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Estimating demographic changes in a population requires the measurement of some minimal combination of several vital rates, including the flux of individuals into a population, the population growth rate, individual growth rates and mortality rates. For larval fishes, the ratio of instantaneous mortality to growth (i.e., their 'recruitment potential') has been used to make inferences of cohort trajectory where measures of population growth rates are not attainable. Attaining estimates of mortality and growth is an arduous task, and use of the recruitment potential metric has been limited. Here, we relate size spectra of the broader plankton community to the recruitment potential of simultaneously sampled larval Pacific sardines (Sardinops sagax), from three voyages off eastern Australia. As the size structure of a population is determined by the ratio of mortality to growth, and there is remarkable consistency in size spectra across ecosystems, we test the hypothesis that the recruitment potential of larval fish is reflected in community‐level measures of plankton size spectra. Contrary to expectations, results from this study demonstrate a negative relationship between the slope of the plankton size spectra and the recruitment potential of larval Pacific sardine. However, we also demonstrate several other stronger relationships between recruitment potential and physical oceanographic parameters. Together, results suggest plankton size spectra are unlikely to reflect recruitment potential directly. Incorporating some size‐based aspects of the plankton community into a broader modelling framework with a range of oceanographic parameters could further our ability to determine how larval success varies across a seascape. [ABSTRACT FROM AUTHOR]

Larval dispersal and connectivity have important implications for fisheries management, especially for species with life cycles influenced by ocean boundary currents. Giant Mud Crab (Scylla serrata) and Blue Swimmer Crab (Portunus armatus) are two estuarine portunid crabs (Family: Portunidae) that support significant commercial and recreational harvest in eastern Australia. Giant Mud Crab migrate to coastal waters to spawn, and while Blue Swimmer Crab spawn primarily within estuaries they occasionally migrate to coastal waters to spawn, followed by larval dispersal in the East Australian Current (EAC). Here, we coupled a high‐resolution oceanographic model with a Lagrangian particle tracking framework to simulate larval dispersal and determine the extent of population connectivity in this region. Our simulations indicate broad‐scale connectivity (~40–400 km), characterised by high inter‐estuary connectivity. Overall, our results suggest a north‐to‐south source‐sink structure for both species, with contributions of particles from the north ranging from 51% to 99%. Recruitment to a given estuary is dependent on the proximity of mesoscale oceanographic features of the EAC. Most notably, the EAC separation acts as a barrier to recruitment between spawning and settlement to the north/south of this region. This significantly limits interjurisdictional connectivity for these species, especially Blue Swimmer Crab, likely due to a shorter pelagic larval duration than Giant Mud Crab. Our results provide evidence to inform the assessment and management of these species. [ABSTRACT FROM AUTHOR]

Some dramatic consequences of climate change are caused by shifting species interactions and associated changes to trophic structure and energy flow. In coastal ecosystems, the relative abundance of feeding guilds indicates dominant energy sources sustaining food webs. Here, we use a space‐for‐time substitution to investigate potential climate change impacts on trophic structure and energy flow in reef fish communities. We investigated latitudinal and seasonal patterns in the biomass distribution of five trophic groups across subtropical to temperate latitudes (29 to 44°S) in eastern Australia. Along western boundary currents, temperatures are increasing up to three times faster than the global average, making them ideal for studying climate change impacts. Using 10 years of Reef Life Survey data, we investigated potential determinants of fish biomass and community composition with generalized additive mixed models. Biomass decreased towards higher latitudes, from 220 g/m2 in the subtropics to 13 g/m2 in the south. Dominant trophic group also changed latitudinally, with herbivores and omnivores dominating lower latitudes (~30°S), zooplanktivores at mid‐latitudes (~35°S) and benthic invertivores at higher latitudes (~40°S). Biomass varied seasonally, with lower latitudes experiencing a 3.2‐fold increase between spring and autumn, while variation at higher latitudes was 1.9‐fold. We found strong evidence that factors linked to latitude and seasonality are important determinants in the distribution of fish trophic structure. As climate‐driven species redistributions accelerate in the 21st century, expected poleward shifts in trophic structure include overall increases in fish biomass linked to enhanced herbivory at mid‐latitudes and increased planktivory at higher latitudes. [ABSTRACT FROM AUTHOR]

