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In this paper we discuss the mechanical design of the GIRMOS Cryostat. GIRMOS is an adaptive optics fed multi-object Integral-Field Spectrograph with a parallel imaging capability and will be installed at the Gemini North Observatory. This instrument includes four separate identical spectrograph channels arranged symmetrically around the central axis of the instrument which provide it its multiplexing capability. Each spectrograph channel starts off at the object selection mechanism. The object selection mechanism contains four motorized fold mirror assemblies which scan the incoming light from the telescope to look at four separate objects simultaneously or combine their efforts to look at a single object in a tiled mode. Each of the four individual beams from the object selection system are then directed into the instrument dewar via separate entrance windows. Within the dewar each IFS beam moves through an anamorphic relay, an optical image slicer assembly and eventually makes it to a Spectrograph unit. All of these assemblies are located on a single cold bench within the dewar. The instrument imager is located along the central axis of the dewar and is housed in the cold bench as well. In this paper we will provide some details regarding the Cryostat design, the mechanical packaging of the IFS and imager along with some of the thermal load mitigation techniques employed. We will also discuss some key performance requirements that were expected from the Cryostat and the design choices we made in order to achieve them.

After more than six years of successful operation at Gemini South, the Gemini Planet Imager (GPI) will be moved to Gemini-North. During this move, the instrument will undergo a series of upgrades. One of these upgrades will be the installation of a new pyramid wavefront sensor (PWFS) with a low noise EMCCD detector that will replace the current Shack-Hartmann WFS. This upgrade is expected to significantly increase the sky coverage of GPI, providing increased level of AO correction and access to fainter targets. The new PWFS will be assembled on a standalone bench that will be aligned and tested independent of the GPI to ensure the required performance is achieved. Once the performance is verified, the completed subassembly will be installed in place of the current WFS hardware during the final integration into the GPI. In this paper, we will present the final design of the new GPI PWFS. Included will be a description of the optical performance simulations completed and their results, and a detailed overview of the opto-mechanical design of the new PWFS bench., SPIE Astronomical Telescopes + Instrumentation, December 14-18, 2020, Online Only, United States, Series: Proceedings of SPIE

Knowledge of aquaculture–environment interactions is essential for the development of a sustainable aquaculture industry and efficient marine spatial planning. The effects of fish and shellfish farming on sessile wild populations, particularly infauna, have been studied intensively. Mobile fauna, including crustaceans, fish, birds and marine mammals, also interact with aquaculture operations, but the interactions are more complex and these animals may be attracted to (attraction) or show an aversion to (repulsion) farm operations with various degrees of effects. This review outlines the main mechanisms and effects of attraction and repulsion of wild animals to/from marine finfish cage and bivalve aquaculture, with a focus on effects on fisheries-related species. Effects considered in this review include those related to the provision of physical structure (farm infrastructure acting as fish aggregating devices (FADs) or artificial reefs (ARs), the provision of food (e.g. farmed animals, waste feed and faeces, fouling organisms associated with farm structures) and some farm activities (e.g. boating, cleaning). The reviews show that the distribution of mobile organisms associated with farming structures varies over various spatial (vertical and horizontal) and temporal scales (season, feeding time, day/night period). Attraction/repulsion mechanisms have a variety of direct and indirect effects on wild organisms at the level of individuals and populations and may have implication for the management of fisheries species and the ecosystem in the context of marine spatial planning. This review revealed considerable uncertainties regarding the long-term and ecosystem-wide consequences of these interactions. The use of modelling may help better understand consequences, but long-term studies are necessary to better elucidate effects.

The productivity of a bivalve farm is largely determined by the availability of organic seston and the level of competition for that naturally limited resource. Farm production may also be curtailed by regulatory or certification frameworks concerned with controlling biodeposition, i.e. the sedimentation of organic material. Fouling communities dominated by filter-feeding tunicates which both compete for food resources and increase biodeposition levels thus have the potential to further limit bivalve farm productivity. In the present study a farm-scale modelling approach was used to quantify the effects of the tunicate Ciona intestinalis on longline mussel farms. Both cultured and fouling species were simulated using physiological modules that took into account their interactions with organic seston dynamics in terms of filtration and biodeposition, and also predicted their growth over a typical growing season. Various treatment scenarios for reducing C. intestinalis infestation levels were also analyzed. Model results showed that C. intestinalis populations can rapidly dominate mussel sleeves in terms of their overall biomass and contribution to organic sedimentation. Early treatments during the tunicate reproductive season were the most effective at controlling the level of infestation and its impacts on sestonic food availability, mussel production and organic sedimentation. The proposed generic modelling approach could potentially become an essential aquaculture management tool, especially in the context of biological invasions. Statement of relevance The growing importance of bivalve aquaculture combined with its vulnerability to environmental conditions compels to ensure its sustainable development and management. Biofouling can potentially disrupt farm productivity and become a nuisance with profound socio-economic consequences. The numerical tool developed in this study provides valuable information for the management and mitigation of fouling by filter-feeding species on mussel farms.

