SCUBA Surveys Research Articles

Quantity, Structure, and Habitat Selection of Natural Spawning Reefs by Walleyes in a North Temperate Lake: A Multiscale Analysis

AbstractSpawning habitat, the cornerstone of self‐sustaining, naturally reproducing walleye Sander vitreus populations, has received limited quantitative research. Our goal was to quantitatively describe the structure and quantity of natural walleye spawning habitat and evaluate potential selection of habitat in Big Crooked Lake, Wisconsin. In 2004 and 2005, we located and delineated walleye egg deposition polygons through visual snorkel and scuba surveys. We also delineated recently deposited, adhesive egg patches daily along one spawning reef in 2005. To determine habitat selection, we quantified and compared spawning and lakewide available habitat at different scales. In both years, walleyes used similar spawning habitat, including three geomorphic types: linear shorelines, a point bar, and an island. Walleyes used only 14% of the entire lake shoreline and 39% of the shoreline comprised of gravel (6.4–76.0 mm), cobble (76.1–149.9 mm), or coarser substrates for spawning in 2005, indicating selection of specific spawning habitat. Lakewide, walleyes spawned close to shore (outer egg deposition polygon boundary mean distance = 2.7 m), in shallow water (outer egg deposition polygon boundary mean depth = 0.3 m), and over gravel substrate (percent coverage mean = 64.3) having low embeddedness (mean = 1.30). Our best nearshore (0–13‐m) resource selection function predicted an increase in the relative probability of egg deposition with the increasing abundance of gravel, cobble, and rubble (150.0–303.9‐mm) substrates and a decrease with increasing distance from shore and water depth (89.9% overall correct classification). Adhesive egg patches confirmed that walleyes actively chose nearshore, shallow‐water, and coarse‐substrate spawning habitat. The quantitative habitat information and predictive models will assist biologists in developing walleye spawning reef protection strategies and potentially aid in designing and evaluating artificial spawning reefs.

Unusual pattern of embryogenesis of Caryophyllia inornata (scleractinia, caryophylliidae) in the mediterranean sea: Maybe agamic reproduction?

While knowledge of the reproductive biology of tropical scleractinian corals is extensive, information from temperate zones is limited. The aim of this study is to describe the reproductive biology of Caryophyllia inornata, a temperate species, and to increase the understanding of the reproductive strategies of Mediterranean corals. Samples of C. inornata were collected during SCUBA surveys at Elba island. Sexually active individuals displayed either male or female germ cells, showing a gonochoric sexuality. C. inornata exhibited an unusual pattern of embryogenesis. Embryos appeared throughout the whole year in males and in sexually inactive individuals, and they did not show a seasonal pattern of development, as usually expected for sexual reproduction. This observation suggests the possibility of asexual origin. These embryogenetic sexually inactive individuals were larger in size than the embryogenetic sexually active ones, and they might be senile polyps that preserve the ability to produce embryos only by agamic reproduction.

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.

Collaborative assessment of California spiny lobster population and fishery responses to a marine reserve network

Assessments of the conservation and fisheries effects of marine reserves typically focus on single reserves where sampling occurs over narrow spatiotemporal scales. A strategy for broadening the collection and interpretation of data is collaborative fisheries research (CFR). Here we report results of a CFR program formed in part to test whether reserves at the Santa Barbara Channel Islands, USA, influenced lobster size and trap yield, and whether abundance changes in reserves led to spillover that influenced trap yield and effort distribution near reserve borders. Industry training of scientists allowed us to sample reserves with fishery relevant metrics that we compared with pre-reserve fishing records, a concurrent port sampling program, fishery effort patterns, the local ecological knowledge (LEK) of fishermen, and fishery-independent visual surveys of lobster abundance. After six years of reserve protection, there was a four- to eightfold increase in trap yield, a 5-10% increase in the mean size (carapace length) of legal sized lobsters, and larger size structure of lobsters trapped inside vs. outside of three replicate reserves. Patterns in trap data were corroborated by visual scuba surveys that indicated a four- to sixfold increase in lobster density inside reserves. Population increases within reserves did not lead to increased trap yields or effort concentrations (fishing the line) immediately outside reserve borders. The absence of these catch and effort trends, which are indicative of spillover, may be due to moderate total mortality (Z = 0.59 for legal sized lobsters outside reserves), which was estimated from analysis of growth and length frequency data collected as part of our CFR program. Spillover at the Channel Islands reserves may be occurring but at levels that are insufficient to influence the fishery dynamics that we measured. Future increases in fishing effort (outside reserves) and lobster biomass (inside reserves) are likely and may lead to increased spillover, and CFR provides an ideal platform for continued assessment of fishery-reserve interactions.

