California Spiny Lobster Panulirus Interruptus Research Articles

Variation in body size drives spatial and temporal variation in lobster-urchin interaction strength.

How strongly predators and prey interact is both notoriously context dependent and difficult to measure. Yet across taxa, interaction strength is strongly related to predator size, prey size and prey density, suggesting that general cross-taxonomic relationships could be used to predict how strongly individual species interact. Here, we ask how accurately do general size-scaling relationships predict variation in interaction strength between specific species that vary in size and density across space and time? To address this question, we quantified the size and density dependence of the functional response of the California spiny lobster Panulirus interruptus, foraging on a key ecosystem engineer, the purple sea urchin Strongylocentrotus purpuratus, in experimental mesocosms. Based on these results, we then estimated variation in lobster-urchin interaction strength across five sites and 9 years of observational data. Finally, we compared our experimental estimates to predictions based on general size-scaling relationships from the literature. Our results reveal that predator and prey body size has the greatest effect on interaction strength when prey abundance is high. Due to consistently high urchin densities in the field, our simulations suggest that body size-relative to density-accounted for up to 87% of the spatio-temporal variation in interaction strength. However, general size-scaling relationships failed to predict the magnitude of interactions between lobster and urchin; even the best prediction from the literature was, on average, an order of magnitude (+18.7×) different than our experimental predictions. Harvest and climate change are driving reductions in the average body size of many marine species. Anticipating how reductions in body size will alter species interactions is critical to managing marine systems in an ecosystem context. Our results highlight the extent to which differences in size-frequency distributions can drive dramatic variation in the strength of interactions across narrow spatial and temporal scales. Furthermore, our work suggests that species-specific estimates for the scaling of interaction strength with body size, rather than general size-scaling relationships, are necessary to quantitatively predict how reductions in body size will alter interaction strengths.

Hyperiid amphipods from the Gulf of Ulloa and offshore region, Baja California: The possible role of the gelatinous zooplankton as a transport vector into the coastal shelf waters.

Hyperiid amphipod species from the Gulf of Ulloa, Baja California, and the adjacent region (from the shelf break to 200 km offshore) were analyzed to evaluate diversity and abundances. This productive area supports small-scale commercial fisheries, including sand bass (Paralabrax nebulifer), California spiny lobster (Panulirus interruptus), abalones, clams, and others. Strong coastal upwelling events were observed during summer seasons of the period 2002–2008 between Punta Eugenia and Punta Abreojos. The upwelling plumes at Punta Abreojos are transported southward in slope waters bordering the coastal shelf of the Gulf of Ulloa, contributing to the separation of coastal and oceanic regions, and explain differences in amphipod diversity and abundances between both regions. In the offshore region, the most abundant species were Vibilia armata, Lestrigonus schizogeneios, Primno brevidens, and Eupronoe minuta, similar to previous findings in northern regions of Baja California and southern California. However, abundances of these species were lower (10–30 individuals/1000 m3), only reaching 20–50% of abundance levels reported off northern Baja California. In the coastal shelf of the Gulf of Ulloa, amphipods were virtually absent during 2002, 2003 and 2006. However, during 2004 and 2005, abundances of P. brevidens increased (54 and 20 ind/1000 m3, respectively). Moreover, during the late summer of 2007, abundances of L. schizogeneios, P. brevidens, Lycaea nasuta, Lycaea pulex, and Simorhynchotus antennarius increased considerably (261, 39, 31, 68, 416 ind/1000 m3, respectively), indicating occasional utilization of the coastal shelf by pelagic amphipods. Changes in gelatinous populations (medusae, siphonophores, ctenophores, doliolids, and salps) paralleled changes in hyperiid populations, with highest abundances in 2005–2008 in the coastal shelf. Significant correlations of 17 amphipod species with gelatinous taxa, which are often used as host organisms by hyperiid amphipods, suggest that gelatinous presence enhanced hyperiid abundance and promoted the progression of hyperiid amphipods onto the coastal shelf during parts of the 2002–2008 period.

