A survey of potential marine reserve locations in Bass Strait

The Tasmanian north coast, King Island, and Tasmania's easten Bass Strait Islands were quantitatively surveyed to identify locations suitable for the establishment of regional marine reserves in Bass Strait. This survey included a re-assessment and further investigation of Rocky Cape and the Kent Group, two locations previously proposed as marine reserves. The Kent Group was identified as the most outstanding location surveyed, with a range of habitats and biota representative of Bass Strait, and including a significant proportion of Peronian species. Biologically this location would be the preferred location for a marine reserve in the Peronian influenced region of Tasmania. Rocky Cape was identified as the most biologically suitable location on Tasmania's north coast due to its diverse range of habitats and species abundance. After Rocky Cape, the next two most desirable locations in the Bass Strait region for marine reserves were considered to be Waterhouse Island in northheast Tasmania and New Year Island off the north west coast of King Island

A Classification of Tasmanian estuaries and assessment of their conservation significance using ecological and physical attributes, population and land use

Physical attributes of Tasmanian estuaries A total of 111 estuaries of moderate or large size were recognised around Tasmania and associated Bass Strait islands. The catchments of these estuaries were mapped using GIS, and available data on geomorphology, geology, hydrology and rainfall collated for each estuary and catchment area. Tasmanian estuaries were classified into nine groups on the basis of physical attributes that included salinity and tidal data collected during a field sampling program. The nine groups primarily reflected the size of estuaries and their tidal, salinity and rainfall characteristics, and the presence of any seaward barrier. Catchments in the west, northwest and south of the state were characterised by high rainfall and high runoff, while catchments in the east and northeast were relatively dry. Estuaries in northern Tasmania possessed much greater tidal ranges than those on the eastern, southern and western coasts and were all open to the sea, whereas many estuaries in eastern Tasmania and the Bass Strait islands were intermittently closed by sand barriers. Biological attributes of Tasmanian estuaries Baseline information on the abundance, biomass and estimated production of macrobenthic invertebrate species was collected during a quantitative sampling program at 55 sites in 48 Tasmanian estuaries. These data were generally obtained at three different intertidal levels and two shallow subtidal depths at each site, and included information on a total of 390 taxa and over 100,000 individuals. Data on the distribution of 101 fish species, as obtained during surveys of 75 Tasmanian estuaries using seine nets by Last (1983) with some supplementary sampling, were also incorporated into the study. Multivariate analyses indicated that the nine estuarine groups identified using physico-chemical attributes were useful for categorising faunal relationships between estuaries, although considerable variation was found between faunas at sites within estuaries, particularly for marine inlet estuaries and drowned river valleys. Variation in faunal composition between sampling dates at the one site was low. The number of species collected at sites also varied with the estuarine groups identified using physicochemical attributes, with highest numbers of species occurring in marine inlets and small open estuaries. Relatively few species were collected at sites in microtidal river estuaries, barred low-salinity estuaries or hypersaline lagoons, with extremely low numbers collected in the western Tasmanian Wanderer estuary. North East Inlet (Flinders Island) and seagrass beds at the mouth of the Tamar estuary possessed exceptionally high diversity for both fishes and invertebrates. The number of macrofaunal species collected at a site was primarily correlated with local salinity and biomass of submerged plant material, particularly seagrass. Species richness also varied with geographic location for both macrofauna and fishes, with highest numbers of species occurring in the Furneaux Group, northeastern Tasmania and southeastern Tasmania. Low numbers of species were collected on the west coast and, to a lesser extent, south coast, central north coast and King Island. These patterns primarily reflected differences in estuary type between regions rather than concentrations of locally endemic species. Nearly all fish and invertebrate species recorded from Tasmanian estuaries occurred widely within the state and have also been recorded in southeastern Australia. Only 1% of estuarine fish species and <5% of invertebrate species were considered endemic to the state. The general pattern of widespread species' ranges around Tasmania was complicated by the absence of most species from the west coast, a small (<10%) component of species that occurred only in the northeast (particularly Flinders Island), and a few localised species that were restricted to different regions of the state. The low number of species recorded from estuaries along the western Tasmanian coast reflected extremely low macrofaunal productivity in that region. Estimated secondary productivity of west coast estuaries was generally at least one, and up to three, orders of magnitude lower than equivalent estuaries on other coasts. This low productivity was attributed to unusually low concentrations of dissolved nutrients in rivers and dark tannin-stained waters which greatly restrict algal photosynthesis and primary production. The estimated productivity and biomass of macrofaunal communities were found to vary little between sites within an estuary compared to variance between estuaries. By contrast, variance in the density of macrofauna was much greater between sites within an estuary than between estuaries, and variance was relatively low at scales of metres and hundreds of metres at similar tidal heights within a site. The environmental factor most highly correlated with animal density was the biomass of plant material, while estimated faunal productivity and biomass were most highly correlated with salinity. Threats to estuarine biota Biological resources within most large Tasmanian estuaries are exploited, with unknown consequences for ecosystem structure and function. In addition, nine major indirect threats to Tasmanian estuaries have been recognised: (i) increased siltation resulting from land clearance and urban and rural runoff, (ii) increased nutrient loads resulting from sewage and agricultural use of fertilisers, (iii) urban effluent, (iv) foreshore development and dredging, (v) marine farms, (vi) modification to water flow through dams and weirs, (vii) acidification of rivers and heavy metal pollution from mines, (viii) the spread of introduced pest species, and (ix) long-term climate change. While all of these factors can potentially disrupt ecosystem processes, the magnitude and spatial scale of these threats vary greatly. The first seven indirect threats affect individual estuaries and can be ameliorated by changing management practices, whereas substantial global warming would affect all estuarine ecosystems within the state through changes to water flow, increased water temperatures and sea level rise. The effects of introduced pests are also increasing and uncontrollable at present. Although only four introduced species – the green crab Carcinus maenas, the tanaidacean Sinelobus stanfordi, the bivalve Theora lubrica and the gastropod Potamopyrgus antipodarum – were collected during the present study, the threat posed by these and other species (including the seastars Asterias amurensis and Patiriella regularis, the molluscs Musculista senhousia, Crassostrea gigas, Maoricolpus roseus and Corbula gibba, the polychaete Sabella spallanzani and the ricegrass Spartina anglica) was considered to be extremely high. Amongst the more localised threats to estuaries, siltation, or a correlate thereof, was found to have an extremely widespread effect on Tasmanian estuaries. Estuaries with moderate or high human population densities in catchments consistently possessed muddy rather than sandy estuarine beds and shores. Although no change in number of macrofaunal species was associated with high human population densities and associated transformations from sandflats to mudflats, a pronounced shift in the faunal composition was evident in populated estuaries. These faunal changes were readily detectable using two disturbance indices described here, DIn and DIp, which are suggested to provide useful indicators of estuarine health. Assessment of the conservation significance of Tasmanian estuaries Human population densities within each estuarine catchment and the extent of legislative protection were estimated using GIS, census statistics, dwellings marked on 1:25,000 maps and land tenure data. The catchment areas of all Tasmanian mainland estuaries were also categorised in terms of land and vegetation use using GIS and data derived from satellite images. Satellite data for the Bass Strait islands were not available so estuaries in that region were not similarly examined. A total of 24 out of the 90 Tasmanian mainland catchments were considered to be pristine, with little human impact within the catchment. These catchments were nearly all distributed in the south and west of the state and on Cape Barren Island. A small number of catchments were severely impacted by urban development and large scale land clearance, and many others were moderately effected by human impacts. The highest levels of land clearance, population and urban development were found in catchments along the south-east, east and north coasts of Tasmania. The conservation significance of each Tasmanian estuary was assessed using the nine groups of estuaries identified by physical criteria. Within each of the nine groups, estuaries were ranked by level of anthropogenic disturbance using human population density data, and the estuary with least disturbance assigned the highest conservation rank (Class A). Each of these Class A estuaries was therefore the least disturbed estuary of a particular type, and between them they spanned nearly all of the biological and habitat diversity found within estuaries in the state. Where more than one estuary within a group was found to be 'pristine', the estuary with highest conservation status was identified using data on the percentage of catchment area included within national parks and crown reserves, and data on size of estuary. In addition to the nine representative estuaries found to possess highest conservation value, North East Inlet was also assigned Class A conservation status because it possessed high species diversity and included species not contained in other Class A estuaries. The ten class A estuaries are North East Inlet, Black River estuary, Bryans Lagoon, New River Lagoon, Thirsty Lagoon, Tamar River estuary, Southport Lagoon, Bathurst Harbour, Payne Bay and Wanderer River estuary. We recommend that plants, animals and habitats within the ten Class A estuaries and associated catchments be protected within an integrated system of Tasmanian estuarine protected areas. We also recommend that catchments and aquatic ecosystems of a further 38 estuaries, which were assigned Class B conservation status on the basis of minimal anthropogenic impacts, be quarantined from future developments, and existing impacts reduced wherever possible

