Search

Abstract Electrofishing for razor clams (Ensis spp.) has gained increasing attention as a commercial harvesting technique due to its apparent efficiency and production of high quality product. In this paper, we report results from combining electrofishing with towed video as a novel method for assessing the density and size distribution of Ensis in shallow subtidal environments. Emergent razor clams could be readily identified and measured from the video recordings. Comparisons of video-based length frequency distributions with direct measurements of clams collected by divers confirmed that reconstructed shell lengths were sufficiently accurate for stock evaluation purposes. Forty tows were subsequently completed at four sites along the Ayr coast (Firth of Clyde, Scotland). Only E. siliqua were found at these locations with average densities between 0.3 and 0.8 m−2. The majority of individuals were less than 200 mm in length. Comparing these results with hydraulic dredge surveys conducted in the early 2000s at one of these sites suggests possible declines in overall density and the abundance of larger animals. However, this conclusion should be interpreted cautiously because although electrofishing is thought to be highly efficient, the effects of varying towing speeds, site and environmental conditions on rates of Ensis emergence in the field are not yet fully understood. [ABSTRACT FROM AUTHOR]

There are substantial concerns that increasing levels of anthropogenic noise in the oceans may impact aquatic animals. Noise can affect animals physically, physiologically and behaviourally, but one of the most obvious effects is interference with acoustic communication. Acoustic communication often plays a crucial role in reproductive interactions and over 800 species of fish have been found to communicate acoustically. There is very little data on whether noise affects reproduction in aquatic animals, and none in relation to acoustic communication. In this study we tested the effect of continuous noise on courtship behaviour in two closely-related marine fishes: the two-spotted goby ( Gobiusculus flavescens ) and the painted goby ( Pomatoschistus pictus ) in aquarium experiments. Both species use visual and acoustic signals during courtship. In the two-spotted goby we used a repeated-measures design testing the same individuals in the noise and the control treatment, in alternating order. For the painted goby we allowed females to spawn, precluding a repeated-measures design, but permitting a test of the effect of noise on female spawning decisions. Males of both species reduced acoustic courtship, but only painted gobies also showed less visual courtship in the noise treatment compared to the control. Female painted gobies were less likely to spawn in the noise treatment. Thus, our results provide experimental evidence for negative effects of noise on acoustic communication and spawning success. Spawning is a crucial component of reproduction. Therefore, even though laboratory results should not be extrapolated directly to field populations, our results suggest that reproductive success may be sensitive to noise pollution, potentially reducing fitness. [ABSTRACT FROM AUTHOR]

Marine tidal-stream renewable energy devices (MREDs) are beginning to move from demonstration to early commercial deployment. However, the ecological impacts which may result when large arrays of these devices are deployed are unknown. This uncertainty is placing a considerable burden on developers who must collect biological data through baseline and post-deployment monitoring programs under the Environmental Impact Assessment process. Regulators and other stakeholders are often particularly concerned about impacts on marine vertebrates (fish, seabirds and mammals) because many of these receptors are of high conservation and public concern. Unfortunately monitoring for most marine vertebrates is challenging and expensive, especially in the energetic waters where tidal-stream MREDs will be deployed. Surveys for marine vertebrates often have low statistical power and so are likely to fail to detect all but substantial changes in abundance. Furthermore, many marine vertebrate species have large geographical ranges so that even if local changes in abundance are detected, they cannot usually be related to the wider populations. Much of the monitoring currently being undertaken at tidal-stream MRED development sites is thus leading to a ‘data-rich but information-poor’ (DRIP) situation. Such an approach adds to development costs whilst contributing little to wider ecosystem-based understanding. In the present article we discuss the issues surrounding the impacts of tidal-stream MREDs on marine vertebrates and address the questions regulators, developers and other stakeholders need to consider when agreeing monitoring programs for these receptors. [ABSTRACT FROM AUTHOR]

