Sustainability of the Western Rock Lobster Fishery: A review of past progress and future challenges

The Western Rock (spiny) Lobster Fishery has 594 boats operating about 57,000 pots. The average annual catch of 11,000 tonnes is valued at around US$150 million. In addition to the commercial catch, recreational fishers take about 600 tonnes a year. Sustainability in this fishery is maintained by analysis of a comprehensive fisheries database, some of which dates back to the 1960s (e.g. catch, effort, length-frequencies, fishery-independent breeding-stock surveys, puerulus settlement monitoring, recreational catch monitoring); an extensive set of management controls (including a limited fishing season and legal minimum and maximum sizes); and an effective compliance program. Effort in the fishery is controlled by input restrictions on the number of pots allowed and number of days fishing, which are implemented after considerable consultation with industry. The principal method of ensuring the sustainability of the fishery is by monitoring the size of the breeding stock, using data from both a commercial at-sea monitoring program and an annual fishery-independent breeding-stock survey. When the breeding stock fell to low levels in the early 1990s, management initiatives succeeded in returning it to what are considered to be safe levels. Catches are currently high, but fishers have acquired sufficient scientific knowledge to understand that catches will fluctuate for environmental reasons and to take this into account in their fishing operations. Environmental effects have been shown to drive the level of settlement in a particular season. These settlement levels are in turn highly correlated with catches three to four years later, which provides a means of predicting future catches and managing the fishery accordingly. There are issues to be considered in assessing the sustainability of this fishery in the future. The fishery may be overly reliant on egg production from the Abrolhos Islands; catching power of the commercial fleet is increasing due to improvements in gear and technological equipment; growth in catches made by the recreational sector are currently unconstrained; pueruli may be harvested for aquaculture in the near future; and regulations protecting the female brood stock more than the male population could lead to reproductive issues. These potential threats are considered to be low, but will need to be monitored. The fishery was awarded Marine Stewardship Council certification in March 2000, the first in the world to receive this imprimatur

Higher water temperature leads to precocious maturation of western rock lobsters (Panulirus cygnus), but are things that simple?

During a rock lobster post-puerulus grow out project, western rock lobsters from three different cohorts (post-puerulus, year-1 and year-2) were held for 12 months under two temperature regimes (ambient and 23oC) and two feed delivery treatments (the same ration of pelleted diet fed once nightly and in the alternate treatment, thrice nightly). At the end of the trial, 43% of females from the largest cohort (2-year post settlement) in the 23oC treatment, had ovigerous setae. However, none of the animals held at ambient temperatures showed signs of maturity. Feed delivery did not influence the presence or absence of ovigerous setae. Male maturity responded to elevated temperature in the same way as for females, as indicated by merus/carapace length ratios. The response of female size at maturity to 23oC was compared to a similar trial in the 1970s in which 2-year post settlement animals wereheld at 25oC. Maturity of females in that study was one year later than in the trial reported here, indicating that there may have been a decrease in age at maturity since the 1970s. The conclusion from this and research on other rock lobster species, is that size/age at maturity is likely to be a complex response to a range of contributing factors of which temperature is an important one

Pilot phase trial to quantify the extent and relevance of any deepwater puerulus settlement that may have taken place in the Western Rocklobster Fishery

This study had two objectives. Firstly to trial modifications to commercial western rock lobster pots, so as to sample as wide a size range of lobsters on the grounds as possible. Sampling took place over a 10 day period between 13-24 September 2009, with seven commercial fishermen being responsible for collection of the data at different sampling locations (Mandurah, Fremantle, Lancelin, Dongara, Geraldton, Abrolhos and Kalbarri). This arrangement proved to be successful in that a wide area of the coast was covered by the sampling regime and good quality catch composition data was achieved across the four depth zones (0-10 fm, 10-20 fm, 20-30 fm and >30 fm) that were sampled. The different pot modifications that were trialled sampled a wide size range (25-144 mm CL), but mostly caught lobsters around the legal size limit (modal size, 80 mm CL). In three of the four areas where more than one pot type was used, there were significant differences (p<0.01) in the catch rates of one or more size classes between the various pot types.The second objective was to establish whether there has been a shift in post-puerulus settlement from shallow to deeper waters. Analysis showed that depth was highly significant (p<0.05) in determining the catch rates of most size classes (≤50 mm CL; 51-65 mm CL; 66-76 mm CL; 77-105 mm CL and ≥105 mm CL). Generally, small size classes were sampled in the shallow depth categories and larger lobsters were sampled in the deeper depth categories, which would suggest that as in the past, recent puerulus settlement has been in shallow depths. Accordingly, it would seem reasonable to conclude that it is unlikely that there has been a major shift in the depths at which pueruli are settling. However, small lobsters were sampled in low numbers in the deep water categories in this survey and this therefore does not exclude the possibility that deep water settlement may be becoming more common than in past.In terms of recommendations, more monitoring of post-puerulus/juvenile lobsters using modified commercial pots similar to those used in this study has the potential to provide inter-annual comparisons of the numbers of small size classes settling at different depths on the grounds. It is only with more data of this type over a longer time period, that it will be possible to show whether there is any indirect evidence of a shift in settlement to deeper water. Should this work continue into the future, it would be beneficial to standardize on a consistent type of modification to the commercial pots so that more reliable comparisons of the relative numbers of juvenile animals can be made between areas