Marine Debris Trends: 30 Years of Change on Ventura County and Channel Island Beaches

The persistence of plastics in marine ecosystems and the physical hazards marine debris pose to wildlife have become issues of global concern. The Santa Barbara Channel is home to a number of important marine and coastal ecosystems, including the 5 islands of Channel Islands National Park, and has a variety of factors that influence marine debris accumulation. We examined the spatial variation of marine debris density and composition across the Santa Barbara Channel by quantifying marine debris on beaches of Santa Rosa and Santa Cruz Islands and the Ventura County mainland. Debris from surveyed beaches was cataloged, weighed, and measured to compare differences in island and mainland marine debris abundance, density, and composition. Derelict fishing gear accounted for a higher proportion of marine debris on island beaches compared to mainland beaches, and marine debris items on island beaches were significantly heavier compared to debris items on mainland beaches. The majority of debris on mainland beaches comprised smaller plastic fragments and single-use plastic items, and debris accumulation rates varied by season and location. Microplastics (plastic fibers and particles 25 mm) that were collected during marine debris cleanups. We compared our data from 2015 and 2016 with historical surveys performed from 1989 to 1994 to examine the temporal variation of marine debris on Santa Rosa Island. We found that there has been a significant increase in the amount of derelict fishing gear found on Santa Rosa Island over the past 27 years, which mirrors expansion of the California spiny lobster (Panulirus interruptus) fishery. This study highlights the importance of marine debris monitoring, as local changes in policy, fisheries, and consumer culture are reflected in accumulations of marine debris found on the California mainland and the uninhabited Channel Islands. Monitoring marine debris can provide insight into anthropogenic impacts and is a useful mechanism in monitoring the health of coastal and marine ecosystems.

Genetic variability and historic stability of the California spiny lobster Panulirus interruptus in the Gulf of California

The California spiny lobster Panulirus interruptus ranges from California into the Gulf of California in Mexico. In Mexico, the lobster supports an economically important fishery. Lobsters in the Gulf of California may belong to a small and genetically distinct population. We determined the genetic diversity and population structure of P. interruptus, using mitochondrial DNA sequences of the control region and the 16SrRNA gene. Samples were collected in the Gulf of California, the west central and southwest coast of the Baja California Peninsula, and the United States. We found a slightly higher genetic diversity in the Gulf of California populations than in the Pacific, but no significant genetic differentiation was shown by an analysis of molecular variance. Using a spatial clustering model and Bayesian methods, the weak population structure was consistent with the absence of a phylogeographic pattern and genetic admixture analysis. However, mismatch distribution analysis suggests that lobster from the gulf represents a more stable and older population than the Pacific, which fitted a model of sudden population expansion. The clinal trend in several genetic parameters between the Gulf of California and the Pacific suggests a historical separation that has not yet resulted in a significant genetic differentiation by genetic drift, mainly because of the large size of the population. Implementation of independent fisheries management practices between these regions could be justified; however, biological and ecological information should be used to support genetic data.

Influence of Hydrographic Conditions on the Distribution of Spiny Lobster Larvae off the West Coast of Baja California

AbstractThe distribution of phyllosoma of California spiny lobster Panulirus interruptus was investigated in relation to the seasonal variability of hydrographic conditions off the west coast of the Baja California Peninsula between 2006 and 2008. Early larval stages were recorded mostly from summer to fall, immediately following the reproductive period. The duration of larval development in plankton is variable (8–12 months), and hence, larvae are found at different times of the year; thus, intermediate and late stages did not show a well‐defined seasonal pattern. The highest phyllosoma density was associated with the relatively warm transitional water mass. However, the peak frequency of occurrence was observed in the colder subarctic water mass. A canonical correspondence analysis identified two distinct seasonal periods: (1) a warm period (summer–autumn), when the abundance of early and intermediate stages was highly correlated with a higher sea surface temperature, and (2) a cold period (winter–spring), when the most advanced stages were associated with a lower water temperature and higher dissolved oxygen. The distribution of larvae and the geostrophic flow patterns suggest that transport by the California Current and mesoscale eddies are the primary dispersal and retention mechanisms from the various breeding centers along the peninsula: northern (Ensenada–Punta Baja), central (Punta Eugenia), and southern (Golfo de Ulloa). In contrast, the data obtained suggest that the recruitment of late larval stages and pueruli in settlement areas might be regulated by the formation of meanders and poleward currents, in addition to the ability of pueruli (self‐recruitment) to reach settlement areas via swimming.

