Jasus Edwardsii Research Articles

Paralytic shellfish toxins in Australian Southern Rock Lobster (Jasus edwardsii): Acute human exposure from consumption of hepatopancreas

ABSTRACTParalytic shellfish toxins (PST) were identified in the hepatopancreas of Southern Rock Lobster (Jasus edwardsii) during Alexandrium tamarense blooms in Tasmania, Australia. Human health risk from PST in lobsters was unknown – this study assesses exposure to PST from hepatopancreas consumption. Lobster hepatopancreas samples collected during blooms (n = 181) were mostly positive for PST (>88%), the highest concentration was 4032 μg STX-2HCl eq/kg. Consumer exposure to PST was estimated using a 2-D Monte Carlo model. Mean PST intake (pi) from hepatopancreas consumption (raw and cooked) was below the lowest-observed-adverse-effect-level (LOAEL) for PST (<2.0 μg/kg bw), however the 97.5th percentile pi for raw meals (2.64 μg/kg bw) exceeded the LOAEL. A total of 4.1% of raw hepatopancreas meals were estimated to exceed the LOAEL. Lobster hepatopancreas consumption during A. tamarense blooms may be concerning for a small proportion of consumers, particularly those that eat large meals at the bloom peak. However, when the model was re-run with PST concentration capped at the bivalve regulatory limit (800 μg STX-2HCl eq/kg) pi decreased, with the 97.5th percentile values below the LOAEL. Thus, issuing public health warnings and harvesting restrictions for lobsters when levels exceed 800 μg STX-2HCl eq/kg would reduce the probability of illness occurring.

Potential virulence factors of bacteria associated with tail fan necrosis in the spiny lobster, Jasus edwardsii.

Tail fan necrosis (TFN) is a common condition found in commercially exploited spiny lobsters that greatly diminishes their commercial value. Bacteria possessing proteolytic, chitinolytic and lipolytic capabilities were associated with TFN in spiny lobsters, Jasus edwardsii. In this study, 69 bacterial isolates exhibiting all the three enzymatic capabilities from the haemolymph and tail fans of J.edwardsii with and without TFN were further characterized and compared, including morphology, biofilm formation, antimicrobial activity, antimicrobial resistance, and production of siderophores, melanin and ammonia. The genomic patterns of the most common Vibrio crassostreae isolates were also compared between TFN-affected and unaffected lobsters. Biofilm formation was stronger in bacterial isolates from both haemolymph and tail fans of TFN-affected lobsters compared to those from the unaffected lobsters, while melanin production and siderophore production were stronger in the isolates from tail fans of lobsters with TFN. By contrast, the other characteristics of isolates were similar in lobsters with and without TFN. The Vib.crassostreae isolates from the affected lobsters had similar genomic patterns. Overall, the results indicate that in addition to proteolytic, chitinolytic and lipolytic activities, the bacteria associated with TFN commonly have enhanced activity of important virulence factors, including biofilm formation, melanin production and siderophore production.

Fate of Paralytic Shellfish Toxins in Southern Rock Lobster (Jasus edwardsii) during Cooking: Concentration, Composition, and Distribution

Paralytic shellfish toxin (PST) producing microalgal blooms have a significant economic impact on the Southern Rock Lobster ( Jasus edwardsii) fishery in Tasmania, Australia. The regulatory level of 0.8 mg of saxitoxin (STX) eq/kg in place for bivalve shellfish fisheries is applied to lobster hepatopancreas during blooms of toxic algae, resulting in harvest closures and ongoing risk management implications for the fishery. This cooking study was undertaken to inform a human health risk assessment, in conjunction with studies on the uptake and elimination of PST in J. edwardsii. Live lobsters in tanks were contaminated through consumption of PST-containing mussels harvested during an Alexandrium tamarense Group 1 bloom event. This resulted in a mean lobster hepatopancreas level of 2.83 ± 0.84 mg of STX·2HCl eq/kg. Other edible tissues contained negligible concentrations of toxin. PST concentrations in all tissues did not significantly change after boiling or steaming, although the amount of hepatopancreas available for consumption did decrease significantly with both cooking methods, because the tissue became more dispersed, resulting in an overall reduction in the toxin exposure per hepatopancreas consumed. The toxin profile was dominated by STX; gonyautoxin 2, 3; N-sulfocarbamoyl-gonyautoxin 2, 3 (C1,2); and gonyautoxin 5. No significant changes to the toxin profile were observed after either of the cooking methods. Pâté, bisque, and soufflé prepared from the hepatopancreas of toxic lobsters contained negligible levels of PST in each serving; on average, a serving of pâté contained 0.01 mg of STX·2HCl eq, whereas a serving of bisque or soufflé contained <0.01 mg of STX·2HCl eq. The findings of this study will inform a risk assessment of PST in J. edwardsii to determine risk management options for this fishery in Australia.

