Document ID: chunk:federal_register_of_legislation:F2016L00300:body:0:p17
Version: federal_register_of_legislation:F2016L00300
Segment Type: other
Provision Reference: 
Character Range: 46996–50024

the deliberate positioning of moorings in shallow and sheltered estuarine embayments (Green, pers comm., 2014). Traditional moorings consist of a concrete block (or other dump weight) with a heavy chain attached and are designed to allow boats to move in response to winds and currents, often resulting in the slack chain dragging across the seabed and scouring the surrounding substrate (DPI, 2014). Scientists conducting spotted handfish surveys at Battery Point in the Derwent Estuary have observed damage to artificial spawning habitat caused by boat mooring chains dragging across the substrate and noted an absence of handfish in these disturbed areas (Green et al., 2014).

4.2.4 Northern Pacific seastar (Asterias amurensis)
Northern Pacific seastars are believed to have been present in the Derwent Estuary since at least the early 1980s when they were introduced via ballast water. The species subsequently spread to areas outside of the estuary (Whitehead, 2008). The Derwent Estuary is now believed to support some of the highest known concentrations of northern Pacific seastars in the world (Whitehead, 2008). Northern Pacific seastars are opportunistic, generalist feeders that are known to affect the abundance of a wide variety of benthic fauna within their native range, including molluscs, ascidians, bryozoans, sponges, crustaceans, polychaetes, fish and echinoderms, (Hatanaka and Kosaka, 1959; Fukuyama, 1994; Fukuyama and Oliver, 1985). Within the Derwent Estuary northern Pacific seastars have been observed feeding on stalked ascidians (Sycozoa sp.) and have been identified as a potential contributing factor in the decline of spotted handfish due to their reduction of available spawning substrate (Bruce and Green 1998). If northern Pacific seastars were to colonise, or increase in abundance, in areas that support red handfish or Ziebell's handfish colonies they may also impact upon the availability of spawning substrate for these species.

4.2.5 Other potential threatening processes
    * Any form of fishing that degrades the benthic habitat can be considered to pose a threat to handfish species (DPIWE, 2002).
    * Reductions in prey abundance, possibly related to decreases in benthic cover of seagrasses and alga that provide habitat for invertebrates, may impact upon handfish survival and reproduction (DPIWE, 2002).

    * Illegal collection for the aquaria trade may also pose a threat to handfish. While experts consider the likelihood of poaching to be low, the consequence of removing even a few individuals from the wild is considered to be severe given the small population size of each species.

    * Climate change and warming ocean temperatures also pose a potential threat to all handfish species. Increased water temperature may impact upon handfish survival and reproductive capacity both directly, as handfish held in aquaria appeared distressed at temperatures above 18°C (Gledhill and Green, unpublished), and indirectly, through the creation of conditions favourable