Juvenile Lobsters Research Articles

Bioenergetics of Nutrient Reserves and Metabolism in Spiny Lobster Juveniles Sagmariasus verreauxi: Predicting Nutritional Condition from Hemolymph Biochemistry.

The nutritional condition of cultured Sagmariasus verreauxi juveniles over the molt and during starvation was investigated by studying their metabolism, bioenergetics of nutrient reserves, and hemolymph biochemistry. Juveniles were shown to downregulate standard metabolic rate by as much as 52% within 14 d during starvation. Hepatopancreas (HP) lipid was prioritized as a source of energy, but this reserve represented only between 1% and 13% of the total measured energy reserve and was used quickly during starvation, especially in the immediate postmolt period when as much as 60% was depleted within 3 d. Abdominal muscle (AM) protein represented between 74% and 90% of the total measured energy reserve in juvenile lobsters, and as much as 40% of available AM protein energy was used over 28 d of starvation after the molt. Carbohydrate reserves represented less than 2% of the measured total energy reserve in fed intermolt lobsters and provided negligible energy during starvation. Eighteen hemolymph parameters were measured to identify a nondestructive biomarker of condition that would reflect accurately the state of energy reserves of the lobster. Among these, the hemolymph Brix index was the most accurate and practical method to predict HP lipid and the total energy content of both the HP and the AM in juvenile S. verreauxi. The Brix index was strongly correlated with hemolymph proteins, triglyceride, cholesterol, calcium, and phosphorus concentrations, as well as lipase activity; all were useful in predicting condition. Electrolytes such as chloride, magnesium, and potassium and metabolites such as glucose and lactate were poor indicators of nutritional condition. Uric acid and the "albumin"-to-"globulin" ratio provided complementary information to the Brix index, which may assist in determining nutritional condition of wild juvenile lobsters of unknown intermolt development. This study will greatly assist future ecological studies examining the nutritional condition of juvenile lobsters in the wild, as well as the development of husbandry protocols and feeds for aquaculture.

Are juvenile Caribbean spiny lobsters (Panulirus argus) becoming less social?

Abstract Caribbean spiny lobsters are one of the most commercially important fisheries due in large part to their highly gregarious nature that facilitates their harvest by the use of traps or aggregation devices containing conspecifics. Aggregation in this species has been shown to be due to strong attraction to conspecific chemical cues that influence movement rates, discovery of crevice shelters, and den sharing behaviours. Although aggregation has been shown to have many potential benefits (reduction in exposure time and predation risk), it may also have significant costs as well (increase in predator encounters, disease transmission, and fishing mortality). We compared the results of three published and three unpublished Y-maze chemical cue choice experiments from 1996 to 2012 to determine if there has been a decrease in conspecific attraction by early benthic juvenile Caribbean spiny lobsters (15–55 mm carapace length, CL). We found that attraction to conspecific chemical cues decreased since 2010 and was significantly lower in 2012. Lobsters showed individual variation in conspecific attraction but this variation was unrelated to size, sex, or dominance status. We also found localized regional variation in conspecific attraction with lobsters from high shelter/high disease areas showing significantly lower conspecific attraction than those from low shelter/low disease areas. Given that conspecific attraction varies among individuals and potentially increases mortality through either natural (increased disease transmission) or fishery-induced (attraction to traps) mechanisms, we should play close attention to this loss of conspecific attraction in juvenile lobsters. Future studies should investigate both the causation and the ecological significance of changes in conspecific attraction in regions that vary in intensity of disease (PaV1) and fishing pressure.

Casitas: a location-dependent ecological trap for juvenile Caribbean spiny lobsters, Panulirus argus

AbstractCasitas are artificial shelters used by fishers to aggregate Caribbean spiny lobsters (Panulirus argus) for ease of capture. However, casitas may function as an ecological trap for juvenile lobsters if they are attracted to casitas and their growth or mortality is poorer compared with natural shelters. We hypothesized that juvenile lobsters may be at particular risk if attracted to casitas because they are less able than larger individuals to defend themselves, and do not forage far from shelter. We compared the nutritional condition, relative mortality, and activity of lobsters of various sizes in casitas and natural shelters in adult and juvenile lobster-dominated habitats in the Florida Keys (United States). We found that the ecological effects of casitas are complex and location-dependent. Lobsters collected from casitas and natural shelters did not differ in nutritional condition. However, juvenile lobsters in casitas experienced higher rates of mortality than did individuals in natural shelters; the mortality of large lobsters did not differ between casitas and natural shelters. Thus, casitas only function as ecological traps when deployed in nursery habitats where juvenile lobsters are lured by conspecifics to casitas where their risk of predation is higher. These results highlight the importance of accounting for animal size and location-dependent effects when considering the consequences of habitat modification for fisheries enhancement.

