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A new Octopus Cuvier, 1797 species, Octopus djinda Amor, 2021 (previously treated as O. cf. tetricus and O. aff. tetricus), is described from the shallow waters off southwest Australia. This species was classified as conspecific with O. tetricus Gould, 1852 from Australia’s east coast and New Zealand but is shown here to be morphologically and genetically distinct. This description is based on 25 individuals across three localities in southwest Australia, encompassing most of its distribution. Greater and non-overlapping sucker counts on the males hectocotylised arm delimit east and west coast forms. DNA barcoding using cytochrome c oxidase subunit I also successfully differentiates between these taxa; 13 polymorphisms along a 349 bp partial fragment (3.7% sequence divergence). A close relative of the O. vulgaris Cuvier, 1797 species-group, O. djinda, sp. nov. supports a highly productive fishery and is currently one of two octopod fisheries worldwide to have received sustainable certification from the Marine Stewardship Council. The taxonomic description presented here provides formal recognition of the taxonomic status of southwest Australia’s common octopus, O. djinda, sp. nov. and facilitates appropriate fisheries catch reporting and management.

The extreme Western Australia 2011 marine heatwave had a lasting effect on the marine ecosystem and after seven years, only parts of the ecosystem have showed good signs of recovery. After the heatwave, scallop fisheries in the Abrolhos Is. and Shark Bay were closed for 3-5 years, while the Shark Bay crab fishery was closed for 18 months; these fisheries at the centre of the heatwave have shown some improvement due to better protection of spawning stock and improved environmental conditions. Also at the centre of the heatwave, Roe’s abalone suffered a catastrophic mortality and has not recovered as spawning stock remains very low. The Perth abalone stock which was outside the peak heatwave area had a major stock reduction but remained opened with reduced catches. The heatwave had a marked indirect effect on brown tiger prawns in Exmouth Gulf due to loss of seagrass habitat. The heatwave also resulted in a decline in western king prawn recruitment in Exmouth Gulf, to the north of heatwave centre, but an improved recruitment in the cooler waters of Shark Bay. Western rock lobsters near the heatwave peak also appear to have been indirectly affected and have not recovered. Factors influencing the recovery rate from the heatwave appeared to be: species near their upper temperature range and/or sensitive to warming temperatures; spatial overlap between the warming event and species distribution; whether spawning stock was affected to the point of recruitment impairment; life-cycle duration of invertebrate (or habitat) species affected; and management intervention. This study provides a framework for managing the consequences of heatwaves on fisheries by highlighting the value of early identification of the event and its effect on fisheries and having flexible harvest strategies for early management intervention. This is particularly important as long-term increases in water temperatures will increase the frequency of marine heatwave events and the fisheries stocks would have less time for recovery

Populations of broadcast spawning marine organisms often have large sizes and are exposed to reduced genetic drift. Under such scenarios, strong selection associated with spatial environmental heterogeneity is expected to drive localized adaptive divergence, even in the face of connectivity. We tested this hypothesis using a seascape genomics approach in the commercially important greenlip abalone (Haliotis laevigata). We assessed how its population structure has been influenced by environmental heterogeneity along a zonal coastal boundary in southern Australia linked by strong oceanographic connectivity. Our data sets include 9,109 filtered SNPs for 371 abalones from 13 localities and environmental mapping across ~800 km. Genotype-environment association analyses and outlier tests defined 8,786 putatively neutral and 323 candidate adaptive loci. From a neutral perspective, the species is better represented by a metapopulation with very low differentiation (global FST = 0.0081) and weak isolation by distance following a stepping-stone model. For the candidate adaptive loci, however, model-based and model-free approaches indicated five divergent population clusters. After controlling for spatial distance, the distribution of putatively adaptive variation was strongly correlated to selection linked to minimum sea surface temperature and oxygen concentration. Around 80 candidates were annotated to genes with functions related to high temperature and/or low oxygen tolerance, including genes that influence the resilience of abalone species found in other biogeographic regions. Our study includes a documented example about the uptake of genomic information in fisheries management and supports the hypothesis of adaptive divergence due to coastal environmental heterogeneity in a connected metapopulation of a broadcast spawner.

