Population-Dynamics of Juvenile Caribbean Spiny Lobster, Panulirus-Argus, in Florida Bay, Florida

Despite a wealth of information on the growth and population dynamics of sub-adult and adult Caribbean spiny lobsters (Panulirus argus), there is far less information about younger juveniles under natural conditions. Here we describe growth and population dynamics of juvenile spiny lobsters (12-68 mm carapace length, CL) that we have studied for 14 months (October 1988-December 1989) using mark-recapture techniques in a hardbottom community in Florida Bay, Florida. We also monitored the supply of postlarvae into the region in 1988 and 1989 using Witham-type surface collectors in an effort to link peak periods of settlement of postlarvae with subsequent cohorts of juveniles. Field estimates of growth were the highest ever reported for this species, averaging 0.95 mm CL.wk-1 (range: 0.35-1.25 mm CL.wk-1 for individuals 20-25 mm CL and 40-45 mm CL, respectively). These results indicate that lobsters in some areas in Florida Bay can reach Florida\u27s legal harvestable size (76 mm CL) 1.5 years after settlement. Season and lobster size had significant effects on growth rates; slower growth occurred during the winter and among small individuals. Differences in growth among size classes resulted from changes in molt increment, whereas seasonal differences were a result of changes in intermolt interval. Using mark-recapture techniques, we estimate that the density of juvenile spiny lobsters \u3c45 mm CL in this prime nursery habitat was 454.ha-1, that the mean monthly probability of survival (reflecting actual mortality plus emigration) was 0.51, and that an average of 131 lobsters entered the population through recruitment and immigration each month. Recruitment of juveniles was significantly correlated (r = 0.83) with the supply of postlarvae to the region 8 months earlier. This relationship is stronger than was previously believed, and may only be manifested in areas with superior nursery habitat

Factors Affecting the Recruitment of Juvenile Caribbean Spiny Lobsters Dwelling in Macroalgae

In south Florida, Caribbean spiny lobsters (Panulirus argus) settle and spend their first few months in macroalgae or seagrass. After a few months, these \u27\u27algal-phase\u27\u27 juveniles emerge from vegetation and, as \u27\u27postalgal-phase\u27\u27 juveniles, seek refuge in crevices, often dwelling in groups. The importance of crevice shelters in determining the abundance of postalgal-phase juvenile spiny lobsters has been studied but we know little about the processes affecting lobster distribution and survival during their cryptic algal-dwelling phase. We found that postlarval supply varied independently of changes in the structure of macroalgal settlement habitat. For this reason, postlarval supply alone can not reliably predict local settlement density. Changes in the size of macroalgal patches in particular tend to increase the variability in settlement density among locations and times. Field and mesocosm experiments indicate that social interactions and individual movements are unlikely to alter the general distribution of algal-phase lobsters established at settlement. But if algal-phase lobsters are aggregated at scales \u3c1 \u3em(2) (e.g., due to patchy settlement), they experience higher mortality than non-aggregated lobsters, as revealed in field experiments where lobsters were tethered alone or in pairs and at varying inter-individual distances. Field manipulations of settlement density indicate that recapture (survival) of microwire tagged algal-phase juveniles is positively associated with features of the habitat that affect lobster density (e.g., site area, macroalgal patch size), but survival and growth of lobsters are unrelated to artificially manipulated settlement density. Collectively, these results imply that the population dynamics of juvenile P. argus dwelling in macroalgae are not typically regulated by density-dependent processes, although density-dependent predation may be locally important in patches when settlement is episodically high

Regional Characterisation of Hard-Bottom Nursery Habitat for Juvenile Caribbean Spiny Lobster (Panulirus argus) Using Rapid Assessment Techniques