Exploited reefs protected from fishing transform over decades into conservation features otherwise absent from seascapes

Tasmanian reef communities within ‘‘no-take’’ marine protected areas (MPAs) exhibited direct and indirect ecological changes that increasingly manifested over 16 years, eventually transforming into communities not otherwise present in the regional seascape. Data from 14 temperate and subtropical Australian MPAs further demonstrated that ecological changes continue to develop in MPAs over at least two decades, probably much longer. The continent-scale study additionally showed recently established MPAs to be consistently located at sites with low resource value relative to adjacent fished reference areas. This outcome was presumably generated by sociopolitical pressures and planning processes that aim to systematically avoid locations with valuable resources, potentially compromising biodiversity conservation goals. Locations that were formerly highly fished are needed within MPA networks if the networks are to achieve conservation aims associated with (1) safeguarding all regional habitat types, (2) protecting threatened habitats and species, and (3) providing appropriate reference benchmarks for assessing impacts of fishing. Because of long time lags, the ubiquity of fishing impacts, and the relatively recent establishment of MPAs, the full impact of fishing on coastal reefs has yet to be empirically assessed

Ecosystem monitoring of subtidal reefs in different management zones of the Jurien Bay Marine Park 1999–2007

Floral and faunal communities associated with shallow reefs in the Jurien Bay Marine Park were investigated using underwater visual census methods on six occasions from October 1999 to November 2007. Densities of fishes, mobile macro-invertebrates, sessile invertebrates and macro-algae were quantified at a total of 42 sites. The magnitude of changes in density at zone locations between years was generally considerably less than spatial variability between zone locations, although some species and community metrics examined showed consistent increases or decreases in numbers over the survey period. The biotic community at different sites showed a major biotic subdivision between reefs located within a kilometre of the coastline and outer lagoonal reefs. Inshore reefs were characterised by sheltered conditions, water with moderate turbidity, and by macro-algae such as Dictymenia sonderi and Neurymenia fraxinifolia. Outer reefs were characterised by clear water, wave-exposed conditions, the kelp Ecklonia radiata, and the red seaweeds Pterocladia lucida and Hennedya crispa. Outer reefs were largely homogeneous with respect to associated plants and animals, whereas inshore reefs showed considerable variation between sites and between management zone locations. Scientific reference zones, in which rock lobster fishing is permitted, largely include outer reef systems. As a consequence, scientific reference zones possess a biota that differs little between zone locations. By contrast, sanctuary zones, where all forms of fishing are prohibited, include only shallow reefs, hence possess a biota that varies greatly between locations, and also differs from the biota encountered in scientific reference zones. The lack of overlap in reef communities between sanctuary zones and scientific reference zones complicated analysis of effects of restrictions on fishing that were enacted in these two zone types in December 2005. Regardless, very few observable ecological changes associated with new fishing restrictions were identified. The strongest relationships associated with fishing restrictions were found in correlation analysis when comparing the level of change from the periods before and after fishing restrictions with areal extent of protected zone. In this analysis, the mean size of breaksea cod (Epinephelides armatus) and silver trevally (Caranx georgianus) was found to increase significantly in the larger protected zones, as did the abundance of large (>250 mm) exploited fishes as a group and also dhufish (Glaucosoma hebraicum). We consider that the trends in breaksea cod size and numbers of exploited fishes are probably real, given that adequate data were available for statistical tests and trends were consistent between years. However, the trends in silver trevally size and dhufish abundance relate to highly patchy data, with the significant correlations best regarded as flags for confirmation or otherwise through the longer term. Several management recommendations arose from the study: Sanctuary zones should be extended to the outer reef area. Extra sites should then be added to the JBMP reef monitoring program to allow improved evaluation of effects of fishing restrictions, particularly with respect to assessment of the ecosystem role of rock lobsters. Other than for an extension of sanctuary zones to the offshore region, the system of protected zones in the JBMP should be maintained with as few changes to regulations and zone boundaries as possible through the long term. This is particularly important for zones that include sites surveyed as part of the long-term JBMP reef monitoring program. Surveys of fishes and mobile invertebrates should be repeated on an annual basis, and surveys of plant assemblages be conducted on a biennial basis, for at least five years from the time of enforcement of fishing restrictions in 2005. The frequency of surveys should be reviewed in 2010 to assess whether a longer period between surveys is warranted on grounds of cost-effectiveness. Monitoring should nevertheless continue through the longer term at least until biotic changes associated with MPA protection stabilise, probably longer given the unique value of the data set in tracking ecological effects of climate change