Fisheries products are globally traded commodities, which have led to varying degrees of social and economic dependency for producing regions. These dependencies become more evident at times of major demand or supply shocks. Resilience to such shocks is intertwined with, and rooted in, the intra-sectoral structure and governance frameworks. This work analyses two large-scale, capital-intensive and export-oriented seafood sectors: Atlantic salmon and North-east Atlantic mackerel, responded to the environmental, economic and geopolitical shocks accompanying their development, from a UK perspective. Intra-firm controls are identified as elements, which have delivered resilience and strength in these two sectors. This work highlights the central, yet different role of the UK government in increasing their resilience and underlying producing regions. Our work contributes to the broader context of regional development and changing global food demand identifying both domestic and external threats to sustainability. Our approach aims to expand the debate around seafood production from ‘food security’ to a transdisciplinary analysis, which incorporates wider economic, social, and ecological sustainability aspects. [ABSTRACT FROM AUTHOR]

Abstract: Over a decade of sampling has shown that there are consistent differences in the sizes of 0-group plaice by late summer comparing 21 nursery sites on the Scottish west coast. However, when young fish were collected from two sites which produce particularly small and large fish and reared using a common garden design, growth rates between fish from the two sites were indistinguishable. Either there is little selection for fast or slow growth up to a few weeks post-settlement, or such effects do not persist sufficiently strongly to influence later growth. There were also no significant correlations between the time-series of fish size comparing sites, although within some sites there was evidence of inter-annual density-dependent effects. Any influences of offshore regional-scale factors, such as sea temperature or pelagic primary productivity on growth thus appear to be heavily modified by local conditions on the nursery grounds. The field observations combined with the experimental results lead us to conclude that the size 0-group plaice attain in late summer is mainly controlled by post-settlement habitat quality. [Copyright &y& Elsevier]

Abstract: We describe a protocol for the preservation, extraction, and detection of plaice (Pleuronectes platessa) DNA from the stomach contents of the brown shrimp, Crangon crangon and the shore crab, Carcinus maenas. These two predatory species are thought to be important sources of mortality of small juvenile plaice on inshore nursery grounds. Previous studies of predation on juvenile plaice have used visual examination of stomach contents but this is time consuming and may under-estimate true predation levels as remains may become unidentifiable due to maceration and digestion. Molecular based tools for detecting the presence of prey tissue in predator stomachs and scat are becoming increasingly used in marine ecology and provide an alternative or complementary approach to visual identification. We sequenced a part of the cytochrome-b region of plaice mitochondrial DNA and designed a species-specific, TaqMan real-time Polymerase Chain Reaction (PCR) based assay which was successfully tested for intra- and inter-species-specificity. For application to predator stomach contents, two tissue preservation and two DNA extraction methods were tested followed by a set of aquarium experiments to determine the effect of digestion time on detectability. The quality of the extracted DNA was comparable for the two preservation and two extraction methods tested and the detectability remained similar for all of them. However, levels of PCR inhibition were significant for samples from both predators but could be overcome using serial dilution and 1.25μg/μl Bovine Serum Albumin to reduce the incidence of false negatives. Successful amplification and detection of plaice DNA from stomach contents was possible up to 24h after ingestion for both predator species. For extracts of C. crangon stomachs the half-life detection rate (T50) was ~10h at water temperatures of 14–16°C. The effects of a wider range of temperatures were tested for stomach contents of C. maenas where the T50s were ~7h at 6–10°C and ~6h at 14–16°C but only 2h at 19–20°C. Our results indicate that the TaqMan method is applicable in field studies providing species-specific T50s, PCR inhibition and water temperatures are taken into account. [Copyright &y& Elsevier]

A Stock Penalty Scoring (SPS) was developed and used to rank the status of fish stocks in the UK EEZ at the time of Brexit. Most of the stocks had negative scores (of relatively less concern) but 19% had positive scores (of more concern). This latter group included many inshore crab and lobster stocks, often assumed to be fished using low-impact methods. Fisheries managers thus need to urgently address problems of over-exploitation in this sector. Policy makers should also not assume that if stock biomass is slightly above B msy.trigger then the stock has been rebuilt to an adequate level consistent with legal obligations. The UK 2020 Fisheries Act states that stocks must be maintained above B msy , not B msy.trigger. For most UK stocks, fishing should be kept below F msy to allow stocks to rebuild which should deliver economic and ecosystem benefits in the medium to longer-term. Of the stocks examined, 43% lacked reference points and could not be ranked using the SPS. Although these stocks only contributed 11% of total landings, they include many of local economic importance, and species of conservation concern. Implementing either regular assessments (e.g. for scallops), developing proxy measures (e.g. for skates and rays), or novel techniques (e.g. eDNA) are urgently required to improve their monitoring. The UK aspires to deliver "world class fisheries management" but this will require adequate resourcing of fisheries science and regular monitoring of progress. The SPS approach may provide an additional useful tool for tracking progress in fisheries management post-Brexit. [ABSTRACT FROM AUTHOR]