Policy- and decision-makers require assessments of status and trends for marine species, habitats, and ecosystems to understand if human activities in the marine environment are sustainable, particularly in the face of global change. Central to many assessments are statistical and dynamical models of populations, communities, ecosystems, and their socioeconomic systems and management frameworks. The establishment of a national system that could facilitate the development of such model-based assessments has been identified as a priority for addressing management challenges for Australia's marine environment. Given that most assessments require cross-scale information, individual models cannot capture all of the spatial, temporal, biological, and socioeconomic scales that are typically needed. Coupling or integrating models across scales and domains can expand the scope for developing comprehensive and internally consistent, system-level assessments, including higher-level feedbacks in social-ecological systems. In this article, we summarize: (i) integrated modelling for marine systems currently being undertaken in Australia, (ii) methods used for integration and comparison of models, and (iii) improvements to facilitate further integration, particularly with respect to standards and specifications. We consider future needs for integrated modelling of marine social-ecological systems in Australia and provide a set of recommendations for priority focus areas in the development of a national approach to integrated modelling. These recommendations draw on--and have broader relevance for--international efforts around integrated modelling to inform decision-making for marine systems. [ABSTRACT FROM AUTHOR]

The fine-scale distribution of pelagic forage fish is shaped by competing factors as fish optimise foraging while avoiding predation. We investigated the distribution of forage fish in surface waters of a dynamic coastal environment during two spring seasons to examine their distribution in relation to environmental variables. Using a multi-frequency echosounder and a towed Laser Optical Plankton Counter (LOPC), we investigated the effects of bathymetry, temperature, chlorophyll a concentration and zooplankton biomass on forage fish density. Relationships between fish density and these variables were consistent between surveys, despite large differences in total acoustic energy attributed to fish. Fish density showed a strong positive relationship with bathymetry and water temperature, and no relationship with surface zooplankton biomass density or chlorophyll a. This mismatch between fish and zooplankton may be caused by differences in the way fish perceive the distribution of prey versus temperature and predators in shallow coastal waters. Seeking out warmer temperatures along the shelf break may also improve fish physiological performance when cooler spring temperatures are below their thermal optimum. Understanding the distribution of coastal forage fish may contribute to interpreting nearshore movements of their predators. • Southern New South Wales regularly experiences reversals in current direction. • Reversals cause alternation state between temperate and subtropical water masses. • The shelf break had more forage fish despite greater zooplankton density near shore. • Forage fish associated with water masses with a positive temperature anomaly. [ABSTRACT FROM AUTHOR]

Zooplankton biomass data have been collected in Australian waters since the 1930s, yet most datasets have been unavailable to the research community. We have searched archives, scanned the primary and grey literature, and contacted researchers, to collate 49187 records of marine zooplankton biomass from waters around Australia (0–60°S, 110–160°E). Many of these datasets are relatively small, but when combined, they provide >85 years of zooplankton biomass data for Australian waters from 1932 to the present. Data have been standardised and all available metadata included. We have lodged this dataset with the Australian Ocean Data Network, allowing full public access. The Australian Zooplankton Biomass Database will be valuable for global change studies, research assessing trophic linkages, and for initialising and assessing biogeochemical and ecosystem models of lower trophic levels. Measurement(s) zooplankton biomass • organic material • planktonic material Technology Type(s) digital curation Factor Type(s) year of data collection Sample Characteristic - Organism zooplankton Sample Characteristic - Environment marine water body Sample Characteristic - Location Australia Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12651425 [ABSTRACT FROM AUTHOR]