Behavioral response to habitat loss in juvenile spiny lobsters

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 521:117-128 (2015) - DOI: https://doi.org/10.3354/meps11125 Behavioral response to habitat loss in juvenile spiny lobsters Katherine A. Heldt1,3,*, William C. Bridges Jr.2, Michael J. Childress1 1Department of Biological Sciences, Clemson University, Clemson, South Carolina 29634, USA 2Department of Mathematical Sciences, Clemson University, Clemson, South Carolina 29634, USA 3Southern Seas Ecology Laboratories, School of Earth, Environmental, and Landscape Sciences, The University of Adelaide, Adelaide 5006 SA, Australia *Corresponding author: katherine.heldt@adelaide.edu.au ABSTRACT: Understanding behavioral changes is important when examining the impacts of rapid environmental change, particularly when critical resources such as protective shelters become locally limited during habitat loss events. In portions of Florida Bay (Florida, USA), cyanobacterial blooms have reduced the availability of large sponges, an important shelter for juvenile Caribbean spiny lobster Panulirus argus. We examined whether juvenile lobsters from regions with and without sponge shelters differed in: (1) aggressive and gregarious behaviors; (2) den use, den sharing, and den fidelity before and after shelter loss; and (3) dispersal from sites with and without artificial shelters. In laboratory experiments where individuals were paired with similar-size conspecifics, habitat type had no influence on aggression and gregariousness, but larger lobsters were more aggressive and shared dens less frequently than smaller lobsters. When these same individuals were placed into groups of 20 in a mesocosm and exposed to shelter loss, individuals from habitats with sponges showed a greater decrease in den use and den sharing than individuals from habitats without sponges. After shelter loss, large lobsters decreased their den use, den sharing, and den fidelity more than small lobsters. When individuals were released at their point of capture in Florida Bay, large individuals were resighted less often than small individuals. This study suggests that lobsters from habitats without sponges may respond differently to future shelter loss and that size plays an important role in determining whether juvenile spiny lobsters share shelters or disperse. KEY WORDS: Caribbean spiny lobster · Social behavior · Panulirus argus · Aggression · Gregariousness · Sponge mortality Full text in pdf format PreviousNextCite this article as: Heldt KA, Bridges WC jr, Childress MJ (2015) Behavioral response to habitat loss in juvenile spiny lobsters. Mar Ecol Prog Ser 521:117-128. https://doi.org/10.3354/meps11125 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 521. Online publication date: February 17, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Influence of predator identity on the strength of predator avoidance responses in lobsters

The American lobster, Homarus americanus, is an important benthic consumer in the Gulf of Maine and supports an extremely valuable fishery in New England and eastern Canada. Meanwhile, there is substantial interest in restoring large predator fish species to the Gulf of Maine, and these predators may impact lobster populations both by consuming them and by inducing them to alter their behavior. Lobster tethering experiments were used to examine the susceptibility of a range of lobster size classes to predation in Saco Bay, Maine. The most susceptible sizes of lobsters were then exposed to three different fish predators (Atlantic striped bass Morone saxatilis, Atlantic cod Gadus morhua, and sea raven Hemitripterus americanus) separately in experimental mesocosm tanks. Juvenile lobsters moved less and spent more time in shelter when in the presence of cod or sea raven. By contrast, striped bass did not induce lobsters to alter their behavior. Striped bass are highly mobile, active pursuit predators, which are thought to induce weaker behavioral responses in prey than sit-and-pursue predators like sea ravens. Thus, differences in lobster sheltering behavior corresponded with differences in predator foraging behavior. These predator-induced changes in behavior can result in less foraging activity, which may translate into reduced lobster growth and reproduction. Efforts to model marine communities and ecosystems will benefit from a more holistic understanding of whether predators induced prey to modify their foraging behavior and habitat usage.