Rock lobster hepatopancreas consumption data for dietary exposure assessment among recreational harvesters in Tasmania and South Australia

ABSTRACTIn 2012 and 2015, blooms of Alexandrium tamarense occurred in Tasmania, Australia, and paralytic shellfish toxins (PST) were identified in the hepatopancreas of Southern Rock Lobsters. The human health risk was unclear, because consumption data were not available for lobster hepatopancreas. Thus, the aim of this study was to investigate the types of lobster tissues consumed, hepatopancreas portion size, and consumption format (boiled, steamed, raw, etc.), for Tasmanian and South Australian recreational harvesters.A significant proportion of harvesters (15%) eat lobster hepatopancreas, with the majority consuming it as a dipping sauce for cooked (boiled or steamed) lobster meat. Two different methods were used to estimate portion size, a recollection-based food consumption questionnaire (FCQ) and a prospective Food Diary – mean portion size estimates showed good agreement: 3.4 g and 4.8 g, respectively. These results are critical for assessing the exposure of recreational harvesters to acute contaminants, such as PST, in lobster hepatopancreas. Results from the FCQ showed that lobster hepatopancreas is not consumed as often as white meat, suggesting that exposure to contaminants in hepatopancreas may be less frequent than white meat. This should be considered when evaluating human health risk from repeated or long term (chronic) exposure to contaminants in lobsters.

Experimental uptake and depuration of paralytic shellfish toxins in Southern Rock Lobster, Jasus edwardsii

In October 2012, paralytic shellfish toxins (PST) were detected in the hepatopancreas of Southern Rock Lobsters (Jasus edwardsii) collected from the east coast of Tasmania, Australia. This resulted in the first commercial closure in Australia for this species. Questions were raised on how the toxins were transferred to the lobsters, how long the toxins would persist, whether PST-contaminated hepatopancreas posed a risk to human health, and what management strategies could be applied. The aim of this study was to investigate whether PST-contaminated mussels are a potential vector enabling toxin accumulation in J. edwardsii and to collect information on toxin uptake, distribution and depuration rates and toxin profiles under controlled experimental settings. Lobsters were fed mussels naturally contaminated with PST for a period of 28 days in an experimental setting; following this, lobsters were allocated to either fed or starved treatment groups. PST were not detected in the tail tissue of lobsters at any stage of the experiment. Lobster hepatopancreas contained mean levels of 2.4 mg STX.2HCl eq/kg after 28 days of uptake, although substantial variability in total toxicity was observed. The PST profile of the hepatopancreas was similar to that of the contaminated mussels used as feed. Significant differences were noted in the PST depuration rates between fed and starved treatment groups. The daily depuration rate for total PST was estimated to be 0.019 and 0.013 mg STX.2HCl eq/kg for the fed and starved treatment groups respectively using a constant-rate decay model. After 42 days of depuration, total PST (STX equivalents) levels in the hepatopancreas of all lobsters were below 0.8 mg STX.2HCl eq/kg, which represents the regulatory level applied to bivalves. This result indicates that long-term holding to depurate PST may potentially be used as a risk management tool.