This paper describes the historical development of blue mussel ( Mytilus edulis ) farming in Tracadie Bay (Prince Edward Island, Canada) and relates the spacing of suspended sleeves ( S S ) on longlines to seston uptake. From 1990 to 2001, mussel biomass in Tracadie Bay increased by a factor of four (from 1137 to 4743 t). By 2001, seston uptake rates were approximately three-fold water renewal rates, and harvest yields (kg sleeve − 1 ) were significantly lower than in the early 1990s. A one-year field experiment was carried out to determine whether a change in S S could restore harvest yields. We found that S S (10, 20, 40, 60, 80 cm) had no significant effect on the condition index of mussels. However, high S S positively affected shell growth and abundance for small seeds that were densely packed within sleeves. A complete husbandry shift toward high S S and high seeding densities (within sleeves) may enhance farm productivity (production per unit of effort) and curtail seston uptake at the bay scale.

Over the past decade, four exotic tunicates (Styela clava, Ciona intestinalis, Botrylloides violaceus and Botryllus schlosseri) have been reported in the Brudenell estuary in Prince Edward Island (PEI), Canada. Styela clava was the first exotic tunicate to arrive in 1997, rapidly establishing, spreading, invading, and eventually becoming a nuisance in several estuaries of PEI. In the Brudenell estuary, S. clava remained the only exotic nuisance tunicate until 2003. In the fall of 2004, the vase tunicate C. intestinalis, was reported in low abundance, followed by the two colonial species, B. schlosseri and B. violaceus, reported in the spring of 2005. The abundance of C. intestinalis rapidly increased post-introduction, eventually replacing S. clava as the foremost nuisance species on mussel farms in the estuary. To date, C. intestinalis continues to colonize this estuary at epidemic proportions, resulting in the continuing drop of S. clava abundance. The current abundance of C. intestinalis is estimated at 5 cm−2, which is similar to S. clava abundance at its height in 2003. The 2006 abundance of S. clava is estimated to have fallen to near 0 cm−2. The dominance of C. intestinalis as a fouling organism on mussel farms is considered a serious threat to this aquaculture industry, mainly due to its unmanageable weight. The process of the detection, establishment, invasiveness, and eventual rise to nuisance level of exotic tunicates in the Brudenell River is presented.

Bivalves have been grown and transported for culture for hundreds of years and the introduction of some species outside of their native range for aquaculture has been suggested to be one of the greatest modes of introduction of exotic marine species. However, there has yet to be a thorough assessment of the importance of aquaculture and bivalve culture in particular, to the introduction and spread of exotic species. This paper reviews some of the environmental and ecological implications of the relationship between bivalve aquaculture and the introduction and spread of exotic species, management implications and mitigation strategies. Two broad classes of introductions of exotic species may result from activities associated with bivalve aquaculture. First, the intentional introduction of exotic species into an area for aquaculture purposes, i.e. the ''target'' species. These are typically foundation or engineering species and may have a considerable influence on receiving ecosystems. Second, the introduction of species that are either associated with introduced bivalves or facilitated by aquaculture activities (i.e. structures or husbandry practices). These may include both ''hitchhiking'' species (organisms that grow in association with or may be transferred with cultured bivalves) and disease causing organisms. Management options should include the use of risk assessments prior to transfers and quarantines. Various types of mitigation for exotic species have been evaluated but are generally not very successful. Because the risk of exotic species to ecosystems and the bivalve farming industry itself may be great, effort should be directed to better predict and halt introductions of potentially harmful species.

