Lobster Jasus Research Articles

Estimating historical commercial rock lobster (Jasus edwardsii) catch inside Australian State territorial waters for marine protected area assessment: the binomial likelihood method

The rock lobster (Jasus edwardsii) fishery of South Australia is the State’s most valuable fisheries resource with an export value exceeding ~AU$100 million. The fishery operates primarily inshore (<60 m), and overlaps with a series of marine protected areas (MPAs) currently proposed for State territorial waters. As a result, the need to quantify the impact of proposed MPAs on commercial landings of rock lobster within territorial waters is an integral part of the MPA assessment process. Removing fishing effort displaced by MPAs prevents a corresponding increase in exploitation outside protected zones. We describe a binomial likelihood method that utilises historical commercial catch data to estimate catch totals of rock lobster inside South Australian State waters. Lobster catches per km2 showed a high level of spatial variation with estimated historical lobster catch in State waters spanning approximately three orders of magnitude. The method identified key areas where high lobster catch (up to 500 kg/km2) overlapped with State waters. Binomial likelihood outputs have particular application to the estimation of net catch loss in situations where fishery buy-back or financial compensation are a considered option as part of the MPA implementation process.

Contrasting fecundity, size at maturity and reproductive potential of southern rock lobster Jasus edwardsii in two South Australian fishing regions

The annual commercial catch from the Southern Zone of the South Australian rock lobster (Jasus edwardsii) fishery is ~1900 tonnes, representing ~50% of total landings from south-east Australia. A single minimum legal size (MLS) of 98.5 mm carapace length (CL) exists across the entire zone. Fecundity (F), size at onset of maturity (SOM) and relative reproductive potential (RRP) of female rock lobsters were investigated in two major fishing regions, i.e. the North Southern Zone (NSZ) and South Southern Zone (SSZ) with a view to providing a basis for future fine-scale spatial management of the resource. F ranged from 45,292 to 466,800 eggs per female and increased proportionally with CL according to the relationship: F = 0.0584 × CL3.1642. F was significantly higher in the NSZ compared to the SSZ but was attributed to differences in lobster size between regions. There was no significant difference in the number of eggs · g−1 of egg mass between areas. SOM, estimated as the size at which 50% of females reached sexual maturity (L50) was higher in the NSZ (104.1 mm CL) compared to SSZ (92.3 mm CL). Approximately 20% of lobsters above the MLS in the commercial catch in the NSZ were under the L50 estimate. RRP, as a measure of egg production, was calculated for each size-class from the product of F, SOM and population length–frequency. The modal RRP size-classes in the NSZ were 117.5–122.5 mm CL, while in the SSZ it was 97.5–102.5 mm CL. Only 6% of RRP was contributed by female rock lobsters below the MLS in the NSZ, compared to 34% in the SSZ. Regional differences in SOM and RRP in the Southern Zone of South Australia suggest that different MLSs may be beneficial, particularly if the fishery is to be effectively managed at finer spatial scales.

Anti-Predator Behavior of Captive-Reared and Wild Juvenile Spiny Lobster (Jasus edwardsii)

Early juvenile lobsters reared in captivity may loose anti-predator behaviors displayed by their wild counterparts. To test this hypothesis in juvenile spiny lobsters (Jasus edwardsii), we conducted a series of experiments in which recently settled pueruli were reared in captivity under differing levels of predation risk. After one year in captivity, these lobsters were exposed to a predator in a tank or released into the wild to assess their ability to recognize and respond to predation. We found that lobsters raised without predators significantly reduced their movement activity outside shelters when subsequently introduced to a predator compared with juveniles raised with predators (F1,45 = 4.33, p < 0.05). This apparent over-compensation may be necessary for lobsters to learn the appropriate anti-predator response. Lobsters raised without predators and released into the wild displayed the same types of behaviors as resident wild lobsters. Released lobsters spent more time defending and fighting amongst themselves than the wild lobsters (G = 13.006 > χ2 0.05,2 = 9.488), but they displayed the appropriate anti-predator responses when approached or attacked by a predator. Our results show that juvenile spiny lobsters habituate to the absence of a predator when reared in captivity for long periods, but display an innate ability to recognize and effectively respond to predators when encountered in a hatchery environment or in the wild.