Abstract: We determined the first complete mitochondrial DNA (mtDNA) sequences for the whiting (Merlangius merlangus, family Gadidae, order Gadiformes) and the haddock (Melanogrammus aeglefinus, family Gadidae, order Gadiformes). The entire mitogenomes were amplified and sequenced by primer walking using newly designed specific internal primers. Lengths were 16,569 and 16,585 bases for whiting and haddock respectively, lengths which lie within the range of previously reported gadiform sequences from Atlantic cod (Gadus morhua, 16,696 bases) and walleye pollock (Theragra chalcogramma, 16,570 bases). Gene arrangement in both species conformed to the order seen in most vertebrate mitochondrial genomes. We identified a long intergenic spacer located between the tRNAThr and tRNAPro genes (of 100 and 70 bp long for whiting and haddock, respectively), as previously described for other species of the order Gadiformes. Using nucleotide and amino acid divergence data of four complete gadoid mitogenomes (M. merlangius, M. aeglefinus, G. morhua and T. chalcogramma), we examined in detail the relative mtDNA mutation patterns across genes and among Gadidae species and tested for the performance of each protein-coding, transfer RNA and ribosomal RNA gene in depicting the expected phylogeny among the four species, as compared with the whole genome dataset. This comparison may be particularly useful in phylogenetic analyses of such a diverse fish family, as well as for the understanding of the patterns of nucleotide substitution of the mtDNA at low levels of divergence. [Copyright &y& Elsevier]

Abstract Habitat mapping is an important tool for marine spatial planning and is required for most ecosystem-based management approaches. The Firth of Lorn Special Area of Conservation (SAC), west Scotland, was originally designated for its rocky reef habitat but it is also an area of high importance for the Flapper skate (Dipturus intermedius) and Harbour porpoise (Phocoena phocoena). Here we present an improved predictive habitat map for the SAC utilising multibeam backscatter and bathymetry data collected as part of the Ireland, Northern Ireland and Scotland Hydrographic Survey Project. Backscatter, bathymetry and bathymetric derivatives were analysed using Principal Component Analysis (PCA) and acoustic signatures were created from drop-down video habitat location data. A predictive habitat map was created from Maximum Likelihood Classification using the PCA. Dominant habitat types identified included; moderate energy circalittoral rock (CR.MCR), sublittoral mixed sediment (SS.SMx) and sublittoral sand and muddy sand (SS.SSa). Drop down video showed variable accuracy with 0–100% correctly classified habitats due to the small sample size. The initial validation points were added and the model was rerun. In areas with no previous sea truthing points, some predictions changed to SS.SMx at depths > 100 m and SS.SSa in depths < 50 m, suggesting that the model can be improved with a greater depth-range of sea truthing data. Modern acoustic surveys undertaken for other purposes, such as navigational charting, can thus be used to generate broad-scale predictive habitat maps in a cost and time effective manner. Such maps have the potential for a wide range of use by marine stakeholders, in particular, for establishing environmental baselines for long term monitoring of benthic habitats. Given the high costs of surveying, such an approach supports the rationale of "Collect once and use many times". Highlights • An improved predictive habitat map is presented for Firth of Lorn, Scotland. • Dominant habitat types identified included; CR.MCR, SS.SMx and SS.SSa. • Sea-truthing displayed variable accuracy with 0–100% correctly classified habitats. • Predictive mapping can be improved with a greater depth-range of sea-truthing data. [ABSTRACT FROM AUTHOR]