Do changes in reef habitats influence relative predation risk on the juvenile Australasian spiny lobster, Jasus edwardsii (Hutton, 1875)?

Kelp habitats are in decline in many temperate coastal regions of the world due to climate change and expansion of populations of grazing urchins. The loss of kelp habitat may influence the vulnerability to predators of the juveniles of commercially important species. In this study relative predation rates for kelp versus barren reef habitat were measured for early juvenile Australasian spiny lobster, Jasus edwardsii (Hutton, 1875), on the northeastern coast of New Zealand using tethering methods. Variation in assemblages of predators over small spatial scales appeared to be more important for determining the relative predation of lobsters, regardless of habitat type. Therefore, the assessment of relative predation risk to early juvenile lobsters between kelp and barren habitats will require more extensive sampling at a small spatial scale, as well as a specific focus on sampling during crepuscular and nocturnal periods when these lobsters are most at risk of predation.

Size-at-age and body condition of juvenile American lobsters (Homarus americanus) living on cobble and mud in a mixed-bottom embayment in the Bay of Fundy

American lobsters, Homarus americanus, prefer structurally complex cobble bottom for settlement and early development, but this habitat is sparse and some juveniles are likely forced to exploit other habitats, such as mud bottom. Size-at-age and body condition of juvenile lobsters may vary between cobble and mud habitats, due to differences in food and shelter the habitats provide. In this study, we used cobble-filled collectors deployed on mud and cobble bottom to capture juvenile lobsters occupying cobble and mud seafloor in a mixed-bottom embayment in the southwestern Bay of Fundy, Canada. We compared their size-at-age using a recently developed age-determination technique, and their body condition using mass–length relationship, RNA/DNA ratio and protein content. Individuals 3 and 4 years of age inhabiting mud bottom had greater carapace length than same-age conspecifics on cobble, which could be due to greater growth of juveniles in the less preferred mud habitat. We also found that for a similar carapace length lobsters on mud had slightly lower body mass than those on cobble. RNA/DNA ratio and protein content did not differ between juveniles sampled from the two habitats. Our results suggest that mud bottom represents a more important habitat for young lobsters than is currently appreciated. We hypothesize that mud bottom has become a more important juvenile habitat in recent years due to high lobster abundance, which may be forcing some juveniles to move from preferred but saturated cobble patches to other habitats, such as mud.

Impact of an Acute Sublethal Exposure of Endosulfan on Early Juvenile Lobster (Homarus americanus)

Anthropogenic chemicals in the environment during critical periods could potentially affect the physiology of the economically valuable American lobster ( Homarus americanus ). Endosulfan (Thiodan™ WP) is a broad-spectrum organochlorine insecticide widely used in agricultural areas in Canada that significantly affects survival and growth of lobster larvae based on acute exposure studies. To detect more subtle physiological effects of an acute (96-h) sub-lethal level (0.1 μg·L -1 ) of formulated endosulfan exposure on early juvenile lobsters, investigations of metabolic rates, growth and the tissue structure of the hepatopancreas were conducted on animals that molted following the exposure. The standard and active metabolic rates were not significantly affected, but their differential, defined as the metabolic scope (MS) was significantly decreased by 25% for exposed animals. Lobster growth and survival were not affected. For the exposed lobsters, minor alterations of the digestive cell structures were observed. These results suggest that the decrease in MS for exposed juvenile lobsters could have consequences in terms of survival in the wild by impairing their abilities to find a shelter, food or protect themselves from predators. The growth and survival in laboratory conditions suggests that lobsters may adjust their metabolism to pesticide exposure by maintaining a positive energy balance with some compensatory mechanisms; however, this may not be possible in their natural environment. This study suggests that conclusions based solely on lethal toxicity assays could be misleading for sublethal effects of contaminants on marine organisms, which could be investigated more thoroughly using an integrated approach based on physiological indicators.

