The Australian marine environment is home to a plethora of species; 33,000 have been catalogued, 17,000 remain to be catalogued, and there may be 5–10 times as many yet to be discovered (Butler et al. 2010, Poore et al. 2015). Surveys of the marine environment regularly record new species even in areas that have been surveyed before, and half of the taxa captured in deep-sea environments may be new to science.
Fourteen species groups for which information and data were available were assessed for SoE 2016. These groups largely comprise those caught by fisheries or protected under the EPBC Act. Information for some species, including marine turtles and seabirds, is largely limited to information on land-based nesting or breeding areas (discussed in greater detail in the Coasts report), with little information available about their life at sea. Several species that use the marine environments of Australia (e.g. marine turtles, marine mammals, seabirds, billfish, tunas, sharks) demonstrate connectivity with regions outside the Australian EEZ, and many of the pressures currently affecting these populations are associated with high fishing effort or high bycatch rates in areas external to the Australian EEZ. Within the Australian EEZ, varying pressures are exerted on species and species groups across their range, because many species and species groups are widely distributed throughout Australia’s marine environment.
Even in areas where biodiversity has been surveyed, a good understanding of what ecosystems may have looked like before they were modified by human impacts is lacking. Apart from assessments on commercially caught species, very few species groups are regularly monitored. Consequently, empirical information on species status and trends is not available. It is also not possible to determine whether local declines in some species groups (e.g. sea snakes at Ashmore Reef) have resulted from declines in overall populations or distributional shifts in populations at particular sites. Species groups that have important ecosystem roles (e.g. algae, sponges, phytoplankton, zooplankton) are covered under assessments of habitats and communities, or biological processes.
The current status of those species targeted by fisheries has been derived from the most recent assessments available and, where possible, under single reporting frameworks. However, not all species are reported under single reporting frameworks. Reporting frameworks differ in their methodologies and may differ slightly in their assessments. Where relevant, details of the reporting framework from which assessments have been derived are provided.
Most species groups assessed are in good condition overall, although information is lacking to assess the condition or trend of some groups. Trends are stable or improving for most fish species, except inner shelf reef species, which are highly spatially variable, with some in good condition and stable, and others in poor condition and deteriorating. State and trends often vary for species within groups:
- Some species have improved from past declines (e.g. long-nosed fur seals—Arctocephalus forsteri, southern Great Barrier Reef green turtles—Chelonia mydas, humpback whales—Megaptera novaeangliae, the eastern stock of orange roughy—Hoplostethus atlanticus).
- Other species are currently stable (e.g. mesopelagic and epipelagic fish species, shy albatross—Thalassarche cauta).
- Several species have declined because of cumulative impacts associated with degradation of their nesting habitat (see the Coasts report for further details); and high mortality as a result of bycatch within fisheries, climate change and potential ingestion of marine debris (e.g. flesh-footed shearwater—Puffinus carneipes, Australian sea lions—Neophoca cinerea, north Queensland hawksbill turtles—Eretmochelys imbricata, some demersal shark species).
Within the Great Barrier Reef Marine Park, the status of populations of most species has been assessed as good, although it had deteriorated from previous assessments; inshore and southern parts of the Great Barrier Reef are in worse condition than those in the north (GBRMPA 2014a). Declines have been reported in some fish, shark and seabird species, and dugongs (detailed in the Coasts report). The bleaching event associated with climate extremes in 2015–16 that had an extensive impact on the less disturbed northern areas of the Great Barrier Reef should be noted (see also Quality of habitats and communities). The flow-on impacts on species and species groups are yet to be quantified. Further detail on the state of species groups in the Great Barrier Reef Marine Park is in GBRMPA (2014a).