Catch predictions based on pre-recruit abundance have proven valuable in the stock assessment and management of major invertebrate fisheries in Western Australia for western rock lobster (Panulirus cygnus), pearl oyster (Pinctada maxima), abalone (Haliotis roei), prawn (Penaeus esculentus), scallop (Amusium balloti), and blue swimmer crab (Portunus armatus). Predictions are based on puerulus stage (post-larval) rock lobster from artificial collectors; 0+ and 1+ pearl oyster spat attached to commercial shell; dive survey of Roe's abalone; and trawl surveys of prawn (shrimp), scallop, and crab. These reliable predictions (R2 = 0.67–0.97) are used in stock assessment and management harvest strategies to ensure that fishing effort or catch quotas are set so that adequate breeding stocks are maintained. This pro-active management based on predicted abundance avoids the pitfall of heavy fishing on poor recruit classes, which is a common cause of recruitment overfishing. The catch-pre-recruit relationship provid...

A cohort of Haliotis laevigata, spawned from wild broodstock, was monitored from settlement at a hatchery until age 8. Animals were released into the wild at 31 mm (± 4 SD), targeting an enhancement size-class of 135–145-mm shell length. Release densities were tailored to match wild-stock densities using a size-dependent mortality model. A total of 7,500 animals were released into 24 sites, and each site was precisely mapped to control release densities. Environmental and husbandry factors were also quantified. Initial survival rates (six months post-release) differed significantly among sites (range: 11–67%) but not beyond this time period. Legal minimum length (140 mm) was achieved, on average, at 5 years of age or 3.5 years post-release, and the cohort entered the fishery over 3 years (age 5–8). Cumulative survival at age 5 varied between 20% at the better sites and 6% at the worst sites, with an average of 13%. Water depth was significantly positively correlated with growth (r = 0.47; p < 0.05), but n...

A series of stock enhancement experiments were carried out on Haliotis laevigata populations. Methodologies included a large-scale BACI (before, after, control, impact) experiment (42 sites); a carrying capacity experiment, which involved a high-density release at two sites; and a detailed survey of abalone populations and ecological parameters. Increased densities were detected for most age classes, although fishing mortality began obscuring the effect by age 5+. Age-4+ animals showed the clearest result, with no difference between enhanced and control sites at 6, 12, and 18 months post-release, and then a 300% increase at enhanced sites at 30 months post-release. Overall, a single release of age-1+ animals in May 2006 had doubled the total density by November 2008. In the carrying capacity experiment, densities initially increased rapidly (by up to 800%) but had stabilized at a 400% increase after 2.5 years, at around 8 per m2. This was the predicted carrying capacity, with the enhanced cohort represent...

This study presents a bioeconomic evaluation of the effect of stock enhancement on biomass, net present value, profitability, and gross value of product of the Australian greenlip abalone (Haliotis laevigata) fishery. Enhancement targets were defined as a function of natural recruitment (Nr) and compared with current harvest strategies. The model was conditioned on a Western Australian fishery, then applied to greenlip stocks throughout Australia. Two levels of releases (50% Nr and 100% Nr) at varying fishing mortality (F), size at harvest, and size at release were evaluated in detail. Model validation was also undertaken by comparing the model-derived spawning biomass (SSb) with an alternative estimate (SSbf) obtained using in-water surveys and a different growth model. Economic profitability and increased spawning biomass were achieved for most stock enhancement scenarios, and optimal profitability occurred with a 10–20% decrease in F from current levels, a 10% decrease in minimum legal length, and an a...