Behavioural responses of draughtboard sharks (Cephaloscyllium laticeps) to rare earth magnets: Implications for shark bycatch management within the Tasmanian southern rock lobster fishery

Catches of draughtboard shark (Cephaloscyllium laticeps) in the Tasmanian Southern Rock Lobster Fishery are considered an economic and potentially ecological issue. Consequently, there is interest in developing strategies to mitigate and minimise shark bycatch within this fishery. This field study examined the behavioural responses of draughtboard sharks to neodymium-iron-boron (Nd2Fe14B) rare earth magnetic rods attached to baited video apparatus. Two magnetic treatments and one control were used in 12 × 1.5 h observational trials conducted in inshore waters of Tasmania, Australia. Results demonstrate that draughtboard sharks: (1) showed substantial individual variation in behaviours both between and within treatments, with no patterns of individual responses observed over time to both magnetic treatments or the control, (2) showed significant differences in initial interactions between the magnetic treatments and the control, and (3) attempted to take bait at the control significantly more often than at the 2-magnet treatment. These findings demonstrate the individualistic and highly variable response behaviours of draughtboard sharks to rare earth magnets. Understanding such behaviours may facilitate the development of effective deterrent strategies in this fishery and improve management of shark-fishery interactions globally.

Temporal genetic patterns of diversity and structure evidence chaotic genetic patchiness in a spiny lobster.

Population structure of many marine organisms is spatially patchy and varies within and between years, a phenomenon defined as chaotic genetic patchiness. This results from the combination of planktonic larval dispersal and environmental stochasticity. Additionally, in species with bi-partite life, postsettlement selection can magnify these genetic differences. The high fecundity (up to 500,000 eggs annually) and protracted larval duration (12-24months) and dispersal of the southern rock lobster, Jasus edwardsii, make it a good test species for chaotic genetic patchiness and selection during early benthic life. Here, we used double digest restriction site-associated DNA sequencing (ddRADseq) to investigate chaotic genetic patchiness and postsettlement selection in this species. We assessed differences in genetic structure and diversity of recently settled pueruli across four settlement years and between two sites in southeast Australia separated by approximately 1,000km. Postsettlement selection was investigated by identifying loci under putative positive selection between recently settled pueruli and postpueruli and quantifying differences in the magnitude and strength of the selection at each year and site. Genetic differences within and among sites through time in neutral SNP markers indicated chaotic genetic patchiness. Recently settled puerulus at the southernmost site exhibited lower genetic diversity during years of low puerulus catches, further supporting this hypothesis. Finally, analyses of outlier SNPs detected fluctuations in the magnitude and strength of the markers putatively under positive selection over space and time. One locus under putative positive selection was consistent at both locations during the same years, suggesting the existence of weak postsettlement selection.

Immune status of the spiny lobster Jasus edwardsii with tail fan necrosis.

Tail fan necrosis (TFN), a disorder commonly found in some populations of commercially fished and cultured lobsters, is thought to be initiated by injuries caused by handling and containment. The unsightly appearance of affected lobster tails significantly lowers their commercial value. Knowledge about TFN is limited. In this study we describe the morphological features of TFN and apply 6 common methods for evaluating the immune status of wild-caught Australasian red spiny lobsters Jasus edwardsii with and without TFN. The disease was more frequent in uropods than in telsons of the tail fan, and more extensive on the ventral versus the dorsal surfaces of the tail fan. Missing appendages (i.e. antenna, pereiopod or pleopod) were significantly more common and greater in number for individual lobsters affected with TFN versus those without, possibly as a result of handling in the fishery or as an indirect effect of the disease. Two immune parameters, total haemocyte count and phenoloxidase activity in the haemocyte lysate supernatant (HLS), were significantly compromised in lobsters with TFN. No differences were found in the other immune parameters, i.e. haemocyte viability, haemolymph bacterial count and the protein content of haemolymph plasma and HLS. The results are consistent with injury sustained during prior capture and handling that initiates TFN in these natural caught lobsters. These results raise some potential concerns about the fitness of lobsters in natural populations that are affected by TFN, and some potential solutions are proposed.

