Acronym NA
Category
Fisheries
Title Evaluering (review) av faktagrunnlaget om påvirkning mellom oppdretts- og villaks: Lakselus, Nofima - Evaluation (review) of the factual basis on the impact between farmed and wild salmon: Salmon lice, Nofima Programme National Programme
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source National Coordinator Solveig van Nes Coordinator email solveig.van-nes@nofima.no
Coordinator institution
NOFIMA - Norwegian Institute of Food, Fisheries and Aquaculture Research (Norway)
Institutions involved
NA
Start year 2010 End year 2011 Funding (€) € 30,470 Website https://www.fhf.no/prosjekter/prosjektbasen/900579/ Summary A factual basis has been reviewed regarding interactions of wild and farmed populations of salmonids with salmon lice. Developments on both sides of the North Atlantic show the same trend in stock development geographically: In recent decades, wild salmon stocks are described as stable in northern areas and declining to the south in both Europe and North America. both sides of the Atlantic). In large parts of the southern distribution area, salmon rivers are considered threatened and / or extinct. This relatively clear north-south gradient and the covariation in stock size of wild salmonids over such a large geographical scale suggests a common response of stocks to large, global or sectoral conditions (changes or fluctuations in stock regulatory effects that are common and / or work together over a large geographical area). There is growing evidence that living conditions for anadromous salmonids in the ocean are the main cause that can explain such a covariation: A plausible explanation for stock-regulating effects on such a large scale is climate change and natural fluctuations in sea temperature that can cause fluctuations in nutrient base and thus marine survival. for salmon. Furthermore, the common denominators for all areas in the south where local populations are extinct or threatened (international level): High population density, a lot of dam construction in the main course of watercourses, pollution and drainage of watercourses. The probability that potentially negative effects of an increased incidence of salmon lice in fish farms can have an effect on such a large geographical scale is virtually non-existent. This is supported by the fact that: 1. The salmon stock is affected in its entire distribution area, even where there is no farming. 2. The decline is greatest in the south, where farming only occurs on a small scale. 3. The decline is smallest or non-existent in northern parts of the distribution area, where the occurrence of farming is greatest. 4. There is no documentation of the causal relationship; elevated salmon lice - decline in stock, which can work on such a large scale. There are few descriptions of the lice population in a more historical perspective. Registrations at that time were usually of salmon infection on incoming spawning fish (large salmon), while today's registration is on migrating smolts. As can be seen, there is currently no documentation that indicates that the level of infection in wild salmon in the sea should have changed in a historical perspective. However, it is also well documented that the incidence of salmon lice in coastal areas (in the immediate vicinity of fish farms) is periodically very elevated, which in turn exposes migrating smolts to a greater infection pressure than it probably would have been without the presence of fish farms. Nofima has reviewed literature that demonstrates variation in salmon lice populations in areas with and without farming, and sees that: 1. The number of salmon lice / occurrence of salmon lice may be periodically increased in areas with farming due to a higher number of hosts (= covariation in the occurrence of salmon lice and farmed fish). 2. Local salmon lice population covaries, and in other cases, varies regardless of the presence of farming. 3. Covariation has been demonstrated in the amount of salmon lice on smolts and elevated salmon lice levels in fish farms (infection can occur from farmed fish to wild fish). 4. It has been documented that high levels of salmon lice can be fatal to smolts. Nofima, on the other hand, cannot see that a cause-effect relationship has been documented between stock size and the presence of salmon lice (as a separate factor). There are no cases that document that salmon lice are the main cause of changes in stock size. At the same time, it is so that many of documentation does not have to mean lack of coherence; It can also mean that it is difficult to document whether there is a connection or not. There is undoubtedly a need for more knowledge in this area. It has been proven that both sea trout, sea trout and other species such as. stingrays can be carriers and act as a reservoir for salmon lice. Sea trout live in fjords and coastal waters all year round and can therefore maintain production of salmon lice throughout the year. It is probable that wild sea trout contribute significantly to the maintenance of local salmon lice populations. It is probable that infection with salmon lice that results in osmoregulatory problems can lead to behaviors such as premature return. Despite the fact that the description of this phenomenon is relatively new, one cannot see that it has been documented that this is a new phenomenon. Weakened fish is possibly more susceptible to lice infestation than a "robust" / non-weakened fish, but it is uncertain how it will be able to affect or contribute to the maintenance of local salmon lice populations. On the other hand, it has been shown that acidification can indirectly affect the survival of smolts in the marine phase in that the smolts that are exposed to an acidic environment (with aluminium) have a higher mortality due to lice infestation compared to smolts from "fresh" freshwater environments. The extent to which Atlantic salmon may have developed resistance (i.e. the extent to which natural selection for lice resistance has taken place) is uncertain. The effect of natural selection will increase with increasing salmon lice-related mortality. In populations where mortality is to a small extent related to (increased) infestation of salmon lice, natural selection for resistance to lice will not be of particular importance either. Based on available facts, it cannot be seen that there is any scientific evidence of a simple relationship between the number of sexually mature female lice, essentially a product of the number of farmed salmon and the number of female lice per fish, and the marine survival of wild salmonids, and that the calculation of sustainable level is therefore not sufficiently knowledge-based. The dispersal dynamics of salmon lice are very complex and correspond to the complexity of the fjord systems and along the coast in general. Variation in topography, climate, geographical location, flow conditions, seasonal effects and local weather conditions can contribute significantly to variation in scattering patterns both in time and space. Assumptions about "smart location of facilities" will therefore involve a significant element of speculation, but if one were to allow oneself to speculate, one can on a general basis mention that some areas in the fjord system generally seem to be more exposed than others. In an ideal situation (where the goal is the most efficient management of wild salmon), it would be desirable for modelling of dispersal patterns to be done more specifically, possibly separately for each fjord system, in order to be able to give better advice on when de-lice will be most effective.
Keywords
Fish;
Parasite;
Salmon;
Escapes;
Environmental impact;
Marine Region
76
Not associated to marine areas
0
Marine Region Map