North Marine Region
Long-term monitoring of populations of species within the marine environment of the North Marine Region—other than those that are the target of commercial fisheries—is sparse. As a result, identified trends in populations are few. Similar to marine habitats and communities, species groups found within, and using, the region are assumed, in the absence of supporting information, to be in good condition, because of the relatively lower use of the marine environment and the remoteness of much of the North Marine Region. Several species that use the area (e.g. marine turtles, dolphins, sharks, rays) demonstrate connectivity with regions to the north, and some populations are impacted by pressures (e.g. high fishing effort, high bycatch rates) in areas external to the Australian EEZ (e.g. Gunn et al. 2010). Sea snakes are known to be regularly caught in trawl fisheries in the region (see Commercial fishing); however, there are no ongoing monitoring programs to identify the current state of populations or trends in populations throughout the marine region. Some sawfish species that occur through the region are listed under the EPBC Act, and research aimed at quantifying population abundance and connectivity of stocks has been initiated since SoE 2011. Recent assessments of species and their stocks currently targeted by fisheries in the region (noting that some also occur within the Coral Sea and North-west marine regions; Flood et al. 2014 and references therein) have classified:
- 24 species or species stocks in good condition and sustainably fished
- 1 species or species stock recovering from past depletion
- 2 species or species stocks in poor condition and currently overfished
- 8 species or species stocks undefined (not enough data to determine state).
Coral Sea Marine Region
Long-term monitoring of populations found within the Coral Sea Marine Region and those that use the region—other than those subject to commercial fishing—is sparse. As a result, identified trends in populations are few. Again, similarly to marine habitats and communities, species groups in the Coral Sea Marine Region are assumed, in the absence of supporting information, to be in good condition because of the remote and offshore nature of the region. Several species that use the area (e.g. marine turtles, whales, tunas, billfish, sharks, rays) demonstrate connectivity with regions to the north and east of the region, and some populations are impacted by pressures (e.g. high fishing effort, high bycatch rates) in areas external to the Australian EEZ; these include hawksbill turtles and many shark species.
Recent research suggests that, in terms of fish communities, the region is more biogeographically complex than previously thought (Last et al. 2011b). Recent assessments of the Coral Sea Fishery managed by the Australian Government (Flood et al. 2014, Hansen & Mazur 2015 and references therein) have classified:
- 5 species or species stocks in good condition and sustainably fished
- 6 species or species stocks in poor condition and currently overfished
- 2 species or species stocks undefined (not enough data to determine state).
Many tunas and billfish commercially caught by fisheries within the region (also caught within the Temperate East Marine Region) are currently regarded to be western and central Pacific Ocean stocks. These species are assessed at a regional level across the western and central Pacific Ocean. Most species are in good condition and not overfished, except for bigeye tuna (Thunnus obesus), which is currently considered to be overfished (Harley et al. 2014), and broadbill swordfish (Xiphias gladius), which is currently likely to be subject to overfishing but not currently overfished. However, uncertainties associated with the biology of broadbill swordfish mean that this assessment is highly uncertain (Davies et al. 2013). Recent research quantifying the age and growth rates of the species (Farley & Clear 2015) will reduce uncertainty when the species is next assessed in 2017.
Temperate East Marine Region
Overall, populations of species groups are in good condition in the Temperate East Marine Region, although—as with other marine regions—populations demonstrate species-specific state and trends. Long-term monitoring of populations found within, and using, the marine region—other than those subject to commercial fishing—is sparse. As a result, identified trends in populations are few (see Box MAR7). Several species that use the area (e.g. marine turtles, whales, seabirds, tunas, billfish, sharks, rays) demonstrate connectivity with regions to the north and east of the region, and some populations are impacted by pressures (e.g. high fishing effort, high bycatch rates) in areas external to the Australian EEZ; these include bigeye tuna, hawksbill turtles, some species of shearwaters and many shark species.
Populations of inner reef fish and invertebrate populations demonstrate varying trends, with most invertebrate populations stable. There is some indication that populations of fish species in marine reserves are in better condition than those in areas that are not protected (Figure MAR27).