In situ video monitoring of by-catch interactions within commercial rock lobster (Jasus edwardsii) fishing traps

ABSTRACTThe incidental capture of non-target and undersized target species during commercial fishing operations has been identified as a major issue and ongoing challenge for fisheries management. In the Northern Zone rock lobster (Jasus edwardsii) fishery (NZRLF) of South Australia, escape gaps have been mandatory in all commercial fishing traps since 2002 to reduce non-target species (by-catch) catch rates and juvenile lobster mortality. This study used in situ video monitoring of by-catch species in traps with and without escape gaps to understand how by-catch species interact within commercial fishing traps. Twenty-two different by-catch species were observed entering commercial rock lobster traps, 20 of which were temperate reef finfish. Overall, on-board by-catch rates were significantly higher in hauled traps without escape gaps and were dominated by reef-dwelling finfish species, particularly Meuschenia hippocrepis and Notolabrus tetricus. However, in situ video monitoring within traps showed no difference in the maximum number of finfish by-catch (MaxN) in traps with or without escape gaps. We suggest that the difference in by-catch rates between hauled traps with and without escape gaps may be driven by species-specific behavioural interactions within traps prior to hauling. Overall, this study shows that the implementation of escape gaps in the NZRLF has considerably reduced fishery by-catch rates. Furthermore, the use of in situ video monitoring has provided a better understanding of by-catch behavioural interactions within traps, not previously identified in on-board sampling research, which may partly explain the mechanisms underpinning escape gap effectiveness.

Overview, opportunities and outlook for Australian spiny lobster fisheries

Australia’s lobster fisheries are relatively small in volume (9500t) compared with global production (289,000t), but are the country’s most valuable in terms of both overall production and value of export (2014 Gross Value of Production of $610 million AUD). Further, they support commercial, recreational and indigenous fishers along most of the continent’s coastline. Here we review similarities and key differences between these lobster fisheries, based on biological characteristics, fishery data collection, assessment and management methods, and supply chain considerations. A diverse range of palinurid lobsters occur in Australia, but only three genera, distributed across eight different management jurisdictions, support significant fisheries. Catches of western rock lobster Panulirus cygnus dominate landings (61%), followed by southern rock lobster Jasus edwardsii, tropical lobster Panulirus ornatus and the eastern rock lobster Sagmariasus verreauxi. Large-scale environmental influences such as climate change are impacting on these fisheries in similar or different ways forcing new management and raising the need for greater resilience in current supply chains. Although these are separate fisheries, the integrated nature of the dominant Chinese export markets suggests potentially important economic and market-related interactions. Our overview highlights the critical role of continued monitoring of recruitment pulses, in combination with robust harvest strategies, to ensure that harvests respond adequately and fisheries achieve biological and economic sustainability. Approaches that also include socio-cultural considerations (triple bottom line) are important given many fisheries include indigenous Australians. Our integrated analysis of Australian lobster fisheries highlights differences and similarities with spiny lobster fisheries worldwide and lessons from opportunities, including adapting to new free trade agreements, enhancing the reputation of wild lobsters as a whole, sharing expertise, and better alignment of supply and demand.

The impact of seismic air gun exposure on the haemolymph physiology and nutritional condition of spiny lobster, Jasus edwardsii

There is a critical knowledge gap regarding the impacts of seismic air gun signals on the physiology of adult crustaceans. We conducted four controlled field experiments to examine the impact of seismic acoustic signals on spiny lobster, Jasus edwardsii. Seismic air gun exposure suppressed total haemocyte count (THC) for up to 120days post-exposure, suggesting a chronic negative impact of immune competency. THC levels after 365days post-exposure, were elevated two fold, potentially indicating an immune response to infection. Haemolymph refractive index was reduced after 120days post exposure in one experiment, suggesting a chronic impairment of nutritional condition. There was no effect of air gun exposure on 24 haemolymph biochemical parameters, hepatopancreas index or survival. Collectively these results indicate that the biochemical haematological homeostasis of J. edwardsii is reasonably resilient to seismic acoustic signals, however, air gun exposure may negatively influence the lobster's nutritional condition and immunological capacity.

Efficiency of ddRAD target enriched sequencing across spiny rock lobster species (Palinuridae: Jasus)

Double digest restriction site-associated DNA sequencing (ddRADseq) and target capture sequencing methods are used to explore population and phylogenetic questions in non-model organisms. ddRADseq offers a simple and reliable protocol for population genomic studies, however it can result in a large amount of missing data due to allelic dropout. Target capture sequencing offers an opportunity to increase sequencing coverage with little missing data and consistent orthologous loci across samples, although this approach has generally been applied to conserved markers for deeper evolutionary questions. Here, we combine both methods to generate high quality sequencing data for population genomic studies of all marine lobster species from the genus Jasus. We designed probes based on ddRADseq libraries of two lobster species (Jasus edwardsii and Sagmariasus verreauxi) and evaluated the captured sequencing data in five other Jasus species. We validated 4,465 polymorphic loci amongst these species using a cost effective sequencing protocol, of which 1,730 were recovered from all species, and 4,026 were present in at least three species. The method was also successfully applied to DNA samples obtained from museum specimens. This data will be further used to assess spatial-temporal genetic variation in Jasus species found in the Southern Hemisphere.