Growth rates and survival of western rock lobster (Panulirus cygnus) at twotemperatures (ambient and 23 C) and two feeding frequencies

Wild caught post-pueruli, year one and year two post settlement juvenile western rock lobster, Panuliruscygnus, were held at ambient temperatures (15.6 C to 23.1 C; mean 19.00.07 C) or at 23 C, and fed thesame ration of a formulated pellet diet either once per night, or 3 times per night, over 12 months, todetermine whether elevated temperatures and multiple feeds per night would stimulate growth throughincreased metabolism and feed utilisation without significant negative impacts on survival. Survival of postpueruli(mean 63%) did not differ between ambient and 23 C. Survival of year 1 and 2 juveniles was higher atambient temperatures (pb0.01 ambient: year 1 juveniles, 68%; year 2 juveniles, 88%; 23 C: 57% and 74%,respectively). Feeding frequency did not affect survival of post-pueruli and year 2 juveniles (mean 63%, 81%respectively), but survival was 9% higher for year 1 juveniles fed three times per night (58% versus 67%;pb0.01). All lobsters grew faster at 23 C than at ambient temperatures (pb0.05), with the growth ofpost-pueruli almost doubled at 23 C (weight gain at 23 C versus ambient: post-pueruli, 18 438 % versus 9915 %; year 1 juveniles 259% versus 165%; year 2 juveniles 23% versus 21%). Feed frequency did not influencethe growth of year 1 and 2 juveniles. However, there was an interaction effect of temperature and feedfrequency on post-pueruli where weight and carapace length were significantly higher at ambienttemperatures when post-pueruli were fed three times a day, whereas at 23 C weight and carapace lengthwere significantly greater when fed once per day (pb0.05). Feed intake (g pellet dry matter lobster-1 day-1)of pellet was higher at 23 C for all lobsters (pb0.05), but was the same between lobsters fed 3 times pernight versus once per night. This study has shown that increasing temperatures to 23 C significantlyimproved the growth of P. cygnus post-pueruli without any adverse effects on survival. The faster growthrates exhibited by year 1 and 2 juveniles at 23 C may potentially offset their lower survival by significantlyreducing culture period. There is no benefit of feeding P. cygnus multiple times at night in terms of growthand survival. The implications for P. cygnus culture are that temperatures should be maintained close to 23 Cduring the entire growout period, with due care taken to minimise mortalities through adequate provision offood and shelter. Feeding P. cygnus once daily to excess just prior to dusk to co-incide with nocturnal feedingbehaviour is recommended

Real-time imaging of Leishmania mexicana-infected early phagosomes: a study using primary macrophages generated from green fluorescent protein-Rab5 transgenic mice

The small GTPase Rab5 is a key regulator of endosome/phagosome maturation and in intravesicular infections marks a phagosome stage at which decisions over pathogen replication or destruction are integrated. It is currently unclear whether Leishmania-infected phagosomes uniformly pass through a Rab5+ stage on their intracellular path to compartments with late endosomal/early lysosomal characteristics. Differences in routes and final compartments could have consequences for accessibility to antileishmanial drugs. Here, we generated a unique gfp-rab5 transgenic mouse model to visualize Rab5 recruitment to early parasite-containing phagosomes in primary host cells. Using real-time fluorescence imaging of phagosomes carrying Leishmania mexicana, we determined that parasite-infested phagosomes follow a uniform sequence of transient Rab5 recruitment. Residence in Rab5+ compartments was much shorter compared with phagosomes harboring latex beads. Furthermore, a comparative analysis of parasite life-cycle stages and mutants deficient in lpg1, the gene encoding the enzyme required for synthesis of the dominant surface lipophosphoglycan, indicated that parasite surface ligands and host cell receptors modulate pathogen residence times in Rab5+ phagosomes, but, as far as tested, had no significant effect on intracellular L. mexicana survival or replication.—Lippuner, C., Paape, D., Paterou, A., Brand, J., Richardson, M., Smith, A. J., Hoffmann, K., Brinkmann, V., Blackburn, C., Aebischer, T. Real-time imaging of Leishmania mexicana-infected early phagosomes: a study using primary macrophages generated from green fluorescent protein-Rab5 transgenic mice