Biological Modeling of Translocation as a Management Tool for a Rock Lobster Fishery

Translocation is a form of sea ranching and involves shifting animals between regions to increase yield or to address sustainability issues. We used a sex and size structured model with yearly time steps to examine the use of translocation for management of the Tasmanian rock lobster (Jasus edwardsii) fishery, which is a fishery characterized by spatial heterogeneity in biology and depletion through fishing. Cohorts of undersize lobsters were translocated from four sites of origin to four release sites to explore outcomes under a range of growth rates. Results of translocations were contrasted against estimated yield and egg production if the lobsters had been left at their original site. Gains in yield of greater than 100% of existing yield appear possible through many scenarios, although gains were largest when distances between sites were greatest (from SW to NW Tasmania). Short-distance translocations from deep to shallow water have been proposed to alter market traits of lobsters, but gains in yield from this type of operation appear trivial. Egg production was increased at the release site for all scenarios, indicating that translocation could complement the current policy of rebuilding northern egg production. Translocation appears to offer an alternative management option for increasing yield and could be integrated with other spatial management tools such as regional size limits.

Tolerance for Ammonia in Early Stage Spiny Lobster (Jasus Edwardsii) Phyllosoma Larvae

Abstract The tolerance of spiny lobster J. edwardsii phyllosoma to the effects of increasing levels of ammonia was assessed at Stages I to IV of larval development. The median lethal concentration (96-h LC50) for total ammonia (and corresponding NH3-N) were 31.6 (0.97) mg l−1, 45.7 (1.40) mg l−1, 52.1 (1.59) mg l−1, and 35.5 (1.01) mg l−1 at Stage I, II, III and IV, respectively. When Stage II larvae were cultured through to Stage III at total ammonia concentrations of 0.5 (control), 1.4, 3.8, 6.3 and 9.5 mg l−1, the intermoult period increased significantly at and above 6.3 mg l−1 (from 11.2 days in controls to 13.2 days at 9.5 mg l−1). Thus, the no-observable-effect-concentration (NOEC) of total ammonia (and corresponding NH3-N) at Stage II of 3.8 mg l−1 (0.12 mg l−1) was used as the divisor in the acute:chronic ratio (i.e., 96-h LC50 ÷ NOEC) to estimate the concentrations at Stages I, III, and IV, which were 2.7 (0.08) mg l−1, 4.4 (0.14) mg l−1, and 3.0 (0.09) mg l−1, respectively. These results provid...

Two monitoring methods that assess species composition and spatio-temporal trends in bycatch from an important temperate rock lobster (Jasus edwardsii) fishery

The effectiveness of two monitoring programs, designed to describe and quantify the bycatch from commercial pots, was examined in the South Australian rock lobster (Jasus edwardsii) fishery (SARLF). The first, logbook sampling, relied on information collected and recorded by fishers in logbooks. The second, bycatch sampling, required fishers to collect bycatch specimens on a nominated day for later scientific analysis. A total of 40 bycatch species were recorded during the study. Finfish, mainly blue-throat wrasse (Notolabrus tetricus) and leather jacket species (Meuschenia hippocrepis and Meushenia australis), were the major component (&gt;90% by number). Data from the logbook program were appropriate for monitoring spatio-temporal trends in bycatch, whereas the bycatch sampling provided more accurate information on bycatch species. Each program was subject to bias when estimating total bycatch numbers and, as a result, a combination of both methods indicated a cost-effective and appropriate way with which to monitor bycatch from the fishery. In comparison with other fisheries, bycatch from the SARLF was relatively low; however, because bycatch was dominated by relatively few species, ongoing monitoring and risk assessment of these populations is needed to ensure long-term sustainability of bycatch levels.

Modelling the effects of Marine Protected Areas (MPAs) on the southern rock lobster (Jasus edwardsii) fishery of Victoria, Australia