A quantitative video baseline survey of reef biota and survey of marine habitats within Bathurst Channel, Southwest Tasmania 2002

Increasing visitation rates within Bathurst Harbour and Bathurst Channel in the Tasmanian Wilderness World Heritage Area have led to concerns that the unique and fragile marine invertebrate communities found there during recent studies may be irreversibly damaged unless the nature and location of threats were identified and managed. An important component of the management process is the establishment of a monitoring program to quantify the biological assemblages present and to detect any human impacts to these assemblages if they occur. This study has successfully established a quantitative baseline dataset on the horizontal and vertical distribution of invertebrate and algal assemblages within Bathurst Channel for use in on-going monitoring of change in the system. Robust estimates of the abundance of most conspicuous species have been obtained at selected sensitive sites (usually on hard substrates), allowing future changes and impacts to be detected and quantified. By utilising a combination of comprehensive quantitative surveys throughout the system and detailed habitat mapping, our understanding of the biological zonation within the system has been enhanced, along with our understanding of the limited extent of habitat available to many of the unique invertebrate assemblages. Specific recommendations arising from this study include: 1. ensuring baseline monitoring continues at an appropriate time-frame (perhaps every five years) 2. gaining a more detailed understanding of the faunal assemblages that occur within the soft sediment habitats that form the vast majority of cover within Bathurst Channel. 3. completing a biological census of the marine species of this area initiated in 1993, to ensure that where possible the distribution and abundance of unique, rare and endemic species can be adequately identified and mapped in subsequent surveys

