Mitigating the impacts of river flow regulation and barriers to fish spawning migrations

Globally, migratory fish are threatened by anthropogenic modification to rivers. These create barriers that prevent fish accessing spawning grounds required for completion of life cycles. In order to make informed decsions, for mitigating the associated negative impacts, an understanding migratory behaviour when reaching barriers during the spawning migration is required. That said, there is a lack of information about the response of migratory fish to operational regimes in regulated rivers and the areas occupied, delays caused and routes taken around infrastructures. This study investigated the behaviour of three migratory fish species under operational regimes of three different infrastructures during each species’ respective spawning season. The efficiency of a bypass channel that utilised the relationship between migratory behaviour and flow was also investigated for a further species.The literature was reviewed to identify the different types of migratory life histories of fish, the impact of different riverine modification on the respective spawning migrations and how this can be mitigated. Fish have evolved in direct response to the natural flow regime and connectivity of riverine habitats, but barriers to migration exist from source to sea. This regulates or disrupts the flow regime and connectivity that fish depend upon, which has had considerable detriment to many migratory fish species globally. The main conclusion of the review was that knowledge gaps exist for the target species, and understanding the behaviour of the study species during the spawning migration is essential to improve access to spawning grounds in regulated rivers and ultimately conserve populations.The effects of timing, magnitude and duration of eleven artificial flow (freshet) releases from two impounding reservoirs on river-resident brown trout (Salmo trutta L.), a species known to undertake spawning migrations, was investigated using radio telemetry in a regulated upland river in northern England. Most did not perform movements characteristic of spawning migrations; all were located within 10 m of the location occupied before freshets, and fish in a control reach behaved comparably. The largest unidirectional movements mostly occurred during elevated river level due to rainfall and reservoir overtopping events; other varied length movements occurred during natural peaks or low flow, indicating artificial freshets were not directly responsible, and may not be suitable to stimulate migration in river-resident fish in regulated rivers.An acoustic telemetry study was conducted to determine the impact of a high- head hydropower station, associated diversion weir and spillway on downstream migrating shortfin eel (Anguilla australis) in the regulated Wairua catchment, Northland, New Zealand. Despite the diversion weir providing an alternative route, 88% (n = 21) of tagged eels that were detected here entered the power station forebay; of these, 52% were impinged onto intake screens, always when turbines were operating at greater than 3.04 MW/day. The rest (48%) passed the spillway and continued their migration, sometimes after long delays and having spent time immediately upstream of the intake where fitness could have been reduced due to high flows. Based on findings, the most effective mitigation here and at similar power schemes is considered to be operational or physical changes at the diversion weir to minimise entry of downstream migrating eels into the power canal during the migration period. Also discussed as potential solutions are turbine shutdowns, ensuring the spillway is available and provision of a bypass channel in the forebay.At a pumping station in the Anglian region, UK, where the upstream river level is maintained primarily by a co-located gravity sluice door, route choice and behaviour of downstream migrating European eel (Anguilla anguilla) (n = 7) immediately upstream of both routes was investigated using acoustic telemetry. During the study, three eels passed through pumps despite only operating for 8% of the time the gravity sluice was open, and only two passed through the gravity sluice after arriving when it was closed; the remaining two retreated upstream. No eels were detected within 15 m of the gravity sluice when it was open and eel behaviour was indicative of reluctance to pass through pumps. Findings are discussed in terms of water resource management to implement operational changes, to make the gravity sluice an attractive downstream passage route for migrating eels and thus reduce passage through hazardous pumps.The efficacy of two bypasses in attracting and passing downstream migrating American eels (Anguilla rostrata), designed to utilise the relationship between eel migratory behaviour and flow through two methods of flow creation, i.e. an airlift and a siphon, was tested in a simulated forebay environment, as a potential remediation measure at infrastructures requiring eel passage. Under entrance velocity of 1.2 m/s in eight test runs, both bypasses performed comparably and eels tested in each readily located, entered and passed. Test findings are discussed in relation to real-world application at sites with different characteristics, and the suitability of each design in successfully providing a safe route for downstream migrating eels

Genome-wide RNAi screens in African trypanosomes identify the nifurtimox activator NTR and the eflornithine transporter AAT6.

