Environmental drivers of Atlantic salmon behaviour in sea-cages: A review

Olfactory toxicity in fishes.

We review factors affecting the within-river spawning migration of Atlantic salmon. With populations declining across the entire distribution range, it is important that spawners survive in the last phase of the spawning migration. Knowledge on the factors affecting migration is essential for the protection of populations, and to increase the success of reintroduction programmes. A number of studies have documented that the upstream migration may be delayed for many weeks at man-made obstacles such as power station outlets, residual flow stretches, dams, weirs and fishways. The fish may also be delayed at natural migration barriers. Often, the magnitude of delay is not predictable; fish may be considerably delayed at barriers that appear to humans to be easily passable, or they may quickly pass barriers that appear difficult. Stressful events like catch-and-release angling may affect upstream migration. Impacts of human activities may also cause altered migration patterns, affect the within-river distribution of the spawning population, and severe barriers may result in displacement of the spawning population to other rivers. Factors documented to affect within-river migration include previous experience, water discharge, water temperature, water velocity, required jump heights, fish size, fish acclimatisation, light, water quality/pollution, time of the season, and catch and handling stress. How each of these factors affects the upstream migration is to a varying extent understood; however, the effects may differ among different river sections and sites. There are likely a number of additional important factors, and the relationship between different factors is complex. The understanding of general mechanisms stimulating fish within-river migration are still lacking, and it cannot be reliably predicted under which conditions a fish will pass a given migration barrier or which conditions are needed to stimulate migration at different sites. The strong focus on the effects of water discharge in past work may have hampered consideration of other factors. Exploration of the influence of these other factors in future studies could improve our understanding of what controls the upstream migration.

Factors affecting the within-river spawning migration of Atlantic salmon, with emphasis on human impacts

Nitrite is an intermediate in the oxidation of ammonium to nitrate. An elevated ambient nitrite concentration is a potential problem for freshwater fish since nitrite is actively taken up across the gills in competition with chloride. Nitrite is a well-known toxicant for fish as well as a disrupter of multiple physiological functions including ion regulatory, respiratory, cardiovascular, endocrine and excretory processes. One critical consequence of nitrite accumulation is the oxidation of haemoglobin to methaemoglobin, compromising blood oxygen transport. Nitrite toxicity to fish varies considerably and depends on a large number of external and internal factors. Among the most important ones are water quality (e.g. pH, temperature, cation, anion and oxygen concentration), length of exposure, fish species, fish size and age, and individual fish susceptibility. Chloride concentration in water is considered one of the most important factors influencing nitrite toxicity to fish. The importance of individual factors is assessed and re-evaluated continuously.

/pdf/nitrite-influence-on-fish-a-review-2pgjqhlx6m.pdf

Nitrite influence on fish: a review

War is an ever-present force that has the potential to alter the biosphere. Here we review the potential consequences of modern war and military activities on ecosystem structure and function. We focus on the effects of direct conflict, nuclear weapons, military training, and military produced contaminants. Overall, the aforementioned activities were found to have overwhelmingly negative effects on ecosystem structure and function. Dramatic habitat alteration, environmental pollution, and disturbance contributed to population declines and biodiversity losses arising from both acute and chronic effects in both terrestrial and aquatic systems. In some instances, even in the face of massive alterations to ecosystem structure, recovery was possible. Interestingly, military activity was beneficial under specific conditions, such as when an exclusion zone was generated that generally resulted in population increases and (or) population recovery; an observation noted in both terrestrial and aquatic systems. Additionally, military technological advances (e.g., GPS technology, drone technology, biotelemetry) have provided conservation scientists with novel tools for research. Because of the challenges associated with conducting research in areas with military activities (e.g., restricted access, hazardous conditions), information pertaining to military impacts on the environment are relatively scarce and are often studied years after military activities have ceased and with no knowledge of baseline conditions. Additional research would help to elucidate the environmental consequences (positive and negative) and thus reveal opportunities for mitigating negative effects while informing the development of optimal strategies for rehabilitation and recovery.

/pdf/the-effects-of-modern-war-and-military-activities-on-251pq0rdyt.pdf

The effects of modern war and military activities on biodiversity and the environment

Upstream movements of radio-tagged and control adult chinook salmon (Oncorhynchus tshawytscha) were monitored during spring and fall 1976 and spring 1977 in the lower Snake River, southeastern Wash...

Spawning Migration of Adult Chinook Salmon (Oncorhynchus tshawytscha) Carrying External and Internal Radio Transmitters

Studies at the Pacific Northwest Laboratory have evaluated fish behavior and migration in response to gas-supersaturated water, thermal discharge, water-soluble fractions (WSFs) of coal liquids and other environmental stresses. Approaches have included biotelemetry in the field, and avoidance/attraction and predator/prey studies in the laboratory. This article specifically addresses three study examples and integrates the results with those of related studies. Overall, major findings included the following: Thermal discharges (surface water Δts 0->17°C) did not block upstream migration of sonic-tagged adult chinook salmon (Oncorhynchus tschawytscha) and rainbow trout (O. mykiss, formerly Salmo gairdneri) in the Hanford Reach of the Columbia River. Juvenile chinook salmon avoided thermal discharges in the laboratory when Δts exceeded 9 to 11°C above ambient. However, juvenile salmon were more susceptible to predation at 10 to 20% of the thermal dose causing loss of equilibrium. Radio-tagged adult chinook salmon swam deeper in supersaturated water than in normally saturated water in the Snake River and, thereby, avoided the upper, critical zone. Carp (Cyprinus carpio) and black bullhead (Ictalurus melas) did not always avoid lethal gas levels in the laboratory and some fish died in the test apparatus. Fathead minnow (Pimephales promelas) avoided the WSF of a coal liquid at concentrations causing acute effects but not at those causing chronic effects. Rainbow trout did not avoid coal liquid WSFs although they reportedly avoid the major constituent, phenol, tested as a pure compound. Susceptibility to predation of juvenile rainbow trout did not increase until phenol concentrations reached the acute LC50. A conceptual model to link avoidance and toxicological data for environmental assessment is presented.

Fish behavior and environmental assessment

Twenty-nine white sturgeon (Acipenser transmontanus) were instrumented in 1975 and 1976 with separately identifiable radio transmitters to study seasonal movements in the mid-Columbia River, southeastern Washington. Tagged fish remained in free-flowing areas of the river and were inactive in winter. Movements occurred in summer and early fall. Activity appeared related to water temperature and sturgeon size.

https://digitalcommons.brockport.edu/cgi/viewcontent.cgi?article=1020&context=env_facpub

Seasonal Movements of White Sturgeon (Acipenser Transmontanus) in the Mid-Columbia River

Since the inception of the U.S. DOE Hanford Site in 1943, numerous studies have been conducted on terrestrial wildlife. Onsite contractors have focused their attention on the role of wildlife in the uptake and transport of radionuclides. Graduate students from across the nation have also completed more than 15 theses on wildlife. This paper discusses the past history of wildlife research at Hanford and the individual species of wildlife that have been observed at Hanford. Forty species of mammals, 187 species of birds, 3 species of amphibians and 9 species of reptiles have been documented on the Hanford Site to date.

The status, distribution and ecology of wildlife on the U.S. Doe Hanford Site: A historical overview of research activities

Heavy metal concentrations in great blue heron fecal castings in Washington State: a technique for monitoring regional and global trends in environmental contaminants.

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