, which borders the western boundary of Bush Heritage's Hamelin Station Reserve. Hamelin Pool is thought to have a low diversity of marine organisms, in particular fishes, due to the high salinity.

A comprehensive species list and an assessment of the abundance, habitat associations and population dynamics of marine fishes has never been systematically documented in Hamelin Pool. A baseline ecological study, for a biologically significant area such as Hamelin Pool is extremely important, as it helps us understand the ecological processes, which can inform management decisions.

This is particularly crucial with the increase of extreme weather events, such as the 2010–11 heatwave that raised the sea surface temperature by up to 5°C. Without baseline data the impact of climate change can't be documented or predicted. 

Due to Hamelin Pool’s marine nature reserve status, the highest level of protection available in Australia, sampling and monitoring techniques that are destructive or involve removing any creatures aren't suitable. Our survey is focused on underwater video techniques.

Due to the well-documented limitations of diver operated systems, such as fish behaviour changes, diver observation bias, and swim speed variation, baited remote underwater video stations (or systems) (BRUVS), have become the dominant method of surveying, providing a higher level of accuracy and precision in data collection.

The main components of a stereo BRUVS include: a light-weight steel frame, a bait arm extending from the frame (0.5m to 1.5m long, with a wire bag attached to the end containing bait. Crushed oily fish such as pilchards or sardines (in Australia Sardinops sagax) are the preferred source. The frame houses a two camera, stereo-video system that has a demonstrated high level of accuracy and precision in length measurements, and the ability to make measurements from a wide variety of distances and orientations.

BRUVS provide a method of monitoring that's cost-efficient and robust in detecting changes in the length and relative abundance of fish. Once the raw data is collected it's analysed using specialised calibration and measurement software, most often EventMeasure (SeaGIS Pty. Ltd), to identify species, length, and relative abundance. 

In addition to providing a platform to collect data for strong statistical analysis, BRUVs also record invaluable information about the immediate habitat, which can be an effective conservation tool, and used to investigate the habitat relationships of fish species.

Project design by Blanche D'Anastasi (JCU) and Erica Suosaari (Bush Heritage), BRUVS provided by the WA Department of Parks and Wildlife.

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