Screening of marine bacteria with bacteriocin-like activities and probiotic potential for ornate spiny lobster (Panulirus ornatus) juveniles

Bacteriocins are ribosomally synthesized antimicrobial peptides, which have been found in diverse bacterial species of terrestrial origins and some from the sea. New bacteriocins with new characteristics, new origins and new applications are likely still awaiting discovery. The present study screened bacteria isolated from marine animals of interest to the aquaculture industry for antimicrobial and bacteriocin-like activities in order to uncover biodiversity of bacteriocin producers, and explore the potential application in aquaculture. In total, 24 of 100 screened isolates showed antimicrobial activities and 7 of these exerted bacteriocin-like activities. Sequencing of 16S rRNA genes identified the isolates as members of the six genera Proteus, Providencia, Klebsiella, Alcaligenes, Bacillus and Enterococcus. In some cases, further analysis of housekeeping genes, rpoB for Proteus and recA for Klebsiella, as well as biochemical tests was necessary for identification to species level, and some of the Proteus isolates may represent novel species. The seven bacteriocinogenic isolates showed a wide antimicrobial spectrum against foodborne and animal pathogens, which opens the way to their potential use as marine drugs and probiotics in food, aquaculture, livestock and clinical settings. As a case study, the protective effect of shortlisted bacteriocinogenic isolates were tested in aquaculture-raised spiny lobster (Panulirus ornatus) juveniles. A single-strain (Bacillus pumilus B3.10.2B) and a three-strain (B. pumilus B3.10.2B, Bacillus cereus D9, Lactobacillus plantarum T13) probiotic preparation were added to the feed of Panulirus ornatus juveniles, which were subsequently challenged with the pathogen Vibrio owensii DY05. Juveniles in the probiotic treatments displayed increased growth and reduced feed conversion rates after 60 days, and increased survival rate after pathogen challenge relative to the control. This study represents the first evidence of bacteriocin production by bacteria associated with lobster, tiger shrimp, snubnose pompano and cobia and the first description of V. owensii as a pathogen in P. ornatus juveniles.

Effect of copper in protein, carbohydrate and lipid contents of the juvenile lobster, Panulirus homarus homarus (Linnaeus, 1758)

Copper is one of the most toxic metals for marine organisms. Biochemical changes occurring in the metabolically active tissues of gills (GL), hepatopancreas (HP) and muscles (MU) of the juvenile lobster, Panulirus homarus homarus on exposure to two sub-lethal doses (9.55 and 19.1 μg l -1 ) of copper were studied for 28 days of exposure (DoE). Sub-lethal doses of copper significantly ( P HP>GL, HP>MU>GL and HP>MU>GL. Results of this study revealed that sub-lethal doses of copper significantly alter the proximate composition of major tissues, particularly the TP levels in the MU tissues and thereby reducing the nutritive value of this economically important spiny lobster. DOI: http://dx.doi.org/10.4038/sljas.v17i0.6853 Sri Lanka Journal of Aquatic Sciences Vol.17: 19-34

The suitability of VIE tags to assess stock enhancement success in juvenile European lobsters (Homarus gammarus)

Assessments of stock enhancement programmes for European lobsters (Homarus gammarus) require mark-recapture analysis of stocked individuals. However, established tag technology is deemed unsuitable for extensive use by many current lobster hatcheries, particularly upon the early juvenile stages. We tested the suitability of fluorescent Visible Implant Elastomer (VIE) tags for use in 5-month-old juvenile lobsters. Three treatment groups comprising 348 cultured lobsters in total were used to examine survival, growth and tag retention, and to assess mobility, shelter use and moulting behaviours. Tagging had no significant effect on lobster survival, growth, mobility, shelter use or moult frequency. Survival over 7 weeks was 75% among lobsters tagged with two elastomers, 76% in those with one elastomer and 74% among untagged controls. Mortality during moulting did not increase in tagged (6%) compared to untagged lobsters (9%). We found no evidence that VIE tags cause any negative effects that would be expected to inhibit survival upon wild release, but tag loss had reached 12% in both tagged treatments after 7 weeks and showed no sign of abating. Our study suggests that VIEs effectiveness in discerning cultured lobsters long after wild release may be limited when used in smaller juveniles.

