Comparison of zooplankton data collected by a continuous semi-automatic sampler (CALPS) and a traditional vertical ring net

We compared and evaluated the performance of a Continuous Automatic Litter and Plankton Sampler (CALPS) against the traditional ring net vertical haul. CALPS is a custom-made semi-automatic sampler, which collects water using a pump system at a single depth along a predetermined transect as the ship sails. CALPS underestimated species abundance compared to the ring net by a factor 1.61, but both datasets illustrated a similar species composition, community size structure and good agreement in the spatial distribution of abundance. Our analysis suggests that avoidance of the CALPS is likely to be the main factor responsible for the observed difference in sampling efficiency, but other factors, such as depth, area sampled and zooplankton patchiness, are also likely to play their part. We conclude that whilst the CALPS is not suitable for investigations that require accurate measures of abundance, it is an ideal tool to identify and quantify changes in plankton communities and diversity. A particular advantage over more traditional vertical sampling methods is that it can be integrated within existing multidisciplinary surveys at little extra cost, thus making the CALPS particularly valuable as part of integrated monitoring programmes to underpin policy areas such as the EU Marine Strategy Framework Directive

State dependence of arousal from torpor in brown long-eared bats (Plecotus auritus)

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Consistent concentrations of critically endangered Balearic shearwaters in UK waters revealed by at-sea surveys

Aim: Europe’s only globally critically endangered seabird, the Balearic shearwater (Puffinus mauretanicus), is thought to have expanded its post-breeding range northwards into UK waters, though its distribution there is not yet well understood. This study aims to identify environmental factors associated with the species’ presence, and map the probability of presence of the species across the western English Channel and southern Celtic Sea, and estimate the number of individuals in this area. Location: The western English Channel and southern Celtic Sea. Methods: This study analyses strip transect data collected from vessel-based surveys in the western English Channel and southern Celtic Sea during the shearwater’s post-breeding period between 2013 and 2017. Using environmental data collected directly and from remote sensors both Generalized Additive Models (GAMs) and the Random Forest (RF) machine learning model were used to determine shearwater presence at different locations. Results: Both models indicated that oceanographic features were better predictors of shearwater presence than fish abundance. Seafloor aspect, sea surface temperature, depth, salinity, and maximum current speed were the most important predictors. Based on the timing of the surveys (mainly in October) it is probable that most of the sighted shearwaters were immatures. Main conclusions: Areas with consistently high probabilities of shearwater presence were identified at the Celtic Sea front. Our estimates suggest that the study area in southwest Britain supports between 2% and 23% of the global population of Balearic shearwaters. This study provides the most complete understanding of Balearic shearwater distribution in UK waters available to date, information that will help inform any future UK conservation actions concerning this endangered 38 species

Assessing the potential of autonomous submarine gliders for ecosystem monitoring across multiple trophic levels (plankton to cetaceans) and pollutants in shallow shelf seas

A combination of scientific, economic, technological and policy drivers is behind a recent upsurge in the use of marine autonomous systems (and accompanying miniaturized sensors) for environmental mapping and monitoring. Increased spatial–temporal resolution and coverage of data, at reduced cost, is particularly vital for effective spatial management of highly dynamic and heterogeneous shelf environments. This proof-of-concept study involves integration of a novel combination of sensors onto buoyancy-driven submarine gliders, in order to assess their suitability for ecosystem monitoring in shelf waters at a variety of trophic levels. Two shallow-water Slocum gliders were equipped with CTD and fluorometer to measure physical properties and chlorophyll, respectively. One glider was also equipped with a single-frequency echosounder to collect information on zooplankton and fish distribution. The other glider carried a Passive Acoustic Monitoring system to detect and record cetacean vocalizations, and a passive sampler to detect chemical contaminants in the water column. The two gliders were deployed together off southwest UK in autumn 2013, and targeted a known tidal-mixing front west of the Isles of Scilly. The gliders’ mission took about 40 days, with each glider travelling distances of >1000 km and undertaking >2500 dives to depths of up to 100 m. Controlling glider flight and alignment of the two glider trajectories proved to be particularly challenging due to strong tidal flows. However, the gliders continued to collect data in poor weather when an accompanying research vessel was unable to operate. In addition, all glider sensors generated useful data, with particularly interesting initial results relating to subsurface chlorophyll maxima and numerous fish/cetacean detections within the water column. The broader implications of this study for marine ecosystem monitoring with submarine gliders are discussed