Inferring absolute recruitment and legal size population numbers of southern rock lobster (Jasus edwardsii) in South Australia's Southern Zone fishery using extended forms of depletion modelling

An extended depletion model (EDM) is presented that estimates both a time-series of the number of animals recruiting to legal size as well as start-year exploitable population size. EDM requires total catch in numbers for all months, but fits only to monthly catch rates of legal size lobsters over a restricted period during each year, aggregating catch and recruitment over the remaining months. Applied to a South Australian southern rock lobster (Jasus edwardsii) fishery over 1994–2014, catch rates for January, February, and March were fit under assumptions of no recruitment and equal catchability during these months of high catches. No assumptions are made about catchability during April–December. A hybrid model, EDM-CSA, combines EDM and catch-survey analysis (CSA), by additionally fitting to a recruitment index. Comparisons were made with estimates from a length-based integrated stock assessment model (LenMod). All parameter estimation was by maximum likelihood. Mean estimates of recruitment from the models differed by no more than 3% and of population size by no more than 12%. Trends in recruitment and population size were similar among models. A likelihood ratio test using EDM detected a significant increase in catchability from 2011 to 2012, which was sustained during 2012–2014, and that was corroborated by fisheries-independent survey data. Hyperstability in fishery catch-rates was also supported.

Application and optimization of the highly efficient and environmentally-friendly microwave-intensified lactic acid demineralization of deproteinized Rock lobster shells (Jasus edwardsii) for chitin production

Chitin, a natural biopolymer with numerous commercial applications, is found in Australian Rock lobster shells at approximately 25% on a dry basis. Mineral removal for chitin production from crustacean shells has conventionally been carried out with corrosive inorganic acids but in addition to negative potential environmental effects the technique generates detrimental impacts on the physiochemical properties of chitin. Demineralization of crustacean shells using organic acids intensified by microwave is another promising alternative. Although the process has been shown to demineralize shrimp shells with very low mineral residue, the use of a large chemical ratio and high temperature due to a lack of optimization could be major limitations for its industrial application. Moreover, the use of this process for difficult demineralization crustaceans as Rock lobster shells has not yet been investigated. In this study, deproteinized Rock lobster shells were demineralized using a food-grade lactic acid intensified by microwave. This process was optimized using a Box-Behnken design for three key process parameters including lactic acid/shells (LA/S) ratio, time, and temperature. Demineralization degrees achieved from the process were used for setting up a mathematical relationship and drawing plots. Analysis results revealed the LA/S ratio was the most influential factor and the optimized process with high demineralization degrees was achieved at a mild condition (LA/S ratio of 18mL/g, 23min). Besides its chemical structure being similar to that of commercially available chitin, lobster chitin obtained from the optimized process had low residues of minerals (0.99%) and protein (1.6%) which could be used for advanced applications. Moreover, composition of minerals recovered from the optimized process contained 87% of calcium potentially providing another value-added product, calcium lactate. All these significant results indicate the microwave-intensified lactic acid demineralization (MILAD) could be used for efficient production of high quality lobster chitin in an environmentally-friendly and sustainable manner.

Spatial Variability in Condition of Southern Rock Lobsters (Jasus edwardsii) at the Start of the Tasmanian Fishing Season.