Surveys of intertidal and subtidal biota of the Derwent Estuary - 2010

Summary This study examines patterns of diversity and abundance of fish, invertebrates and algae on intertidal to subtidal rocky reefs and their adjacent sediments within the Derwent Estuary. It is based on two quantitative survey methods that formed the basis of a detailed survey of the estuary, primarily undertaken between February-April 2010. The survey area ranged from Claremont Point to Tinderbox and encompassed up to 24 sites along this estuarine gradient, surveying the typical range of depths that rocky reefs and adjacent sediments occur in along that gradient. The primary aims of the study were: (1) to provide a substantial quantitative baseline of current biological assemblages in these habitats as a snapshot by which future change could be measured, spatial patterns could be recognised, and management issues identified; (2) to undertake a detailed search for the threatened seastar Marginaster littoralis, and other rare seastar species that could be resident in the Derwent estuary to better understand their conservation status; (3) to quantitatively describe the current distribution of introduced species within the estuary and better understand the threats they might provide to native species. The two survey methods utilised included (1) a standard belt transect methodology widely used by TAFI for biodiversity surveys in temperate Australia; (2) a 20 minute timed swim (and intertidal search) with multiple replicates at multiple depth bands, recording fishes, readily identifiable fishes, invertebrates and brown and green macroalgae. For method 1, fifty four species of fish, thirty five species of mobile macro-invertebrates, twenty one species of sessile invertebrates and seventy two species of brown, green and red algae were recorded along standard subtidal rocky reef surveys. Fish, invertebrate and algal diversity generally increased from northern to southern-most sites within the estuary, in a pattern typical of estuarine diversity gradients. Fish species such as Trachinops caudimaculatus (Hulafish), Latridopsis forsteri (Bastard trumpeter), Dinolestes lewini (Long-fin pike), Notolabrus tetricus (Blue-throat wrasse) and Acanthaluteres vittiger (Toothbrush leatherjacket) were the most abundant. The abundance of these species increased towards the southern sites of the estuary with the exception of Hulafish which were more abundant towards the northern parts of the estuary. The most abundant invertebrates were the echinoderms Patiriella regularis (introduced regular seastar), Heliocidaris erythrogramma (Purple urchin), Meridiastra calcar (Eight-armed seastar), Amblypneustes ovum (Short-spined urchin) and the Triton shell Cabestana spengleri. Introduced species of echinoderms and crustaceans were more abundant in the northern sites of the estuary whereas native invertebrates were more abundant in the southern part of the estuary. Overall, introduced species numerically dominated the mobile macro-invertebrates within the estuary from Claremont Point to Bellerive Bluff. Dominant algae included species of encrusting Peyssonnelia (red algae) and the brown kelp Ecklonia radiata, Lessonia corrugata and Carpoglossum confluens, but the distribution of most foliose algae was restricted to sites seaward of Rosny Point, with filamentous red algae in particular dominating the northern section of the estuary. Bellerive Bluff to Rosny Point marked the most significant transition in algal assemblages and corresponded with a change from silty tube-worm matting dominated reef systems to reefs with an increasing cover of encrusting corraline algae and encrusting sponges. Notable features of the algal surveys included the abundance of the red algae Aodes nitidissima in the Rosny Point region where other foliose algae are rare, and the presence of the North Pacific kelp Undaria pinnatifida between the Grange and Alum Cliffs. Undaria is an introduced species of brown algae that is seasonally abundant with peaks in early summer. We suspect that Aodes is also an introduced species given its restricted range in this survey and the distribution of past specimens collected in Tasmania that are also restricted to the estuary. For method 2, seventy four species of fish, one hundred and forty seven species of macro-invertebrates and forty six species of brown and green algae were recorded throughout the timed intertidal and subtidal surveys. As with results from standard surveys, diversity of fish, invertebrate and algae increased from northern to southern-most sites within the estuary. Fish species such as T. caudimaculatus, N. tetricus, Fosterygion varium (introduced Many-rayed threefin), Grahamina gymnota (introduced Estuarine threefin) and Neoodax balteatus (Little rock whiting) had the largest rank abundances. Spatial distribution patterns were clearest for the two introduced threefin species which were most strongly associated with the mid-upper estuarine sites. The upstream assemblage was characterised by high abundance of gobies, blennies and threefins. A similar, but reversed pattern was evident with many marine species, particularly the numerically abundant N. tetricus, a species essentially absent upstream from Rosny Point. The most abundant invertebrates were Mytilus galloprovincialis (Blue mussel), Petrolisthes elongatus (introduced New Zealand porcelain crab), the introduced echinoderms Asterias amurensis (Northern Pacific seastar), P. regularis and the introduced fan worm Myxicola infundibulum. Some clear patterns of species distribution occurred along the estuary, including an increased abundance of P. regularis at sites