Active acoustic tracking suggests that soft sediment fishes can show site attachment: a preliminary assessment of the movement patterns of the blue-spotted flathead (Platycephalus caeruleopunctatus)

Background It is generally considered that on relatively homogenous marine soft sediment habitats, such as sand, fish are unlikely to show site attachment. This poses challenges for management and the evaluation of the efficacy of marine protected areas, in which soft sediments often make up more than 70 % of habitats. The blue-spotted flathead is a commercially and recreationally targeted species found on soft sediments in coastal marine waters of south-eastern Australia. There are no published data on its movement patterns. Here, using active acoustic telemetry, we aim to (a) quantify movement and habitat use of blue-spotted flathead, (b) compare area usage to no-take sanctuary zone size and (c) obtain data to aid in the design of a large passive receiver array to be used in long-term comprehensive tracking of soft sediment fish. Results Three of five blue-spotted flathead that were tagged exhibited strong site attachment and were detected close to their release points for the entire 60-day study period. The two other fish were not detected after 4 and 25 days and were likely to have moved out of the study area (search radius ≈ 3 km). For the three fish tracked over 60 days, the area used was compact (mean ± SE = 0.021 km2 ± 0.037) and two patterns of movement were apparent: (1) a small activity space used in its entirety each day (two fish) and (2) a larger activity space in which a separate area is utilised each day (one fish). Conclusions Our study is the first to document the movement of blue-spotted flathead, and these preliminary results demonstrate two broad movement patterns shown by this species on soft sediments in Jervis Bay. Over the course of 60 days, a majority of fish in this study showed strong site attachment; however, a number of fish also made larger-scale movements. Finally, our study suggests that a tightly spaced, passive acoustic array would provide meaningful results for this species, although strategically placed receivers outside this array would be required to detect any longer range movements