Stocking density and shelter type for the optimal growth and survival of western rock lobster Panulirus cygnus (George)

The growth and survival of three size classes of wild caught western rock lobster, Panulirus cygnus (post-pueruli: mean 2.140.07g, 13.20.1mm CL; year1: post-settlement juveniles, 57.11.1g, 38.70.28mm CL; and year2 post-settlement juveniles, mean 138.22.26g, 51.90.25mm CL) were examined at combinations of two stocking densities (post-pueruli: 50 and 100myear1: 11 and 23m2; year2: 10 and 19m2) and two shelter types (a novel rigid plastic mesh shelter or bricks) over a period 6months. Survival of lobsters held at the lower densities (90 95%) was significantly greater than for lobsters held at higher densities (post-pueruli=78%, year1=86%, year2=88%). Post-pueruli survival was significantly higher in tanks with mesh shelters (91.7%) than brick shelters (75.8%) with a similar trend exhibited by year1 and year2 lobsters. Densities tested did significantly affect lobster growth for any size class. Growth of post-pueruli was considerably higher in tanks with mesh shelters (641.7% weight gain; specific growth rate 1.07BWday1) (p&lt;0.05) but there was no difference in the growth of year1 and lobsters between mesh and brick shelters. Feed intake (g pellet dry matter lobster1day1) was not significantly different between densities. This study has shown that P. cygnus is well suited for aquaculture based on the collection and ongrowing of wild caught pueruli, as this species exhibits good survival at high densities (up to 100m2) without adverse effects on growth, and shows captivity-related health problems. We recommend mesh shelters, with stocking densities of 50m2 for post-pueruli and between and 25m2 for year1 and year2 juveniles, to maximise survival and production

Spatial scales of genetic patchiness in the western rock lobster Panulirus cygnus

In planktonic dispersers, impediments to dispersal, local selection or large variance in the reproductive success among individuals (sweepstakes reproductive success) can create genetic heterogeneity at local scales. While these processes are well recognized, relatively few studies have investigated the spatial scales over which genetic heterogeneity occurs and how it is distributed across species’ ranges. We investigate population structure in the western rock lobster Panulirus cygnus, a commercially exploited species found in shallow and deep-water reef habitats along the Western Australia coastline. We screened 631 individuals from 9 locations across the species’ range for genetic variation at 22 microsatellite loci. Consistent with expectations of extensive larval mixing during an extended planktonic stage, we found no significant genetic differentiation among locations (FST = 0.003, G’’ST = 0.007). Despite the lack of large-scale geographic structure, small but significant positive spatial autocorrelation (SA) was detected over distances up to 40 km. Two-dimensional local SA analysis confirmed that fine-scale genetic heterogeneity was common throughout the species’ range. An intriguing aspect of these results is that SA was based on juvenile and adult lobsters, suggesting restricted movement or spatial cohesion of individuals after settlement

Building bacterial knowledge: Games as teaching aides for higher-order thinking skills

Bacteria Builder is a videogame designed to teach student nurses about bacterial form and function within the context of a university fundamental science module. It challenges players to design and build bacteria with appropriate structures for surviving in different environments. This paper describes two studies undertaken to explore the most effective way to use the game as part of teaching on the module. 152 student nurses took part in the first evaluation, which used a control group to compare learning gains for a) only the game b) only the lecture and c) the game plus a reflective activity. All three conditions demonstrated improvements over the control, but there were no significant differences in learning gains between the experimental conditions. In a second evaluation, 124 student nurses took part in a study which compared the lecture on its own to the lecture and game together. Learning gains were found to be over 50% higher in the lecture and game condition, and subsequent analysis showed that the nurses who had played the game made greater improvements in questions designed to test higher-order thinking skills. The design and motivation behind the Bacteria Builder game is described and the results of these studies are discussed with respect to the role of teaching in maximising the effectiveness of game-based learning. Correlations between interaction data for different parts of the game are explored with respect to learning outcomes, and implications for the design of future studies are discussed