First insight of meso- and bentho-pelagic fish dynamics around remote seamounts in the South Atlantic Ocean

Seamounts have long been recognised as hotspots for pelagic productivity and diversity in the world’s open ocean habitats. Recent studies have suggested that productivity may vary greatly between different seamounts, depending on complex interactions between the bathymetric features and local oceanography. These processes may enhance local primary production which support elevated biomass at higher trophic levels. In addition to enhancing local biomass, seamounts may also act as aggregative features, attracting pelagic species from the surrounding waters. Such characteristics make seamounts attractive targets for fisheries. However, as these unique habitats are localised and relatively small, they are vulnerable to overexploitation, which may have detrimental impact on the wider region. Mapping and quantitative assessments of the fish biomass at different seamounts are crucial prerequisites to identifying vulnerable seamounts and will aid toward understanding the dynamics of these important ecosystems and their vulnerability to fishing pressures. We used fisheries acoustics during two expeditions in 2018 and 2019, to investigate the distribution and abundance of fish and micronekton on and around five little studied seamounts of Tristan da Cunha, a remote archipelago in the South Atlantic Ocean. The results confirmed increased productivity at the seamounts, compared to the surrounding open ocean with higher acoustic backscatter values, a proxy for biomass, particularly at the shallower (~200 m depth) seamounts. Fish largely dominated the backscatter on most of the seamounts especially over the plateau areas where large densities of prey fish, primarily the mesopelagic Maurolicus inventionis, were detected. Very large aggregations, thought to consist of bentho-pelagic fish, were also observed over the slope of McNish Seamount that resulted in very high biomass estimates. Aggregations of this size and magnitude, have, to our knowledge, never been mapped or quantified on seamounts, using acoustic methods. Specific physical processes, such as enhanced retention and vertical mixing that were identified by an oceanographic model, may be some of the drivers of the enhanced fish biomass detected at McNish. The characteristics of the seamounts observed in this work suggest that these habitats are highly suitable for the presence of large predatory fish that can utilise these areas as their primary habitat or as important foraging grounds

Benchmark Workshop on selected stocks in the Western Waters in 2021 (WKWEST).

The goal of a benchmark is consensus agreement on an assessment methodology that is to be used in future update assessments. This assessment methodology can be an analytical assessment, but can also be non-analytical, for instance based on trends in an assessment or in a selected set of (survey) indicators, with or without forecasts. The result will be the 'best available' method that ICES advice will be based on. WKWEST 2021 dealt with the following stocks: Sardine (Sardina pilchardus) in Subarea 7 (southern Celtic Seas, and the English Channel); Pollack (Pollachius pollachius) in subareas 6-7 (Celtic Seas and the English Channel); Red gurnard (Chelidonichthys cuculus) in subareas 3–8 (Northeast Atlantic); Plaice (Pleuronectes platessa) in divisions 7.h–k (Celtic Sea South, southwest of Ireland); Sole (Solea solea) in divisions 8.c and 9.a (Cantabrian Sea and Atlantic Iberian waters)

A scale-based framework to understand the promises, pitfalls and paradoxes of irrigation efficiency to meet major water challenges

An effective placement of irrigation efficiency in water management will contribute towards meeting the pre-eminent global water challenges of our time such as addressing water scarcity, boosting crop water productivity and reconciling competing water needs between sectors. However, although irrigation efficiency may appear to be a simple measure of performance and imply dramatic positive benefits, it is not straightforward to understand, measure or apply. For example, hydrological understanding that irrigation losses recycle back to surface and groundwater in river basins attempts to account for scale, but this generalisation cannot be readily translated from one location to another or be considered neutral for farmers sharing local irrigation networks. Because irrigation efficiency (IE) motives, measures, effects and technologies play out at different scales for different people, organisations and purposes, and losses differ from place to place and over time, IE is a contested term, highly changeable and subjective. This makes generalisations for science, management and policy difficult. Accordingly, we propose new definitions for IE and irrigation hydrology and introduce a framework, termed an ‘irrigation efficiency matrix’, comprising five spatial scales and ten dimensions to understand and critique the promises, pitfalls and paradoxes of IE and to unlock its utility for addressing contemporary water challenges