Since 2002, 5.3% of the Victorian coastal waters have been declared as Marine Protected Areas (MPAs). These are aimed at safeguarding important marine habitats and species, significant natural features, and areas of cultural heritage and aesthetic value. However, MPAs impact the fishery for southern rock lobster (Jasus edwardsii), as total allowable catches (TACs) were previously set to allow the biomass to recover to pre‐specified target levels. The model on which assessments and risk analyses are based is extended to include the impact of MPAs. The MPAs and the area open to fishing are modelled as subpopulations with different levels of mortality and consequently different density and population size‐structure. A range for the probability of a lobster moving from a MPA to the fished area from 0 to 15% is considered, based on the results of tagging studies. The reduction of biomass available to the commercial fishery because of the introduction of MPAs is estimated to be 8% and 16% (Western and Eastern Zones) respectively. The results of a risk assessment show that if the current TACs are maintained, the time to increase the biomass available to the commercial fishery by 50% would be delayed 5–9 years in the Western Zone and 1–4 years in the Eastern Zone because of the impact of displaced effort. In contrast, spawning biomass in the Eastern Zone is currently below the agreed limit reference point, and the introduction of MPAs would enhance the rate of recovery, although only marginally initially, faster than the absence of the MPAs.

Can additional abundance indices improve harvest control rules for New Zealand rock lobster (Jasus edwardsii) fisheries?

Although New Zealand rock lobster (Jasus edwardsii) fisheries can be assessed with a sophisticated Bayesian length‐based model, these assessments are expensive and time consuming; they cannot be conducted for each area every year. Harvest control rules are increasingly important management tools in New Zealand rock lobster fisheries. Recent work has developed and evaluated procedures for rebuilding or maintaining lobster stocks based on criteria agreed by stakeholders. Most management procedures depend on a single abundance index, often catch per unit of effort (CPUE). When management procedures react slowly to changes in vulnerable biomass, allowable catches get out of phase with the stock, causing large oscillations in both catches and CPUE. Lags between data and management actions and “latent years” are features of rules that reduce responsiveness. This study explores ways to improve the responsiveness of harvest control rules by using additional data to predict changes in vulnerable biomass. Four data sets are examined: CPUE trends, pre‐recruit indices, puerulus settlement indices, and size frequencies. Only pre‐recruit indices, which were explored with a simple delay‐difference model based on parameter estimates from recent assessments, appeared to have immediate potential for use in improving management procedures.

Distribution and abundance of recruits of the eastern rock lobster (Jasus verreauxi) along the coast of New South Wales, Australia

In the mid 1990s, the New South Wales government introduced management measures to increase the size of the population of the eastern rock (spiny) lobster, Jasus verreauxi. A fully orthogonal sampling design was begun in July 1995 to test, amongst others, the hypothesis that the relative abundance of recruits (stages of peuruli to early juveniles combined) to the eastern rock lobster population will change over space and time. In the design for the full sampling strategy were the factors of Year (eight levels) and Location (four levels). Three replicate collectors at each of three sites at each location were sampled during the first quarter of each lunar month between August and January between 1995–96 and 2002–03 (inclusive). Recruits occurred on collectors between September and January each year. Results of the two‐factor ANOVA showed a significant interaction between Year and Location, meaning that differences in mean relative abundance of recruits between years will depend upon the location. Comparison of means (SNK test) show that in each year the relative abundance of recruits was greatest at the southern locations, but no pattern in mean relative abundance between years for each location was apparent. Management measures introduced in the mid 1990s to increase population size have not to date resulted in increasing levels of recruitment. Considering this, levels of recruitment to the population appear to be influenced most by variation in environmental factors rather than levels of egg production from the stock.

Evolution of operational management procedures for the South African West Coast rock lobster (Jasus lalandii) fishery

The commercial fishery for Jasus lalandii, the South Africa West Coast rock lobster, began in the late 1800s and at its peak in the early 1950s yielded an annual catch of 18 000 t. Although this annual catch has dropped to only some 2000 t over recent years, the fishery remains South Africa's third most valuable for landed value. The primary reason for the low total allowable catch (TAC) over these recent years has been a marked drop in somatic growth rate that occurred at the end of the 1980s, for reasons that remain unexplained. A key problem in formulating TAC recommendations with longer‐term objectives in mind, has been uncertainties about likely future trends, particularly in somatic growth and recruitment. To address this problem, an “operational management procedure” (OMP) was adopted in 1997 and has twice been re‐evaluated and modified (in 2000 and 2003) in the light of further data and changing perceptions of resource dynamics. The history of this process is reviewed, concentrating on the most recent modification. In particular, a summary is given of the process by which the merits of alternative management procedures were evaluated over a range of important uncertainties about the dynamics of the resource. This summary includes a discussion of the key trade‐offs between resource rebuilding, future TAC trends and TAC variability, and the eventual choice that was made. The paper concludes by listing a number of lessons learnt concerning best practice for OMP development as this process evolved.

