Comment on 'a global map of human impact on marine ecosystems'

Halpern et al. (Reports, 15 February 2008, p. 948) integrated spatial data on 17 drivers of change in the oceans to map the global distribution of human impact. Although fishery catches are a dominant driver, the data reflect activity while impacts occur at different space and time scales. Failure to account for this spatial disconnection could lead to potentially misleading conclusions

A view from above : changing seas, seabirds and food sources

In this review we summarize what is known about mechanisms by which climate change may be affecting the populations of seabirds around the UK. Breeding success and adult survival are the key factors affecting changes in seabird populations, and food intake is implicated as a major determinant of both. The diet of most UK seabird species is almost exclusively sandeels, small clupeoid fish or zooplankton and it is clear that the marine pelagic food web is the key ecological system determining food supply. Hence, we develop the review by first considering how climate changes may affect primary production, and then examine how this propagates through the food web to zooplankton and fish culminating in fluctuations in seabird numbers. A trend of increasing numbers of many seabird species since 1970, particularly puffins, guillemots and razorbills, appears to have been reversed since 2000. The proximate cause of the recent declines seems to be a succession of 5 years of low breeding success for a range of species due to a shortage of food, especially sandeels. However, the connection with climate change remains uncertain, though there are indications that declines in the productivity of sandeel populations may be linked in some complex way to warming sea temperatures. The main conclusion is that no part of the marine food web, including fisheries, can be considered in isolation when trying to understand and predict the consequences of climate change for seabirds. Impacts can be expected in all parts of the system, and all parts of the system are interconnected

Risks to North Sea Fish Stocks and Wildlife if Post-Brexit Fishery Negotiations Fail to Reach Agreement on Quotas and Access to UK Waters : Summary Report

"Taking back control of fisheries" became one of the totemic issues uniting supporters of the campaign to leave the EU. Having left, the issue is again high on the agenda in the 'future relationship' negotiations. The UK Government has indicated that getting a better deal for UK fishermen is a "red line" in the negotiations. This includes increases in quota for UK vessels, and restrictions on access to UK waters by foreign vessels. However, the EU has linked access to UK waters and maintenance of quotas enshrined in the Common Fisheries Policy (CFP) with securing tariff-free trade in fish and other products. This report focuses on the North Sea and provides an assessment of the risks to stock and ecosystem conservation associated with the post-Brexit fisheries negotiations. The report first sets out the history behind the allocation of quota shares (Relative Stability) and compares the UK shares with those under proposed alternative rules based on the distribution of fish ("zonal attachment"). Unless a negotiated agreement can be reached to resolve these different views on quota allocation there is a risk that unilateral actions will result in the combined catches by all states exceeding the levels required for long-term maximum sustainable yields. The report sets out a narrative for the impact of such unilateralism on harvesting rates, and then presents results from models which show the risks that these would pose for key fish stocks and wildlife

Risks to North Sea Fish Stocks and Wildlife if Post-Brexit Fishery Negotiations Fail to Reach Agreement on Quotas and Access to UK Waters : Extended Technical Report

"Taking back control of fisheries" became one of the totemic issues uniting supporters of the campaign to leave the EU. Having left, the issue is again high on the agenda in the 'future relationship' negotiations. The UK Government has indicated that getting a better deal for UK fishermen is a "red line" in the negotiations. This includes increases in quota for UK vessels, and restrictions on access to UK waters by foreign vessels. However, the EU has linked access to UK waters and maintenance of quotas enshrined in the Common Fisheries Policy (CFP) with securing tariff-free trade in fish and other products. This extended technical report focuses on the North Sea and provides an assessment of the risks to stock and ecosystem conservation associated with the post-Brexit fisheries negotiations. The report first sets out the history behind the allocation of quota shares (Relative Stability) and compares the UK shares with those under proposed alternative rules based on the distribution of fish ("zonal attachment"). Unless a negotiated agreement can be reached to resolve these different views on quota allocation there is a risk that unilateral actions will result in the combined catches by all states exceeding the levels required for long-term maximum sustainable yields. The report sets out a narrative for the impact of such unilateralism on harvesting rates, and then presents results from models which show the risks that these would pose for key fish stocks and wildlife

Spring production of Calanus finmarchicus at the Iceland-Scotland Ridge

Distribution and reproduction activity of the calanoid copepod Calanus finmarchicus were studied in the waters between Scotland and Iceland in April 1997 during the expected time of the animals' ascent to surface waters following diapause. Ascent was taking place on both sides of the Iceland-Scotland Ridge, apparently from two separate overwintering centers. The population on the Faroe Shelf (FS) most likely came from the overwintering population in the Faroe Shetland Channel (FSC). Per capita egg production was highest on the FS (> 30 eggs female -1d-1) and lowest in the Iceland Basin (10 eggs female -1d-1). The maximum clutch size recorded was on the FS (145 eggs). As the maximum clutch sizes that females produced were between 40% and 77% (area averages of the station maximum rates) of their size-specific reproduction potential, it is argued that egg production rates were generally food-limited. Chlorophyll a concentrations were, at all but one station, under 1 ugL-1. Chlorophyll-based ingestion could, theoretically, support the observed average egg production rates in the Iceland Basin and on the FS but only about 30% of the observed production at the stations in the East Icelandic Current (EIC). The carbon assimilated through ingestion of phytoplankton, Calanus own eggs andnauplii in the EIC was estimated to be too low to support the frequently observed production of clutches consisting of over 100 eggs. Cannibalism on eggs and nauplii was not likely to have constituted a significant component of dietary carbon intake. However, a combination of feeding and assimilation of reserved lipid remaining from overwintering could be sufficient to explain the observed per capita egg production rates. C. finmarchicus copepod stages 1-3 were only recorded in considerable numbers only on the FS. This suggests higher survival rates of eggs in the shelf waters