Combining geomorphologic, biological and accessibility values for marine natural heritage evaluation and conservation

Natural heritage is the complex of geomorphologic and biological elements worthy of conservation. 2. Especially in the marine environment, conservation effort is often focused on the biological elements only, while multi-disciplinary approaches, including abiotic elements and social issues, are needed. 3. A procedure to evaluate the Marine Natural Heritage (MNH) as a whole, integrating geomorphology and biology, was tested in two coastal areas in the Ligurian Sea (NW Mediterranean): Punta Manara, a European Site of Community Interest (SCI), and Finale - Vado Ligure (non-SCI). In each area, scuba surveys were carried out at six sites to categorize subtidal landforms and habitats, and these were then used as evaluation units for assigning scores to subcategories of both geomorphological (Integrity, Representativeness, Rarity, Paleogeographic, Aesthetic) and biological (Naturalness, Vulnerability, Rarity, Economic, Aesthetic) categories. 4. Four sites in the area of Punta Manara obtained high scores, thus fully justifying the special management measures required for SCI implementation. However, two sites in the Finale - Vado Ligure area exhibited biological heritage values higher than those of Punta Manara, while a third site exhibited values comparable with those of Punta Manara when considering both biology and geomorphology. This highlighted the presence of features worth conserving also in non-SIC situations. 5. Accessibility to scuba divers was evaluated by means of a simple scheme, and added information on the perception of MNH in the study sites. 6. It is suggested that the evaluation system may be used, with appropriate benchmarking, in other areas for the selection of sites proposed for legal protection or special management measures, based on their natural heritage values. Copyright # 2011 John Wiley & Sons, Ltd.

Predator–prey dynamics between recently established stone crabs (Menippe spp.) and oyster prey (Crassostrea virginica)

Range expansion and population establishment of individual species can have significant impacts on previously established food webs and predator–prey dynamics. The stone crab (Menippe spp.) is found throughout southwestern North Atlantic waters, from North Carolina through the Gulf of Mexico and the Central American Caribbean, including the Greater Antilles. Recent observations suggest that stone crabs have become better established on certain oyster reefs in North Carolina than in the early 1900s when they we first observed in NC. To assess the predatory impact of stone crabs on oysters, we (1) quantified stone crab densities on subtidal oyster reefs in Pamlico Sound, NC using scuba surveys, and (2) conducted laboratory predation experiments to assess the functional response of stone crabs to varying densities of oysters. We then (3) analyzed previously unpublished functional response data on another important oyster predator, the mud crab Panopeus herbstii. Finally, we (4) compared and contrasted potential predatory impacts of stone, mud and blue crabs (Callinectes sapidus). The functional response data and analyses for both stone crabs and mud crabs were consistent with a type II functional response. Mud crabs, on a m2 basis, inflicted the highest proportional mortality on oysters over a 24 hour period, followed by stone and then blue crabs. Proportional mortality did not vary significantly with oyster size; however, relatively small and large oysters were consumed disproportionately less than medium-sized oysters, likely due to the mechanical inability of stone crabs to handle small oysters, and the inability to crush large oysters. Although stone crabs appear to be established in Pamlico Sound at densities equivalent to densities in other systems such as the U.S. Florida Panhandle, their predatory activities on oysters are not expected to have as significant a negative impact on oyster populations compared to other resident predators such as mud crabs.

Deep 1.1 mm-wavelength imaging of the GOODS-S field by AzTEC/ASTE - I. Source catalogue and number counts

