Science & Mathematics

The littoral macroinvertebrate assemblages of Lakes Albina, Blue, Club andCootapatamba in the Mt. Kosciuszko region were sampled by two methods: sweeps and cobble picks. Thirty-six species were collected with total abundance and species richness greatest in Lake Albina. Common species included themolluscs Pisidium kosciusko and Glacidorbis hedleyi, the crustaceans Metaphreatoicus australis and Neoniphragus n. sp., and an unidentified limnephidtrichoperan. Community structure was influenced by the nature of the substrate, with cobble sites having greater richness and abundance than boulder sites. The importance of the major taxonomic groups (crustaceans, insects and molluscs) varied with sampling method and among lakes. Crustaceans (isopods and amphipods) usually dominated in sweeps, with molluscs and insects varying in importance among lakes, while insects mostly dominated in cobble pick samples. Oligotrophic lakes are typically thought to be dominated by insects, however this study shows such lakes may appear to be dominated by insects or crustaceans depending on the sampling method used and the presence of fish.

Rocky reef habitat is common in many estuaries yet its role as a habitat for fishes is poorly known. There is also limited understanding of how access of coastal species into estuaries and habitat quality can affect the distribution of rocky reef fishes within estuaries. This study used baited remote underwater video stations (BRUVS) to determine spatial patterns in fish assemblages associated with rocky reef habitat throughout a barrier estuary with a permanently open but restricted inlet. Estuarine rocky reefs provided habitat for a diverse assemblage of fishes, many of which were large juveniles and subadults. In the absence of a pronounced salinity or temperature gradient a clear transition in fish assemblages occurred from coastal waters, through the inlet channel, to the central estuary, and into the inner estuary. The inlet channel, notably its narrowness and length, limit tidal input into this estuary which acts as a significant impediment to the dispersal of many coastal fishes and insufficient habitat excludes many coastal rocky reef species from the inner estuary. This study highlights the need to recognise estuarine rocky reefs as providing habitat for diverse fish assemblages and the role inlets play in restricting access of coastal species.

Before 2003, unique assemblages of aquatic invertebrates in Lake Cootapatamba and Lake Albina lived in a fishless environment. A sequence of events in 2003 following a large-scale bushfire in the area allowed the native Mountain Galaxias Galaxias olidus to enter Lake Cootapatamba. This study determines the extent of any temporal changes in the invertebrate assemblages of each lake and whether the introduction of fish into Lake Cootapatamba affected these assemblages. The littoral and benthic fauna of both lakes were found to have changed since the earliest studies of these lakes in 1997/1998 and 1976, respectively. In particular, there has been a large decrease in the abundance of the isopod Metaphreatoicus australis and planarians, and the gastropod Glacidorbis hedleyi and amphipod Neoniphargus sp. have apparently disappeared. The effect is greatest in the benthos and in Lake Cootapatamba, so while fish seemed to have affected some invertebrates in some habitats, other factors may be acting. Sometime since 1976, the exotic worm Lumbriculus variegatus arrived into Lake Albina. Shifts in the representation of other taxa, such as ephemeropterans, plecopterans, tricopterans, dipterans and coleopterans, are thought to reflect natural year-to-year fluctuations but more data are needed.

The foraging behaviours and dietary compositions of three co-occurring labrids (Ophthalmolepis lineolatus, Notolabrus gymnogenis and Pictilabrus laticlavius), which are conspicuous on rocky reefs in temperate south-eastern Australia, were investigated between 2003 and 2005. SCUBA observations at two locations showed that the feeding intensity, and hence the associated effects of these fishes on rocky reef invertebrate prey, was temporally consistent. Relative differences in the contributions of ingested prey and use of different feeding microhabitats demonstrated that the feeding ecology differed significantly among the three species. Thus, O. lineolatus fed on proportionately higher volumes of polychaetes, polyplacophorans, marginellid gastropods (especially Austroginella sp.), bivalves and echinoids, which were sighted opportunistically in a wide selection of microhabitats, but particularly in sand/rubble. Ambush hunting was used regularly by smaller N. gymnogenis and all sizes of P. laticlavius to forage on amphipods, small decapods and small gastropods at algal bases or fronds and Diopatra dentata tubes. Amphipods were similarly important in the diet of smaller O. lineolatus. Larger N. gymnogenis foraged opportunistically over an increased reef area and made greater use of microhabitats that oVered minimal prey refuge (e.g. sand/rubble, bare rock/steel) from which common prey, in particular decapods, were obtained. The significant intra- and inter-specific differences in dietary compositions, allied with differences in the use of feeding microhabitats, would facilitate co-occurrence of these three conspicuous species and contribute to maintaining high richness of labrid species in reef systems. Echinoids were regularly consumed by each species but they made a moderate contribution to the diet of only O. lineolatus, which suggests that only one of the three labrids is likely to play a significant role in regulation of echinoid densities in these rocky reef habitats. However, the broad diets and diverse forging strategies employed by these labrid species imply that they have a system-wide influence on invertebrate prey on rocky reefs.

Habitat variability is an important factor structuring fish assemblages of rocky reefs in temperate Australia. Accepting the generality of this model requires that habitat-related variation is consistent through time, across multiple spatial scales, and applies to all life-history stages. We used repeated underwater visual surveys at multiple spatial scales over a 22-month period to test whether three distinct rocky-reef habitats had different wrasse assemblages and whether these assemblages were subject to spatial, temporal and ontogenetic variability. Overall, the strongest and most consistent habitat association was with sponge gardens, which had the most distinct assemblage, and the greatest species richness and density of individuals. Habitat associations in fringe and barrens were less consistent. A substantial increase in the abundance of small individuals, coinciding with warmer sea temperatures, contributed to temporal fluctuations in the density of wrasses. Overall, habitats were not strongly partitioned among larger individuals of the most abundant species, suggesting that adults are largely habitat generalists whereas small, recruiting individuals showed greater habitat specialisation. The present study emphasises the importance of incorporating spatial, temporal and ontogenetic variability into surveys of fish assemblages to understand more fully the dynamics of temperate rocky-reef systems.