Nutritional condition and gonad development of juvenile and subadult California spiny lobster Panulirus interruptus in two habitats

Se analizo la condicion nutricional y el desarrollo gonadico de juveniles y sub-adultos de langosta roja (Panulirus interruptus) en 2 sitios de la Peninsula de Baja California cercanos geograficamente, pero con condiciones ambientales contrastantes, el mas norteno con condiciones subtropicales y el sureno con condiciones semitempladas. Se estimaron el indice hepatosomatico y el indice refractivo de la sangre, y se cuantificaron las proteinas, lipidos y carbohidratos del hepatopancreas en 62 langostas. Adicionalmente, se comparo el desarrollo gonadico de los organismos en ambos sitios. El indice hepatosomatico y la cuantificacion de lipidos mostraron que la condicion nutricional de los organismos fue diferente en cada sitio. Se observo que los indices de condicion nutricional son afectados por el desarrollo gonadico debido al uso de reservas para la maduracion de las gonadas. La condicion nutricional y el desarrollo gonadico estan fuertemente relacionados con las condiciones ambientales donde se encuentran las langostas, lo cual es informacion util para el manejo de la pesqueria de P. interruptus.

Pilot California Spiny Lobster Postlarvae Sampling Program: Collector Selection

Lobster (infraorder Astacidea) is perhaps the most intensively studied shellfish around the world due to its economic importance (Phillips 2006). Fishery management tools almost universally include catch reporting, but fishery-dependent data such as this often fails to adequately inform managers about the true state of the population (Erisman et al. 2011). Increasingly, fishery-independent surveys are being relied upon to provide the robust information fishery managers require, such as the California Cooperative Oceanic Fisheries Investigation (CalCOFI). The CalCOFI program attempts to understand and predict variations in the Pacific Sardine (Sardinops sagax) fishery, among others, in California through quarterly sampling of fish larvae and other biological and hydrographic data. This focus on larval stages stems from Hjort’s seminal work in 1914, which hypothesized the recruitment and transition of larval forms into postlarval and juvenile life stages is a critical period in population dynamics (Houde 2008). In modern times, fishery management agencies expend significant effort towards cataloging and understanding recruitment levels and patterns which provide the foundation for most fishery management tools (e.g. stock assessments). Recruitment monitoring is at the core of many of global lobster fishery management programs (Cruz et al. 1995; Acosta et al. 1997; Cruz and Adriano 2001; Phillips et al. 2005; Phillips and Melville-Smith 2005; Phillips et al. 2006; Arteaga-Rios et al. 2007; Phillips et al. 2010). Recruitment monitoring of numerous lobster taxa globally have been well correlated with future catch-rate predictions, typically with a 4 to 5 year time lag (e.g. Gardner et al. 2002; Caputi and Brown 2011; Linnane et al. 2014). Long-term recruitment monitoring programs, such as that in Australia (Linnane et al. 2010), are vital in assessing future stock levels and setting the total allowable commercial catches. Like many lobster species, the California Spiny Lobster (Panulirus interruptus) is an economically important fishery species, supporting one of California’s most valuable fisheries with annual ex-vessel values exceeding $9 million (Porzio et al. 2012). However, unlike many of the world’s lobster fisheries, no California Spiny Lobster recruitment monitoring program exists. Recent attempts to address this data gap have been made using plankton collection (Koslow et al. 2012) and power plant entrapment records (Miller 2014). Plankton collections were unable to reliably predict recent landings while entrapment records were more successful, but both articles noted the likely effect of unknown recreational harvest levels impacting the analyses and final conclusions. While informative, neither existing program fulfills the need for targeted information on California Spiny Lobster recruitment in southern California. Furthermore, as southern California power plants shift away from once-throughcooling, lobster entrapment data may soon be unavailable, in which case no regular abundance estimates of California Spiny Lobster postlarvae will be available. Noting the clear need for lobster recruitment monitoring in California, a pilot program was initiated in Orange County, California with the hopes of establishing a model that Bull. Southern California Acad. Sci. 113(3), 2014, pp. 180–186 E Southern California Academy of Sciences, 2014

California spiny lobster preference for urchins from kelp forests: implications for urchin barren persistence