[Abridged] We present the first results from a 1.1 mm confusion-limited map of the GOODS-S field taken with AzTEC on the ASTE telescope. We imaged a 270 sq. arcmin field to a 1\sigma depth of 0.48 - 0.73 mJy/beam, making this one of the deepest blank-field surveys at mm-wavelengths ever achieved. Although our GOODS-S map is extremely confused, we demonstrate that our source identification and number counts analyses are robust, and the techniques discussed in this paper are relevant for other deeply confused surveys. We find a total of 41 dusty starburst galaxies with S/N >= 3.5 within this uniformly covered region, where only two are expected to be false detections. We derive the 1.1mm number counts from this field using both a "P(d)" analysis and a semi-Bayesian technique, and find that both methods give consistent results. Our data are well-fit by a Schechter function model with (S', N(3mJy), \alpha) = (1.30+0.19 mJy, 160+27 (mJy/deg^2)^(-1), -2.0). Given the depth of this survey, we put the first tight constraints on the 1.1 mm number counts at S(1.1mm) = 0.5 mJy, and we find evidence that the faint-end of the number counts at S(850\mu m) < 2.0 mJy from various SCUBA surveys towards lensing clusters are biased high. In contrast to the 870 \mu m survey of this field with the LABOCA camera, we find no apparent under-density of sources compared to previous surveys at 1.1 mm. Additionally, we find a significant number of SMGs not identified in the LABOCA catalogue. We find that in contrast to observations at wavelengths < 500 \mu m, MIPS 24 \mu m sources do not resolve the total energy density in the cosmic infrared background at 1.1 mm, demonstrating that a population of z > 3 dust-obscured galaxies that are unaccounted for at these shorter wavelengths potentially contribute to a large fraction (~2/3) of the infrared background at 1.1 mm.

Complementary Sampling Methods to Inform Ecosystem-Based Management of Nearshore Fisheries

Area-based fishery management and ecosystem-based management strategies are considered beneficial marine resource management tools, but they require finite information about the structure and function of ecosystems to evaluate populations and describe the effects of fishing on ecosystems. The required information is not likely to be obtained from sporadic, fishery-dependent data collected from data-poor fisheries, and funding constraints preclude extensive fishery-independent surveys. This situation has led to an interest in relating or combining information from a variety of disparate sampling methods. From 2003 to 2006, we investigated the relationships between estimates of catch per unit effort (CPUE) and the abundance of fishes generated from typical nearshore commercial fishing operations and estimates of density and abundance derived from scuba surveys in the same locations. The relationships between CPUE and the density estimates derived from different sampling methods were found to be statistically significant in the case of many of the common species sampled across sites in Carmel Bay, California. The compounding effects of within-sample variance and the error associated with the regression equations, however, would result in poor confidence in the values translated from one sampling method to another. Different sampling methods may provide reasonable estimates of population trends, but they are sufficiently different and variable as to preclude the use of a scaling factor to standardize population estimates among sampling methods. Also, the differences in species composition (i.e., relative CPUE or density among species) produced by each sampling method were significant and were also affected by habitat relief and sample depth. Nonetheless, our results suggest the value of a cost-benefit analysis that would allow managers to design optimal sampling strategies for characterizing CPUE relationships within a region of interest. A sampling program that benefits from the complementary strengths of fishing gear and scuba sampling will probably result in the most comprehensive description of nearshore fish assemblages.

Estimating dispersal from genetic isolation by distance in a coral reef fish (Hypoplectrus puella)

The spatial scale of dispersal in coral reef fishes eludes ecologists despite the importance of this parameter for understanding the dynamics of ecological and evolutionary processes. Genetic isolation by distance (IBD) has been used to estimate dispersal in coral reef fishes, but its application in marine systems has been limited by insufficient sampling at different spatial scales and a lack of information regarding population density. Here, we present an analysis of IBD in the barred hamlet (Hypoplectrus puella, Serranidae) at spatial scales ranging from 10 to 3200 km complemented with SCUBA surveys of population densities covering 94000 m2 of reef. We used 10 hypervariable DNA markers to genotype 854 fish from 15 locations, and our results establish that IBD in H. puella emerges at a spatial scale of 175 km and is preserved up to the regional scale (3200 km). Assuming a normal or a Laplace dispersal function, our data are consistent with mean dispersal distances in H. puella that range between 2 and 14 km. Such small mean dispersal distances is a surprising result given the three-week pelagic larval duration of H. puella and the low level of genetic structure at the Caribbean scale (Wright's fixation index, F(ST), estimate = 0.005). Our data reinforce the importance of considering population density when estimating dispersal from IBD and underscore the relevance of sampling at local scales, even when genetic structure is weak at the regional scale.

