Factors affecting variation in mortality of marine Atlantic salmon Salmo salar in Scotland

Abstract

Databases of site production have an important role to play in the investigation and understanding of diseases, since they store valuable amounts of disease and management data. Diseases pose an important constraint to economic expansion of aquaculture. They are dependent on the complex interacting factors of pathogen, environment, and host, and the causes of death can be related to nutritional, environmental, and genetic factors of the host or infectious agents. We examined the drivers of mortality from a single site-production database, which represented one-third of Scottish farmed salmon Salmo salar L. production in 2005, to determine whether mortality 'benchmarking' data could be generalised across sites and production cycles. We show that farm mortality records play an important role in studying mortality losses and identifying of management problems in production. We found that mortalities varied across the months of the year and with the time of year of initial stocking. Production cycles that started in the third quarter of the year had the highest mortality overall. Furthermore, we found site-to-site variation in mortality that may have been caused by either random occurrence of epidemics and environmental events or other local effects.KEY WORDS: Mortality · Disease · Database · Aquaculture Resale or republication not permitted without written consent of the publisherDis Aquat Org 103: [101][102][103][104][105][106][107][108][109] 2013 host (Snieszko 1974, Hedrick 1998. Prevention is a key element in the control of disease establishment (Wagner et al. 2002). A good level of understanding of the various factors predisposing to or causing diseases in farmed fish (Menzies et al. 1996) allows more efficient disease control in fish populations. Early and precise diagnosis, effective prevention measures and accurate epidemiological surveys are essential for minimizing the impact of infectious and non-infectious diseases in fish culture.In the production of marine salmon, the variation in data management among sites is broad, as is seen in other agricultural sectors such as the dairy industry (Kelton et al. 1997). Site management databases may vary from simple and paper-based through to complex computerised systems (Soares et al. 2011). A wide range of information is recorded in these databases, which often includes water temperature, stock origin, age, feed intake and mortality. These databases have an important role to play in the investigation and understanding of diseases, since they store valuable data for epidemiologists and can allow quantification of production losses over time. Furthermore these data can facilitate development of effective disease control strategies (Menzies et al. 1996, Crockford et al. 1999) through epidemiology.One of the most important variables recorded at the farm level is fish mortality rate (MacIntyre 2008, Anonymous 2009, Soares et al. 2011, which may include the cause of death, e.g. environmental problems, predators or disease (MacIntyre 2008, North et al. 2008...

Ultrastructure of intracytoplasmic Rickettsia-like infection of the gills of the teleost Archosargus probatocephalus (Sparidae) in northeastern Brazil

“…Considering that the present study resulted from a chance finding during the course of a myxozoan survey conducted on Archosargus probatocephalus (work in progress), we are unable to say whether the RLOs described here can increase host mortality. Nevertheless, a previous study showed that infection by RLOs may occur through weakened host immunity, as a result of abiotic changes to the aquatic environment (Soares et al, 2013).…”

“…These are commonly associated with differing pathogenicity in many geographical regions (Athanassopoulou & Karagouni, 2004;Azevedo, 1993;Azevedo et al, 2005;Birkbecka & Ringøb, 2005;Bower et al, 1994;Cusack et al, 2002;Fryer et al, 1990;Fryer & Lannan, 1994;Guo et al, 2004;Molloy et al, 2001;Turnbull, 1993;Villalba et al, 1999;Yuksel et al, 2006). Rickettsial and bacterial diseases that affect a wide range of freshwater, brackish water and marine fish (Bower et al, 1994;Mauel et al, 2003;Soares et al, 2013;Weinert et al, 2009), including ornamental species (Mauel et al, 2007) have been described. Elevated economic losses due to occurrences of rickettsial infections in cultivated fish have also frequently been reported (Branson & Diaz-Munoz, 1991;Chern & Chao, 1994;Corbeil et al, 2005;Cusack et al, 2002;Fryer et al, 1990;Mauel et al, 2003).…”

Applicability of a food chain analysis on aquaculture of Atlantic salmon to identify and monitor vulnerabilities and drivers of change for the identification of emerging risks

“…Water temperature may also affect salmon health and its capacity to cope with stressors. For example, Soares et al (Soares et al, 2013) found that cohorts of smolts transferred to the marine environment in the third quarter of the year, when water temperatures are increasing, showed the highest mortality. Stene et al (2014a) observed that cohorts of salmon that become infected when the sea temperature decreases have longer incubation periods and may therefore sere longer as asymptomatic reservoir than when the water temperature is increasing.…”

“…Prevention is a key element in the control of disease establishment. Early and precise diagnosis, effective prevention measures and accurate epidemiological surveys are essential for minimizing the impact of infectious and non-infectious diseases in fish culture (Soares et al, 2013). The viral infectious salmon anaemia (ISA) and pancreatic disease (PD) together with salmon sea lice are considered to be the main health management issues in Atlantic salmon farming.…”