upstream from Bellerive Bluff and high abundance of M. calcar at sites seaward of that location. For algae, the most abundant brown and green taxa were Ulva spp., E. radiata, Codium fragile, L. corrugata and Dictyopteris muelleri. These algae generally increased towards the southern part of the estuary with the exception of Ulva spp., which was consistently present in most sites. Most foliose algae were not present at sites upstream of Bellerive Bluff. Ecklonia radiata, present at Bellerive Bluff in depths to below 5 m, was not present at Rosny Point at any depth, despite the close proximity, indicating a very strong environmental gradient between these sites that was also reflected in the distribution of many other species, and the extent of cover of silt laden tube-worm matting that was prevalent across depths at the more upstream sites. Overall, this survey has successfully provided a comprehensive quantitative snapshot of the current distribution of much of the epifaunal biodiversity associated with reef systems in the Derwent estuary. It revealed many strong spatial patterns in species distributions and should provide a robust baseline from which to measure and assess future change. The clear break in biological assemblages between Rosny Point and Bellerive Bluff deserves further investigation to assess causes underlying this, including the extent that the tube-worm matting dominating the reef at Rosny Point and upstream sites plays. This matting may represent an alternative stable state to the algal dominated reef historically described from Rosny Point, the restoration of which may be seen to be an ultimate management goal with respect to amelioration of human impacts within the estuary. Despite thorough searching for the presence of the threatened Derwent river seastar Marginaster littoralis, none were found. This is despite extensive searching both intertidally and subtidally within the core habitat of this species. The co-occurrence and super-abundance of P. elongatus and P. regularis in these habitats suggests that if any individuals of M. littoralis are left they would be subject to severe competition and predation by these species. Consideration of the difficulty of exploiting an intertidal habitat within the core range of M. littoralis suggests that winter low salinity coupled with summer desiccation during spring tides and high temperatures would make an obligate mid-estuarine intertidal niche’ impossible. If the species is valid and continues to persist, in addition to the intertidal zone it is described from, it must also occupy subtidal habitats below salinity lows during winter, or additional intertidal habitats away from the influence of physical extremes. Our searches included many of these habitats but failed to detect any specimens. As P. regularis displayed great morphological variability within the central area of occupancy of M. littoralis, some specimens of which displayed similar features (such as an off-white marginal fringe), we suggest a revision of the taxonomy of this species be undertaken with regard to the variability of M. calcar characters, and a molecular genetic comparison to be made between these species once molecular techniques evolve to cope with the formalin preserved type specimens. Despite the rare species focus of our surveys, and the possibility of encountering several species of rare seastars known from adjacent coastal areas, no such species were found. If they are present, they would presumably be in low numbers and in isolated populations. Clearly, such species are difficult to detect, and require greater intensity of search effort to delineate their range than was possible in this survey. This was illustrated from our soft sediment searches undertaken adjacent to the reef margins, as these searches detected only one Spotted handfish Brachionichthys hirsutus despite many of our survey sites falling within the range and core habitat of this species. Introduced species numerically dominate the mobile invertebrate fauna at most of the sites we surveyed upstream from Bellerive Bluff. At many sites they contributed well over 80% of all invertebrate individuals counted along transects. In addition to the species described previously, they include the Piecrust crab (Metacarcinus novaezelandiae) and the green shore crab (Carcinus maenus), a species recently established in the estuary. A similar pattern is evident with sedentary invertebrates, with the Pacific oyster (Crassostrea gigas) distributed throughout the estuary and being particularly abundant in the upper sites examined. The fanworm Myxicola infundulibulum was abundant throughout soft silty sediments. Two species of introduced threefin Fosterygion varium and Grahamina gymnota were abundant in mid estuarine sites (Bedlam Walls to Bellerive Bluff) and several introduced species of algae were found at the more seaward sites. These were the large brown algae Undaria pinnatifida and the recently arrived red algae Grateoloupia turuturu. A further species of red algae, Aodes nitidissima is also suspected to be introduced, due to its restricted range within mid-estuarine sites. Many of these introduced species are in pest abundances, and the super-abundance of P. elongatus and P. regularis at many sites clearly threaten a range of native species at these sites and suggests that they may pose a biodiversity threat more widely, particularly to rare species such as Parvulastra vivipara and Smilasterias tasmaniae, seastars that occupy similar sheltered rocky shoreline habitats in nearby environments. Further investigation is urgently needed to quantify the threats that abundant introduced taxa pose