To be effective, therapeutic compounds must typically enter target cells and, in some cases, must be concentrated or modified. Thus, uptake and activation mechanisms often form the basis of selectivity against infectious agents. Loss-of-function screens can be used to identify proteins involved in drug uptake and metabolism and may also identify clinically relevant potential resistance mechanisms. We used a genome-scale RNA interference (RNAi) library to identify loss-of-function resistance mechanisms in bloodstream-form Trypanosoma brucei. Nifurtimox-Eflornithine Combination Therapy (NECT) was recently introduced for Human African Trypanosomiasis and we focus on these drugs here. Screens for resistance to nifurtimox and a related drug, benznidazole, identified loss of nitroreductase (NTR) pro-drug activator function. A screen for resistance to the amino-acid analogue, eflornithine, identified loss of amino-acid transporter (AAT6) function. Our results confirm recent findings and suggest that NTR or AAT6 loss-of-function represent major potential mechanisms of resistance to these drugs. Thus, bloodstream-form T. brucei RNAi libraries present a versatile tool for selective genetic screening and for the rapid identification of drug-activation, uptake and potential resistance mechanisms

Transcriptional regulators of arteriovenous identity in the developing mammalian embryo

The complex and hierarchical vascular network of arteries, veins, and capillaries features considerable endothelial heterogeneity, yet the regulatory pathways directing arteriovenous specification, differentiation, and identity are still not fully understood. Recent advances in analysis of endothelial-specific gene-regulatory elements, single-cell RNA sequencing, and cell lineage tracing have both emphasized the importance of transcriptional regulation in this process and shed considerable light on the mechanism and regulation of specification within the endothelium. In this review, we discuss recent advances in our understanding of how endothelial cells acquire arterial and venous identity and the role different transcription factors play in this process

Evaluating the impact of hydropower on downstream migrating anguillid eels: Catchment-wide and fine-scale approaches to identify cost-effective solutions

Hydropower is an increasingly popular source of renewable and ‘green’ (in terms of emissions) energy, but reduced longitudinal connectivity and diverting flow through turbines can have negative impacts on catadromous anguillid eel species that have declined globally. There is an urgent need for environmental managers to perform remediation actions, such as protecting flows for migratory fish and providing passage solutions at infrastructure, under increasing legislative pressure. To deliver this, a more comprehensive understanding of eel migration in catchments with hydropower is required. Here, we illustrate the importance of catchment-wide and fine-scale acoustic telemetry, coupled with the influence of eel maturation (i.e. sex steroid levels), to determine the impact of Wairua run-of-river Power Station (WPS) on downstream migrating shortfin eels (Anguilla australis; n = 25) in Wairua River, New Zealand. Migration speed through the unregulated reach upstream of WPS was positively correlated with flow, but not eel length or sex steroids. Three eels passed a diversion weir (DW) to follow the natural watercourse and eight entered the WPS canal. Eels predominantly entered (95.2%) and were last detected (85.7%) in WPS forebay during hours of darkness. Eleven (52%) of the 21 eels that entered WPS forebay were impinged or entrained, all when three or four turbines were in operation (power generation >3.04 MW). Ten (48%) passed WPS spillway during significantly higher spill than impinged or entrained eels, with four passing during no turbine operation, after experiencing high flows near the intake (multiple receivers in WPS forebay used to quantify fine-scale behaviour). On average, eels were impinged or entrained at WPS significantly quicker (6.40 ± 11.13 days) than eels that entered the spillway (25.17 ± 15.12 days), but eel length and sex steroids did not significantly influence fate. Of the eels that migrated through the entire 55 km study reach, passage time at DW and WPS equated to 0.01–0.02% and 47.62–92.17% of their migration, respectively. Mitigation for WPS (and similar power schemes) should focus on operational or physical changes at DW to minimise eels entering power station forebay(s). Turbine shutdowns, ensuring WPS spillway is available and the provision of a bypass channel in WPS forebay are also discussed as ways to conserve the species with the potential to save costs for water resource managers