Shallow, hard-bottom habitat constitutes approximately 30% of the coastal waters of south Florida, United States, yet it is a chronically understudied feature of the marine seascape in this region. In this study, we characterised the general biogeographic and structural features of shallow benthic hard-bottom communities in the Florida Keys, and related those to the abundance of juvenile Caribbean spiny lobster (Panulirus argus), the target of one of Florida\u27s most economically valuable fisheries. We used rapid assessment techniques to survey more than 100 hard-bottom sites in the Florida Keys to estimate the percentage bottom coverage of vegetation (seagrass and macroalgae) and the abundance of sponges, octocorals, hard corals, and other crevice-bearing structures, as well as the abundance of juvenile lobsters. Using a multivariate statistical approach, we evaluated the relationship between habitat and size-specific juvenile lobster abundance and quantitatively verified the existence of six generally accepted biogeographic subregions. Although the types of hard-bottom shelters used by juvenile lobsters varied somewhat among these subregions, in all regions, branching-candle sponges and octocorals were under-used by lobsters, whereas loggerhead sponges, coral heads, and solution holes were over-used (i.e., used more frequently than expected based on their availability). There was also an ontogenetic transition in the shelter preference of juvenile lobsters; small juveniles tended to occupy a variety of sponges, whereas large juveniles preferred hard structures such as coral heads and solution holes. This study yields the first quantitative biogeographic description of hard-bottom communities of the Florida Keys, and confirms the suspected relationship between the structural features of hard-bottom habitat and the value of these communities as nurseries for juvenile spiny lobster

Recruitment in Degraded Marine Habitats: A Spatially Explicit, Individual-Based Model for Spiny Lobster

Coastal habitats that serve as nursery grounds for numerous marine species are badly degraded, yet the traditional means of modeling populations of exploited marine species handle spatiotemporal changes in habitat characteristics and life history dynamics poorly, if at all. To explore how nursery habitat degradation impacts recruitment of a mobile, benthic species, we developed a spatially explicit, individual-based model that describes the recruitment of Caribbean spiny lobster (Panulirus argus) in the Florida Keys, where a cascade of environmental disturbances has reconfigured nursery habitat structure. In recent years, the region has experienced a series of linked perturbations, among them, seagrass die-offs, cyanobacteria blooms, and the mass mortality of sponges. Sponges are important shelters for juvenile spiny lobster, an abundant benthic predator that also sustains Florida\u27s most valuable fishery. In the model, we simulated monthly settlement of individual lobster postlarvae and the daily growth, mortality, shelter selection, and movement of individual juvenile lobsters on a spatially explicit grid of habitat cells configured to represent the Florida Keys coastal nursery. Based on field habitat surveys, cells were designated as either seagrass or hard-bottom, and hard-bottom cells were further characterized in terms of their shelter- and size-specific lobster carrying capacities. The effect of algal blooms on sponge mortality, hence lobster habitat structure, was modeled based on the duration of exposure of each habitat cell to the blooms. Ten-year simulations of lobster recruitment with and without algal blooms suggest that the lobster population should be surprisingly resilient to massive disturbances of this type. Data not used in model development showed that predictions of large changes in lobster shelter utilization, yet small effects on recruitment in response to blooms, were realistic. The potentially severe impacts of habitat loss on recruitment were averted by compensatory changes in habitat utilization and mobility by larger individuals, coupled with periods of fortuitously high larval settlement. Our model provides an underutilized approach for assessing habitat effects on open populations with complex life histories, and our results illustrate the potential pitfalls of relying on intuition to infer the effects of habitat perturbations on upper trophic levels

Curves on Heisenberg invariant quartic surfaces in projective 3-space

This paper is about the family of smooth quartic surfaces $X \subset \mathbb{P}^3$ that are invariant under the Heisenberg group $H_{2,2}$. For a very general such surface $X$, we show that the Picard number of $X$ is 16 and determine its Picard group. It turns out that the general Heisenberg invariant quartic contains 320 smooth conics and that in the very general case, this collection of conics generates the Picard group.Comment: Updated references, corrected typo

Is Seagrass an Important Nursery Habitat for the Caribbean Spiny Lobster, Panulirus argus, in Florida?

Caribbean spiny lobster (Panulirus argus) settle preferentially in macroalgal-covered hard-bottom habitat, but seagrass is more prevalent in Florida (United States) and the Caribbean, so even low settlement of lobsters within seagrass could contribute substantially to recruitment if post-settlement survival and growth were high. We tested the role of seagrass and hard-bottom habitats for P. argus recruitment in three ways. We first explored possible density-dependent regulation of early benthic juvenile lobster survival within cages deployed in seagrass and hard-bottom habitats. Second, we compared settlement and survival of P. argus in both habitats, by comparing the recovery of microwire-tagged early benthic juveniles from patches of seagrass and hard-bottom. Finally, we assessed the relative abundance of juvenile lobsters in each habitat by deploying artificial structures in seagrass sites and compared these data with data from similar deployments of artificial structures in hard-bottom habitat in other years. More early benthic juvenile lobsters were recovered from cages placed in hard-bottom than in seagrass, but mortality of the early benthic life stage was high in both habitats. In regional surveys, the mean number of lobsters recovered from artificial shelters deployed within seagrass was lower than in any year that we sampled hard-bottom, indicating that fewer lobsters reside naturally in seagrass, particularly large juveniles \u3e40 mm carapace length. The greater abundance (and likely survival) of juvenile P argus that we observed in hard-bottom habitat as opposed to seagrass, combined with previous studies demonstrating that postlarval P. argus are attracted to, settle in, and metamorphose more quickly in red macroalgae, confirm that macroalgae-dominated hard-bottom habitat appears to be the preferred and more optimal nursery for Caribbean spiny lobster