Overfishing of urchin predators, in combination with natural disturbances, has been linked to an increase in the occurrence of urchin barrens. Marine reserves have been proposed as a means to re-establish the interactions between urchins and their predators in California kelp forests. Whether increased densities of lobsters and other predators in reserves are sufficient to convert barrens back to kelp forests depends on the degree to which predators avoid urchins from barren habitats. Urchins from these barrens may be less appealing to predators due to their diminished gonad production and thus decreased quality. In this study, we compared consumption rates of California spiny lobster Panulirus interruptus on purple urchins Strongylocentrotus purpuratus that were collected from kelp forests or from urchin barrens. All size classes of lobster prefer urchins from kelp forests relative to those from barrens and will actively select kelp-bed urchins when given a choice. Lobsters also showed higher consumption rates of kelp-bed urchins when either kelp-bed or barren urchins were presented alone. The large size class of lobsters consumed more and larger urchins than did smaller size classes of lobsters. These results suggest a potential mechanism for the persistence of urchin barrens despite high lobster densities and indicate that lobster foraging preferences may delay phase shifts from barrens back to kelp forests. The results also suggest that preferential foraging by lobsters on kelp-bed urchins may increase the resistance of kelp-beds to changes in state.

Effects of marine reserves on California spiny lobster are robust and modified by fine-scale habitat features and distance from reserve borders

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 451:137-150 (2012) - DOI: https://doi.org/10.3354/meps09592 Effects of marine reserves on California spiny lobster are robust and modified by fine-scale habitat features and distance from reserve borders Matthew C. Kay1,*, Hunter S. Lenihan1, Matthew J. Kotchen2, Christopher J. Miller3 1Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106-5131, USA 2School of Forestry & Environmental Studies, Yale University, New Haven, Connecticut 06511, USA 3California Lobster and Trap Fishermen’s Association, PO Box 2294, Capo Beach, California 92624, USA *Email: mattckay@gmail.com ABSTRACT: Studies of marine reserves often describe mean differences in organism size or abundance inside versus outside reserves, but recent work indicates that these differences are influenced by habitat and proximity of sites to reserve borders. In this study, we measured mean effects of reserves and the influence of distance from reserve borders on the number and size of legal (≥82.5 mm carapace length [CL]) California spiny lobster Panulirus interruptus trapped at sites across a reserve network at the Santa Barbara Channel Islands, California, USA. Additionally, we controlled for habitat variability across sites (1) by measuring relative abundance of sublegal adult lobsters (i.e. those not removed through fishing) and (2) through visual SCUBA surveys on which we quantified fine-scale habitat features. Traps placed in reserves yielded more (4.81 trap−1) and larger (7.03 mm CL) legal-sized lobsters than traps placed outside. Multiple linear regression revealed that 2.43 more legal lobsters per trap were captured for every 1 km moved from borders towards reserve centers. Additionally, lobsters tagged and released immediately inside reserve borders were recaptured in areas open to fishing at a higher rate than lobsters tagged and released farther inside reserves. These results suggest that abundance gradients inside reserve borders were caused by net emigration of lobsters (spillover). Sublegal lobsters were more abundant inside reserves and nearer to reserve centers, but these increases were much smaller in magnitude than for legal-sized lobsters. Our results indicate that the differences we observed for legal-sized lobsters were driven primarily by reserve effects but were partially influenced by habitat heterogeneity. KEY WORDS: Reef · Structure · Spillover · Fishing the line · Catch · Marine reserve · Marine protected area · MPA · Marine reserve border · Habitat · Collaborative · Panulirus interruptus Full text in pdf format PreviousNextCite this article as: Kay MC, Lenihan HS, Kotchen MJ, Miller CJ (2012) Effects of marine reserves on California spiny lobster are robust and modified by fine-scale habitat features and distance from reserve borders. Mar Ecol Prog Ser 451:137-150. https://doi.org/10.3354/meps09592 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 451. Online publication date: April 11, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Spatially explicit mortality of California spiny lobster (Panulirus interruptus) across a marine reserve network

SUMMARYStudies of marine reserves typically focus upon differences in the size and abundance of target organisms inside versus outside reserve borders, but they seldom provide spatially explicit measurements of how reserves influence mortality rates. This study investigated mortality rates for female California spiny lobster (Panulirus interruptus) at multiple sites inside and outside of three marine reserves at the Santa Barbara Channel Islands, California, USA. Mean total mortality (Z) of female lobsters was lower at sites inside reserves (Z = 0.22 [± 0.05 SE]) than at sites outside reserves (Z = 0.59 [± 0.02 SE]). Mean mortality at all sites inside reserves, and among sites near reserve centres (where Z = 0.17 [± 0.05 SE]), was similar to estimates of natural mortality for other temperate spiny lobster species. Among sites inside reserves, there was a positive relationship between mortality and proximity to reserve borders, but this relationship was absent among sites outside reserves. Mortality estimates were much more variable among sites inside reserves than at sites in fished areas. This variation is probably due to differential emigration rates from the three reserves, as well as site-specific ecological factors that influence population structure, demonstrating the importance of spatially explicit reserve sampling and understanding how ecological heterogeneity influences fisheries models.

