Application of non-destructive methods for assessing rock pool fish assemblages on Lord Howe Island, Australia

Abstract

Rock pool fish assemblages can be highly diverse, though are poorly studied in many locations. Where rock pool fishes have been studied, sampling has often been undertaken using destructive techniques, causing fish mortality and damage to pool ecosystems. There is, therefore, a need for greater understanding of non-destructive methods for evaluating rock pool fish assemblages. To improve knowledge in this area, we tested three non-destructive techniques: mini baited remote underwater videos (mini-BRUVs) which utilised a stationary video camera to record fish, visual censuses (VCs) where a roving observer recorded fish using a slate and observer operated videos (OOVs) where fish were recorded by an observer using a video camera.These methods were tested for their effectiveness in assessing fish assemblages, using data from rock pools on Lord Howe Island (LHI), in New South Wales (NSW), Australia. VCs and OOVs required significantly less total survey time than mini-BRUVs, whereas mini-BRUVs provided advantages in the detection of fishes in small pools (<25 m3). Examination of mini-BRUVs’ data, for 30 min samples, identified that the vast majority of fish species were detected within 15 min and indicated that a shorter 15 min sampling period would generally be suitable for collecting fish data from rock pools. The base-line data collected on fishes in LHI rock pools demonstrated the uniqueness of LHI assemblages, which were significantly different from those on the NSW coast. This study demonstrates that non-destructive sampling methods can be used in rock pool environments, making these methods suitable for sampling in inter-tidal habitats, especially within marine protected areas.