Recent debates have arisen as to whether productivity and subsequent ecological processes increase linearly with increasing intensity of upwelling, or whether productivity responds more favourably to upwelling of intermediate magnitude, as predicted by the intermittent upwelling hypothesis (IUH). Most studies on the topic take place within eastern boundary systems, where the intensity and frequency of upwelling are high. Here, we test the generality of the IUH towards the other end of the upwelling spectrum, within two regions located at similar latitudes along western boundary currents of two continents. We measured barnacle recruitment and colonisation, which we expected to be linked positively to productivity, across eight rocky shores along the east coasts of South Africa and Australia selected to capture a range of upwelling regimes. Based on Bakun Upwelling Indices (BUI), the four South African sites experienced persistent to intermittent levels of upwelling, whilst the four sites along the east coast of Australia were predominantly downwelling sites with occasional upwelling events. Satellite chlorophyll a concentrations ([Chl-a]) also showed a marked difference between the two continents, with 2–3 times higher concentrations in South Africa than Australia. In situ sea temperature measurements revealed slightly different oceanographic patterns, which were nonetheless compatible with both BUI and [Chl-a] measurements. Barnacle recruitment was typically greater within South Africa and but was generally found to vary unimodally with mean BUI (i.e. being greater at sites that experienced moderate upwelling conditions) and to increase linearly with increasing upwelling frequency between January and April when barnacle larvae are known to be most abundant in the water column. Viewed in isolation, our data provide moderate support for the IUH. But when placed in a broader context, with our eight study locations representing just one end of the upwelling continuum, they provide strong evidence for the IUH. [ABSTRACT FROM AUTHOR]

Many seabird communities are declining around the world, a trend frequently linked to climate change and human impacts on habitat and prey. Time series observations of seabirds away from breeding colonies are generally rare, which limits our understanding of long-term changes for conservation actions. We analysed a dedicated citizen science dataset of pelagic seabird abundance (86 species – 30 used for modelling analysis - from 385 trips) from two locations over 17 years (2000–2016) and a third for seven years, over the continental shelf and slope of south-eastern Australia. To estimate temporal trends and environmental drivers, we used generalised additive modelling and species archetype modelling for groups. Almost half (43%) of the most abundant seabird species declined in our study area over the 17 years. The declines may be associated with human-induced ecosystem change and represent poleward shifts in distribution out of our study area, changes in population abundance, or both. Winter-dominant groups, primarily species rarely frequenting warmer water, were often negatively associated with SST anom , while summer-dominant groups, composed of species more tolerant of temperate and tropical environments, were generally positively associated with SST anom. Widespread local declines in seabird populations are of increasing concern. Understanding the extent to which these observed declines represent real declines in abundance, or range shifts, should be a priority. Changing sea temperatures are probably contributing to both. These results from the coast of south-eastern Australia need to be placed in the context of the highly mobile study organisms and the vast spatial scale of the ocean. Long-term citizen science observations, from an array of locations around the world, promise to provide valuable insights into seabird ecology, playing a key part in seabird conservation. • We used citizen science data to describe long-term seabird trends in an understudied coastal shelf region. • Seabird occurrences were linked with oceanographic environmental variables for species and groups (i.e., archetype modelling). • Almost half (43%) of the most abundant seabird species declined in our study area over the 17 years. • We encourage use of similar pelagic birding datasets, integrated with oceanographic variables, worldwide. [ABSTRACT FROM AUTHOR]