This paper describes several methods to estimate the amount of sponge erosion in pearl oyster shells (Pinctada maxima Jameson, 1901). Internal erosion can be calculated from non-destructive surface area estimates because a clear relationship was found between the eroded area on the surface of the shells and internal erosions. Grading shells into three different categories, according to the severity of erosion, also proved to be a suitable method to quickly assess the amount of sponge erosions. All methods were more accurate in shells with larger amounts of erosions. Using the described methods, the Lacepedes fishing ground was more diverse in bioeroding sponge species compared with sites at the 80-Mile fishing ground locations. Pione velans Hentschel, 1909 was the dominant bioeroding sponge species but Cliona dissimilis Ridley and Dendy, 1886 eroded more shell material than P. velans. Observed patterns suggest that P. velans had a more recent recruitment than C. dissimilis. We suggest that visual grading together with estimates from the shell surface will be sufficient to determine the general long-term trends in bioeroding sponge severity. However, results of monitoring programmes need to be supplemented by histological examination to confirm sponge activity and species identity.

An evaluation of a digital video survey programme (DVI surveys) to provide cost-effective stock assessment information for Haliotid (abalone) fisheries was undertaken. Cost effectiveness was achieved by using commercial abalone industry divers to collect abundance and length–frequency data from remote locations using a custom designed video survey unit. Production of training DVD/video, training regimes, and a comprehensive suite of experimental tests on two abalone species ( Haliotis laevigata ; Haliotis roei ) were utilised to achieve this outcome. Estimates of density and size–frequency of the populations of interest were achieved (0.5–1.0 m −2 for H. laevigata ; 6–18 m −2 for H. roei ), and appeared reasonable in comparison with existing studies. Although results were not be used as a basis for management decisions due to their preliminary nature, they provided evidence of the potential usefulness of the method for detecting change at the population level. Importantly, the DVI surveys performed favorably against a traditional area-based survey technique, providing the same level of precision in abundance estimation of recruited H. laevigata (greenlip abalone), for 40% of the sampling effort and costs. Overall, this work has expanded the role of DVI surveys as applied to fish and fish habitat assessment, however the abundance and size estimates generated by DVI surveys need to be primarily considered as relative indices, useful for detecting trends over time, provided that the selectivity and sampling issues have appropriately considered.

Growth, mortality, recruitment and sex-ratio of wild stocks of the silver-lipped pearl oyster Pinctada maxima were studied at sites spanning the geographic extent of the commercial fishery using mark-recapture experiments, recruitment cohort analysis and research surveys of stock abundance and reproductive status. Growth parameters (L∞, K) from the von Bertalanffy growth equation were estimated at 210 mm dorso-ventral measurement (DVM) (±16 mm SD) and 0.74 at the Lacepede Islands, L∞ of 199 mm DVM (±6 mm SD) and K of 0.79 on 80 Mile Beach, and L∞ of 194 mm (±6 mm SD), and K of 0.72 at Exmouth Gulf respectively. Estimates of natural mortality (M) by tagging were very low (0.02–0.03), compared with catch-curve analysis, which estimated M to be between 0.1 in deeper (30–34 m) populations and 0.18 in shallow (9–12 m) populations. Settled P. maxima spat (0 + and 1 + age classes) on adult shell were quantified (e.g., 1,317 spat found on 119,000 shell in 2003) to obtain an annual recruitment index, whic...

Silver-lip pearl oyster (Pinctada maxima) spat surveyed in the Eighty Mile Beach section of the North West Shelf have been used in conjunction with outputs from a particle dispersion model to identify likely spawning grounds. The dispersion model consisted of a 3-dimensional regional circulation model in which large numbers of individual particles were tracked over the period 1994 to 1999. From the settlement areas defined by the spat data, larvae were tracked back in time over their estimated pelagic phase of 24–31 days within the main spawning period of mid October to late December. The reverse calculation was also undertaken looking at larval dispersion from known broodstock populations. Results demonstrate that large tidal currents in the region move larvae back and forth across the shelf, whereas lower frequency currents influence their net transport. Whereas some model larvae traveled more than 60 km, most were transported less than 30 km. The model results suggest that spawning in the Eigh...

