Ichthyoplankton Adjacent to Live-Bottom Habitats in Onslow Bay, North Carolina

The abundance and distribution of ichthyoplankton adjacent to live-bottom habitats (rock outcroppings containing rich, sessile invertebrate communities and many species of tropical and subtropical fishes) in open-shelf waters « 55-m isobath) in Onslow Bay, North Carolina, were investigated. Larvae of reef-associated genera, especially the economically important subtropical and tropical members of the families Haemulidae (Haemulon), Lutjanidae (Lutjanus and Rltomboplites), Serranidae (Mycteroperca and Epinephelus), and Sparidae (Calamus and Pagrus) were targeted. Larvae representing 40 families were collected in neuston tows. Commonly collected reef-associated families were Balistidae, Blenniidae (dominated by the reef-associated Parablennius marmoreus) , Mullidae, and Gobiidae. Larvae representing 70 families were collected in subsurface tows. Reef-associated families commonly collected included Apogonidae, Balistidae, Gobiidae, Haemulidae, LutJanidae, Scaridae, and Serranidae. Larval Haemulon sp (p)., Lutjanus sp(p)., and Rltomboplites aurorubens were commonly collected and thus it is likely that these taxa spawn in Onslow Bay and recruit to live-bottom sites within the area. Other families of fishes commonly collected but generally not considered reef-associated included Bothidae, Callionymidae, Carangidae, Clupeidae, Engraulidae, and Ophidiidae. Estuarine-dependent species (e.g. the clupeid Brevoortia tyrannus and the sciaenids Leiostomus xanthurus and Micropogonias undulatus) were an important component of the ichthyoplankton during late fall and winter. The frequent occurrence of larvae from oceanic species (e.g. gonostomatids and myctophids) indicated that Gulf Stream waters had intruded onto the shelf, transporting these larvae to open-shelf waters off North Carolina.(PDF file containes 36 pages.

The Liquid Annular Reactor System (LARS) propulsion

A concept for very high specific impulse (greater than 2000 seconds) direct nuclear propulsion is described. The concept, termed the liquid annular reactor system (LARS), uses liquid nuclear fuel elements to heat hydrogen propellant to very high temperatures (approximately 6000 K). Operating pressure is moderate (approximately 10 atm), with the result that the outlet hydrogen is virtually 100 percent dissociated to monatomic H. The molten fuel is contained in a solid container of its own material, which is rotated to stabilize the liquid layer by centripetal force. LARS reactor designs are described, together with neutronic and thermal-hydraulic analyses. Power levels are on the order of 200 megawatts. Typically, LARS designs use seven rotating fuel elements, are beryllium moderated, and have critical radii of approximately 100 cm (core L/D approximately equal to 1.5)

Sphaerodactylus fantasticus

Number of Pages: 8Integrative BiologyGeological Science

Evidence Of Recent Recruitment In The Ocean Quahog Arctica Islandica In The Mid-Atlantic Bight

We report results of a survey explicitly focused on ocean quahog recruitment in the Mid-Atlantic Bight. The recruitment survey resampled all NMFS survey sites south of Hudson Canyon and a selection of sites north and east of Hudson Canyon off the Long Island coast over the entire depth range of this species with the exception of the most inshore reaches off Long Island. More ocean quahogs were encountered, on a per tow basis, in the vicinity of and north of Hudson Canyon. The proportion of recruits in the size-frequency distribution was higher in the south and the most recent recruitment events were concentrated there. Analysis of the 104 size-frequency distributions delineated regions of recent recruitment, areas that have not seen significant recruitment for many decades and areas that received heavy recruitment some decades previously but not recently. Overall, the survey suggests that three regionally distinctive processes determine the size-frequency distributions of ocean quahog assemblages and recruitment therein. The area northeast of Hudson Canyon is unique in the regionally extensive uniformity of size-frequency distributions among sampled assemblages. the near absence of recent recruitment and the presence of large numbers of older recruits, 65-80 mm in size. The inshore (by ocean quahog standards) area off New Jersey is unique in the dominant presence of the largest size classes of ocean quahogs and the remarkable absence of significant recruitment over an extraordinary time span. The area south of 39 degrees N is unique in the widespread presence of relatively young recruits, including some animals with ages within the time span of the present fishery. Recruitment events in ocean quahog populations, although rare in the sense of occurring only once in a score or two of years, are frequent in the context of the +200-year life span of this species, yet also rare in the context of stock survey timing and fishery dynamics. This study strongly supports the assumption that long-lived species recruit successfully only rarely when at carrying capacity. This study also suggests that the history of recruitment over the last perhaps two-score years, revealed by this survey, may be a poor measure of the recruitment dynamics to be anticipated over the next two-score years when the population abundance is reduced to what is anticipated to approximate the biomass at maximum sustainable yield. Given the long time span required for ocean quahogs to grow to fishable size, a substantive disequilibrium may exist between the recruitment anticipated from the relationship of adult biomass to carrying capacity and the contemporaneous number of recruits for minimally 20 y after adult abundance is reduced from circa-1980 carrying capacity to biomass. maximum sustainable yield

Why Oyster Restoration Goals In The Chesapeake Bay Are Not And Probably Cannot Be Achieved

