Juvenile Lobsters Research Articles

Synchronising an IMX219 image sensor and AS7265x spectral sensor to make a novel low-cost spectral camera

A low-cost novel spectral camera able to be used for near infrared spectroscopy was made by using a Jetson Nano to synchronize a Sony IMX219 NOIR autofocus image sensor, an AMS AS7265x 18-channel spectral sensor and Osram SFH 4737 broadband infrared LED’s. Synchronizing an image sensor and spectral sensor augments a standard RGB image with light spectrum information; capturing the light distribution information normally lost in RGB image capture. Sutherland et al. [1] used this novel spectral camera to examine the dorsal surface of juvenile lobsters as a possible pre-moult detector. Having the image and spectrum in combination allowed the incomplete and unmineralized post-moult dorsal surface to be characterized with 86.7% accuracy for the first time. A proposed application for the spectral camera is to omit the local SFH 4737 light source and use the camera in daylight, effectively making a low-cost substitute hyperspectral snapshot camera. In this configuration the camera may have application for low-cost drone deployment for small scale agriculture.

Displaced juvenile and subadult Caribbean spiny lobsters show strong orientation toward home dens

Caribbean spiny lobsters are known to undergo migration as adults, but the dispersal and homing ability of subadults and juveniles is not well characterized. Given that settlement habitat for juveniles is inshore seagrass / hardbottom and reproductive habitat is offshore coral reefs, dispersal during ontogeny serves as a bottleneck potentially limiting adult population density. Previous studies have examined factors associated with movement and den selection by juvenile lobsters such as shelter type, predators, and conspecific density. Their attraction to odors of healthy conspecifics plays a significant role in aggregation of lobsters in casitas and traps. But what is unknown is whether juvenile lobsters possess the map and compass orientation found in adults. To examine the ontogeny of homing ability, we conducted multiple mark / displace tracking studies using acoustic telemetry in juvenile hardbottom and subadult coral patch reef habitats. All lobsters regardless of size tend to relocate to new crevice shelters when handled, even if returned to their original shelter. Thus, for non-displaced lobsters tagged and returned to their point of capture, distance and angle travelled appears to be random with distance increasing as function of body size. However, for juvenile and subadult lobsters tagged and displaced away from their point of capture, the distance and angle travelled when released is significantly directed toward the point of capture. Thus, it appears that the map and compass ability of Caribbean spiny lobsters appears early in ontogeny and may allow for individuals to safely explore unfamiliar locations while retaining knowledge of how to return to known shelter. This ability to expand their known habitat map while maintaining knowledge of critical diurnal shelter locations is expected to facilitate their ontogenetic dispersal to adult habitat.

Functional morphology and ontogeny of mouthparts and mouth aperture of Panulirus ornatus and Sagmariasus verreauxi: Implications towards formulated feeds development

Development of formulated feed is now a focal point in advancing the aquaculture of spiny lobster species. This study investigated the functional morphology of two spiny lobsters, Panulirus ornatus and Sagmariasus verreauxi, by analysing mouthpart morphology and mouth aperture. The analysis is focussed on determining likely feed preference based on morphology with the aim to provide knowledge for the development of formulated feeds. There is a strong correlation between the mouth aperture being approximately 4.0 and 7.5% of the carapace length of S. verreauxi and P. ornatus juvenile and adult lobsters, respectively. This finding provides knowledge for development of a species-specific tool that could be used in experimental studies to define optimal dimensions of artificial manufactured pellets in relation to the size of the lobster. Differences in mouthpart morphology through ontogeny included increase of calcification and robustness, and this is likely to reflect a different requirement in the texture (softness/hardness) of the pellet as the animals develop. Spines and setation are a prominent feature of the mouthpart morphology and differ between species and during ontogeny. Spines on maxillipeds II and III and crista dentata on maxillipeds III are likely to play an important role in holding and manipulation of feed prior to ingestion. Pellet texture may need to accommodate these differences in species and age specific mouthpart ontogeny. Ontogenetic changes in setation were found, with much richer setation proportionally to the size of mouthpart in first instar juvenile lobsters, which decreases with size increase. Furthermore, species-specific differences indicate function shifts in mouthparts with life stages. This may indicate differences in filter feeding capacity with age and between species, as reported for other decapods. This is unlikely to be of high importance in pellet feeding but may represent an avenue of investigation for first feeds in juveniles. Collectively, the differences during ontogeny and between species suggest that formulated feeds may need to be tailored to species and life stage, particularly regarding pellet dimensions and texture.