A biological monitoring survey of reef biota within Bathurst Channel, Southwest Tasmania

The benthic reef communities of Bathurst Channel represent an important feature for the ongoing management of Tasmania’s marine ecology and diversity. Containing a number of fragile deep-water invertebrate species growing at accessibly shallow depths, the reef habitats are both susceptible to impacts and of scientific importance. The foundation for this study was the continuing need for a practical, quantitative monitoring program which will provide information on species composition, species distribution throughout the channel, and detect any changes occurring over time. The survey, conducted in March 2010, collected digital image data from depth intervals ranging from the intertidal zone to 20 metres depth at 13 monitoring sites extending throughout Bathurst channel, and compared it to baseline imagery taken in 2002. The high resolution imagery collected in 2010 was used to create a descriptive catalogue of the biota observed, which can be used for future monitoring and species referencing. Species and substrate percentage cover in the photos was analysed using an easily repeatable point count method (CPCe) where data files can be stored and reanalysed. The information collected described the changes in species composition along Bathurst Channel, and thus provided some insight into the relevant environmental and biological factors limiting the distribution of algal and invertebrate species throughout the estuary. Results were consistent with previous descriptions of the community types within the Channel, showing that this system is inherently stable over these time frames. Patterns in assemblage distribution reflected strong species’ responses to gradients in tannin levels and salinity throughout the estuary, distance from the ocean and the strength of currents/mixing. Percentage abundances of key species and species groupings (e.g. lace bryozoans) between 2002 and 2010 data were also comparable, albeit with a few differences resulting from an improvement in image quality between surveys. One notable change was an apparent 50% decline in sea whip abundance at both Munday Island and Forrester Point at 5 metres depth. This is presumed to be a consequence of drought conditions leading up to the 2010 survey, reducing the tannin concentration to a point where algal growth became possible in this zone, smothering components of the invertebrate fauna. Ongoing monitoring will enable recovery rates to be determined, and improve our understanding of the natural variability of these fragile assemblages in a changing climate. The decline in sea whip numbers does indicate that there is a delicate balance between invertebrates and algae in the lower photic zone within the Channel, one that corresponds with the depth occupied by many fragile invertebrate species, and that this balance could be significantly altered under climate change scenarios that relate to reduced rainfall. Due to new image analysis protocols established during this study, and the development of high resolution digital photography since 2002, further surveys and analysis of data will now be more easily comparable using the same sites, depths, and the methods of analysis as established here. This will allow for the successful provision of reliable monitoring data to feed into ongoing management and conservation of the unique ecosystems found in Bathurst Channel

