Recent advances in understanding the environmental footprint of trawling on the seabed

Bottom trawling accounts for nearly a quarter of wild-capture seafood production, but it is associated with physical disturbance of the seabed leading to changes in benthic abundance, habitat structure, and biogeochemical processes. Understanding the processes of benthic depletion and recovery in relation to different types of fishing gears, and in different seabed types, is an important pre-requisite to inform appropriate management measures to limit or reduce the effects of trawling on the seabed. The combined approaches of meta-analysis and modelling that link fishing-gear penetration of the seabed to benthic depletion, and recovery to taxon longevity, have enabled the development of a modelling framework to estimate relative benthic status in areas subject to trawling. Such estimations are highly sensitive to the spatial resolution at which fishing footprint (trawl track) data are aggregated, and this leads to overinflated estimates of fishing impacts on benthos when coarse-level aggregation is applied. These approaches present a framework into which other “sustainability” criteria can be added, e.g., the consideration of carbon footprints of fishing activities.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Eleutherodactylus pinchoni

Number of Pages: 3Integrative BiologyGeological Science

Correlation of structural and spectroscopic properties of a photosynthetic reaction center

Polarized spectra of absorption and light-induced absorbance changes are presented for the crystallized reaction centers of Rhodopseudomonas viridis. We find that a model based on extended dipole interaction between all six pigments is capable of interpreting detailed features such as the contributions from the individual pigments to the various absorption peaks. Even though the pigments are arranged in approximate C2 symmetry, the optical spectra together with the calculations reflect deviations from this symmetry, which may be important in understanding the electron pathway

Spatial Heterogeneity in Fishing Creates de facto Refugia for Endangered Celtic Sea Elasmobranchs

The life history characteristics of some elasmobranchs make them particularly vulnerable to fishing mortality; about a third of all species are listed by the IUCN as Threatened or Near Threatened. Marine Protected Areas (MPAs) have been suggested as a tool for conservation of elasmobranchs, but they are likely to be effective only if such populations respond to fishing impacts at spatial-scales corresponding to MPA size. Using the example of the Celtic Sea, we modelled elasmobranch biomass (kg h(−1)) in fisheries-independent survey hauls as a function of environmental variables and ‘local’ (within 20 km radius) fishing effort (h y(−1)) recorded from Vessel Monitoring Systems data. Model selection using AIC suggested strongest support for linear mixed effects models in which the variables (i) fishing effort, (ii) geographic location and (iii) demersal fish assemblage had approximately equal importance in explaining elasmobranch biomass. In the eastern Celtic Sea, sampling sites that occurred in the lowest 10% of the observed fishing effort range recorded 10 species of elasmobranch including the critically endangered Dipturus spp. The most intensely fished 10% of sites had only three elasmobranch species, with two IUCN listed as Least Concern. Our results suggest that stable spatial heterogeneity in fishing effort creates de facto refugia for elasmobranchs in the Celtic Sea. However, changes in the present fisheries management regime could impair the refuge effect by changing fisher's behaviour and displacing effort into these areas

Commercial and non-target species of deep water trawled muddy habitats on the Maltese continental shelf

Prior to joining the European Union, Malta operated a 25nm Exclusive Fishing Zone that was retained as a Fisheries Conservation Zone (FCZ) following EU membership. The present study was conducted in this FCZ as part of the ongoing MEDITS trawl survey programme. Otter trawl samples were collected from muddy bottoms at depths of 100-300m. The catch from each haul was sorted into commercial and non-commercial components, and fauna were identified and counted. Samples for analyses of infauna and sediment characteristics were collected using a 0.0625m² capacity box-corer. Macrofaunal abundance data for the stations were analysed using ordination techniques (nMDS) and relationships between environmental variables and faunal assemblages were explored by superimposing individual variables on the two-dimensional nMDS plots. The analyses clearly separated the commercial species into two distinct groups of assemblages that seemed to be defined principally by depth: those from inshore and south-eastern stations (depth range 100-250m) and those from north-western stations (depth range 250-300m). The non-commercial species showed a similar pattern with assemblages from inshore stations grouping together; however, the offshore stations had a greater variability in non-target species composition, especially for infauna. For the offshore stations, geographical position seemed to be important since stations off the north-western coast of the Maltese islands grouped separately from those off south-eastern Malta.peer-reviewe