Effect of Dietary Protein to Energy Ratios on Growth, Digestive Enzyme Activity and Body Composition of Captive Juvenile Spiny Lobsters, Panulirus Ornatus (Fabricius, 1798)

Abstract An evaluation of six dietary protein-to-energy (P/E) ratios was conducted to the early juvenile lobsters (Panulirus ornatus) by investigating the ratio effects on physiology, digestive enzyme activities, body composition, and amino acid profiles. Juvenile lobsters (0.25±0.01 g) were individually kept in aquaria and treated with six isoenergetic formulated diets of P/E ratios of 21.8, 22.5, 23.5, 24.6, 25.3 and 26.6 mg KJ–1. After 8 weeks of feeding experiment, the differentiation on dietary P/E ratios was found to have affected the specific growth rates, but not the survival, moult increment, moulting rate, moult interval and average daily moulting rate of juvenile lobsters. The dietary P/E ratio also influenced the protease, lipase, superoxidase dismutase activities, and body composition of juvenile lobster. The increase in dietary protein levels significantly affected the increase of the specific growth rate, while increased dietary lipid levels only affected the length increments. Both protein and lipid content were found in the whole body of the juveniles which reflected the treated dietary composition. Results indicated that a P/E ratio of 26.6 mg KJ–1 (55% dietary protein and 9% dietary lipids) can yield the maximum growth and digestive enzyme activities from among the studied diets.

Physiological impacts of climate change on juvenile American lobster Homarus americanus (Decapoda: Astacidea: Nephropidae), a commercially important species

Abstract The American lobster, Homarus americanus, H. Milne Edwards, 1837 is an ecologically, economically, and culturally valuable marine resource for the coastal communities in the Gulf of Maine. Lobsters in the Gulf of Maine are experiencing the effects of rapid warming and acidification due to climate change. Lobster shells are comprised of chitin with precisely precipitated minerals (calcite, amorphous calcium carbonate, and carbonate apatite) that provide structural integrity to the shell and protection against predators and microbial intrusion. We examined the combined effects of ocean warming and acidification on shell mineralogy, epibiont abundance, and growth in early benthic juveniles. Lobsters were grown under six different temperature/pCO2 treatment conditions over 52 days (three replicates per treatment) aligned with environmentally relevant as well as predicted future extremes. Elevated pCO2 and temperature led to a decrease in shell calcium and magnesium content, suggesting that these environmental stressors inhibit shell biomineralization. There was an interactive effect of the stressors on epibiont abundance with the probability of epibiont coverage increasing with increasing pCO2 and temperature. Elevated pCO2 alone was significantly correlated (P = 0.002) to decreased growth, but only for female lobsters. Ocean acidification and warming significantly affect shell integrity in juvenile lobster, increasing risk to injury and disease with potential downstream consequences for the lobster fishery.

Inshore juvenile lobsters threatened by warming waters and migratory fish predators in southern New England