Development and metabolic rate of stage I spiny lobster (Jasus edwardsii) larvae under constant and fluctuating salinities

The effects of fluctuating salinity on the development and metabolic rate of stage I Jasus edwardsii larvae were investigated. J. edwardsii larvae were reared from hatching through to stage II under continuous salinity regimes at 28, 31, 34, and 37 psu, and under repeated exposure to 28, 31, and 37 psu from a salinity of 34 psu. Continuous exposure to salinities between 28 and 37 psu did not affect the duration of larval development. In the repeated exposure treatments, only larvae subjected to 28 psu developed slower than those in the 34 psu continuous exposure group. Although post‐moult growth to stage II was not suppressed by fluctuating salinity in the 31 and 37 psu groups, larvae repeatedly exposed to 28 psu and larvae under continuous salinities of 28, 31, and 37 psu were significantly smaller than those from the 34 psu continuous treatment. The effect of salinity acclimation on the respiratory response of mid‐stage I larvae was examined in a second experiment. The reduced oxygen consumption of acclimated larvae at subnormal salinities (i.e., 28 psu) was characteristic of stenohaline organisms, and overall there was little relationship between metabolic rate and larval growth performance. From the results obtained in this study we recommend the monitoring and control of environmental salinity for the propagation of J. edwardsii larvae to prevent prolonged exposure to suboptimal salinities.

Effects of diet on the growth, survival, and condition of sea‐caged adult southern rock lobster, Jasus edwardsii

Live‐holding of fisheries‐caught adult southern rock lobster (Jasus edwardsii) presents a means of value‐adding to the South Australian commercial catch through strategic marketing and product enhancement. This study investigated the effects of live mussel and three manufactured diets on the survival, growth, and condition of sea‐caged adult J. edwardsii held for an extended period of 29–30 weeks during the closed fishing season. Two trials were conducted in existing industry cage systems. All four diets tested were successful in keeping lobsters alive, promoting growth at moult, and maintaining/improving the condition of lobsters. Unfed lobsters had lowered survival, negative or zero growth at moult, and lowered condition. All lobsters moulted during the trials. Addition of 1% mussel mince to pellets as a feeding stimulant did not increase survival or growth. Males showed substantially greater weight gain at moult than females (means of 8% for females and 17% for males). Biomass of male lobsters increased by up to 16% in one trial treatment, where growth of individual lobsters more than compensated for weight loss caused by mortality. Two different levels of carotenoid (0.15% and 0.25%) proved sufficient to maintain and/or improve colour. Where females were held separate from, but adjacent to, males there was some spawning activity (up to 14%). The one negative outcome of the study was that tail fan damage was found to be a major problem, occurring in both trials and across all diets without apparent pattern. The causes and management of tail fan damage need to be addressed before a long‐term live‐holding industry can be developed. However, in terms of survival and weight gain, results were very encouraging as improvements in pellet formulation, pellet production, and food delivery can be expected.

Causes of tail fan necrosis in the southern rock lobster, Jasus edwardsii

Tail fan necrosis (TFN) is a recognised constraint on the advancement of the South Australian rock lobster (Jasus edwardsii) liveholding industry because of a reduction in value of afflicted lobsters. Trials were run in the laboratory and at a shore‐based experimental live‐holding facility (LHF) to determine the influence of at‐sea post‐harvest handling, feeding frequency (LHF only), density (LHF only), and temperature (laboratory only) on the advent of the condition. Lobsters were caught during normal fishing operations and either immediately placed in protective fine‐mesh nylon bags and stored in the boat's well or placed unbagged in the well. At the laboratory, the tail fans of half the bagged lobsters were deliberately damaged with sterile instruments. At the LHF the TFN level increased significantly over 4 months. The bagged treatment showed significantly less late‐stage TFN than unbagged daily or weekly‐fed treatments with 60% of bagged lobsters showing no TFN at 4 months. With unbagged lobsters, 50% showed erosion in the <25% category and 30% showed erosion of >25% of the tail fan. Lobster density and feeding frequency had no effect on TFN incidence. In the laboratory, bagged and bagged‐damaged treatments had no advanced TFN after the 6‐week period suggesting that post‐harvest bagging minimises TFN and that inflicting physical damage to lobster tail fans with aseptic instruments does not lead to its development. Temperature had no effect on TFN development. The highest incidence of TFN was found in lobsters given normal post‐harvest handling, that is, communal holding in boat holds and tanks (i.e., without bags). These conditions are normally associated with physical damage inflicted by conspecifics. Such damage will presumably also involve infection of wounds by the bacterial flora of the crayfish exoskeleton, leading to development of TFN.