The southern rock lobster (Jasus edwardsii) industry in Australia favours red lobsters, which are usually caught in shallow waters, over paler (brindle) lobsters. This preference is driven partly by the Chinese market, where red is associated with luck and prosperity, and additionally, by the widely held perception within the industry that brindles have greater mortality rates during out of water transport than reds. Limited scientific evidence supports these industry observations; however, these studies did not evaluate the initial condition of lobsters. This study aimed first, to determine which variables better describe condition in J. edwardsii and second, to compare condition among lobsters in several sites around Tasmania at the typical time of high transport mortality. Male lobsters were collected from the South West, South East, East and North coast of Tasmania in late November/December 2014, which correspond to the start of the Tasmanian fishing season. A comprehensive condition assessment was applied by measuring tissue proximal composition, Brix index, Total Haemocyte Count, pH, haemocyanin and another 16 haemolymph parameters of interest. A useful framework to compare condition in J. edwardsii was established by first, using Brix index as a measure of nutritional condition, second, using pH, magnesium, and bicarbonate to evaluate differences in physiological condition and finally, using THC counts as a proxy for lobster health condition. Lobsters from different sites had different nutritional, physiological and health condition, consistent with industry observations, however our results indicate that some red shallow water lobsters exhibited poorer nutritional and health condition, while some deep water brindle lobsters were in good condition. Differences in condition could not be directly associated to catch depth of lobsters and was related to other spatially discrete factors which sometimes vary over distances <3 km.

Decision rules for quota setting to support spatial management in a lobster (Jasus edwardsii) fishery

The Northern Zone rock lobster fishery in South Australia is extensive, covering ca. 207 000 km2. Managed under transferable quotas, the majority of the annual total allowable commercial catch (TACC) is taken on eastern inshore grounds, targeting the smaller redder lobsters favoured by Chinese buyers. The confined nature of fishing under the TACC system has led to concerns of localized spatial depletion and suggested a need for spatial management. A regional partition of the TACC was proposed. Formal prescriptive decision-rule tables for setting regional TACCs annually were constructed based on target exploitation rates. A target exploitation rate of 20% historically produced zero average yearly change in biomass and, in previous bioeconomic projection modelling, achieved near-optimal net economic return. Using an age-based fishery assessment model that fits to catch totals by both weight and number landed, conditioning on fishing effort and mean weights-at-age, we estimated harvestable biomass for three regions. The management response was to establish inner and outer subzones where separate TACC decision rules are now adopted. Basing the harvest strategy on a target exploitation rate underlies a simple direct method for constructing decision-rule tables for setting TACC using the indicator of previous year’s catch per unit effort (cpue). In the normal cpue range, a constant target exploitation rate is applied. At lower levels of stock abundance, below a designated upper limit reference point of cpue, the exploitation rates used to assign TACCs are set to decline linearly from the normal target level, reaching zero at a designated lower-limit reference cpue point below which the fishery is closed. At higher levels of cpue, stakeholders agreed to a TACC cap, under which exploitation rate decreases if biomass rises. This case study applies where formal harvest strategy decision rules for quota-based lobster fisheries are considered at finer spatial scales.

Relative predation risk in two types of habitat for juvenile Australasian spiny lobsters, Jasus edwardsii

ABSTRACTThe decline in kelp habitat on coastal reefs resulting from changes in ocean climate and the distribution and abundance of herbivorous species is common in many temperate regions of the world. Kelp habitat is highly productive, biodiverse and provides a complex habitat into which many organisms recruit, including spiny lobsters, such as the Australasian red spiny lobster, Jasus edwardsii. The displacement of kelp habitat by less-complex barren reef habitat has the potential to influence the risk of predation for early juvenile lobsters. Therefore, relative predation risk on the juvenile spiny lobster, J. edwardsii, was compared for kelp and barren habitats on the northeast coast of New Zealand using juvenile lobsters held in transparent containers and recording predators with a video recorder. In total, 188 predation attempts were observed within 420 h of video recordings gathered over 3 weeks of sampling. There was an overall higher predation risk in barren habitats. Daytime predation attempts were higher in barren compared to kelp habitat; however, there was no difference between the habitats for night time, dawn or dusk observations, when juvenile lobsters are emergent from shelters and vulnerable to predation. Similar numbers of predatory species were identified in kelp (13) and barren habitat (12). Other factors, such as food availability and time spent away from shelter, especially during night and crepuscular periods, need consideration in future studies when investigating the cause of differences in juvenile lobster mortality among habitats.