Fishers’ perception of a 35-year old exclusive Fisheries Management Zone

Fishers’ attitudes and perceptions are critical for the success of fisheries protection areas with their associated biota, and a failure to understand fishers’ behaviour may undermine the success of such fisheries management measures. In this study, we examine fishers’ perception of a long-established exclusive fisheries zone around Malta and to investigate if the perceptions depend on fishers’ demographic, economic, social characteristics and fishing activity of the fishers. A questionnaire survey was undertaken to evaluate the demographic characteristics, economic situation (costs and revenue) and fishers’ activity and behaviour, together with their perception of the Fisheries Management Zone (FMZ). A total of 241 interview responses were analysed which was a response rate of 60%. The perception of most fishers was that the establishment of the FMZ has had an overall negative impact on their fishing activity and that the zone is not important for the protection of local fish stocks. When asked about the beneficial effect of the zone for fishers, most fishers from all backgrounds said that the zone does not benefit commercial fishers, but benefits mainly recreational fishers. The most evident differences in the perceptions and attitudes were between the full-time, part-time and recreational fishers. Fishers that have been fishing for more than 35 years and fishers from the main fishing village also had different attitudes from other fishers towards the FMZ. The results of this study suggest that the proportion of individual income derived from fishing was the strongest factor that influenced attitudinal differences, with home port and fishing experience having less important effects. The main differences in attitude among fishers were related to the protection and conservation effects of the zone, enhancement of resources and conflicts among user groups. The heterogeneity among fishers’ attitudes revealed by the present study has important implications for the implementation of spatial closures. Some sectors of stakeholders may require additional incentives to accept restrictions on access if spatial management is to achieve its intended objectives.peer-reviewe

Using Machine Vision to Estimate Fish Length from Images using Regional Convolutional Neural Networks

An image can encode date, time, location and camera information as metadata and implicitly encodes species information and data on human activity, for example the size distribution of fish removals. Accurate length estimates can be made from images using a fiducial marker; however, their manual extraction is time-consuming and estimates are inaccurate without control over the imaging system. This article presents a methodology which uses machine vision to estimate the total length (TL) of a fusiform fish (European sea bass). Three regional convolutional neural networks (R-CNN) were trained from public images. Images of European sea bass were captured with a fiducial marker with three non-specialist cameras. Images were undistorted using the intrinsic lens properties calculated for the camera in OpenCV; then TL was estimated using machine vision (MV) to detect both marker and subject. MV performance was evaluated for the three R-CNNs under downsampling and rotation of the captured images. Each R-CNN accurately predicted the location of fish in test images (mean intersection over union, 93%) and estimates of TL were accurate, with percent mean bias error (%MBE [95% CIs]) = 2.2% [2.0, 2.4]). Detections were robust to horizontal flipping and downsampling. TL estimates at absolute image rotations >20° became increasingly inaccurate but %MBE [95% CIs] was reduced to −0.1% [−0.2, 0.1] using machine learning to remove outliers and model bias. Machine vision can classify and derive measurements of species from images without specialist equipment. It is anticipated that ecological researchers and managers will make increasing use of MV where image data are collected (e.g. in remote electronic monitoring, virtual observations, wildlife surveys and morphometrics) and MV will be of particular utility where large volumes of image data are gathered

Accurate estimation of fish length in single camera photogrammetry with a fiducial marker

Videogrammetry and photogrammetry are increasingly being used in marine science for unsupervised data collection. The camera systems employed are complex, in contrast to "consumer"digital cameras and smartphones carried by potential citizen scientists. However, using consumer cameras in photogrammetry will introduce unknown length estimation errors through both the image acquisition process and lens distortion. This study presents a methodology to achieve accurate 2-dimensional (2-D) total length (TL) estimates of fish without specialist equipment or proprietary software. Photographs of fish were captured with an action camera using a background fiducial marker, a foreground fiducial marker and a laser marker. The geometric properties of the lens were modelled with OpenCV to correct image distortion. TL estimates were corrected for parallax effects using an algorithm requiring only the initial length estimate and known fish morphometric relationships. Correcting image distortion decreased RMSE by 96% and the percentage mean bias error (%MBE) by 50%. Correcting for parallax effects achieved a %MBE of -0.6%. This study demonstrates that the morphometric measurement of different species can be accurately estimated without the need for complex camera equipment, making it particularly suitable for deployment in citizen science and other volunteer-based data collection endeavours

Differences in demersal community structure and biomass size spectra within and outside the Maltese Fishery Management Zone (FMZ)

We examined the protection effect of a long-established fisheries protection zone by studying the demersal communities and the biomass size spectra of specific taxonomic groups. The results and the relevant management implications of the community analysis are discussed within the context of the MEDITS trawl survey program, from which the data was derived. The demersal fishery resources on the muddy bottoms of Maltese trawling grounds were found to be stratified in four main depth ranges: 83 to 166 m (outer continental shelf), 140 to 230 m (shelf break), 270 to 440 m (shallow slope), and 466 to 701 m (deep slope). Significant differences were detected between the inside and outside zones of the outer continental shelf. Stations from this stratum inside the protected zone had twice as much biomass as those outside as well as larger individuals of some species (e.g. elasmobranchs). The depth strata identified do not coincide with those sampled in existing trawl survey programmes in the Sicilian Channel, which were set up without reference to demersal assemblage structure and its relation to depth. It is therefore clear that characterisation of the biotic assemblages is important in order to obtain a better sampling representation of each depth-stratum/assemblage type, and this should be considered in the survey design.peer-reviewe