The southern New England stock of the American lobster Homarus americanus has declined since its peak in the 1990s. While the decline of lobsters has been directly attributed to warming sea temperatures, indirect effects such as migratory fish species shifting north may also be important. Two sets of experiments and a survey of gut contents collected from wild-caught scup Stenotomus chrysops and black sea bass Centropristis striata during the summer were performed to assess thermal and predatory stressors on juvenile lobsters. A temperature experiment compared the growth and survival of young-of-year (YOY) and 1 yr old lobsters in ambient seawater and seawater warmed or cooled by 3°C. Two predation experiments compared the survival of juvenile lobsters in treatments with scup, black sea bass, and Asian shore crabs Hemigrapsus sanguineus. Increased water temperature did not increase mortality in juvenile lobsters, but it did tend to have a negative impact on growth and weight gain of YOY lobsters and weight gain of 1 yr old lobsters. In the predation experiments, fewer lobsters survived in mesocosms with black sea bass and scup than in the control treatment. Fish gut contents contained few lobsters, but black sea bass stomachs contained many juvenile cancer crabs, signifying that the fish prey in cobble habitat that is preferred by both juvenile cancer crabs and lobsters. While juvenile lobsters can survive current temperatures, they may face compounding challenges as warmer water slows their growth and leaves them more susceptible to predation by increasing numbers of migratory scup and black sea bass.

The Effect of Supplementation of Fish Protein Hydrolysate to the BSF‐Based Aquafeed on the Growth, Survival, Fatty Acids, and Histopathology of Juvenile Lobster (Panulirus ornatus)

The present study aims to evaluate the effect of liquid fish protein hydrolysate (FPH) following fishmeal substitution with full‐fat and defatted BSF (black soldier fly, Hermetia illucens) meal in the feeds of juvenile ornate spiny lobster, Panulirus ornatus. The physiological aspects of juvenile lobsters including growth, fatty acids profile, and histopathology were observed. Six isoenergetic experimental feeds having a protein‐to‐energy ratio of 26 CP mg kJ−1 were formulated with the substitution of fishmeal at 25% using liquid FPH, full‐fat BSF (FBSF), defatted BSF (DBSF), and their combination. The specific growth rate, final body weight, final total length, and length increment of juvenile lobsters (initial weight was 0.21 ± 0.01 g and total length was 20.53 ± 0.12 mm) were significantly affected by the fishmeal substitution (P < 0.05) and improved with the addition of liquid FPH in the feeds containing FBSF and DBSF. The whole body proximate analysis showed that the liquid FPH to the feeds containing DBSF increased the ash and protein content significantly (P < 0.05). The total monounsaturated fatty acids (∑MUFA), saturated fatty acids (∑SFA), and omega 9 fatty acids (∑n−9 FA) of juvenile lobsters’ whole bodies fed with dietary DBSF and FPH supplementation were significantly higher than those of others (P < 0.05). The histopathological analysis indicated that the villus size and the muscle thickness in the intestine were not significantly affected by FPH supplementation. However, the hepatopancreas histopathology indicated the presence of B‐cells and R‐cells in the juvenile lobsters fed with FPH‐supplemented feeds. The present results suggested the supplementation of liquid FPH to the formulated feed with FBSF and DBSF for juvenile lobsters can improve the lobsters’ growth and fatty acids availability.

Effect of Feed Texture and Dimensions, on Feed Waste Type and Feeding Efficiency in Juvenile Sagmariasus verreauxi

The “messy” feeding behaviour of spiny lobsters remains an obstacle for formulated feed development. This study examined the relationship between feeding efficiency and feed waste by juvenile spiny lobster, Sagmariasus verreauxi, fed different formulated pellet diameters or lengths across two separate experiments. Feed texture (hard and dry pellet, HDP; soft and moist pellet, SMP) was also examined. Juvenile lobsters were fed experimental feeds at 0.5% BW daily over a 6 h duration. The resulting feed waste was categorised as either feeding-related waste (FRW) or non-feeding-related waste (NFRW). For all feed types, the FRW increased with increasing pellet diameter and pellet length. The increase in FRW corresponded with a decrease in NFRW, particularly for HDP, resulting in no difference in total feed waste in any treatment investigated. Thus, even with improved feeding efficiency with small feed dimensions, feed intake was not improved. Feed leaching rate decreased with increasing pellet size, suggesting a more rapid decline in feed attractiveness for smaller pellets. This finding indicates that currently a counteractive interaction exists between pellet size and feed attractiveness and suggests improving attractiveness would further enhance feeding. Future research should aim at optimising feed dimensions simultaneously to support efficient feeding whilst enhancing attraction/gustatory stimulations.

