Modelling climate change effects on Atlantic salmon: Implications for mitigation in regulated rivers.

Climate change is expected to alter future temperature and discharge regimes of rivers. These regimes have a strong influence on the life history of most aquatic river species, and are key variables controlling the growth and survival of Atlantic salmon. This study explores how the future abundance of Atlantic salmon may be influenced by climate-induced changes in water temperature and discharge in a regulated river, and investigates how negative impacts in the future can be mitigated by applying different regulated discharge regimes during critical periods for salmon survival. A spatially explicit individual-based model was used to predict juvenile Atlantic salmon population abundance in a regulated river under a range of future water temperature and discharge scenarios (derived from climate data predicted by the Hadley Centre's Global Climate Model (GCM) HadAm3H and the Max Plank Institute's GCM ECHAM4), which were then compared with populations predicted under control scenarios representing past conditions. Parr abundance decreased in all future scenarios compared to the control scenarios due to reduced wetted areas (with the effect depending on climate scenario, GCM, and GCM spatial domain). To examine the potential for mitigation of climate change-induced reductions in wetted area, simulations were run with specific minimum discharge regimes. An increase in abundance of both parr and smolt occurred with an increase in the limit of minimum permitted discharge for three of the four GCM/GCM spatial domains examined. This study shows that, in regulated rivers with upstream storage capacity, negative effects of climate change on Atlantic salmon populations can potentially be mitigated by release of water from reservoirs during critical periods for juvenile salmon.

Understanding and managing fish populations: keeping the toolbox fit for purpose.

Wild fish populations are currently experiencing unprecedented pressures, which are projected to intensify in the coming decades. Developing a thorough understanding of the influences of both biotic and abiotic factors on fish populations is a salient issue in contemporary fish conservation and management. During the 50th Anniversary Symposium of The Fisheries Society of the British Isles at the University of Exeter, UK, in July 2017, scientists from diverse research backgrounds gathered to discuss key topics under the broad umbrella of 'Understanding Fish Populations'. Below, the output of one such discussion group is detailed, focusing on tools used to investigate natural fish populations. Five main groups of approaches were identified: tagging and telemetry; molecular tools; survey tools; statistical and modelling tools; tissue analyses. The appraisal covered current challenges and potential solutions for each of these topics. In addition, three key themes were identified as applicable across all tool-based applications. These included data management, public engagement, and fisheries policy and governance. The continued innovation of tools and capacity to integrate interdisciplinary approaches into the future assessment and management of fish populations is highlighted as an important focus for the next 50 years of fisheries research.

Pop-up satellite archival tag effects on the diving behaviour, growth and survival of adult Atlantic salmon Salmo salar at sea.

The effects of large, externally attached pop-up satellite archival tags (PSATs) were compared with those of small implanted data storage tags (DSTs) on adult Atlantic salmon Salmo salar during their ocean migration in regards to depth utilization, diving depth, diving rate, diving speed and temperatures experienced. Additionally the return rate and growth of individuals tagged with PSATs was compared with those of small acoustic tags and DSTs. Overall, the depth distribution of individuals tagged with PSATs was similar to that of those tagged with DSTs, reflecting the pelagic nature of S. salar at sea. Individuals tagged with PSATs, however, dived less frequently and to shallower depths, and dived and surfaced at slower velocities. Sea surface temperatures experienced by individuals tagged with PSATs were similar to those experienced by those tagged with DSTs for the same time of year, suggesting that there were no large differences in the ocean migration. Return rates did not depend on whether individuals were tagged with PSATs or not, indicating that survival at sea was not impacted by PSATs in comparison to small internal tags. Individuals tagged with PSATs, however, had a smaller increase in body mass than those tagged with acoustic tags or DSTs. It was concluded that PSATs are suitable for use in researching large-scale migratory behaviour of adult S. salar at sea, but that some effects on their behaviour from tagging must be expected. Effects of PSATs may be largest in the short term when S. salar are swimming in bursts at high speeds. Even though individuals tagged with PSATs performed deep and frequent dives, the results of this study suggest that untagged individuals would perform even deeper and more frequent dives than tagged individuals.

Ice-dependent winter survival of juvenile Atlantic salmon.