Regional variability in the trophic requirements of shelf sea fisheries in the Northeast Atlantic, 1973-2000

Hydrographic, plankton, benthos, fisheries landings, and fish diet data from shelf sea areas in the Northeast Atlantic have been combined into an analysis of the foodweb structure and secondary production requirements of regional fisheries. Fish landings from the Baltic and North Sea are shown to be taken from a lower trophic level and are shown to be overall more planktivorous than those from shelf edge regions. The secondary production required per unit of landed fish from the North Sea was approximately half that for landings from the southwest approaches to the UK, referred to as the Celtic Seas, where zooplankton production accounted for only a small fraction of the secondary production demands of the fisheries. In the North Sea, variability in zooplankton production seems to have exerted a bottom-up effect on fish production, which in turn has exerted a top-down effect on the benthos. Conversely, Celtic Seas benthos production has been a bottom-up driver of fish production, which seems to have been independent of variability in plankton production.Thus, climate and fishing pressures can be expected to influence these regional fisheries in very different ways. Overall, the results indicate very strong spatial patterns in the fish foodweb structure and function, which will be important considerations in the establishment of regional management plans for fisheries

Investigating trends in the growth of five demersal fish species from the Firth of Clyde and the wider western shelf of Scotland

Demersal fish landings from the Firth of Clyde peaked in 1973, then declined rapidly until the targeted demersal fishery ceased in 2005. The abundance of large fish decreased during this period, and their numbers have not recovered since 2005. We aim to determine whether changing growth rates have con- tributed to the decline in the abundance of large fish. Bottom trawl survey data from 1980–2012 was used to calculate the annual mean length-at-age and time series of von Bertalanffy growth parameters of five demersal species; cod, haddock, whiting, Norway pout and saithe. Two regions were considered: the Firth of Clyde and the neighbouring seas west of Scotland (the western shelf). There have been substantial decreases in the lengths of most age groups of Clyde haddock and whiting due to declines in both asymptotic length and von Bertalanffy growth rate. Lengths-at-age have also declined in western shelf populations, but at markedly slower rates than within the Clyde. Trends in temperature and year class strength tended to contribute little to changes in the growth parameters, so declines in length-at-age have been largely due to other factors. Fishing intensity is greater in the Clyde than western shelf, and the size selectivity of the fisheries differ as more Clyde vessels use Nephrops trawling gear. Since trends in growth were also more extreme in the Clyde, it appears as though size-selective fishing may have caused reductions in the lengths of these fish. If the changes in growth are partially due to fishing induced evolution then it may take many generations for the changes to reverse

Flow optimization study of a batch microfluidics PET tracer synthesizing device.

We present numerical modeling and experimental studies of flow optimization inside a batch microfluidic micro-reactor used for synthesis of human-scale doses of Positron Emission Tomography (PET) tracers. Novel techniques are used for mixing within, and eluting liquid out of, the coin-shaped reaction chamber. Numerical solutions of the general incompressible Navier Stokes equations along with time-dependent elution scalar field equation for the three dimensional coin-shaped geometry were obtained and validated using fluorescence imaging analysis techniques. Utilizing the approach presented in this work, we were able to identify optimized geometrical and operational conditions for the micro-reactor in the absence of radioactive material commonly used in PET related tracer production platforms as well as evaluate the designed and fabricated micro-reactor using numerical and experimental validations

A model of meta-population dynamics for North Sea and West of Scotland cod - the dynamic consequences of natal fidelity

It is clear from a variety of data that cod (Gadus morhua) in the North Sea do not constitute a homogeneous population that will rapidly redistribute in response to local variability in exploitation. Hence, local exploitation has the potential to deplete local populations, perhaps to the extent that depensation occurs and recovery is impossible without recolonisation from other areas, with consequent loss of genetic diversity. The oceanographic, biological and behavioural processes which maintain the spatial population structures are only partly understood, and one of the key unknown factors is the extent to which codexhibit homing migrations to natal spawning areas. Here, we describe a model comprising 10 interlinked demes of cod in European waters, each representing groups of fish with a common natal origin. The spawning locations of fish in each deme are governed by a variety of rules concerning oceanographic dispersal, migration behaviour and straying. We describe numerical experiments with the model and comparisons with observations, which lead us to conclude that active homing is probably not necessary to explain some of the population structures of European cod. Separation of some sub-populations is possible through distance and oceanographic processes affecting the dispersal of eggs and larvae. However, other evidence suggests that homing may be a necessary behaviour to explain the structure of other sub-populations. Theconsequences for fisheries management of taking into account spatial population structuring are complicated. For example, recovery or recolonisation strategies require consideration not only of mortality rates in the target area for restoration, but also in the source areas for the recruits which may be far removed depending on the oceanography. The model has an inbuilt capability to address issues concerning the effects of climate change, including temperature change, on spatial patterns of recruitment, development and population structure in cod

Molecular transport junctions: Current from electronic excitations in the leads

Using a model comprising a 2-level bridge connecting free electron reservoirs we show that coupling of a molecular bridge to electron-hole excitations in the leads can markedly effect the source-drain current through a molecular junction.In some cases, e.g. molecules that exhibit strong charge transfer transitions, the contribution from electron-hole excitations can exceed the Landauer elastic current and dominate the observed conduction.Comment: 4 pages, 2 figures, submitted to PR