Application Of Airlift Diffuser Technique In Lobster (Panulirus Sp) Breeding

With the issuance of Ministerial Regulation of the Ministry of Fisheries Number 56 of 2016 concerning catching lobsters, crabs and blue swimming crabs, it can encourage the development of lobster farming businesses. The main problem in lobster nursery activities (Panulirus spp) is still having problems, namely the low survival rate at the juvenile lobster stage. This is presumably due to water quality, especially the low oxygen demand. Another factor is the cannibalistic nature of the juvenile lobsters. This service activity aims to provide understanding to the community, especially lobster collectors in Rangai Tri Tunggal Village, Katibung District regarding the application of airlift technology in lobster hatchery activities. In general, the level of knowledge and skills of group members regarding the manufacture of airlift diffusers is still low, namely 10%. However, after the training was held, knowledge and skills increased to 75%. Airlift diffuser technology is very appropriate to be used to help overcome production costs by reducing the use of electrical energy to assist in maintaining and managing water quality. Lobster cultivation can be used as a community business on a small scale and can be used as an alternative when there are restrictions on lobsters with sizes below those specified in KP Ministerial Decree No. 56 of 2016.

Wooden traps can replace coral stone traps harvesting the wild lobster seed in mitigating the negative impact on the marine environment

Lobster seacage aquaculture has a significant social-economic contribution to many coastal communities throughout the central provinces of Vietnam. One of the issues of lobster aquaculture is that the industry entirely relies on the wild juvenile lobster (lobster seed) captured using traps made of coral stones, which affects the coastal ecology and environment. The present study was carried out to compare the catch efficiency of traps made of round timber poles (wooden trap) with conventional dead corals (coral stones) during the juvenile lobster fishing season in 2019 in the coastal area of Nha Trang city, Vietnam. Results showed that experimental wooden traps maintained the conventional catch rate level, with a significant proportion of Panulirus ornatus caught at larger carapace length than those caught by the coral stone traps. Our findings show the biological and environmental benefits of using alternative fishing methods would eliminate collecting coral stones to make lobster seed traps and contribute to coastal protection while maintaining the fishing operation and seed supplies for the lobster seacage farmers.

Application of a stoichiometric bioenergetic approach and whole-body protein synthesis to the nutritional assessment of juvenile Thenus australiensis

The present study successfully combined a stoichiometric bioenergetic approach with an endpoint stochastic model to simultaneously determine specific dynamic action, metabolic substrate use and whole-body protein synthesis in juvenile slipper lobster Thenus australiensis. Juvenile lobsters were fasted for 48 h to investigate routine metabolism before receiving a single meal of formulated feed containing 1% 15N-labeled Spirulina. Postprandial oxygen consumption rate, dissolved inorganic carbon, and total nitrogen excretion returned to the pre-feeding level within 24 h. The rate of whole-body protein synthesis was 0.76 ± 0.15 mg CP g−1 day−1, with a significant reduction from 24 to 48 h post-feeding. The postprandial increase in whole-body protein synthesis accounted for 13–19% of total oxygen uptake. Protein was the primary energy substrate for 48 h fasted (45% oxygen consumption) and post-feeding lobster (44%), suggesting that dietary protein was not efficiently used for growth. The secondary energy substrate differed between carbohydrates in 48 h fasted and lipids in post-feeding lobsters. The present study recommends integrating protein synthesis into protein requirement experiments of marine ectotherms to acquire a more comprehensive picture of protein and energy metabolism and nutritional physiology crucial for formulating cost-effective aquafeeds.