Effects of the Iron Barren oil spill - impact and recovery of sub tidal reefs

The impact of the Iron Baron oil spill on subtidal reef communities in Bass Strait was assessed by quantitatively censusing plant and animal populations after the spill and comparing these data with information obtained using similar techniques prior to the spill. Natural changes at control sites were of a similar magnitude to changes in reef assemblages following the spill at sites with moderate and heavy oil contamination on nearby shores. Any effects of the oil spill on subtidal reef assemblages were therefore considered to be minor. By contrast, the grounding of the hull at Hebe Reef caused complete destruction of plant and animal life within a localised zone extending for z 170 m by 20 m. The fish population within this disturbed zone largely recovered to predisturbance levels within three months of the impact whereas very little recovery of invertebrate and virtually no recovery of macroalgal populations occurred during this time period. Given the lack of significant impact of the oil spill on coastal reefs, further monitoring of reef communities is not considered necessary. Limited monitoring of the impact zone and two nearby control sites on Hebe Reef is recommended in order to identify the timescale required for assemblages in this region to recover

Evaluating the effectiveness of Marine Protected Areas as a fisheries management tool

Marine Protected Areas (MPAs) are being proclaimed around the world with the stated primary purposes of enhancing fisheries stocks and/or conserving marine biodiversity. In Australia, in response to a joint State/Commonwealth agreement to establish a National Representative System of MPAs (NRSMPA) to protect marine biodiversity, the focus is on their conservation role. However, fisheries enhancement is often suggested as an additional benefit of protection, potentially offsetting the cost of area closure in some cases. This study aimed to contribute to the debate on the positive and negative effects of the establishment of MPAs, documenting changes that have occurred in reserves following establishment, and particularly, attempting to understand more about their role as a fisheries management tool. It builds on a program initiated following the establishment of Tasmania's first 'no-take' MPAs a decade ago. Changes within the MPAs over the period indicated that fishing has had a substantial influence on the demographic structure of many species, particularly those targeted by fishers. The magnitude of change detected appeared to be dependant on the susceptibility of species to capture, the remoteness of protected locations and to the MPA configuration itself. Changes within the more remote Maria Island reserve (the largest area studied), relative to fished reference sites, included increases in the abundance of lobsters and certain fish species and increases in the mean size of rock lobsters (responses typical of protected areas studied elsewhere in the world), as well as a decrease in the abundance of prey species such as urchins and abalone. Not all species increased in size and/or abundance, and for several fish species there was no significant change. At Maria Island there was also a 30% decline in the abundance of common urchins within the reserve, which may be the first Tasmanian evidence of cascading ecosystem effects related to protection from fishing. Abalone numbers were also observed to decline sharply over the period sampled. This change was interesting in that one possible explanation was an inverse relationship between predators (lobsters) and prey (abalone). If shown to be correct this finding is likely to have significant consequences for integrated, ecosystem based management of these two species. Clearly the survey showed that MPAs, even of a relatively small size (Maria Island covers 7km of coastline), could effectively achieve conservation objectives, especially for exploited species that were resident or sedentary in nature. A study of small-scale movement patterns of fishes showed that with few exceptions fish species showed high fidelity to site. Animals were generally resighted <100 m from initial tagging site and with individuals remaining near the tagging site throughout the 1-year duration of study. Influences on distance moved attributable to the variables body length, sex, water temperature and time since tagging were insignificant compared to variation between individuals. Patterns of movement were also generally consistent at all three study sites. Home ranges of some species were found to be affected by the presence of macroalgae, with animals emigrating from artificially cleared patches. The sedentary nature of these small- to medium-sized reef fish species indicated that relatively small marine protected areas (1 km diameter) could provide adequate protection to these fishes but suggest limited 'spillover' benefits to fisheries in the form of emigrants to surrounding areas. The population structure of lobsters (J. edwardsii) within the Maria Island reserve after a decade of protection was substantially changed from levels prior to protection. Relative to adjacent fished areas, the abundance of females was 2.4 times greater and the abundance of legal sized females 16.8 times greater. For males these values were 4.1 and 18.6 greater respectively. The recovery of the lobster population in the Maria Island provided a reference against which the effects of fishing on a range of population biological characteristics could be examined. These included movement, growth and maturity. Modelling the effects of MPAs was focussed on rock lobsters and abalone due to the importance of both fisheries, extensive historical datasets and differences in certain biological characteristics such as larval dispersal. Some aspects of the biology of lobsters required additional research prior to this modelling, such as the effect of increased density inside MPAs on growth, reproduction and movement. This research revealed the following: - There was no evidence of large-scale, unidirectional migration. Tag-recaptures indicated high site fidelity with the majority of animals moving no detectable distance after periods of one to two years between capture events. This low level of movement suggested limited potential for spillover of biomass from MPAs. - Growth in the reserve appeared slower than it was adjacent to the reserve and when closely examined it was apparent that a small proportion of the females outside the reserve were able to moult more than once in a year. It suggested that stock rebuilding inside MPAs might be slower than predicted by extrapolation of growth data collected from fished areas. - There was a distinct spatial cline of carapace length at 50% maturity with the largest sizes being found at northwestern sites (110 mm carapace length) and the smallest sizes at southwestern sites (59 mm carapace length). This cline in size at maturity was the reverse of that described for the same species at similar latitudes in New Zealand and suggests that maturity in J. edwardsii is not primarily regulated by temperature as suggested previously. To model the effects and implications of MPAs on fisheries, a strategy was adopted of first exploring the properties of a generally applicable simple model followed by a length-based model that was specific to the rock lobster fishery and which incorporated catch and catch rate history. The simple model predicted population increases in both biomass and size-structure for the reserve and could be used to support the claim that, under certain constraints, a fishery managed solely through the agency of MPAs could provide a similar yield to one managed through more traditional means. However, for many species with limited larval dispersal rates the use of MPAs alone would lead to areas of relatively high quality marine environment literally surrounded by a sea of overfished and depleted areas. The more complex model highlighted a major concern when displaced effort was focused on a few of the more productive blocks. This led to these areas becoming depleted, serial displacement of catch and ultimately rapid fishery decline. It was concluded that closures displacing large amounts of abalone catch were thus a very risky management option because of a pre-disposition to serial depletion in this species. Because abalone larval dispersal was limited, further more complex modelling was confined to rock lobster where several general conclusions became apparent. Firstly, because of the dynamics of growth and recruitment, there was a time lag before any positive effects of an MPA became apparent. The effects of large MPAs (affecting > 5% catch) tended to only become apparent after several years and the effects of small MPAs (affecting < 0.5% catch) would be hard to detect. Secondly, in an exploited population, introducing an MPA was equivalent to increasing the Total Allowable Catch or the effort outside the reserve. Introducing an MPA without reducing catch was likely to have negative effects upon most fisheries where adult movement was limited in extent, leading to reductions in total stock size and egg production. The effects would be least in lightly depleted stocks where total biomass was high relative to an unfished state. Thirdly, the impact of introducing an MPA would depend on the biology of the species concerned and the state of depletion of the stock. If the stock was already in a highly depleted state, an MPA could hasten fishery collapse. On the other hand, if a stock had already collapsed then a reserve could provide some benefit in terms of protecting mature biomass and egg production. Finally, given the assumptions of the generalized model, it appeared that it would be better to improve current management controls, in particular the match between size limits and the growth characteristics, rather than introduce large MPAs to improve the fishery. In the Tasmanian lobster and abalone fisheries where catch and effort are effectively limited, it was concluded that the introduction of MPAs as a fisheries management tool would be inferior to present management options. Indeed, if introduced without reducing catch or effort by amounts equivalent to that in the prospective closed area, closed areas were a risky strategy that could lead to a degradation of the fishery (this appears to be a general conclusion for species with low movement rates). Furthermore, if a fishery is being managed in accordance with ESD principles, which by definition means that the ecosystem in which it operates is not threatened by the fishery or fishing practices, then fishing should not be a key threatening process. It follows from this argument that true ESD fisheries management offers a potentially better outcome than no-take MPAs for biodiversity conservation. This is not to suggest that MPAs do not have a place in marine and coastal management. Spatial management of fisheries has a long tradition (eg spawning grounds) and there are a number of fisheries that benefit from spatial closures. In addition they are useful where other forms of fisheries management are unavailable or poorly applied. Importantly, this study clearly demonstrates the value of MPAs as reference areas for research on the biology of exploited species and in understanding the ecosystem effects of fishing. Both add to the fisheries management toolbox and lead to a greater fisheries resource security

Condition of rocky reef communities: A key marine habitat around Tasmania

A detailed resurvey of rocky reef fishes, large mobile invertebrates and seaweeds at 136 sites around the entire Tasmanian coastline was conducted during 2006/2007, to assess the current condition of reef communities and determine whether there have been any substantial changes to inshore marine biota since 1994. The results of analysis of floral and faunal community changes during the period between surveys and values of key biological indicators, developed specifically for Tasmanian reef communities, are presented in this report