Scallop dredging has profound, long-term impacts on maerl habitats

Maerl beds are mixed sediments built by a surface layer of slow-growing, unattached coralline algae that are of international conservation significance because they create areas of high biodiversity. They are patchily distributed throughout Europe (to ∼ 30 m depth around the British Isles and to ∼ 120 m depth in the Mediterranean) and many are affected by towed demersal fishing. We report the effects of Newhaven scallop dredges on a previously unfished maerl bed compared with the effects on similar grounds that have been fished commercially in the Clyde Sea area, Scotland. Sediment cores were taken to assess the population density of live maerl thalli prior to scallop dredging on marked test and control plots. These plots were then monitored biannually over a four-year period. Live maerl thalli were sparsely distributed at the impacted site, and experimental dredging had no discernible effect on their numbers. The previously unfished ground had dense populations of live maerl and scallops (both Aequipecten opercularis and Pecten maximus). While counts of live maerl remained high on the control plot, scallop dredging led to a >70% reduction with no sign of recovery over the subsequent four years. The vulnerability of maerl and associated benthos (e.g., the delicate bivalve, Limaria hians) is discussed in relation to towed demersal fishing practices. © 2000 International Council for the Exploration of the Sea

Observations and possible function of the striking anterior coloration pattern of Galathea intermedia (Crustacea: Decapoda: Anomura)

Galathea intermedia is common, but cryptic, on Clyde maerl deposits where it lives in small groups of mixed sex and age, sharing shelters (typically dead Dosinia shells) to avoid predation. Its appearance is marked by six iridescent blue spots which may play an important role in intra- or interspecific interactions

An experimental study of the ecological impacts of hydraulic bivalve dredging on maerl

This paper describes the main characteristics of sardine schools detected in the Spanish-Atlantic surveys carried out from 1992 to 1997 (except 1994). A series of parameters were obtained for each school (morphological, positional and energetic) as well as environmental factors (temperature and salinity). The relationships between the school parameters were analyzed by a PCA and then the school parameters per se were described using both univariate and multivariate analyses (Box-plots, ANOVAs, MANOVA, and discriminant analysis). The results show that significant differences exist between years and geographic areas in that the Rías Baixas schools were smaller in size and of higher density than those from the Cantabric area. These differences could be related to the facts that the Rías Baixas is a nursery zone and sardine length and age are smaller than in the Cantabric Sea. It would seem that the differences in school morphology and energetic characteristics related to length and age of individuals allow us to distinguish between the sardine echo traces in this area. There is a high annual variability in the number of schools and this is not a function of either survey design or strategy and it is not related to the abundance estimates of sardine. These results are important for both future species identification and the improvement of survey design and strategy.

Development of Eagle3D solver for wall modeled LES of transonic flows

Wall modeled Large Eddy Simulation (LES) is an area of interest due to its ability to lower computational costs of LES simulation. Even with the application of wall models, LES still proves to have practicality issues when it comes to use in industry, due to the expertise, time, and computational resources required to get results. A case described by an axisymmetric transonic bump is explored utilizing the Embry-Riddle Aeronautical Universities in house unstructured finite volume multi-element CFD code, Eagle3D. Eagle3D, has been brought to the state of the art and validated against current research using this transonic bump case as a benchmark. Added to Eagle3D includes features such as an HLLC and skew symmetric scheme switched via Ducros sensor, integrated Synthetic Eddy Method (SEM) such that realistic turbulence can be produced at domain inlets, and the implementation of a wall model. Additionally, a novel technique for generating a lean LES grid is explored. The technique utilizes a RANS solution to extract turbulence information and infer a lean grid optimized for wall modeled LES. The solution found by the generated grid is then compared against the validation cases ran in Eagle3D

Development of Eagle3D Solver For Wall Modeled LES of Transonic Flows

Wall modeled Large Eddy Simulation (LES) is an area of interest due to its ability to lower computational costs of LES simulation. Even with the application of wall models, LES still proves to have practicality issues when it comes to use in industry, due to the expertise, time, and computational resources required to get results. A case described by an axisymmetric transonic bump is explored utilizing the Embry-Riddle Aeronautical Universities in house unstructured finite volume multi-element CFD code, Eagle3D. Eagle3D, has been brought to the state of the art and validated against current research using this transonic bump case as a benchmark. Added to Eagle3D includes features such as an HLLC and skew symmetric scheme switched via Ducros sensor, integrated Synthetic Eddy Method (SEM) such that realistic turbulence can be produced at domain inlets, and the implementation of a wall model. Additionally, a novel technique for generating a lean LES grid is explored. The technique utilizes a RANS solution to extract turbulence information and infer a lean grid optimized for wall modeled LES. The solution found by the generated grid is then compared against the validation cases ran in Eagle3D

The impact of Rapido trawling for scallops, Pecten jacobaeus (L.), on the benthos of the Gulf of Venice

Rapido trawls are used to catch sole around the coast of Italy and to catch scallops in the northern Adriatic Sea but little is known about the environmental impact of this gear. Benthic surveys of a commercial scallop ground using a towed underwater television (UWTV) sledge revealed an expansive area of level, sandy sediment at 25 m characterized by high population densities of scallops (2.82 m-2 Aequipecten opercularis but fewer Pecten jacobaeus) together with ophiuroids, sponges, and the bivalve Atrina fragilis. Rapido trawls were filmed in action for the first time, providing information on the selectivity and efficiency of the gear together with its impact on the substratum and on the benthos. The trawls worked efficiently on smooth sand with ca. 44% catch rate for Pecten jacobaeus, of which 90% were >7 cm in shell height. Most organisms in the path of the trawl passed under or through the net; on average by-catch species only formed 19% of total catch by weight. Of the 78 taxa caught, lethal mechanical damage varied from 50% in soft-bodied organisms such as tunicates. A marked plot surveyed using towed UWTV before, then 1 and 15 h after fishing by Rapido trawl showed clear tracks of disturbed sediment along the trawl path where infaunal burrow openings had been erased. Abundant, motile organisms such as Aequipecten showed no change in abundance along these tracks although scavengers such as Inachus aggregated to feed on damaged organisms. There were significant decreases in the abundance of slow-moving/sessile benthos such as Pecten, Holothuria, and Atrina. Juvenile pectinids were abundant on the shells of Atrina. The introduction of a scheme of areas closed to trawling would protect highly susceptible organisms such as Atrina and enhance the chances of scallop recruitment to adjacent areas of commercial exploitation

AN ANALYSIS OF USMC SERVICE CONTRACTS UNDER THE SIMPLIFIED ACQUISITION THRESHOLD, AND THE EFFECTS CAUSED BY CONTINUING RESOLUTIONS

Daily operations within the United States Marine Corps (USMC) are reliant upon the effective and uninterrupted operations of services contracts in both garrison and field environments. From fiscal years 2010–2021, the federal government began the fiscal year with a continuing resolution (CR) in 11 out of 12 years. With the consistency of budget uncertainties at the onset of every fiscal year, purchasing and operations are affected resulting in interruptions to services. Additionally, across the Marine Corps, there is no organizational level standard operating procedures (SOP) for budget execution under a CR. Meshing CRs and the lack of standardization across the organization has potential to affect the deliverability of services. Analyzing data received from a Purchase Request Builder across fiscal years with and without CRs can develop a better understanding of what types of services, dollar amounts, and time are affected most by CRs. This project aims to better identify and understand efficiencies that can be implemented to affect services contracting when operating under a CR and provides recommendations that increase effectiveness of using unit and contracting professionals.Captain, United States Marine CorpsCaptain, United States Marine CorpsApproved for public release. Distribution is unlimited