Commercial fishery effort for California spiny lobster (Panulirus interruptus) off Orange County, California before State Marine Reserve implementation

Abstract The California spiny lobster (Panulirus interruptus) commercial fishing effort along the southern Orange County, California coastline was examined using fishery-independent counts of trap marker buoys and fishery-dependent information submitted to the California Department of Fish and Game in the required commercial logbooks. Buoy counts were conducted in spatially-discrete subsections of the coastline inshore of the 30-m isobath to determine the density of fishing effort at a scale finer than is afforded by the standard fishing blocks used by the Department of Fish and Game. Both the buoy densities and fisherman-reported trap pull counts recorded declining effort across the area as the season progressed. Effort was more diffuse at the beginning of the season, but increasingly focused on areas covered by giant kelp canopy, including the boundary of a previously existing, small no-take marine reserve located in the study area. General effort declined as the frequency of capturing a harvestable Cal...

Behavioral responses to variable predation risk in the California spiny lobster Panulirus interruptus

Shelter dwelling and gregariousness are behavioral strategies used by benthic marine organisms to reduce the risk of predator-induced mortality. For spiny lobsters, the relative and syner- gistic success of shelter dwelling and aggregation in reducing mortality may vary with the perceived risk of predation as well as the availability and size distribution of conspecifics and shelters. We tested how these factors influence antipredator behavior in the California spiny lobster Panulirus interruptus in southern California kelp forests. We measured shelter and lobster characteristics, predator density, relative lobster mortality outside of shelter, and quantified lobster antipredator behaviors in (1) the La Jolla Ecological Reserve (LJER), a marine protected area with high densities of large fishes known to be lobster predators, and (2) the Point Loma kelp forest, a nearby, heavily fished area. Predator densities and the relative mortality of tethered juvenile and adult lobsters were much higher in the LJER than in Point Loma, as was mean lobster size. In response to higher preda- tion risk, solitary lobsters in the LJER used shelters more closely scaled to their body size than lob- sters in Point Loma, thereby restricting predator access to shelters. In addition, aggregations of 2 or more lobsters were more frequent than expected by chance in the LJER, but not in Point Loma. Lobsters in Point Loma commonly were found outside of shelter during the day, whereas no lobsters ever were observed outside of shelter during daylight hours in the LJER. Overall, our results indicate that California spiny lobsters modify their antipredatory behaviors with level of predation risk and that behaviors designed to minimize predator-induced mortality are similar between California spiny lobsters and other spiny lobster species.

Taking the chaos out of genetic patchiness: seascape genetics reveals ecological and oceanographic drivers of genetic patterns in three temperate reef species

Marine species frequently show weak and/or complex genetic structuring that is commonly dismissed as 'chaotic' genetic patchiness and ecologically uninformative. Here, using three datasets that individually feature weak chaotic patchiness, we demonstrate that combining inferences across species and incorporating environmental data can greatly improve the predictive value of marine population genetics studies on small spatial scales. Significant correlations in genetic patterns of microsatellite markers among three species, kelp bass Paralabrax clathratus, Kellet's whelk Kelletia kelletii and California spiny lobster Panulirus interruptus, in the Southern California Bight suggest that slight differences in diversity and pairwise differentiation across sampling sites are not simply noise or chaotic patchiness, but are ecologically meaningful. To test whether interspecies correlations potentially result from shared environmental drivers of genetic patterns, we assembled data on kelp bed size, sea surface temperature and estimates of site-to-site migration probability derived from a high resolution multi-year ocean circulation model. These data served as predictor variables in linear models of genetic diversity and linear mixed models of genetic differentiation that were assessed with information-theoretic model selection. Kelp was the most informative predictor of genetics for all three species, but ocean circulation also played a minor role for kelp bass. The shared patterns suggest a single spatial marine management strategy may effectively protect genetic diversity of multiple species. This study demonstrates the power of environmental and ecological data to shed light on weak genetic patterns and highlights the need for future focus on a mechanistic understanding of the links between oceanography, ecology and genetic structure.