Trophic discrimination factors and stable isotope variability in a captive feeding trial of the southern rock lobster Jasus edwardsii () (Decapoda: Palinuridae) in Tasmania, Australia

Abstract Trophic discrimination or fractionation factors (TDFs), such as ∆15N and ∆13C, are used in stable isotope mixing models to account for differences between source tissues (diet/prey) and consumer tissues (predator). We aimed firstly to obtain TDF values for a spiny lobster, the southern rock lobster Jasus edwardsii (Hutton, 1875), to better understand lobster diet in the wild and secondly to investigate variability in isotope signature within tissues of individuals and across a temporal scale to test if non-lethal sampling can be used in an ecological context. We conducted an 18-mo captive feeding trial with juvenile lobsters using three diet treatments and analysed dorsal and leg muscle, along with dorsal and leg exoskeleton for δ13C and δ15N values. Average TDFs for the three diet treatments were 3.86 ± 0.98‰ (∆13C) and 5.06 ± 0.65‰ (∆15N) for leg muscle, and 4.45 ± 1.04‰ (∆13C) and 4.36 ± 0.6‰ (∆15N) for dorsal muscle. When tested against wild lobsters and prey, these TDFs outperformed multi-taxa TDFs found in the literature. Isotope values from lobster leg muscle were not identical to associated dorsal muscle but the two were highly correlated, indicating that non-lethal sampling is acceptable. Values for exoskeleton isotope were significantly different from muscle, likely due to the exoskeleton not being in a constant state of growth and replacement, unlike the muscle tissue, which constantly incorporates new material. We conclude that our experimentally derived TDFs are suitable for mixing model analysis for J. edwardsii and when tested on a wild sample of lobsters they outperformed other TDFs reported in the literature. We show that non-lethal sampling using leg muscle is an appropriate sampling method, since this tissue is highly correlated to the commonly used dorsal muscle. This option for non-lethal sampling enhances the potential to widely sample wild populations or sample during industrial processing without the need to sacrifice whole animals.

Limited holding space reduces growth and behavioural performance in juvenile European lobsters

Conservation aquaculture offers important tools to secure sustainable animal supplies for human use. However, intensive aquaculture practices are increasingly raising concerns about the welfare conditions of farmed animals, which typically face high mortality rates due to diseases, cannibalism, and aggression. Here we focus on the European lobster (Homarus gammarus), an economically and ecologically important decapod species that has been subjected to conservation programs for decades. While standard husbandry procedures typically result into large numbers of juvenile lobsters produced and released, it remains poorly known whether such standard settings alter the development of behavioural and life-history traits of ecological importance for the animals to survive in the wild. Here, we investigate whether the size of the individual holding spaces affects the behavioural traits (exploration, space use, and sheltering) and growth (carapace length, intermoult period, and percentage moult increment) of juvenile lobsters during their early benthic stages. Our results offer solid evidence that rearing lobsters into small holding spaces not only limits and slows down their overall growth, but also compromises the development of ecologically-relevant behaviours that are essentials for these animals to survive in a complex and risky environment. We point the attention toward the benefits of adopting better rearing procedures to improve the welfare conditions of hatchery-cultured lobsters that can, in turn, result into faster growth rates and the development of competent behavioural repertoires of these valuable organisms—likely to improve the effectiveness of conservation programs.

Cannibalism in cultured juvenile lobster Panulirus ornatus and contributing biological factors

Cannibalism is a major limitation to communally culturing the spiny lobster, Panulirus ornatus, and although frequently reported in research it is yet to be thoroughly investigated. To support continued innovation in culture, we must understand the contribution of cannibalism to juvenile mortality and identify influencing factors. This was accomplished through 900 h of time-lapse photography of three populations of juvenile lobsters over 30 d, including all ecdysis and cannibalism events to inspect individual weight, tank biomass, moult-stage, sex, and injury, as possible contributing factors. Total mortality was over 50% and attributed to the attack and cannibalism of moulting lobsters. Between 20 and 25% of moulting events in P. ornatus resulted in cannibalism of the moulting lobster. Population control and biomass stabilisation appear to be consequences of cannibalism, determined by fluctuations in tank biomass. Additionally, the moult stage of killer cannibals may suggest a nutritional benefit for lobsters in the latter half of the moult cycle. An increase in the average locomotor activity within a population during the hour before cannibalism occurs indicates that the factors driving cannibalism are present up to an hour before a moult. Here we demonstrate the flaws of previous assumptions related to the type and frequency of cannibalism in cultured P. ornatus systems and highlight contributing factors which warrant further study. Building from this research we may identify drivers of cannibalism among juvenile P. ornatus, with the aim of mitigating this behaviour in research and industry culture.