Changes in snow and ice conditions are some of the most distinctive impacts of global warming in cold temperate and Arctic regions, altering the environment during a critical period for survival for most animals. Laboratories studies have suggested that reduced ice cover may reduce the survival of stream dwelling fishes in Northern environments. This, however, has not been empirically investigated in natural populations in large rivers. Here, we examine how the winter survival of juvenile Atlantic salmon in a large natural river, the River Alta (Norway, 70°N), is affected by the presence or absence of surface ice. Apparent survival rates for size classes corresponding to parr and presmolts were estimated using capture-mark-recapture and Cormack-Jolly-Seber models for an ice-covered and an ice-free site. Apparent survival (Φ) in the ice-covered site was greater than in the ice-free site, but did not depend on size class (0.64 for both parr and presmolt). In contrast, apparent survival in the ice-free site was lower for larger individuals (0.33) than smaller individuals (0.45). The over-winter decline in storage energy was greater for the ice-free site than the ice-covered site, suggesting that environmental conditions in the ice-free site caused a strong depletion in energy reserves likely affecting survival. Our findings highlight the importance of surface ice for the winter survival of juvenile fish, thus, underpinning that climate change, by reducing ice cover, may have a negative effect on the survival of fish adapted to ice-covered habitats during winter.

River and estuary movements of yellow-stage American eels Anguilla rostrata, using a hydrophone array.

Patterns of summertime movement and habitat use of yellow-stage American eels Anguilla rostrata within York River and estuary and Gaspé Bay (Gaspesia, Québec, Canada) were examined using acoustic telemetry. Fifty fish were tagged with acoustic transmitters and released, either in the river or in the upper estuary, and their patterns of movement and habitat use were monitored at short spatial and temporal scales during the summer months using a dense hydrophone array. Approximately half of the fish released in the river swam to the estuary; two-thirds of the fish released within the estuary did not move out of the estuary. Anguilla rostrata were detected more frequently and had a greater areal range of detections during night, suggesting greater nocturnal activity. Longitudinal movements within the estuary tended to occur nocturnally, with upstream movements from early to late evening, and downstream movements from late evening to early morning. Approximately one-third of fish showed a regular pattern of movement, tending to reside in the deeper, downstream part of the estuary during day and in the shallower, more upstream part of the estuary during night. Approximately a quarter of fish, located in the upper estuary, remained upstream during both night and day. The remaining fish showed patterns intermediate between these two.

A new enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against foot-and-mouth disease virus. I. Development and method of ELISA.

A liquid-phase blocking sandwich ELISA has been developed for the quantification of antibodies against foot-and-mouth disease virus which may replace the virus neutralisation (VN) test. This test employs the incubation of a constant amount of antigen with a range of test serum dilutions in the liquid-phase before being assayed using a trapping ELISA. Thus it does not rely on the availability or growth of tissue culture cells. The assay is rapid and relatively simple to perform, reagents are used economically and results may be recorded within 24 h. The ELISA is sensitive and results are more specific and more reproducible than those obtained by VN. Results are expressed as reciprocal antibody titres which are analogous and of a similar order to those recorded by VN. Individual titres, therefore, may be easily assessed by workers in the field who are already familiar with VN.

Foot-and-mouth disease and the African buffalo (Syncerus caffer). 1. Carriers as a source of infection for cattle.

Ten pregnant buffalo cows, six of which were subsequently shown to be carriers of SAT 1, 2 and 3 viruses, were captured in the Kruger National Park (KNP) and allowed to calve in captivity. The buffalo cows and calves were separated by a fence from 6 FMD susceptible cattle but the buffalo and cattle were obliged to use common drinking troughs and hay racks. Over a period of 15 months, during which the buffalo calves lost their maternally-derived immunity, neither the buffalo calves nor the susceptible cattle became infected with FMD virus. By the end of the observation period, however, only 1 buffalo cow still had detectable virus in its oesophageal/pharyngeal specimens.

Simultaneous vaccination of cattle against foot-and-mouth disease and rinderpest.

A total of 118 local cattle in the Sultanate of Oman were divided into three groups, one which received a trivalent inactivated foot-and-mouth disease vaccine, another which received attenuated tissue culture rinderpest vaccine and a third which received both vaccines simultaneously at separate sites on opposite sides of the neck. The serological response to vaccination was monitored at day 0, 21 and 42 in virus neutralisation tests. The simultaneous administration of the two vaccines produced no ill effects and the serological responses did not differ significantly from the response to either vaccine given separately.

A study of antigenic variants of foot-and-mouth disease virus by polyacrylamide gel electrophoresis of their structural polypeptides.