Approximating turbulent and non-turbulent events with the Tensor Train decomposition method

Low-rank multilevel approximation methods are often suited to attack high-dimensional problems successfully and they allow very compact representation of large data sets. Specifically, hierarchical tensor product decomposition methods, e.g., the Tree-Tucker format and the Tensor Train format emerge as a promising approach for application to data that are concerned with cascade-of-scales problems as, e.g., in turbulent fluid dynamics. Beyond multilinear mathematics, those tensor formats are also successfully applied in e.g., physics or chemistry, where they are used in many body problems and quantum states. Here, we focus on two particular objectives, that is, we aim at capturing self-similar structures that might be hidden in the data and we present the reconstruction capabilities of the Tensor Train decomposition method tested with 3D channel turbulence flow data

Sensory traits, color, and shelf life of low-dose irradiated, raw, ground beef patties

Irradiation of raw ground beef patties had minimal effects on flavor and aroma of patties after cooking. Oxidative rancidity increased when patties were irradiated in aerobic but not in vacuum packages. Irradiation of vacuum-packaged ground beef patties produced a more stable color. In both packaging types, irradiation significantly reduced microbial growth during storage

Sensory traits, color, and shelf life of low-dose irradiated, precooked, ground beef patties

Irradiation did not influence bitter, bloody, burnt, chemical, fat-like, juiciness, liver-like, beef identity, metallic, rancid, sour, sweet, and toughness flavor/textural attributes, beef aroma, or off-odor in precooked ground beef patties. Irradiation slightly increased the animal hair flavor note, but intensity levels were <1 on the 15-point sensory scale. Except for 10% fat non-irradiated controls, reheated precooked patties had a slight sour, ammonia-like, top note. Irradiation at 3.5 kilograys (kGy) increased external redness in vacuum-packaged patties, but not in aerobic packages. Aerobic packaging with or without irradiation decreased external precooked redness. Oxidative rancidity increased when patties were irradiated in aerobic but not in vacuum packages. Reduction of oxygen in vacuum bags extended the shelf life of the precooked ground beef patties, at least in terms of oxidative rancidity. Precooking ground beef patties, irrespective of irradiation or packaging type, posed sensory disadvantages, and improvements to the precooking process are needed before irradiating at low-dose levels is appropriate

Cascading Disturbances in Florida Bay, USA: Cyanobacteria Blooms, Sponge Mortality, And Implications For Juvenile Spiny Lobsters Panulirus Argus

Florida Bay, the shallow lagoon separating mainland Florida and the Florida Keys, USA, is experiencing an unprecedented series of ecological disturbances. In 1991, following reports of other ecosystem perturbations, we observed widespread and persistent blooms of cyanobacteria that coincided with the decimation of sponge communities over hundreds of square kilometers. Juvenile Caribbean spiny lobsters Panulirus argus, among other animals, rely on sponges for shelter; the impact of sponge loss on the abundance of lobsters and their use of shelter, in particular, has been dramatic. The loss of sponges on 27 experimental sites in hard bottom habitat in central Florida Bay resulted in the redistribution of juvenile lobsters among the remaining shelters, an influx of lobsters into sites where artificial shelters were present, and a decline in lobster abundances on sites without artificial shelters. Diver surveys of sponge damage at additional sites in central Florida Bay confirmed that the sponge die-off was widespread and its occurrence coincided with areas that had been exposed to the cyanobacteria bloom. This cascade of disturbances has dramatically altered the community structure of affected hard bottom areas and demonstrates the coupled dynamics of this shallow marine ecosystem