FOOD PREFERENCES OF EARLY JUVENILE SCALLOPED SPINY LOBSTER IN EKAS BAY, LOMBOK, INDONESIA

Ekas Bay is the largest bay on the island of Lombok which is the location for catching and cultivating spiny lobsters. This research was conducted from May to July 2021 on the Scalloped spiny lobster (Panulirus homarus). This study aims to identify the types of natural foods consumed and determine the preferred types of food, as well as the early juvenile feeding time of Scalloped spiny lobster located in Ekas Bay, East Lombok Regency, West Nusa Tenggara Province (NTB). Puerulus samples were collected in the last week of May 2021, enlarged puerulus was performed in submerged cages measuring 15 cm × 15 cm × 15 cm, mesh size <3 mm, with a density of 4 puerulus/m2. The cages are placed at a location 70 m to the sea from the shoreline, at a depth of 0.5, 1.0, and 1.5 m. After reaching the juvenile phase, lobsters are collected during the new and full moon phases (06.00 am, 06.00 pm and 12.00 am, respectively) in June to July 2021. A total of 60 individual juvenile lobsters (algal phase) were analyzed for their stomach contents. The average percentage of the total Index of Relative Important (IRI) obtained for the identified taxa were bivalves (22.32%), copepods (23.64%), demosponges (24.98%), while digestibdle material was 29.06%. The electivity index data (Ei) shows that lobsters prefer bivalves over other taxa. Lobster samples taken in the morning had a stomach fullness rate of 50%, indicating active feeding at night.

The effect of defatted black soldier fly meal (Hermetia illucens) inclusion in the formulated diet on the growth, gene expression, and histopathology of juvenile lobster (Panulirus ornatus Fabricius, 1798)

The present study investigated the potential use of defatted black soldier fly (Hermetia illucens) meal as a protein source in the formulated feed for juvenile lobsters, Panulirus ornatus. A total of 160 heads of juvenile lobsters with initial weight of 0.24 ± 0.01 g and initial length of 21.77 ± 0.32 mm were distributed evenly into 16 rectangular fiberglass aquaria and kept individually for 8 weeks of the feeding experiment. Four formulated feeds containing defatted BSF meal as fishmeal replacements at 0%, 25%, 35%, and 50% and total dietary protein to energy ratio of ~ 26 g CP MJ−1 were prepared and assigned as BSF0, BSF25, BSF35, and BSF50, respectively. Fishmeal is technically a suitable aquafeed ingredient in terms of crude protein, moisture, and amino acid compositions. The partially substituted defatted BSF meal has higher crude lipid and ash content than fishmeal. At the end of week 8 of feeding trial, the specific growth rate, length increment, survival rate, and moulting rate of juvenile lobster were not significantly (P > 0.05) affected by the fishmeal replacement. The fishmeal replacement with the defatted BSF meal did not significantly (P > 0.05) alter the whole-body proximate composition of the juvenile lobster. However, it significantly (P < 0.05) affected the superoxidase dismutase of juvenile lobsters. The cytokine cell expression analysis indicated that up to 35% of fishmeal replacement increased the inflammatory cytokine cells (Interleukin 8 and 17) of juvenile lobster, while an adverse impact was observed on juvenile lobster receiving 50% of fishmeal replacement by BSF meal. Histopathological analysis showed that the hepatopancreas cells of juvenile lobsters were damaged following fishmeal replacement beyond 35%. The present study indicated that up to 35% of defatted BSF meal can be used as fishmeal replacement in the formulated feed of juvenile lobster.

Artificial shelters and marine infectious disease: no detectable effect of the use of casitas to enhance juvenile Panulirus argus in shelter-poor habitats on a viral disease dynamics.

