A survey of aquatic invertebrates of the Somerset Levels, August 13-14, 1981

Since 1975 the wildlife interest of the Somerset Levels and Moors have been assessed. Detailed information has been obtained on the conservation interest of meadows, breeding and wintering bird populations and the botany of aquatic habitats (rhynes). Little work to date has been carried out on the terrestrial and aquatic invertebrate fauna. The prime aim of this survey was to sample a wide variety of rhynes in order to obtain information on the nature and distribution of aquatic invertebrates.

The Lune catchment abstraction management strategy. Consultation document September 2003

This consultation document sets out the proposed future licensing strategy for the Lune Catchment Abstraction Management Strategy (CAMS) area. Following the three month consultation period, the Environment Agency will determine the final licensing strategy and publish it in the CAMS document. The strategy will provide an indication of whether new abstraction licences are likely to be available and the conditions that should be expected on licences. Water plays a vital role in the Lune catchment, providing water for public supply, supporting recreation, such as angling and canoeing, and providing sustainable flows to preserve numerous designated sites. There is minimal abstraction throughout much of the catchment, apart from the lower reaches of the River Lune. The document is split into five sections relating to the CAMS process. Sections 1 to 4 outline the CAMS process, and Section 5 outlines the proposed licensing strategy for the Lune CAMS areas. It is important to note that this strategy deals with groundwater and surface water abstractions separately; Sections 4 and 5 are split to differentiate between the surface water and groundwater results and strategy.

River Ure: fisheries drought report 1996

Yorkshire Water Services (YWS) are currently granted a Time Limited Licence (TLL) for abstraction at Kilgram Bridge which is due for renewal in 1999. The Environment. Agency requires information on fish populations with regards to drought conditions and any possible effects that abstraction may have when considering licence renewal. In' order to evaluate any effects of drought and abstraction a three year study was instigated to examine fish populations. Surveys were conducted at nine main River Ure sites and two tributaries in which the triennial rolling programme formed the basis of site selection. Multi-method sampling techniques were carried out at several sites in order to evaluate capture efficiency. High densities of brown trout juveniles were observed in the tributaries with an indication that fish had become crowded as a result of low flows. Recruitment of brown trout in the tributaries was not directly related to flow levels in the main R. Ure. However, it is concluded that salmonids are at risk during drought flows and high temperatures from increased susceptibility to disease, predation, poor water quality and the direct lethal effect of high temperatures in shallow water.

Effect of different salinity levels on the fertilization and hatching of Heterobranchus bidorsalis

The success of induced spawning for the production of fish seed depends on many factors which affect hatchery conditions. This paper discusses the results of an investigation on the effects of six different levels of salinity on the fertilization and hatching of Heterobranchus bidorsalis eggs. The results indicate that spermatozoa of H. bidorsalis can survive under a wide range of saline concentrations, with survival increasing with an increase in salinity from 0 to 0.4% and then decreasing as the level of salinity increases. Survival was optimum of 0.4% saline concentration.

The fisheries Aspects of North West Water AuthoritySchemes to Increase Water Abstraction in West Cumbria

This is the report on the Fisheries Aspects of North West Water Authority Schemes to Increase Water Abstraction in West Cumbria by the Egremont and District Anglers’ Association. Existing river pollution and water abstraction in the Ennerdale Lake-River Ehen system is shown to have caused a major deterioration in the conditions in the Ehen fishery. This is reflected by the fact that catches of salmon, sea trout and smelts on the Ehen have all fallen to roughly 6% of the 1965 level; wich is far worse than the deterioration shown in salmon catches for S. W. Cumberland as a whole. Recommendations are made, in the light of proposals by North West Water Authority to increase water abstraction in West Cumbria, to prevent further deterioration in the Ehen fishery in the short term and to improve the situation in the longer term. It contains sections on pollution, water abstraction and fisheries background, flow statistics for and discussion of high water-droughts on the River Ehen, effects of droughts on Tidal Water and a discussion of N.W.W.A. Paper entitled `Water Resources in West Cumbria’ in the light of conditions on the River Ehen.

The effect of abstraction on fish and fisheries

This is the report on the Effect of Abstraction on Fish and Fisheries presented at the 24th IFM Annual Study Course, The Changing Face of Fisheries September 1993 at Cardiff. Water is abstracted from rivers for a wide variety of uses and causing potential for conflicts between abstracters, fisheries and conservation interests, especially during natural low flows. It looks at the potential effects that flow reduction has over various stages of salmonids at various stages of their life history. The flow at the time of smolt migration has been found to be positively correlated with the number of returning adults, and flow is considered to be one of the most important environmental factors inducing salmonids to enter fresh water and ascend rivers. The importance of time series data on fish stocks and angling success together with models which ultimately relate discharge to standing stock are discussed in relation to the setting up of Minimum Acceptable Flows.

The assessment of the flow requirements for upstream migration of salmonids in some rivers of North West England

This is the assessment of the flow requirements for upstream migration of salmonids in some rivers of North West England produced by the North West Water Authority in 1985. This report focuses on the automatic fish counters operating on the resistivity principle used for several years in North West England. This report aims to investigate the flow requirements for upstream migration of salmon and migratory trout. The data obtained confirmed that during summer months most fish movement occurs in the higher range of the available flows, but the migration flow range varied from year to year, depending on prevailing river levels. Of the other environmental variables measured, only water temperature and incident light intensity appear to have any direct association with fish movement. Information on migration flow ranges were used in conjunction with computer simulations of the effects of abstraction proposals on historical flows to assess the implications of these proposals for migratory fish.