A major problem for the mussel aquaculture industry on Prince Edward Island, Canada surfaced in the late 1990s with the introduction of a fouling organism commonly known as the clubbed tunicate, Styela clava. This organism has the ability to infest mussel cultivation equipment to the point where productivity is severely compromised. This study examined the effects two anti-fouling treatments, air exposure and acetic acid, had on experimental mussel populations. Socked mussel seed obtained from a mussel farm on Prince Edward Island was exposed to three treatment regimes and subsequently placed on a long-line in New London Bay, P.E.I. The treatments were a 40-h air exposure, 30-s 5% acetic acid immersion and a 2-min 5% acetic acid immersion. Treatment effects on mussels were measured after seven months in the field, along with untreated controls. Mussel quality was assessed using mussel sock weights, length, condition index and changes in genetic characteristics measured at allozyme loci. A significant decrease in mean sock weights was found for all three treatments compared to control sock weights (p

In the past decade, many aquatic invasive species have been introduced into Prince Edward Island, Canada, coastal waters, and they have had adverse effects on the aquaculture and fisheries industry. For instance, the mussel aquaculture industry has been overwhelmed by extremely high abundances of the invasive ascidian Styela clava in some areas. To understand and minimize the risk of spread of S. clava to other shellfish aquaculture sites, basic information on the reproductive biology of the ascidian is needed. This study investigated Styela gonad development, larval abundance and recruitment. Gonad development, using histological methods, indicated ovaries were ripe from late June through late October, 2004. Weekly water samples indicated larvae were present from 24 June to 29 October, with a distinct abundance peak in mid-August. Recruitment occurred from 24 June to 21 October. Timing of larval sampling was judged to be a crucial part of evaluating recruitment potential for monitoring purposes and a field experiment was carried out to document spatio-temporal larval concentrations. Data were gathered over 30 h sampling periods on 4 August and 14 September 2004. Water samples were taken simultaneously on an hourly basis at three depths: surface, 2 m and 4 m below the surface. Results indicated peaks in larval abundance were, in most cases, limited to a 3 h time interval in the early afternoon. Larval concentrations increased with water depth.

The first objective of this study was to document the design of subsurface longlines used for the farming of blue mussels ( Mytilus edulis ) in Prince Edward Island (PEI), Canada; the second objective was to identify possible associations between longline design and mussel growth. In 2003, SCUBA divers visited 54 farms distributed in 16 culture embayments; they measured the spacing between longlines and the spacing between individual socks (sleeves) attached to longlines; they also sampled one-year-old mussels for the determination of the shell length, condition index, and sock weight. Here we report a remarkable degree of variation in longline configuration, with the following range of values: 1.2 to 3.0 m for sock length, 1.5 to 29.5 m for longline spacing, 26.4 to 62.4 cm for sock spacing, and 6.2 to 179.9 socks/100 m 2 for stocking density at the farm scale. A negative correlation was found between stocking density at the farm scale and total farming area at the bay scale, suggesting that growers adjusted husbandry in relation to the surrounding level of farming activity. In one major culture bay, Tracadie Bay, measurements were repeated over a three-year period (2002–2004). This monitoring led to the discovery of a coordinated effort by growers in raising the average sock spacing by 30% (+ 11 cm). Multiple regression analyses identified sock spacing as the only explanatory variable correlated with mussel weight in Tracadie Bay. The model suggests that an 11-cm increase in sock spacing can lead to an 18% weight gain for pre-market mussels (∼ 34 mm), the size group investigated in the study. However, this correlation between sock spacing and sock weight was tenuous over the three-year study period, showing up only in 2002. A similar correlation was found between sock spacing and condition index, although only in 2004. We conclude by suggesting that close spacing of mussel socks can negatively affect mussel yield, although only under certain conditions.

Models and tools for assessing the carrying capacity of an area of interest for bivalve culture can be classified according to their level of complexity and scope. In this report, we discuss and outline four hierarchical categories of carrying capacity studies: physical, production, ecological, and social carrying capacity. The assessment of carrying capacity for progressively higher categories of models is based on a sound understanding of preceding categories. We discuss each in brief and the third in more detail as this is the level at which knowledge is the most lacking and for which science may make the most advances. (1) Physical carrying capacity may be assessed by a combination of hydrodynamic models and physical information, ideally presented and analysed within a Geographic Information System (GIS). (2) Most scientific effort to date has been directed towards modelling production carrying capacity and some of the resulting models have been used successfully to this end. Further development of these models should pay attention to (i) better modelling of feedback mechanisms between bivalve culture and the environment, (ii) a consideration of all steps in the culture process (seed collection, ongrowing, harvesting, and processing), and (iii) culture technique. (3) The modelling of ecological carrying capacity is still in its infancy. The shortcomings mentioned for models for production carrying capacity estimates are even greater for ecological carrying capacity models. GIS may be employed to consider interactions between culture activities and sensitive habitats. (4) It is recommended that social carrying capacity be evaluated only after the preceding levels have been completed so that an unbiased assessment is obtained. This however does not exclude direction from managers for scientists as to which factors (such as water clarity, specific habitats, etc.) should be evaluated. The use of expert systems to aid in management decisions is briefly discussed with a suggested application of a fuzzy expert system to this end. (c) 2006 Elsevier B.V. All rights reserved. info:eu-repo/semantics/publishedVersion