Pomatomus saltatrix is an important recreational fishing species with seven major populations worldwide. The reproductive biology of the southwest Pacific Ocean (east Australian) population is uncertain, with both an extended spawning and multiple spawning periods previously hypothesised. Here we demonstrate an altered sex ratio biased towards females and a larger length at 50% maturity (L 50) compared to those recorded for the population 40 years ago, before comprehensive management strategies were implemented. We also report a second, previously undescribed, late-summer spawning event which was identified by analysing patterns in a gonadosomatic index across the whole population and an historical larval fish database. P. saltatrix are capable of spawning multiple times per season with estimates of batch fecundity ranging from 99,488 to 1,424,425 eggs per fish. When combined with the length frequency distribution of the population, the majority of eggs (64%) were shown to be produced by fish ≤40 cm fork length (FL). L 50 was estimated at 30.2 and 31.5 cm FL for male and female P. saltatrix respectively, 4 cm larger than 40 years ago. The sex ratio of the population was found to have significantly shifted over the last 40 years from an equal sex ratio to a female dominated population (1.58 females:1 male). These dramatic alterations to the sex ratio and L 50 highlights the value of monitoring the reproductive biology of exploited fish populations to ensure that management plans remain appropriate. • Increasing management of P. saltatrix in east Australia began in 1990, reducing fishing pressure. • Length at 50% maturity of P. saltatrix has increased ∼4 cm in 40 years. • Sex ratio of P. saltatrix has changed in the last 40 years towards female biased. • A previously unrecognised late summer spawning period in this population is described. • Raising the minimum legal length may increase egg production for P. saltatrix. [ABSTRACT FROM AUTHOR]

Seasonal forecasting of environmental conditions and marine species distribution has been used as a decision support tool in commercial and aquaculture fisheries. These tools may also be applicable to species targeted by the recreational fisheries sector, a sector that is increasing its use of marine resources, and making important economic and social contributions to coastal communities around the world. Here, a seasonal forecast of the habitat and density of dolphinfish ( Coryphaena hippurus ), based on sea surface temperatures, was developed for the east coast of New South Wales (NSW), Australia. Two prototype forecast products were created; geographic spatial forecasts of dolphinfish habitat and a latitudinal summary identifying the location of fish density peaks. The less detailed latitudinal summary was created to limit the resolution of habitat information to prevent potential resource over-exploitation by fishers in the absence of total catch controls. The forecast dolphinfish habitat model was accurate at the start of the annual dolphinfish migration in NSW (December) but other months (January - May) showed poor performance due to spatial and temporal variability in the catch data used in model validation. Habitat forecasts for December were useful up to five months ahead, with performance decreasing as forecast were made further into the future. The continued development and sound application of seasonal forecasts will help fishery industries cope with future uncertainty and promote dynamic and sustainable marine resource management. [ABSTRACT FROM AUTHOR]

Larval fishes are a useful metric of marine ecosystem state and change, as well as species-specific patterns in phenology. The high level of taxonomic expertise required to identify larval fishes to species level, and the considerable effort required to collect samples, make these data very valuable. Here we collate 3178 samples of larval fish assemblages, from 12 research projects from 1983-present, from temperate and subtropical Australian pelagic waters. This forms a benchmark for the larval fish assemblage for the region, and includes recent monitoring of larval fishes at coastal oceanographic reference stations. Comparing larval fishes among projects can be problematic due to differences in taxonomic resolution, and identifying all taxa to species is challenging, so this study reports a standard taxonomic resolution (of 218 taxa) for this region to help guide future research. This larval fish database serves as a data repository for surveys of larval fish assemblages in the region, and can contribute to analysis of climate-driven changes in the location and timing of the spawning of marine fishes.

Chlorophyll a is the most commonly used indicator of phytoplankton biomass in the marine environment. It is relatively simple and cost effective to measure when compared to phytoplankton abundance and is thus routinely included in many surveys. Here we collate 173, 333 records of chlorophyll a collected since 1965 from Australian waters gathered from researchers on regular coastal monitoring surveys and ocean voyages into a single repository. This dataset includes the chlorophyll a values as measured from samples analysed using spectrophotometry, fluorometry and high performance liquid chromatography (HPLC). The Australian Chlorophyll a database is freely available through the Australian Ocean Data Network portal (https://portal.aodn.org.au/). These data can be used in isolation as an index of phytoplankton biomass or in combination with other data to provide insight into water quality, ecosystem state, and relationships with other trophic levels such as zooplankton or fish.