Twenty-nine foot-and-mouth disease (FMD) type A virus strains, previously classified serologically as distinct subtypes were analysed by polyacrylamide gel electrophoresis (PAGE) to determine the extent of variation in the pattern of the structural polypeptides and to evaluate the technique as an aid to existing subtyping techniques. The majority of the subtypes examined had distinct polypeptide patterns, however, some variation also occurred between strains within a subtype. The position of VP2(1B) and VP3(1C) was often unchanged in different strains within a subtype and between geographically related subtypes over long periods of time. Changes in the position of VP1(1D) were also observed within a subtype. The technique was considered to be of value for the screening of isolates prior to conventional serological subtyping procedures and in the tracing of the possible origin of FMD outbreaks.

The duration of the foot-and-mouth disease virus carrier state in African buffalo (i) in the individual animal and (ii) in a free-living herd.

The maintenance of a virus depends on a number of factors, including the duration of infectivity and the size of the available host population. In this work, foot-and-mouth disease virus was shown to persist in individual African buffalo (Syncerus caffer) for up to at least five years; thus, the duration of infectivity is more than adequate to cover the normal periods between calving peaks. In a small isolated free-living population which varied from 30 to 100 buffalo, two immunological types of foot-and-mouth disease virus were maintained for at least 24 years and through several generations.

Hepatitis A-induced remission of minimal change nephropathy.

A two-month remission of minimal change disease induced by hepatitis A infection occurred. The remission was substantiated by clinical, biochemical, and pathologic methods. To our knowledge, this is the first such case reported in the literature.

A rapid enzyme-linked immunosorbent assay for the detection of foot-and-mouth disease virus in epithelial tissues.

A rapid double sandwich enzyme-linked immunosorbent assay (ELISA) has been used for the identification and type differentiation of foot-and-mouth disease (FMD) viruses in epithelial tissue samples submitted for diagnosis from the field. No difficulty was experienced in the direct typing of freshly harvested epithelium from recently ruptured vesicles by the complement fixation (CF) test or ELISA. The ELISA was more sensitive and specific, but proved no more efficient than the traditional CF test in the direct typing of samples of poorer quality from many countries overseas where communications are often difficult. However, when both tests were used concurrently, FMD virus typings were confirmed in 27 more samples. Some possible reasons for the failure of ELISA to detect virus in certain cases are discussed.

Serological response of cattle to simultaneous vaccinations against foot-and-mouth disease and haemorrhagic septicaemia.

In Malaysia, where vaccination campaigns against foot-and-mouth disease and haemorrhagic septicaemia are routinely carried out, it was desirable to determine whether it was safe and efficacious to administer both vaccines simultaneously. A trial group of 104 cattle was divided into three groups; group 1 animals received both vaccines simultaneously, group 2 animals received only foot-and-mouth disease vaccine and group 3 animals received only haemorrhagic septicaemia vaccine. The serological response to vaccinations was monitored at 0, 21 and 35 days by the virus neutralisation test for foot-and-mouth disease and the mouse-protection and indirect haemagglutination tests for haemorrhagic septicaemia. The simultaneous administration of the two inactivated vaccines produced no adverse effects and the serological response did not differ from the response to either vaccine given separately, thus indicating that cattle may be safely and effectively vaccinated simultaneously in this way.

Neutralising antibodies to wildebeest-derived malignant catarrhal fever virus in African wildlife.

A total of 2,722 sera collected between 1963 and 1983, from 43 different species of wildlife in 11 African countries was examined for neutralising antibodies against the wildebeest-derived strain of malignant catarrhal fever (MCF) virus. Antibodies were demonstrated in 10 species of Bovidae which included eight species from the sub-family Hippotraginae and one species each from Bovinae and Antilopinae. Neutralising antibodies were also recorded in hippopotamus. It is suggested that the high prevalence of antibodies recorded in sera from waterbuck and reedbuck indicate infection with MCF. However, titres in other species may be due to antigenically related viruses.

Neutralising antibodies to lumpy skin disease virus in African wildlife.

A total of 3445 sera from 44 different wild species collected between 1963 and 1982 in 11 African countries south of the Sahara, were examined for neutralising antibodies to Lumpy Skin Diseases (LSD) Virus (prototype Neethling). Antibodies were demonstrated in six species but were of low prevalence. It was concluded from the generally negative results, that wildlife in Africa probably does not play a very important part in he perpetuation and spread of LSD Virus.