The impact of Eastern oyster culture (Crassostrea virginica) on the benthic environment at a shellfish farm in New Brunswick, Canada, was assessed using recommended methods for routine environmental monitoring, specifically measurements of sediment redox and sulfide levels. Maximum culture density was equivalent to 4000 oyster bags per hectare, or a final oyster biomass of 8 kg m− 2. Two culture sites, one with floating bags and one with oyster tables, as well as two reference sites were monitored over 17 months (June 2002–October 2003). Seasonal variations in sediment redox and sulfide levels were observed, but no significant differences were detected between the culture and the reference sites. Biodeposition associated with the oyster biomass contributed to increased sedimentation rates of organic matter at the oyster table site, but there was no indication of organic enrichment in the sediment. Macrofauna biomass, abundance and number of species were higher at the oyster table site than at the other sites in September 2002, but values were similar for all sites in September 2003. In this region of eastern Canada, the bays are typically shallow and the upper layers of the sediment are frequently subjected to re-suspension by wave activity and physical erosion by winter ice. Given these highly dynamic conditions and the relatively low stocking densities per hectare, we would argue that the potential impact of oyster culture on the environment should be assessed on the basis of parameters other than sediment redox and sulfide levels.

Mussel aquaculture on Prince Edward Island (PEI), Canada, is an important but relatively new industry. Although seed manipulation using hatcheries for mussel culture occurs on the west coast of North America, seed supply on the east coast of Canada, including Prince Edward Island (PEI), is based solely on wild collection. Two techniques for culling seed (

The nemertean, Cerebratulus lacteus Verrill (Nemertinea: Heteronemertini), has been identified as an important threat to soft-shell clam (Mya arenariaL.) populations in Atlantic Canada. The biology of this species, however, is still largely unknown. Field and laboratory studies were undertaken in 1998 and 1999 in Prince Edward Island, Canada, to test certain control measures to reduce predation on soft-shell clam populations and to better describe the relationship between C. lacteus and M. arenaria. Field abundance of C. lacteus, M. arenaria and Nereis virens Sars were evaluated in relation to particular habitat modifications that were used as control measures. Sediment manipulations tested were: (1) addition of shells and (2) use of a hydraulic rake. No difference was observed on the abundance of C. lacteus, M. arenaria and N. virens after treatments were applied. In the laboratory, C. lacteus was shown to be an efficient predator of M. arenaria. Clam mortalities reached 100% in the presence of C. lacteus while 0% mortality was observed in its absence. A complementary set of experiments was carried out to see if the sympatric polychaetes N. virens and Glycera dibranchiata Ehlers had any impact on the relationship between C. lacteus and M. arenaria. N. virens showed no impact on C. lacteus predation on clams. The presence of G. dibranchiata significantly reduced the nemertean predation rate. Analysis of clam size selection revealed no significant preference by C. lacteus. Other experimental studies revealed that high predator densities did not impede predation on clams and that C. lacteus preferred soft-shell clams among other commercial bivalve species presented (Mercenaria mercenariaL., Crassostrea virginica Gmelin and Mytilus edulisL.). This study should provide a better understanding of the relationship between C. lacteus and M. arenaria and lead to the development of improved nemertean control measures.

This paper presents an overview of a step scanning mechanism employing a flexure stage coupled with a dynamically aligned mirror used in the SpIOMM (Spectrometre Imageur de l'Observatoire du Mont Megantic) instrument, an Imaging Fourier Transform Spectrometer (IFTS) concept for ground based telescopes produced in collaboration with ABB and Universite Laval. This instrument can acquire spectra of variable resolutions up to R = λ/Δλ = 10 000 from the near UV to the near IR (350 nm to 900 nm). It is designed to fit the f/8 focus of the Mont Megantic (Quebec, Canada) 1.6m optical telescope. The innovative aspect of this instrument compared to other imaging spectrometers is the spatial coverage. The FOV covers spans of 12 arc minutes in diameter with a pixel sampling of 0.55 arc seconds. Hence spectra of more than a million scene elements are acquired at each measurement.