Efforts to restore the native oyster in the Chesapeake Bay enjoy enormous public support and have consumed and continue to consume vast, some would argue unreasonable and unjustifiable, amounts of funding. Despite this support the stated goals of restoration efforts are poorly defined and consequently provide no realistic measures of success in terms of time, space, or biomass. Quantitative approaches used successfully in management of and rebuilding plans for other marine and estuarine species have not been appropriately applied. Basic information in oyster population dynamics and ecology has been inadequately appreciated in defining the quantitative problem. Given these limitations it is not surprising that little success has been achieved despite the massive investment. We note a lack of ability to predict recruitment, and limit the ingress and impact of disease. Without control of both of these functions, populations cannot be managed in a self-sustaining rebuilding mode within the footprint that they either currently occupy or formerly occupied. Sustained expansion of that footprint through substrate provision is prohibitively expensive, beyond the limits set by availability of substrate material, and futile in the presence of disease and susceptible oysters. Without attaining a substantially increased and rebuilding population, ecological services will be limited. Water quality impacts will, in reality, be modest, local and seasonal, and still subject to being overwhelmed by periodic storm events. Coherent and rational evaluation of biological limitations will lead to more realistic, and indeed very modest goals for ecological restoration. We must accept the fact that efforts to date to restore native oyster populations have failed and the prognosis for improvement of this situation is continued failure. The argument is proffered that stabilizing the present bed footprint with a realistic and sustainable population and the promotion of aquaculture to increase commercial yield is a more predictable and stable economic investment. Each of these options is consistent with the most realistic ecological outcome and should take priority in future efforts

Biological reference points for Atlantic surfclam (Spisula solidissima) in warming seas

Atlantic surfclam (Spisula solidissima) are a large, commercially important shellfish in the United States faced with several important management challenges. Compared to many harvested fish and shellfish, their life history is relatively unknown. They are undergoing contraction in the southern and inshore parts of their range, as well as expansion into deeper water. Atlantic surfclam are thermally sensitive, and the changes in their distribution track changes in maximum bottom temperature. Sessile species cannot emigrate and are limited to recruitment and mortality as mechanisms for redistribution in response to changing climate. Management of Atlantic surf clam should account for these challenges. We describe a simulation designed to calculate biological reference points that will work well for Atlantic surfclam relative to biological and fishery goals, over a range of life history parameters, assessment uncertainties, and increases in temperature. Simulations of the trade-off between somatic growth and mortality under increased temperature led to target fishing mortality rates higher than the status quo, but also to increased variability in yield. Results suggest that increasing temperature may adversely affect the Atlantic surfclam industry, which prefers stable catches to short term increases in yield, due to market limitations. The results of this analysis are specific to Atlantic surfclam, but the methods described here could be used to enhance management for other harvested species facing similar challenges

Using Multi-Instructional Teaching and Technology-Supported Active Learning Strategies to Enhance Student Engagement

University professors are developing an increasing awareness of how creative teaching is contributing to active learning in the classroom. Much is being learned from research that explores the significance of engaging students in activities designed to increase their learning. This article examines essential components of active learning, discusses ways in which multi-instructional teaching and technology can be used to generate active learning in the classroom, and provides examples of strategies, models, and tools that can be implemented to enhance student engagement and active learning in today\u27s classroo

Decadal Trends In Age Structure And Recruitment Patterns Of Ocean Quahogs Arctica Islandica From The Mid-Atlantic Bight In Relation To Water Temperature

Occan quahogs (Arctica islandica) are long-lived bivalves. Distributionl patterns and biology of ocean quahogs ill the Mid-Atlantic Bight (MAB) off the cast coast of North America are directly related to bottom water temperatures. We examined long term recruitment patterns for ocean quahogs across temporal (decadal) and spatial (latitudinal. bathymetric) scales Using a spatially defined (Long Island Sound to Chesapeake Bay mouth) population encompassing a broad size (age) range of animals that had not yet recruited to the commercial fishery [(SL)], An age-at-length relationship for quahogs less than 80 mm SL is described using a power function. Quahog age did not vary significantly with depth or region, nor were any interaction terms between age and length with depth or region significant. An age-length key was developed for ocean quahogs to generate age frequencies for each station. Principal components analysis (PCA) oil the resulting age-frequency distributions standardized per low enabled construction of characteristic age-frequency distributions for similar stations identified by the PCA factor scores. These characteristic age-frequency distributions identified quahog cohorts with modal ages corresponding to recruitment during the 1948-1950. 1954-1959 1972-1980 and 1978-1983 time periods. Observed recruitment patterns in MA B ocean quahogs are strongly related to bottom water temperature patterns. Years it) Which the number of months with water temperatures averaging 6 degrees C to 10 degrees C exceeds the number of months with water temperatures less than 6 degrees C by at least two months are also years that contriute Strongly to the modal year classes in the population age-frequency distributions. In general. years with above average bottom water temperatures during January, February. and March lend to produce year classes that are distinct in the age-frequency distributions front the MAB (quahog populations. The observed time series of quahog recruitment Operates at a different time scale than stock surveys and most estimates of fishery dynamics. The 50-60-y lag between quahog recruitment to the benthos and recruitment to the fishery presents challenges for fishery forecasting in that changes in adult biomass and subsequent effects oil stock-recruit relationships will only become evident oil this this scale