Searching for massive galaxies at z ≥ 3.5 in GOODS-North

We constrain the space density and properties of massive galaxy candidates at redshifts of z>=3.5 in the GOODS-N field. By selecting sources in the Spitzer+IRAC bands, a highly stellar mass-complete sample is assembled,including massive galaxies which are very faint in the optical/near-IR bands that would be missed by samples selected at shorter wavelengths. The z>=3.5 sample was selected down to 23 mag at 4.5 micron using photometric redshifts that have been obtained by fitting the galaxies SEDs at optical, near-IR and IRAC bands. We also require that the brightest band in which candidates are detected is the IRAC 8 micron band in order to ensure that the near-IR 1.6 micron (rest-frame) peak is falling in or beyond this band. We found 53 z>=3.5 candidates, with masses in the range of M~10^10-10^11M_sun. At least ~81% of these galaxies are missed by traditional Lyman Break selection methods based on UV light. Spitzer+MIPS emission is detected for 60% of the sample of z>=3.5 galaxy candidates. Although in some cases this might suggest a residual contamination from lower redshift star-forming galaxies or AGN, 37% of these objects are also detected in the sub-mm/mm bands in recent SCUBA,AzTEC and MAMBO surveys, and have properties fully consistent with vigorous starburst galaxies at z>=3.5. The comoving number density of galaxies with stellar masses >= 5x10^10M_sun(a reasonable stellar mass completeness limit for our sample) is 2.6x10^-5Mpc^-3 (using the volume within 3.5<z<5), and the corresponding stellar mass density is ~2.9x10^6M_sunMpc^-3, or~3% of the local density above the same stellar mass limit.For the sub-sample of MIPS-undetected galaxies,we find a number density of ~0.97x10^-5Mpc^-3 and a stellar mass density of ~1.15x10^6M_sun Mpc^-3.[abridged]

The influence of protected area management on the status of coral reefs at Misali Island, Tanzania following the 1998 bleaching event in the western Indian Ocean

AbstractThe reefs of Misali Island, Tanzania suffered serious coral mortality as a result of the 1998 coral bleaching event in the western Indian Ocean. Four years after this event, Frontier‐Tanzania assessed reef substrate in Misali Island Marine Conservation Area (MIMCA) using scuba surveys. Substrate cover was compared between sites within and outside the nonextraction zone (NEZ) of MIMCA and recovery rates were estimated through reference to previous studies. Coral recovery at Misali Island following the bleaching event has generally been slow, but nonextractive management of MIMCA has enhanced coral recovery within the NEZ. The absence of fishing activities in the NEZ has sustained herbivorous fish populations and thus reduced algal overgrowth; however, outside the NEZ, diving and anchoring activities have caused further coral damage and led to increased levels of debris. Awareness‐raising programmes could lessen these problems and the NEZ appeared to be well‐placed to capitalize on nonmanageable factors that are thought to mitigate the effects of coral bleaching. In addition, the implementation of flexible zoning schemes could improve recovery rates after future bleaching events.

Star formation in Perseus

Context. In our SCUBA survey of Perseus, we find that the fraction of protostellar cores increases towards higher masses and the most massive cores are all protostellar.

Submillimeter observations of the J2142-4423 Ly$\sf \alpha$ protocluster at z = 2.38

Aims. We present observations aimed at exploring both the nature of Lyα emitting nebulae (Lyα blobs) at z=2.38 and the way they trace large scale structure (LSS), by exploring their proximity to maximum starbursts through submillimeter emission. Our most important objectives are to make a census of associated submillimeter galaxies (SMGs), check their properties, and look for a possible overdensity in the protocluster J2142-4426 at z=2.38. Methods: We used the newly commissioned Large APEX Bolometer Camera (LABoCa) on the Atacama Pathfinder EXperiment (APEX) telescope, in its Science Verification phase, to carry out a deep 10' × 10' map at 870 μm}, and we performed multiple checks of the quality of data processing and source extraction. Results: Our map, the first published deep image, confirms the capabilities of APEX/LABoCa as the most efficient current equipment for wide and deep submm mapping. Twenty-two sources were securely extracted with 870 μm flux densities in the range 3-21 mJy, rms noise ~0.8-2.4 mJy, and far-IR luminosities probably in the range ~5-20 x 10^(12) L_⊙. Only one of the four 50 kpc-extended Lyα blobs has a secure 870 μm counterpart. The 870 μm source counts in the whole area are marginally higher than in the SHADES SCUBA survey, with a possible over-density around this blob. The majority of the 3.6-24 μm SEDs of the submillimeter sources indicate they are starburst dominated, with redshifts mostly ≳2. However, there is evidence of a high-z AGN in ~30% of the sources.