Effects of trap‐shape, bait, and soak‐time on sampling the eastern rock lobster, Jasus verreauxi

It is important when analysing catch and effort information from either fishery‐dependent or fishery‐independent sources, to understand how external factors influence catches so that data can be standardised to be more representative of the abundance of the target species. In New South Wales, Australia, commercial fishers primarily use trapping as the method to capture the eastern rock (spiny) lobster (Jasus verreauxi) and consider trap‐shape, bait‐type, and soak‐time to be the most important factors affecting their catches. Two experiments were done to test hypotheses about the influence of these factors upon catches of lobsters on inshore grounds (<15 m depth). There were no differences in mean numbers caught between bait‐types (flathead, redfish, or blackfish) and soak‐times (1–3 days), but trap‐shape (beehive, rectangular, or “D"‐shaped) affected catches. D‐shaped and rectangular traps caught more lobsters than beehive traps. There were no differences in the sizes of lobsters caught between trap‐shapes and the sex ratios did not differ from unity, suggesting that there were no differences in selectivity between trap‐shapes. It is recommended that the compulsory daily log sheets in place in the fishery require commercial fishers to provide information about the shape of the traps they use. When designing fishery‐independent surveys to sample juvenile J. verreauxi, it is recommended that: (1) groups of rectangular traps be set as a single replicate to saturate a defined area; (2) as many replicates as practically possible be included; (3) any of the bait‐types described in this paper be used; and (4) the soak‐time for the gear be one day.

Stock enhancement of rock lobsters (Jasus edwardsii): timing of predation on naïve juvenile lobsters immediately after release

The success of enhancement programmes hinges on the survival of released animals. One factor greatly influencing short‐term survival of reseeded lobsters is the timing and intensity of predation relative to the time of release. The activity and abundance of predators varies over daily, seasonal, and annual scales and knowing the best time to release juveniles will minimise mortality. We used chronographic tethering devices and remote video equipment at 10 sites near Wellington, New Zealand and Hobart, Tasmania, Australia, to assess the relative timing and intensity of predation for released lobsters. Our studies showed that predation was greatest within the first 2 h after release (χ 2 = 60.425, d.f. = 9, P < 0.001) suggesting that the disturbance associated with the release itself may draw the unwanted attention of predators. Relative predation rates also peaked on each of the following two mornings, possibly because of the emergence of daytime predators. The video footage obtained at the Tasmanian sites revealed that most predation was by fish (46%), but surprisingly, cannibalism comprised 16% of predation events. The limitations of tethering as a method are discussed in numerous reviews but proved useful as a relative measure for these highly mobile and cryptic animals. Further consideration needs to be given to methods of release that minimise mortality of recently seeded lobsters.

A bio-economic application to the Cape Rock Lobster resource using a delay difference modelling approach

In many species, like the Cape Rock Lobster (Jasus lalandii), the life cycles of males and females differ. This may motivate the use of two-sex models in a stock-assessment analysis. It is also true for this resource, that juveniles do not reach sexual maturity immediately. Therefore a delay-difference model is appropriate. In this study we follow a bio-economic approach and use a two-sex delay-difference model to determine a maximum economic yield strategy. Thus we determine an economic optimum steady state solution at which to harvest this resource subject to the biological constraints of the species.