Comparison of attraction, entrance and passage of downstream migrant American eels (Anguilla rostrata) through airlift and siphon deep entrance bypass systems

© 2018 Downstream migrating anguillid eels face many barriers including turbines and pumps at impoundments for water abstraction, power generation and water level control, when attempting to exit the freshwater catchment to reach spawning grounds. Multiple eel species worldwide are facing different levels of endangerment and alleviating the impacts of barriers to migration is essential to allow completion of the life cycle. Deep bypass systems with entrances located near the riverbed hold some promise for increased effectiveness compared to traditional downstream guidance and bypass facilities with entrances near the surface, as eels typically occupy the bottom of the water column. Here we evaluate two deep entrance bypass designs; an airlift (the Conte Airlift) and a conventional gravity siphon of the same entrance dimensions. Tests were performed using migratory silver-phase American eels (Anguilla rostrata), at night, in a simulated forebay environment. Passage performance was monitored over a 3 h test period using both PIT (passive integrated transponder) tag and video recording equipment. Entrance velocity was fixed at 1.2 m s−1 in each of 8 test runs with cohort size fixed in six runs at 14 and in two runs at 42. Test eels readily located, entered and passed both bypass designs. Differences in performance metrics between the airlift and siphon were not statistically significant (P > 0.05) with linked mean values of 74.5%, 90.5% and 100%, respectively. Eel length did not affect passage speed (P > 0.05) or slip ratio, i.e., the measured eel velocity relative to fluid velocity. The slip ratio was, however, greater in the siphon than in the airlift (P < 0.01) within identical vertical upflow sections of the test equipment. Siphon slip ratios in the upflow vertical section were comparable to those established for the horizontal and downflow sections. Fish density did not affect attraction and passage through the airlift or siphon. No mortality or signs of injury were observed on any of the test eels through a 48 h post-test observation period. Both airlift and siphon downstream bypass systems show promise as effective technologies for protection of downstream migrating eels at a variety of water diversion or hydroelectric sites that pose threats of impingement, entrainment, and turbine mortality

Interview with Kenneth Baker, 22 October 2009

Lord Baker of Dorking was Secretary of State for Education and Science from May 1986 until July 1989. He was responsible for the 1988 Education Reform Act which introduced,for the first time, a National Curriculum in England and Wales. He set up a series of working groups to devise the new school curriculum. He discusses the reasons for introducing a national curriculum and his expectations of the History Working Group. His preference was for an overarching 'timeline' in the history curriculum. He reflects on the benefits which have resulted from the National Curriculum, but regrets that history was not made compulsory between the ages of 14 and 16, as he has initially intended. Interviewed by Nicola Sheldon

The low recombining pericentromeric region of barley restricts gene diversity and evolution but not gene expression

The low-recombining pericentromeric region of the barley genome contains roughly a quarter of the genes of the species, embedded in low-recombining DNA that is rich in repeats and repressive chromatin signatures. We have investigated the effects of pericentromeric region residency upon the expression, diversity and evolution of these genes. We observe no significant difference in average transcript level or developmental RNA specificity between the barley pericentromeric region and the rest of the genome. In contrast, all of the evolutionary parameters studied here show evidence of compromised gene evolution in this region. First, genes within the pericentromeric region of wild barley show reduced diversity and significantly weakened purifying selection compared with the rest of the genome. Second, gene duplicates (ohnolog pairs) derived from the cereal whole-genome duplication event ca. 60MYa have been completely eliminated from the barley pericentromeric region. Third, local gene duplication in the pericentromeric region is reduced by 29% relative to the rest of the genome. Thus, the pericentromeric region of barley is a permissive environment for gene expression but has restricted gene evolution in a sizeable fraction of barley's genes