Identification of predators using a novel photographic tethering device

Tethering prey is often used to help determine the impact of predators in aquatic communities. In this study, a novel photographic tethering device was used to make digital recordings of predation events on juveniles of the spiny lobster, Jasus edwardsii. Predation of lobsters was significantly higher during the day (76%) than at night (33.4%). This was consistent with a SCUBA survey that found greater numbers of diurnal predators than nocturnal predators at the study site. However, the abundance of predators was not consistent with the number of predation events for individual species as recorded by the photographic tethering device. The snapper, Pagrus auratus, was the most abundant species at the study site (45% of all diurnally active fishes), but was only responsible for 12% of predation events during the day. In contrast, wrasse species were responsible for the greatest number of predation events during the day (60%), yet made up only a small proportion of the diurnal fish population (25%). The results of this study indicate the importance of determining the identity of potential predators, through the use of a photographic tethering device, for increasing the value of results generated from tethering experiments.

Effects of macroalgal structural complexity on nearshore larval and post-larval crab composition

Larval and post-larval crab distribution was surveyed in three different habitats in Kachemak Bay, Alaska to determine temporal and spatial variability. Distribution varied temporally and spatially from June 2005 to September 2006. Nine sites of varying habitat complexity were surveyed monthly using scuba surveys and light traps to measure habitat variables and quantify crab zoeae and megalopae. A total of 10,016 crabs belonging to seven families were identified. Four species comprised the majority (97%) of the total crab assemblages and included Cancer oregonensis, Fabia subquadrata, Telmessus cheiragonus, and Pugettia gracilis. Peak abundances occurred in summer but varied on small temporal scales with species. No single bay-wide variable determined the appearance of all species. Depending on species, appearance may be influenced by seasonality of environmental variables. Spatially, highest abundances occurred in habitats with less structural complexity. Spatial differences in crab abundance may have resulted from variability on large scale physical transport mechanisms and not kelp-mediated flow alterations.

Abundance estimates of the Indo-Pacific lionfish Pterois volitans/miles complex in the Western North Atlantic

Less than a decade after being observed off Florida, the invasive Indo-Pacific lionfish is now widely distributed off the southeast coast of the United States. As a step towards measuring invasion impacts to native communities, we examine the magnitude and extent of this invasion by first, compiling reports of lionfish to provide range information and second, estimate lionfish abundance from two separate studies. We also estimate native grouper (epinepheline serranids) abundance to better assess and compare lionfish abundances. In the first study we conducted SCUBA diver visual transect surveys at 17 different locations off the North Carolina coast in water depths of 35–50 m. In the second study, we conducted 27 Remote Operated Vehicle (ROV) transect surveys at five locations from Florida to North Carolina in water depths of 50–100 m. In both studies, lionfish were found to be second in abundance only to scamp (Mycteroperca phenax). Lionfish were found in higher abundance in the shallower North Carolina SCUBA surveys (\(\bar{x}= 21.2\) ha−1) than in the deep water ROV surveys (\(\bar{x} = 5.2\) ha−1). Lionfish reports continue to expand most recently into the Bahamas, raising the specter of further spread into the Caribbean and Gulf of Mexico. The potential impacts of lionfish to native communities are likely to be through direct predation, competition and overcrowding. The high number of lionfish present in the ecosystem increases the potential for cascading impacts throughout the food chain. Within the southeast region the combined effects of climate change, overfishing and invasive species may have irreversible consequences to native communities in this region.

The Bryozoa of subantarctic Marion and Prince Edward Islands: illustrated keys to the species and results of the 1982–1989 University of Cape Town surveys

The Bryozoa of subantarctic Marion and Prince Edward Islands were sampled over the period 1982–1989 by dredging, SCUBA-diving and intertidal surveys. This paper comprises illustrated keys to all 82 species of Bryozoa collected during these and previous surveys, including 15 new species, 17 new records and 8 species identified to generic level. Summaries are provided of the depth distributions, abundances and habitats of the species. In all, 15 species were recorded in the shallow subtidal SCUBA surveys with Bicrisia edwardsiana in 70% of these samples, Celleporella bougainvillei and Celleporella alia in 58%, Figularia philomela in 47% and Fenestrulina majuscula in 44%. A total of 78 species was recorded from the dredged survey.