Spatial linkages between settling young-of-year and older juvenile lobsters

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 499:143-155 (2014) - DOI: https://doi.org/10.3354/meps10625 Spatial linkages between settling young-of-year and older juvenile lobsters Victoria H. M. Burdett-Coutts1,*, Richard A. Wahle2, Paul V. R. Snelgrove1, Rémy Rochette3 1Biology Department and Ocean Sciences Centre, Memorial University of Newfoundland, St. John’s, Newfoundland A1C 5S7, Canada 2School of Marine Sciences, University of Maine, Darling Marine Center, Walpole, Maine 04573, USA 3Biology Department, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada *Corresponding author: vbcoutts@gmail.com ABSTRACT: We examined spatial association between young-of-year (YoY) and older juvenile (Juv) American lobsters Homarus americanus across multiple spatial scales using 8 years (2001 to 2008) of field measurements of a long-term settlement index time series from New England, USA. Complementary laboratory experiments examined behavioural responses of settling postlarvae to conspecific presence. Regional scale (10s to 100s of kilometres) data aggregation showed significant association between YoY recruitment and Juv densities in the same year for all 8 years examined. These broad-scale positive associations support previous research showing the importance of circulation-driven patterns of larval supply in linking newly settled YoY and Juv lobsters. Analysis at the quadrat scale, however, showed greater than expected association between YoY and Juv, suggesting a behavioural component. Early benthic-phase Juv lobsters (~0 to 2 yr old) strongly associate with structurally complex habitats; however, little is known of other habitat quality variables that may enhance successful recruitment. Resident conspecifics may represent one of several habitat quality proxies for postlarval lobsters despite post-settlement risk in settling among conspecifics, such as competition and predation. In short-term (4 min) laboratory behavioural experiments, postlarvae spent significantly more time on the bottom in the presence of conspecific juveniles. In longer-term (24 h) experiments, postlarvae initially (<1 h), though not significantly, settled more rapidly in the presence of conspecific juveniles, and any weak effect dissipated with time. Lack of suitable habitat in experimental chambers may have inhibited a longer-term response. While conspecifics may initially attract postlarvae, settlement may require additional habitat cues. KEY WORDS: Lobster · Postlarvae · Bottom-searching behaviour · Conspecific cues · Behaviour · Scaling · Recruitment Full text in pdf format PreviousNextCite this article as: Burdett-Coutts VHM, Wahle RA, Snelgrove PVR, Rochette R (2014) Spatial linkages between settling young-of-year and older juvenile lobsters. Mar Ecol Prog Ser 499:143-155. https://doi.org/10.3354/meps10625 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 499. Online publication date: March 03, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Advection-diffusion models of spiny lobster Palinurus gilchristi migrations for use in spatial fisheries management

Advection-diffusion models were constructed to simulate migration patterns of juve- nile and adult spiny lobsters off southern South Africa. Models based on tag-recapture informa- tion collected between 1978 and 2005 (2665 tag recaptures) were used to quantify directional movements and to estimate distances moved along a bathymetric gradient. Sex, length at tagging, tagging area and time at large were the main explanatory variables considered. Empirical tests showed that tagging did not delay the onset of advective movements. Lobsters were advected from west to east, and no return migrations were observed. Advection was strongly size depend- ent, with juvenile and small mature individuals moving further than larger adults. Advection was also area dependent, decreasing from west to east, and lobsters at the easternmost site were not advected and did not receive immigrants from elsewhere. Juvenile lobsters tagged at a recruit- ment hotspot at the westernmost site migrated 100 to 250 km onto the Agulhas Bank (90% prob- ability after 5 yr at large), or continued along the coast to more distant sites (400 to 900 km; 10% after 5 yr). This effect was stronger in males, but we could not detect a trade-off in growth rate. Two theories are advanced to explain these migration strategies: evolutionary effects of past range expansions and density dependence. A novel approach for quantifying migrations in spiny lob- sters is demonstrated, for potential use in spatial fisheries management.

Mortality and deformities in European lobster (Homarus gammarus) juveniles exposed to the anti-parasitic drug teflubenzuron