The use of floating photovoltaic systems in freshwater and marine environments is forecast to increase dramatically worldwide within the next decade in response to demands for accelerated decarbonisation of the global economy whilst avoiding competition for land, particularly near population centres. The potential environmental impacts of this expanding, novel technology are gradually becoming apparent and warrant consideration. This study reviews and evaluates the various potential environmental impacts of introducing floating photovoltaic arrays into aquatic (freshwater and marine) ecosystems based on the current state of floating photovoltaic technology and known impacts of similar industries. Environmental impacts of floating photovoltaic systems fall into several categories including shading, impacts on hydrodynamics and water-atmosphere exchange, energy emissions, impacts on benthic communities, and impacts on mobile species. The social acceptability of floating photovoltaic systems and the ability for long-term coexistence with other activities and interests are also discussed. Floating photovoltaic systems have an important role to play in global decarbonisation, but close collaboration between stakeholders will be required to better understand potential environmental and social impacts of this new technology. Development and validation of appropriate monitoring methods at scale, and consideration of long-term, equitable solutions to identified impacts, is important to enable sustainable expansion of this industry. [Display omitted] • Floating photovoltaic systems may impact their environment at different scales. • Main impacts include shading and provision of additional substrate for epibiota. • Interactions with mobile species are important, at least at local scales. • Further work is needed to understand social impacts of large-scale FPV. • Monitoring approaches should be refined to address key impacts. [ABSTRACT FROM AUTHOR]

Alien species and bottom trawl fisheries are of significant concern in the Eastern Mediterranean as both can put pressure on coastal systems whilst some alien species also constitute an important component of the trawl catches. Using an Ecopath model representing the Gulf of Mersin (Northeastern Mediterranean) for the period September 2009 to September 2013, this study describes the impacts of alien species and bottom trawl fisheries on the structure and functioning of this Northeastern Mediterranean food web. Our results show that the increase in alien species has had an important ecological impact on ecosystem structure and function. The alien species have had mostly negative impacts on native taxa, and trawl fisheries may have helped some alien species gain an advantage over native species, particularly at lower trophic levels. The Mixed Trophic Impact analysis showed that trawling and trawl discards had a noticeable direct and indirect impact on the food web, to the extent that trawling now affects the ecological role of the alien species. The cumulative overall impact of alien demersal functional groups on the pelagic domain, and vice versa suggest that alien species now play a role in benthic-pelagic coupling, and that this role is mediated by the fisheries. These results support the idea that alien species and trawling are now both important factors in structuring the Northeastern Mediterranean food web. It will thus be critical to consider both factors, as well as their interactions, when developing ecosystem-based management approaches for the region. • Alien species have become important components in the food web. • Alien species play a key role in benthic-pelagic coupling. • Trawling affects the ecological role of the alien species. • Trawling mediate the role of the alien species in the benthic-pelagic coupling. [ABSTRACT FROM AUTHOR]

Highlights • We investigate how dietary uncertainty data can strengthen model-derived ENA indicators. • 10,000 parameterisations for the Irish Sea food web reveal plausible indicator distributions. • Higher trophic levels are controlled by mid-to-low trophic levels. • Fisheries discards control the flow of energy to seabirds, Nephrops , and crabs and lobsters. • Uncertainty analyses for ENA enabled stronger ecological inferences which are crucial for management. Abstract Ecological Network Analysis (ENA) can inform marine management decisions by producing indicators that describe ecosystem health and function. Reporting ENA indicators with uncertainty boundaries lets end-users draw stronger inferences and can increase confidence in model results. However, few studies developing these indicators have estimated uncertainty due to data limitations and computational challenges. In this study, we used Linear Inverse Modelling with an Ecopath model of the Irish Sea to investigate how the incorporation of uncertainty in dietary data can strengthen inferences based on model-derived ENA indicators. A Monte Carlo approach was used to generate ten thousand data-bound parameterisations for the Irish Sea food web and provide plausible distribution estimates for functional group diets. ENA results captured the plausible range of state-indicators and provided robust estimates of the control exerted by components within the food web. Results suggest that, higher trophic components, such as mammals, birds, and elasmobranchs in the Irish Sea are controlled by mid-to-low trophic components, such as small pelagic fish, invertebrates, and plankton. Fisheries discards also played an important role in the flow of energy to groups such as Nephrops (Norway lobster), crabs and lobsters, and seabirds. These results bolster our understanding of food web dynamics in the Irish Sea and demonstrate how information derived from ENA indicators can have implications for effective and sustainable ecosystem based management. Finally, the methods established here represent an important step in the maturation of marine ecosystem modelling and ENA for management purposes. [ABSTRACT FROM AUTHOR]