Impact of fish farms on maerl beds in strongly tidal areas

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 326:1-9 (2006) - doi:10.3354/meps326001 Impact of fish farms on maerl beds in strongly tidal areas Jason Hall-Spencer1,*, Nicola White2, Ewan Gillespie3, Katie Gillham4, Andy Foggo1 1Plymouth Marine Institute, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK 2Haskoning UL Ltd, Elizabeth House, Emperor Way, Exeter EX1 3QS, UK 3Scottish Environment Protection Agency, Dingwall IV7 9X8, UK 4Scottish Natural Heritage, Westercraigs, Inverness IV3 8NW, UK *Email: jhall-spencer@plymouth.ac.uk ABSTRACT: In Scotland, Atlantic salmon Salmo salar cages are being moved out of areas with slow water movements, to disperse wastes and reduce impacts on benthic communities. This first study of the effects of fish farms on maerl beds (red algal coralline gravels of high conservation importance) demonstrated major impacts on the benthos, even in strongly tidal areas. SCUBA surveys of 3 fish farms located over maerl revealed a build-up of waste organic matter and 10 to 100-fold higher abundances of scavenging fauna (e.g. Necora puber, Pagurus bernhardus) than on 6 reference maerl beds. Visible waste was noted up to 100 m from cage edges, and all 3 farms caused significant reductions in live maerl cover, upon which this habitat depends. Near-cage infaunal samples showed significant reductions in biodiversity, with small Crustacea (ostracods, isopods, tanaids and cumaceans) being particularly impoverished in the vicinity of cages, and significant increases in the abundance of species tolerant of organic enrichment (e.g. Capitella spp. complex, Ophryotrocha hartmanni). Relocation of fish farms to areas with strong currents is unlikely to prevent detrimental effects to the structure and organisation of the benthos, and ‘fallowing’ (whereby sites are left unstocked for a period of time to allow benthic recovery) is inadvisable where slow-growing biogenic habitats such as maerl are concerned, as this may expand the area impacted. KEY WORDS: Salmon farming · Maerl · Organic enrichment · Benthos · Scotland Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 326. Online publication date: November 17, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

A SCUBA survey of L1689 - the dog that didn't bark

We present submillimetre data for the L1689 cloud in the ρ Ophiuchi molecular cloud complex. We detect a number of starless and pre-stellar cores and protostellar envelopes. We also detect a number of filaments for the first time in the submillimetre continuum that are parallel both to each other, and to filaments observed in the neighbouring L1688 cloud. These filaments are also seen in the 13 CO observations of L1689. The filaments contain all of the star-formation activity in the cloud. L1689 lies next to the well-studied L1688 cloud that contains the ρ Oph-A core. L1688 has a much more active star-formation history than L1689 despite their apparent similarity in 13 CO data. Hence, we label L1689 as the dog that didn’t bark. We endeavour to explain this apparent anomaly by comparing the total mass of each cloud that is currently in the form of dense material such as pre-stellar cores. We note firstly that L1688 is more massive than L1689, but we also find that when normalized to the total mass of each cloud, the L1689 cloud has a much lower percentage of mass in dense cores than L1688. We attribute this to the hypothesis of Loren that the star formation in the ρ Ophiuchi complex is being affected and probably dominated by the external influence of the nearby Upper Scorpius OB association and predominantly by σ Sco. L1689 is further from σ Sco and is therefore less active. The influence of σ Sco appears none the less to have created the filaments that we observe in L1689.

Quasars in the MAMBO blank field survey

Our MAMBO 1.2 mm blank field imaging survey of ∼0.75 sqd has uncovered four unusually bright sources, with flux densities between 10 and 90 mJy, all located in the Abell 2125 field. The three brightest are flat spectrum radio sources with bright optical and X-ray counterparts. Their mm and radio flux densities are variable on timescales of months. Their X-ray luminosities classify them as quasars. The faintest of the four mm bright sources appears to be a bright, radio-quiet starburst at z ∼ 3, similar to the sources seen at lower flux densities in the MAMBO and SCUBA surveys. It may also host a mildly obscured AGN of quasar-like X-ray luminosity. The three non-thermal mm sources imply an areal density of flat spectrum radio sources higher by at least 7 compared with that expected from an extrapolation of the lower frequency radio number counts.