This study describes experiments carried out to examine effects of the antiparasitic drug teflubenzuron, used in delousing farmed salmon, on a non-target species, the European lobster (Homarus gammarus). Juvenile lobsters were fed two doses of teflubenzuron, 10 and 20mg/kg successively for 7 days corresponding to a standard medication of the fish (10mg/kg day) and twice the standard dose (20mg/kg day). Monitoring lasted 3 months to include at least one moulting period for all individuals. Cumulative mortality was higher in all replicates given medicated feed compared with the control group. Mean cumulative mortality for each dosing was 41±13% for 10mg/kg and 38±8% for 20mg/kg, i.e. no difference. Drug residue was analysed in all juveniles that died, in addition to 12 juveniles at day 8 and the first 12 surviving lobsters. A decline in concentration of teflubenzuron from over 8000ng/g (day 5) to 14ng/g (day 70) was observed in the juveniles that died during the experiment. Twelve individuals that died contained 82ng/g or less whereas the mean concentration in the first 12 lobsters that survived moulting was 152ng/g. Following a single oral administration, the half-life of teflubenzuron in lobster was estimated to 3.4 days and the initial concentration (C0) to 515ng/g at time t0. At the end of the study a considerable number of juvenile lobsters were observed with deformities in various organs; carapace, walking legs, cheliped, tail fan, abdomen and antenna. The occurrence of observed deformities varied from 0 to 15% in treated replicates and will most likely affect ability to locate and consume food (antenna, claw and walking legs), respiration (carapace) and ability to move/swim (walking legs, tail fan and abdomen). In total, the mortality and senescent damages were close to 50% in all replicates. Juveniles that survived medication without deformities however, moulted and increased in size at each moult equally well as the unmedicated controls.

Protein synthesis in crustaceans: a review focused on feeding and nutrition

Abstract This review aimed to place crustacean research on in vivo protein synthesis into a broader context, assess its potential for providing further insights into crustacean nutrition and physiology, and recommend future directions relevant to crustacean aquaculture. In crustaceans the flooding dose measurement of protein synthesis is the only method that has been used, it is relatively complex, time consuming and uses radioactive labels. Protein synthesis provides a subtle approach to assessing imbalances and deficiencies in dietary amino acid and energy. In addition, the calculation of protein synthesis retention efficiency (SRE) is recommended in order to understand and optimize parameters such as feeding regime and diet composition. For prawns, SRE was highest at optimum dietary protein content and quality. Similarly the most efficient feeding regimes in juvenile lobsters were demonstrated by the highest efficiency of retaining synthesized protein. Understanding how various abiotic and biotic factors influence protein synthesis has great potential for improving different aspects of crustacean aquaculture but very few studies have done this; better knowledge of how abiotic and biotic factors affect crustacean protein synthesis will contribute to optimising growth of crustaceans in culture.

Effect of body mass and activity on the metabolic rate and ammonia-N excretion of the spiny lobster Sagmariasus verreauxi during ontogeny

Intraspecific analyses of the relationship between metabolic rate and mass have rarely been considered during complete ontogeny. Spiny lobsters are fascinating candidates to examine metabolic changes during ontogeny because their life cycle includes an extended planktonic, nektonic, and benthic life stages. The effect of body mass on metabolic rates, aerobic scope, and ammonia-N excretion of Sagmariasus verreauxi juveniles were examined to determine energetic demands through juvenile development. Mass-independent routine oxygen consumption increased allometrically during juvenile development with a mass scaling exponent of 0.83. The mass scaling exponent of active metabolism (0.81) was reduced compared to standard metabolism (0.91) of juvenile lobsters. The aerobic scope of juvenile lobsters decreased with larger body mass. To examine if the mass scaling exponent varies with ontogeny, we compared our data with previous measurements made with larvae of the same species. Comparison between mass scaling exponents showed they were higher for phyllosoma (0.97) compared to juvenile (0.83) development. Higher scaling exponents for phyllosoma may be attributed to increased growth rates of phyllosoma compared to juveniles, which increase oxygen consumption due to the higher energy cost of growth. The mass scaling exponent for complete ontogeny (0.91) of S. verreauxi was larger than the commonly cited 0.67 (1/3) and 0.75 (3/4) mass scaling exponents, indicating that species-specific differences can be a large factor affecting allometric relationships of animals.