Casitas, low-lying artificial shelters that mimic large crevices, are used in some fisheries for Caribbean spiny lobsters (Panulirus argus). These lobsters are highly gregarious and express communal defense of the shelter. Scaled-down casitas have been shown to increase survival, persistence, and foraging ranges of juveniles. Therefore, the use of casitas has been suggested to help enhance local populations of juvenile P. argus in Caribbean seagrass habitats, poor in natural crevice shelters, in marine protected areas. Following the emergence of Panulirus argus virus 1 (PaV1), which is lethal to juveniles of P. argus, concern was raised about the potential increase in PaV1 transmission with the use of casitas. It was then discovered that lobsters tend to avoid shelters harboring diseased conspecifics, a behavior which, alone or in conjunction with predatory culling of diseased lobsters, has been proposed as a mechanism reducing the spread of PaV1. However, this behavior may depend on the ecological context (i.e., availability of alternative shelter and immediacy of predation risk). We conducted an experiment in a lobster nursery area to examine the effect of the use of casitas on the dynamics of the PaV1 disease. We deployed 10 scaled-down casitas per site on five 1-ha sites over a reef lagoon (casita sites) and left five additional sites with no casitas (control sites). All sites were sampled 10 times every 3-4 months. Within each site, all lobsters found were counted, measured, and examined for clinical signs of the PaV1 disease. Mean density and size of lobsters significantly increased on casita sites relative to control sites, but overall prevalence levels remained similar. There was no relationship between lobster density and disease prevalence. Dispersion parameters (m and k of the negative binomial distribution) revealed that lobsters tended to avoid sharing natural crevices, but not casitas, with diseased conspecifics. These results confirm that casitas provide much needed shelter in seagrass habitats and that their large refuge area may allow distancing between healthy and diseased lobsters. On eight additional sampling times over two years, we culled all diseased lobsters observed on casita sites. During this period, disease prevalence did not decrease but rather increased and varied with site, suggesting that other factors (e.g., environmental) may be influencing the disease dynamics. Using scaled-down casitas in shelter-poor habitats may help efforts to enhance juvenile lobsters for conservation purposes, but monitoring PaV1 prevalence at least once a year during the first few years would be advisable.

Thermal physiology of tropical rock lobster (Panulirus ornatus); defining physiological constraints to high temperature tolerance

This study investigated the effect of chronic temperature acclimation (24, 26, 28, 30, and 32 °C) on growth, aerobic metabolism, feeding, and gut evacuation rate of early juvenile spiny lobster, Panulirus ornatus (initial weight = 0.48 ± 0. 03 g) to determine thermal optima for growth and identify physiological constraints at high temperatures for this emerging aquaculture species. Groups of 7 juvenile lobsters were communally cultured (n = 4) for 45 days post-acclimation and solely fed on a formulated feed. Lobster specific growth rate (SGR), apparent feed intake (AFI), and specific feed consumption (SFC) displayed unimodal response to temperature peaking at 28.0, 27.9, and 26.2 °C, respectively. Similarly, survival had a significant quadratic relationship with temperature; however, it displayed an inverse relationship to SGR, AFI, and SFC where the lowest survival was found at 29.1 °C. Continuous exponential increases in lobster standard, routine and maximum metabolic rates, and aerobic scope were observed up to a maximum non-lethal temperature of 32 °C. Gastrointestinal evacuation rate (GIER) (>96%) increased minimally between 24 and 30 °C from 2.5 h to 2.9 h and substantially rose to 5.1 h at 32 °C. While the feed conversion ratio improved with increasing temperature, the temperature optimum for metabolic feeding efficiency closely matched specific growth rate and apparent feed intake. These findings show that optimum temperature for growth performance of juvenile P. ornatus does not align with maximum aerobic scope, rather growth was limited by prolonged GIER (up to 5.1 h) at high temperatures 32 °C which constrained food consumption. These findings contribute to the growing body of literature debating the universality of aerobic scope to define physiological thermal boundaries of aquatic ectotherms suggesting thermal performance of lobsters under sub-lethal temperatures to be regulated by feed intake and driven by digestive processes such as GIER. Future research should focus on lobster feed formulation and its influence on digestive processes such as GIER, foregut evacuation, and digestibility which may influence the thermal tolerance of spiny lobsters in culture.