Post-larval settlement of California spiny lobster Panulirus interruptus in Bahía Tortugas, Baja California and its relationship to the commercial catch

Based on data series for 8 consecutive years of settlement of post-larvae of the California spiny lobster Panulirus interruptus, its relationship to commercial catch was examined. The purpose was to establish a database to build a model for prediction of commercial catches of this lobster. The study area is a rocky shelf southwest of the bay entrance of Bahía Tortugas in Baja California Sur. A set of artificial collectors was placed at this site to obtain postpuerulus and early juveniles settlement for each month. Different simple regression analyses were performed on annual series of mean rates of post-larval settlement vs. commercial catches by the Bahía Tortugas fishing cooperative. We tested several delay periods between the series (4–8 years to approximate the age of fishery recruitment) to find the best-fit relationship. The relationship with a 5-year delay showed the highest positive correlation (0.7925) and was statistically significant. This delay period was used to regress the data for the years 1993–2001. The results showed that variations in the abundance of settled post-larvae in a given year are reflected in the commercial catch 5 years later and exhibit the same upward or downward trend. The one exception was the high post-larval settlement rate in 1997–1998, coinciding with the El Niño event, which was not mirrored by a similar increase 5 years later in the 2002–2003 catch. The pre-recruit index seems a very promising tool for predicting catches for this lobster fishery.

Spatial and Temporal Patterns of Lobster Trap Fishing: A Survey of Fishing Effort and Habitat Structure

Abstract The patterns of distribution and abundance for the California spiny lobster (Panulirus interruptus) within the kelp forest off La Jolla, CA (USA) were compared to the distribution of fishing effort during the 2005/2006 lobster season over an area of ∼20.25 km2. Fishing intensity was greatest at the beginning of the season (3333 traps on opening day) decreasing to 258 traps a few days before the end of the 24 week-long season. The collective effort of the trap fishermen primarily targeted the best habitats at the scale of the kelp forest, but fishing effort at smaller scales (250m, the smallest scale of our study) was less correlated to the best lobster habitats, especially near the beginning of the season. Fishing efficiency (CPUE) decreased linearly throughout the season, decreasing by more than an order of magnitude despite the fact that the distribution of fishing effort was better correlated with habitat quality and distribution near the end of the season. Fishing effort was greatest througho...

Genetic differentiation of the California spiny lobster Panulirus interruptus (Randall, 1840) along the west coast of the Baja California Peninsula, Mexico

Identifying reproductive stocks in commercial species is relevant to fishery management strategies. We obtained muscle samples of California spiny lobster (Panulirus interruptus) from six localities along the west coast of the Baja California Peninsula and analyzed the genetic structure using mtDNA RFLPs. Our results indicated that all localities shared the same major haplotypes and showed a spatial homogeneity in the distribution of haplotype frequencies. An analysis of molecular variance indicated that only 0.84% of the genetic variability was explained by differences among localities and was not significantly different from zero. Weak divergences were found between Bahia Magdalena, the most southerly locality, in relation to other populations. Major oceanographic processes along this coast, combined with a long larval period that supports passive transport among localities, are suggested to explain the results.

Determination of preferred habitats of early benthic juvenile California spiny lobster, Panulirus interruptus, on the Pacific coast of Baja California Sur, Mexico

The habitat requirements of early benthic stage juveniles of California spiny lobster Panulirus interruptus are known only from studies conducted near its northernmost geographic range, where environmental conditions differ markedly from those along the Pacific coast of the southern Baja California Peninsula (Mexico). We determined the natural habitat of this stage of P. interruptus in the central portion of their range from sampling the available dominant vegetated habitats included various seagrasses and macroalgae. Additionally, experiments on habitat selection by early benthic juvenile P. interruptus were performed under laboratory conditions to test natural substrate selection and whether selection of substrata is affected by odour signals. Despite the abundance of different macrophytes as habitat, 93% of the juvenile lobsters were found at the base of the blades of Phyllospadix spp. in the intertidal zone at 0 to 3 m. The highest juvenile densities were found in September at both sites. In laboratory experiments, juvenile lobsters preferred, in order of preference, Gelidium robustum, Phyllospadix, Plocamium pacificum, and holdfasts of the kelp Macrocystis pyrifera. A second laboratory experiment showed that these preferences were affected by odour signals. Results indicate that the ecology of juvenile P. interruptus off the coast of the Mexican Baja is similar to that observed off the coast of southern California.