Differing environmental drivers of settlement across the range of southern rock lobster (Jasus edwardsii) suggest resilience of the fishery to climate change

AbstractTemporal and spatial trends in settlement of the southern rock lobster, Jasus edwardsii, were examined to identify the influence of environmental variables over different spatial scales. Settlement data were collected from 1994 to 2011 along the Southern Australian and New Zealand coasts. We identified common settlement trends at a regional scale (100–500 km): the magnitude of settlement at sites from South Australia (SA) and Victoria (VIC) were similar, but different to sites in Tasmania (TAS). In New Zealand, three spatial regions were identified: northern (NNZ), middle (MNZ) and southern regions (SNZ). Higher settlement in SA, VIC and MNZ occurred in years with higher rainfall and storms in spring and El Niño conditions. In TAS and SNZ, higher settlement occurred during La Niña conditions. These results suggest that settlement over regional scales is modulated by oceanic processes, but outcomes vary between regions. At a local scale, a higher wave period and wind relaxation were relatively more important than the sea surface temperature (SST) in SA and VIC. In TAS, the current velocity also influenced the strength of settlement. However, much of the local settlement variability was not explained by the models suggesting that settlement in J. edwardsii is a complex process where larval behaviour, biological factors and oceanographic processes interact over different scales. The apparently complex processes affecting settlement showed that environmental conditions that reduced settlement strength in one region of the fishery often increased settlement strength in other regions. This could provide resilience to climate change at the stock level.

Outlier SNPs enable food traceability of the southern rock lobster, Jasus edwardsii

Recent advances in next-generation sequencing have enhanced the resolution of population genetic studies of non-model organisms through increased marker generation and sample throughput. Using double digest restriction site-associated DNA sequencing (ddRADseq), we investigated the population structure of the commercially important southern rock lobster, Jasus edwardsii, in Australia and New Zealand with the aim of identifying a panel of SNP markers that could be used to trace country of origin. Four ddRADseq libraries comprising a total of 88 individuals were sequenced on the Illumina MiSeq platform, and demultiplexed reads were used to create a reference catalog of loci. Individual reads were then mapped to the reference catalog, and variant calling was performed. We have characterized two single-nucleotide polymorphism (SNP) panels comprised in total of 656 SNPs. The first panel contained 535 neutral SNPs and the second, 121 outlier SNPs that were characteristic of being putatively under selection. Both neutral and outlier SNP panels showed significant differentiation between the two countries, with the outlier loci demonstrating much larger F ST values (F ST outlier SNP panel = 0.134, P < 0.0001; F ST neutral SNP panel = 0.022, P < 0.0001). Assignment tests performed with the outlier SNP panel allocated 100 % of the individuals to country of origin, demonstrating the usefulness of these markers for food traceability of J. edwardsii.

Effectiveness of lobster fisheries management in New Zealand and Nova Scotia from multi-species and ecosystem perspectives

In New Zealand and Nova Scotia, lobster (Jasus edwardsii and Homarus americanus, respectively) is the most valuable export fishery. Although stock assessments and indicators assist in evaluating lobster fisheries, ecosystem effects are largely unknown, hindering ecosystem-based fisheries management (EBFM). We employed ecosystem models for the Cook Strait, New Zealand and western Scotian Shelf, Nova Scotia, Canada, to evaluate trade-offs between catches and ecosystem impacts in lobster fisheries from single- and multi-species perspectives. We ran simulations to independently determine exploitation rates that produced maximum sustainable yield (MSY) for lobster, and for all fished groups. We then ran simulations using these MSY exploitation rates simultaneously, and simulations to maximize multi-species MSY (MMSY). Our results indicate that current lobster exploitation rates in both regions are greater than those producing MSY, and have significant ecosystem impacts. Simulating multi-species fisheries, in both systems the sum of single-species MSY for all fished groups was less than the sum of catches where exploitation rates were run simultaneously. Runs maximizing MMSY across the entire ecosystem increased exploitation rates on many fished groups, and produced even greater total catch—yet with much greater ecological costs—and in Nova Scotia, collapses of sharks, large predators, and lobster themselves. As fisheries management moves towards multi-species and ecosystem-based approaches, we suggest that MMSY targets should be treated similarly to MSY—not as a target, but a limit. Even then, careful evaluation is required before implementation to ensure that there are no undesirable economic or ecological consequences.