Characterisation of the Gut Bacteria of Cultured and Wild Spiny Lobster Panulirus ornatus

The commercial onshore aquaculture of the spiny lobster Panulirus ornatus, while in its infancy, has progressed rapidly from the enabling research that continues at the University of Tasmania. The development of lobster feeds, both fresh and manufactured, has been critical to the success of this emerging aquaculture sector. Fresh feeds derived from mussel represent the gold standard in terms of the growth performance of juvenile lobsters. Nonetheless, concerns regarding availability, sustainability, and potential biosecurity issues of fresh feeds highlight the importance of developing manufactured feeds for lobster aquaculture. Wild lobsters are assumed to have a balanced natural diet that allows for standard growth and development, and as such natural diets are often used as a reference for feed development. Similarly, the gut microbiota associated with a natural diet is assumed to reflect a healthy microbial assemblage. The aim of this study was to compare the microbiota of the hindgut and hepatopancreas of cultured P. ornatus fed with a commercial prawn pellet or mussel to that of wild spiny lobster juveniles. Gut samples were analysed using Oxford Nanopore 16S rRNA gene sequencing. Based on principal coordinate analysis, the gut bacteria of cultured lobsters were different from the wild juveniles. The core microbiota of the hindgut and hepatopancreas libraries were phyla Proteobacteria (Gamma, Alpha) and Bacteroidetes. Vibrio was the most dominant genus in both organs. The differences in bacterial relative abundance were mainly between cultured (pellet-, mussel-fed) and wild lobsters. In conclusion, bacteria in the cultured lobsters had significantly different profiles to that of the wild juveniles, indicating that current onshore aquaculture practices alter the gut microbiota. A number of different feeding and culture practices may be required if the aim of closed culture practices is to attain a gut microbiota in cultured animals that is representative of that found in wild spiny lobsters.

The effect of defatted black soldier fly (Hermentia illucens) meal inclusion in the formulated feed on the pellet stability at different salinity levels

Black soldier fly ( Hermentia illucens ) meal has become a promising alternative substitution of fishmeal as protein resources in aquafeeds. However, the effect of defatted BSF meal inclusion on the juvenile lobster feed stability have not been assessed. The present study is aimed to evaluate the effects of the inclusion of defatted BSF meal (25, 35 and 50 % replacement), the salinity level of seawater (30 and 35 ppt) and the immersion time (15, 30, 60, 90 and 120 minutes) on the pellet stability of formulated feed for juvenile lobster. The pellet stability was determined by calculate the dry matter loss of the feed (wet durability test). Results has shown that the dry matter loss of the feed ranged from 3.17 ± 0.03 % to 4.87 ± 0.26 % for the salinity of 30 ppt, and 3.27 ± 0.04 % to 4.46 ± 0.66 % for the salinity of 35 ppt. The dry matter loss was affected by the levels of defatted BSF inclusion level, the salinity, and the immersion time. The means of dry matter loss in formulated feeds were conversely affected by the salinity level and consistent in all formulated feeds. The means of dry matter loss in BSF25, BSF35 and BSF50 feed were significantly affected by the immersion time (P&lt;0.05). At the salinity 30 ppt, significant differences of dry matter loss were observed after 120 minutes of immersion. Meanwhile, at 35 ppt the significant differences of dry matter loss were observed after 60 minutes after immersion. Significant differences (P&lt;0.05) of dry matter loss were observed in the feed with the inclusion level of BSF of more than 25%. In conclusion the dry matter loss of formulated feeds for juvenile lobster is affected by the inclusion level of the defatted BSF, the salinity levels and the immersion times at acceptable level.