Artemia prey size and mode of presentation: Effects on the survival and growth of phyllosoma larvae of southern rock lobster ( Jasus edwardsii )

Performance of phyllosoma of thesouthern rock lobster (Jasus edwardsii)was examined after feeding Artemia-baseddiets. Survival and growth of newly-hatchedlarvae cultured to Stage III were lower(p < 0.05) when fed 0.8 mm Artemia than1.5 mm or 2.5 mm Artemia alone or 1.5 mmArtemia in combination with pieces ofmussel (Mytilus edulis planulatus) gonad.This could not be attributed to deficiencies inthe composition of fatty acids but appeared tobe due to the inability of larvae to capturesufficient appropriate-sized, enrichedArtemia for their nutritional requirements.There was an indication that survival andgrowth were higher between Stages III and Vwhen fed 2.5 mm Artemia than 1.5 mmArtemia alone or in combination with musselpieces. However, Stage VI larvae grew to asimilar size at Stage VIII when fed 1.5 mm or2.5 mm Artemia. Unexpectedly, larvae fedthe combination of 1.5 mm Artemia plusmussel supplement had lower survival than foundpreviously, and generally lower than when fed≥ 1.5 mm Artemia alone. This was despitean apparent nutritional profile (lipid contentand fatty acid composition) of mussel more akinto that of newly-hatched phyllosoma thanenriched Artemia. On the other hand,survival and growth to Stage VIII were higherwhen larvae were fed alginate pelletscontaining Artemia than when fed 1.5 mmor 2.5 mm Artemia alone.

Evaluation of visible implant fluorescent elastomer (VIE) as a tagging technique for spiny lobsters (Jasus edwardsii)

Tagging crustaceans for growth studies is often difficult because external tags/marks may be shed or cause mortalities during moulting. In this investigation, the effectiveness of visible implant fluorescent elastomer (VIE) as an invasive tagging technique for spiny lobsters (Jasus edwardsii) was investigated over a 6-month period. Tagged lobsters were either tagged with the tag running transversely across the ventral abdominal superficial flexor muscle block (transverse VIE) in the second abdominal segment, or in-line with the ventral abdominal superficial flexor muscle block (longitudinal VIE). Non-tagged lobsters were used as the control. At the conclusion of the investigation there were no differences in growth or survival between tagged lobsters and untagged controls and tag retention rates were 100% for both tagging treatments over the 6-month period. Tag visibility was high after six months in both tagging treatments, although higher in the longitudinal VIE treatment. Tag fragmentation was frequent in the transverse VIE treatment, but infrequent in the longitudinal VIE treatment. We conclude that VIE is an effective tagging technique for J. edwardsii in terms of the high degree of tag visibility, retention, and non-detrimental impact on the growth and survival of tagged animals, provided the VIE tag is injected in-line with the orientation of the muscle fibres/tissue.

Estimating length-transition probabilities as polynomial functions of premoult length

In length-based lobster stock-assessment models where the population is subdivided into discrete length classes, growth is represented as a matrix of length-transition probabilities. At specific times during the model year, the length-transition probabilities specify the proportions growing into larger length classes. These probabilities are calculated by integration of gamma or normal distributions over the length intervals of each larger length class. The mean growth from any given length category is commonly modelled by a von Bertalanffy or other continuous growth curve. The coefficients of variation, describing variance among individuals, are modelled by functions constant or linear with length. These approaches have yielded good descriptions of growth for males and juveniles, but the von Bertalanffy curve does not capture the rapid decrease in mean growth rate after maturity for females. We generalized this length-transition model by writing the parameters of the growth distributions as polynomial functions of carapace length. This generalization procedure increases the number of parameters depending on the degree of polynomial employed. In fits to South Australian rock lobster (Jasus edwardsii) tagrecovery data, each increase in polynomial degree yielded a significantly better fit for females and successfully represented the decrease in growth at maturity. For males, the von Bertalanffy description was little improved by higher polynomials.

Interrelations among rock lobsters, sea urchins, and juvenile abalone: implications for community management

Field and laboratory experiments demonstrate that juveniles of South African abalone (Haliotis midae) depend vitally on the protection from predation that they gain from living concealed beneath Cape urchins (Parechinus angulosus). Recent reports suggest that rock lobsters (Jasus lalandii) have increased substantially in the region where the commercial abalone fishery is centered. This increase has been blamed for a recorded collapse of urchin populations and dramatic reductions in the numbers of juvenile abalone. We verified the substantial increase in rock lobster abundance there. Surveys covering 200 km of coastline showed that densities of urchins were negatively correlated with those of large lobsters (>68 mm carapace length) and that densities of juvenile abalone were positively correlated with those of urchins. The indirect negative effects of rock lobsters on juvenile abalone clearly pose a major threat to the abalone industry, already under stress from poaching. Quantification of the relationship...