REGIONAL DIFFERENCES IN ALLOMETRIC GROWTH IN ATLANTIC CANADIAN LOBSTER (HOMARUS AMERICANUS)

Abstract Allometric growth in three groups of American lobsters (Homarus americanus) found along the Northumberland and Atlantic coasts of Nova Scotia was compared. Three morphometric parameters were measured: (1) abdomen area, (2) carapace length, and (3) chelae length. Abdomen area and chelae length measurements were related to both carapace length and nominal length, which is (body mass)1/3, while carapace length was related to nominal length. The scaling factors of abdomen area with carapace length for female lobsters were regionally different and were significantly greater than the isometric value of 2. Comparisons were made to published data for the scaling factors of abdomen area for the California spiny lobster (Panulirus interruptus) and differences were found. The data for Homarus were compared to previous measures of the scaling of fecundity for lobsters collected from similar regions of the province. The comparisons suggest that fecundity estimates used in current management strategies should ...

The Dynamics and Scaling of Force Production During the Tail-Flip Escape Response of the California Spiny Lobster Panulirus Interruptus

The tail-flip escape behavior is a stereotypical motor pattern of decapod crustaceans in which swift adduction of the tail to the thorax causes the animal to rotate, move vertically into the water column and accelerate rapidly backwards. Previous predictions that a strong jet force is produced during the flip as the tail adducts to the body are not supported by our simultaneous measurements of force production (using a transducer) and the kinematics (using high-speed video) of tail-flipping by the California spiny lobster Panulirus interruptus. Maximum force production occurred when the tail was positioned approximately normal to the body. Resultant force values dropped to approximately 15% of maximum during the last third of the flip and continued to decline as the tail closed against the body. In addition, maximum acceleration of the body of free-swimming animals occurs when the tail is positioned approximately normal to the body, and acceleration declines steadily to negative values as the tail continues to close. Thus, the tail appears to act largely as a paddle. Full flexion of the tail to the body probably increases the gliding distance by reducing drag and possibly by enhancing fluid circulation around the body. Morphological measurements indicate that Panulirus interruptus grows isometrically. However, measurements of tail-flip force production for individuals with a body mass (Mb) ranging from 69 to 412 g indicate that translational force scales as Mb0.83. This result suggests that force production scales at a rate greater than that predicted by the isometric scaling of muscle cross-sectional area (Mb2/3), which supports previously published data showing that the maximum accelerations of the tail and body of free-swimming animals are size-independent. Torque (tau) scaled as Mb1.29, which is similar to the hypothesized scaling relationship of Mb4/3. Given that tau is proportional to Mb1.29, one would predict rotational acceleration of the body (alpha) to decrease with increasing size as Mb(-0.37), which agrees with previously published kinematic data showing a decrease in alpha with increased Mb.

Synchronous behavior of two coupled electronic neurons.

We report on experimental studies of synchronization phenomena in a pair of analog electronic neurons (ENs). The ENs were designed to reproduce the observed membrane voltage oscillations of isolated biological neurons from the stomatogastric ganglion of the California spiny lobster Panulirus interruptus. The ENs are simple analog circuits which integrate four-dimensional differential equations representing fast and slow subcellular mechanisms that produce the characteristic regular/chaotic spiking-bursting behavior of these cells. In this paper we study their dynamical behavior as we couple them in the same configurations as we have done for their counterpart biological neurons. The interconnections we use for these neural oscillators are both direct electrical connections and excitatory and inhibitory chemical connections: each realized by analog circuitry and suggested by biological examples. We provide here quantitative evidence that the ENs and the biological neurons behave similarly when coupled in the same manner. They each display well defined bifurcations in their mutual synchronization and regularization. We report briefly on an experiment on coupled biological neurons and four-dimensional ENs, which provides further ground for testing the validity of our numerical and electronic models of individual neural behavior. Our experiments as a whole present interesting new examples of regularization and synchronization in coupled nonlinear oscillators.