Slow dissolving plaster standards (SLODS™) were developed to obtain integrated water flow measurements over a time scale of 20–30 days, and tested in giant clam farms in the Solomon Islands under steady flow environments. SLODS™ are composed of a gypsum plaster formulation known as Specially Prepared Gypsum (SPG). This plaster has a considerably higher compressive strength; 10 000–13 000 psi, compared with approximately 1000 psi for more common formulations of Plaster-of-Paris. Experimental calibrations in a water motion simulator over 12 days demonstrated a highly significant relationship between fractional weight loss (FWL) of SLODS™ per day, and water velocity (r2=0.96). The SLODS™ simultaneously measured water flow (over a 21 day period in August 1997) at 12 giant clam grow-out sites spread across 400 km of island archipelagoes. Mean water velocity ranged from 5 to 11 cm s−1 and significantly influenced growth of giant clams. SLODS™ compared well with the established methodology of clod cards (r=0.69; P

A series of large-scale grow-out trials for giant clams ( Tridacna derasa , T. maxima , T. crocea ) were undertaken at 11 village farms in Solomon Islands. Eight hundred juveniles of each species, measuring 20–30 mm shell length (SL), were distributed equally between four replicate cages at each site. Growth and survival of the clams were then monitored for up to 24 months. Environmental and husbandry variables were measured throughout these experiments. T. derasa had the best growth and survival, attaining a mean SL of 150 mm±19.8 s.d., and mean weight of 710 g±26 s.d., after 24 months grow-out. Mean survival of T. derasa over this period was 92.2%±9.1 s.d. T. maxima grew to a mean size of 78.4 mm±14.9 s.d. in 19 months, and T. crocea reached 50.2 mm±8.1 s.d. in 22 months. After 19 months grow-out, survival of T. maxima was 38.9%±16.6 s.d., and survival of T. crocea after 17 months was 39%±22.6 s.d. Factors influencing growth of all species included water temperature, exposure to wave action, water clarity and water flow. Together, these factors explained between 66% and 79% of variation in growth, depending on the species. Regressions of environmental factors against survival were a poorer fit, they explained 15% ( T. derasa ), 53% ( T. maxima ), and 52% ( T. crocea ) of variability among sites. Estimated net revenue for village farmers growing giant clams for the aquarium market was greatest for T. derasa , due to high survival. Although T. crocea is in great demand by the aquarium trade, it was the least suitable species for village farming because it has slow growth and low survival. Unless survival rates at village farms can be enhanced considerably, T. crocea can probably be reared more successfully in a land-based system.

Assessments of three replicate populations of blacklip abalone (Haliotis rubra) were made utilising a range of techniques, enabling critical assumptions to be tested in an empirical manner. Methods included catch-effort (Leslie), change-in-ratio (CIR), mark-recapture (MR) and diver-survey techniques. Population assessments were carried out under the same experimental protocol and within adjacent, closed areas of 5 ha. To establish a Leslie estimate, a 50% stock reduction of each population was carried out using commercial abalone divers. The principal objective was to make a comparative evaluation of methods with respect to their accuracy, precision, robustness and data requirements. A total of 8 tonnes (35729 individuals) of abalone (≥ 10 cm) was harvested. The diver-survey (30 m2 transect), MR and CIR (using 30 m2 transect data) methods were given the highest overall rating. In general, the CIR (using timed collection data) did not perform as well as the CIR (using transect data). Leslie estimators were inaccurate and imprecise for two out of the three populations. Furthermore, the correction of unit effort from total dive time into searching and handling time for both the Leslie and timed collection population estimators did not improve the reliability of the estimate. The timed collection diver-surveys, while precise, were highly inaccurate and their use for abundance estimation in abalone is not recommended.