Labrids are abundant on temperate rocky reefs yet their life histories are poorly known. Three co-occurring Australian labrids (Ophthalmolepis lineolatus, Notolabrus gymnogenis and Pictilabrus laticlavius) exhibited protogynous hermaphroditism typical of labrids. Juveniles reached sexual maturity at 184 mm total length (TL) (2.1 years) in O. lineolatus, 177 mm TL (1.8 years) in N. gymnogenis and (P. laticlavius. Individuals were sexually active initial phase females until changing to a terminal phase male at 295 mm TL (5.2 years) in O. lineolatus, 273 mm TL (4.5 years) in N. gymnogenis and 138 mm TL (2.0 years) in P. laticlavius. The occurrence of males only at greater lengths and older ages suggests that O. lineolatus and N. gymnogenis are monandrous, whereas P. laticlavius appears to be diandrous. Reproduction was asynchronous among species with reproductive activity peaking in January–March for O. lineolatus, April–October for N. gymnogenis and October–December for P. laticlavius. Sectioned otoliths revealed that O. lineolatus and N. gymnogenis grew rapidly to 300 mm TL (6 years) and P. laticlavius to 180 mm TL (3 years). Longevity was at least 13.8, 9.6 and 4.8 years respectively. These life history data will aid management of these frequently harvested species.

The reduction of saltmarsh habitat at a global scale has seen a concomitant loss of associated ecosystem services. As such, there is a need and a push for habitat rehabilitation. This study examined an innovative saltmarsh restoration project in Australia which sought to address the threats of mangrove encroachment and sea level rise. The project was implemented in 2017, using automated hydraulic control gates, termed“SmartGates,”to lower the tidal regime over one site, effectively reversing sea level rise at a local level. Measured indicators of saltmarsh cover, number of species, seedling counts, and saltmarsh assemblages all showed significant positive development over time, with trends varying based on saltmarsh zone. The saltmarsh, predominantly Sarcocornia quinque flora, developed from remnant supralittoral (previously high) marsh which remained at 45% cover to achieve over 15% coverage across the cleared habitat after 3 years. Slower development in the low marsh (

The Australian edible oyster industry has been severely impacted by disease and declining yields since the 1970s. Selective breeding of Saccostrea glomerata is one measure addressing these problems by producing fast‐growing, disease‐resistant oysters. Farmers report that selected oysters have different growth characteristics than their wild counterparts using conventional grow‐out methods. This study investigated how different grow‐out methods influence commercially valuable oyster characteristics including shell length, shape, surface growth deformities and meat condition. In June 2015, selectively bred S. glomerata spat were deployed in two estuaries (Hawkesbury River and Georges River) in NSW, Australia, using three grow‐out methods (fixed trays, Stanway cylinders and floating baskets). In November 2015, oysters were transferred among grow‐out methods to test for the effects of changing grow‐out methods on oyster growth patterns. Oysters transferred from baskets to cylinders and from trays to cylinders had, on average, deeper and wider shells, a higher meat condition and fewer shell surface deformities than oysters in other grow‐out method combinations. However, these oysters were smaller than oysters not grown in cylinders. While there were some differences in growth patterns between the estuaries, overall it was the grow‐out methods that most influenced oyster characteristics. This was attributed to differences in the amount and magnitude of movement oysters experienced in the grow‐out methods, as recorded by motion sensors. This study demonstrates how grow‐out methods can be managed to achieve desired growth trajectories and therefore improve marketability among selective bred S. glomerata.

Worldwide, spoil from maintenance dredging of navigation channels is increasingly used to opportunistically nourish beaches. This is often justified on the presumption that nourishment will improve public beach amenity and restore sandy beach habitat. However, this is not necessarily the case, especially for beaches that do not have an immediate threat of significant erosion. We addressed the ecological impacts and benefits of a backshore sand nourishment project conducted along an off-road vehicle (ORV) damaged section of Blacksmiths Beach, New South Wales, Australia. Sediment, sourced from dredging the inlet of nearby Lake Macquarie, was placed on the foredune, ORVs were excluded and low-density vegetation was planted. Sampling before and after the management interventions, at the Impact (nourished) site, two Control sites (with ORVs), and two Reference sites (without ORVs), assessed ecological impacts of nourishment and the efficacy of the interventions in rehabilitating vegetation and invertebrate communities degraded by ORVs. Nourishment initially had large negative impacts on vegetation cover, as well as on invertebrate abundance and richness. Recovery to a pre-nourished state was, however, observed for vegetation cover after 9 months and invertebrate communities after 21 months. Nevertheless, by the end of our study that extended 21 months post-nourishment and ORV exclusion, there was no evidence of change in the nourished site towards the state of Reference sites. Overall, our study suggests that small-scale backshore sand nourishments of ocean beaches may have only short-term negative impacts on foredune ecosystems when accompanied with some replanting. Nevertheless, where the frequency of sand disposals is greater than the required recovery time, or cumulative effects amass, longer-term or sustained impacts may occur. Our study does not support the efficacy of sand nourishment as a tool for ecological restoration, at least in the short term, without sustained replanting and weeding efforts aimed at reinstating the vegetation community.

This work is a photographic identification guide to Intertidal Rocky Shore Life