River Leith fluvial aufit. Final project report

This is the River Leith fluvial audit: Final project report produced by Lancaster University in 1998. Freeze cores extracted from the upper and lower ends of River Leith illustrate that the bed is highly compacted in the downstream reach. Fine material is locally derived from bedrock at depths of only 32 cms into the bed and in one core fine material is 66% of the extracted core. Levels of fines that are believed to be detrimental to fish are put at 20 to 30%. Reduced flow and stream power from water abstraction may lead to a greater infiltration of fine material if gravels are not regularly flushed through with flood flows. Infiltration of fine material can lead to river bed compaction and concretion. A small abstraction may have no effect on the morphology of a river if the reduced discharge is within the normal range of flows experienced. However if the impact on flows is small it is still possible that fine sediment problems will develop progressively and the effects may not be noticed for several years.

Extreme tides and sea levels in California [abstract]

During the winter of 1982-1983, a combination of high tides, higher than normal sea level and storm-induced waves were devastating to the coast of California. Damage estimates for public and private property destruction in the coastal counties of California totaled over $100,000,000. Much higher than average sea levels played a very important contributory role in the flooding damage. These unusually high sea levels were due to a combination of higher than normal mixed layer temperature associated with a strong, 2-year El Nino, storm surge due to low atmospheric pressure and persistent winds, and the cumulative effect of steady, "global" rise in relative sea level. Higher than average high tides coincided to an unusual extent with the peak sea levels reached during the numerous storms between November 1982 and March 1983. Important cyclical variations occur in California's mixed tide regime and the consequences of these on extreme tides have not been properly considered previously. In fact, erroneous "predictions" of much higher tides in the 1990's appearing in the popular press during the 1982-83 flooding, caused much public apprehension.

U.S. west coast relative sea levels from tide gauges [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Examining secular changes in relative sea level along the U.S. west coast, we have identified strong tectonic signals. Tectonism exists not only on a coherent plate-wide scale (assuming a rigid plate approximation), but also on a sub-plate scale. In fact, differential tectonism between exotic or suspect geological terrain explains much of the spatial patterns of west coast tide-gauge data. Peltier's isostatic model appears not to explain the spatial pattern, implying glacio-isostatic adjustment is not the dominant contribution to the low-frequency signals. Eustatic effects cannot be identified unambiguously. These studies suggest several major questions/observations with regard to relative sea-level studies ...

Severe droughts reduce estuarine primary productivity with cascading effects on higher trophic levels

Using a 10-yr time-series data set, we analyzed the effects of two severe droughts on water-quality and ecosystem processes in a temperate, eutrophic estuary (Neuse River Estuary, North Carolina). During the droughts, dissolved inorganic nitrogen concentrations were on average 46–68% lower than the long-term mean due to reduced riverine input. Phytoplankton productivity and biomass were slightly below average for most of the estuary during a spring–autumn drought in 2002, but were dramatically lower than average throughout the estuary during an autumn–winter drought in 2007–2008. Droughts affected upper trophic levels through alteration of both habitat condition (i.e., bottom-water dissolved oxygen levels) and food availability. Bottomwater dissolved oxygen levels were near or slightly above average during the 2002 drought and during summer 2007. Concomitant with these modest improvements in bottom-water oxygen condition, fish kills were greatly reduced relative to the long-term average. Low-oxygen bottom-water conditions were more pronounced during summer 2008 in the latter stages of the 2007–2008 drought, and mesozooplankton abundances were eight-fold lower in summer 2008 than during nondrought years. Below-average mesozooplankton abundances persisted for well over 1 yr beyond cessation of the drought. Significant fish kills were observed in summer 2008 and 2009, perhaps due to the synergistic effects of hypoxia and reduced food availability. These results indicate that droughts can exert both ephemeral and prolonged multiyear influence on estuarine ecosystem processes and provide a glimpse into the future, when many regions of the world are predicted to face increased drought frequency and severity due to climate change.

Tag-reporting levels for red drum (Sciaenops ocellatus) caught by anglers in South Carolina and Georgia estuaries

A total of 1784 legal-size (≥356 mm TL) hatchery-produced red drum (Sciaenops ocellatus) were tagged and released to estimate tag-reporting levels of recreational anglers in South Carolina (SC) and Georgia (GA). Twelve groups of legal-size fish (~150 fish/group) were released. Half of the fish of each group were tagged with an external tag with the message “reward” and the other half of the fish were implanted with tags with the message “$100 reward.” These fish were released into two estuaries in each state (n=4); three replicate groups were released at different sites within each estuary (n=12). From results obtained in previous tag return experiments conducted by wildlife and fisheries biologists, it was hypothesized that reporting would be maximized at a reward level of $100/tag. Reporting level for the “reward” tags was estimated by dividing the number of “reward” tags returned by the number of “$100 reward” tags returned. The cumulative return level for both tag messages was 22.7 (±1.9)% in SC and 25.8 (±4.1)% in GA. These return levels were typical of those recorded by other red drum tagging programs in the region. Return data were partitioned according to verbal survey information obtained from anglers who reported tagged fish. Based on this partitioned data set, 14.3 (±2.1)% of “reward” tags were returned in SC, and 25.5 (±2.3)% of “$100 reward” tags were returned. This finding indicates that only 56.7% of the fish captured with “reward” tags were reported in SC. The pattern was similar for GA where 19.1 (±10.6)% of “reward” message tags were returned as compared with 30.1 (±15.6)% for “$100 reward” message tags. This difference yielded a reporting level of 63% for “reward” tags in GA. Currently, 50% is used as the estimate for the angler reporting level in population models for red drum and a number of other coastal finfish species in the South Atlantic region of the United States. Based on results of our study, the commonly used reporting estimate may result in an overestimate of angler exploitation for red drum.