Annual and Long-Term Movement Patterns of Spiny Lobster, &lt;I&gt;Panulirus Marginatus,&lt;/I&gt; and Slipper Lobster, &lt;I&gt;Scyllarides Squammosus&lt;/I&gt;, in the Northwestern Hawaiian Islands

Crustaceans exhibit diverse movement behaviors, which can complicate sustainable management if poorly understood. Annual and long-term movement patterns by hawaiian spiny lobster, Panulirus marginatus (Quoy and Gaimard, 1825), and scaly slipper lobster, Scyllarides squammosus (H. Milne-Edwards, 1837), at four locations in the Northwestern Hawaiian Islands (NWHI) were estimated by using tag/recapture methods. Both species exhibited very limited movement, moving 5 km, there was no evidence of regular long-distance migrations or directed movements. Sex and location significantly affected distance moved by both species; however, there was no clear pattern. Size-at-tagging was a significant factor for S. squammosus, for which distances moved varied directly with increasing size; however, this is not necessarily indicative of large-scale unidirectional movements and may simply indicate that larger S. squammosus have larger home ranges. The lack of large-scale movements of both species probably reflects habitat characteristics. The NWHI do not provide the typical habitats juvenile lobsters require, there are no large seasonal temperature changes, and contranatant migrations are unnecessary because newly hatched larvae have access to offshore currents. The small home ranges of these species suggest that marine protected areas may be a viable conservation option.

Effects of temperature on the moulting and locomotory activity of hatchery-reared juvenile lobsters (Homarus gammarus) at Helgoland (North Sea)

Optimized release conditions of hatchery-reared juvenile lobster (Homarus gammarus) can reduce loss in the field. The effect of seasonal temperature on the behavioural and physiological activity of lobsters was examined, observing the timing of moulting and locomotory activity in juvenile lobsters maintained at increasing temperatures under standardized laboratory conditions. The juveniles of three different year and size classes mostly moulted when a threshold temperature between 12 and 14°C was reached. In addition, the locomotory activity of lobsters showed significant responses to seasonal temperatures between 12 and 15°C in the dark-phase. The knowledge about the temperature-dependent activity of lobsters may be helpful to explain behaviour in the field and in assessing the chances of a future large-scale stock enhancement programme.

The geography and bathymetry of American lobster benthic recruitment as measured by diver-based suction sampling and passive collectors

We present results of an international collaboration to survey American lobster Homarus americanus Milne-Edwards, 1837 nurseries in Atlantic Canada and the northeast United States from 2007 to 2009 under a standardized protocol involving two sampling methods, diver-based suction sampling and passive collectors. We surveyed young-of-year and older juveniles at 191 sampling sites over 39 sampling areas considerably expanding the known depth range and geographic limits of benthic recruitment. Young-of-year densities were strongly correlated in space with the abundance of older juveniles, signifying consistently strong settlement in the Gulf of Maine, lower Bay of Fundy, southwestern Nova Scotia and southern Gulf of St. Lawrence, and relatively weak settlement in southern New England, eastern coastal Nova Scotia and Newfoundland, a pattern consistent with commercial lobster harvests. Passive collectors elucidated bathymetric patterns of young-of-year recruitment in oceanographically contrasting regions. Although we observed young-of-year lobsters as deep as 80 m, they were most abundant above the thermocline in summer-stratified regions, such as the western Gulf of Maine and southern New England, and depth-wise differences were less extreme in thermally mixed waters of the eastern Gulf of Maine–Fundy region, a finding consistent with previous observations that postlarvae concentrate above the thermocline. Between the two samplers, we detected no sampling bias for young-of-year lobsters, although collectors may slightly under-represent older juveniles entering from the surrounding sea bed. Finally, we found that interactions between juvenile lobsters and suspected predators or competitors in collectors, such as crabs and fishes, are weak and unlikely to bias collector results.

Strong preference for decapod prey by the western rock lobster Panulirus cygnus

Western rock lobsters, Panulirus cygnus are an abundant benthic consumer distributed along the temperate west coast of Australia and constitute the largest single species fishery in Australia. As a dominant consumer, it is important to understand their predator–prey interactions as they can potentially exert strong trophic effects, and may influence ecosystem function as seen in other spiny lobster species. While previous field studies have focused on the diet composition of P. cygnus, this study investigated their preference for various benthic invertebrate prey to better understand the likely predator–prey interactions of P. cygnus. Prey preferences of small sub-legal juvenile lobsters, as well as medium and large legal-sized mature lobsters were investigated using laboratory feeding trials to identify size-associated differences in lobster prey preference. Handling time and diet quality were investigated to estimate energetic cost and gain from consuming different prey which may explain prey choice by lobsters. It was found that large lobsters preferred crabs and mussels while medium and small lobsters preferred crabs over mussels, gastropods, and sea urchins. This suggests that strong predator–prey interactions between P. cygnus and crabs may occur in the wild.