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HAVBRUK2-Stort program for havbruksforskning

Understanding and monitoring mortality in farmed fish towards sustainable growth in aquaculture

Alternative title: Bedre forståelse og overvåking av dødelighet i oppdretttsfisk for en bærekraftig vekst i akvakultur

Awarded: NOK 6.9 mill.

Project Number:

294647

Application Type:

Project Period:

2019 - 2022

Location:

Limiting mortality must be top priority in an ethical, sustainable production of fish. Low mortality is one of several indicators of good animal welfare, and it is important to highlight the possibilities the industry has to limit the mortality in its production. This project will therefore help the industry, the authorities and others to understand what causes mortality in the aquaculture industry. The goal is to develop a portal where mortality is displayed in real time in an interactive map or other graphic representation. Unexpectedly high mortality or unusual occurrences of mortality will be flagged in the portal as soon as it occurs, allowing a quick launch of investigations to uncover the causes. The first objective of the project was to provide an in-depth description of mortality and how it varies with season and year and between farms and geographical areas. Through analyzes of data reported to Altinn, it emerged that mortality rates have increased for cohorts slaughtered in 2016-2018 compared with those slaughtered in 2014-2015. It also emerged that mortality is greatest during the first two months after sea-transfer, where there are very large variations between farms. Some farms report mortality up to 50% during this period. Mortality is lowest in months 3-9 after sea-transfer, and with little variation between farms, but in months 12-20 there is increased mortality and with some variation between farms. It also appears that mortality is greatest in production zones with high density of farms. The results has been published in the article: Spatio-temporal variations in mortality during the seawater production phase of Atlantic salmon (Salmo salar) in Norway (https://doi.org/10.1111/jfd.13142) Subsequently, a model has been developed based on the same data, and with the inclusion of salinity data and reported treatments for salmon lice. The model showed that the number of dead fish per 1000 fish per month depends on surface temperature and salinity, production zone, weight at sea-transfer, time of sea-transfer (month), average weight and treatments against salmon lice. Of these, non-medicinal treatment against salmon lice is the single factor with the greatest significance for mortality, but non-medicinal treatment is also a significant factor. The model show that the baseline mortality was 3.05 dead fish out of 100 fish per month. (50% range: 1.58 - 6.53). The results has been published in the article: Factors associated with baseline mortality in Norwegian Atlantic salmon farming (https://doi.org/10.1038/s41598-021-93874-6) During the project period, we have gained access to data on mortality and production also in the freshwater phase. These data contain less information than those for the marine phase, but it was an important goal to try to find out if the data could be used to say something about survival and welfare in hatchery production. Therefore, we used a similar approach as for the first article on this data, and ended up with a model that describes the mortality in juvenile fish production. This is the first time this has been done in Norway, and the work has been published in the article: Mortality patterns during the freshwater production phase of salmonids in Norway (https://doi.org/10.1111/jfd.13522) In another model, where we have a finer time resolution than the previous one, detailed daily production data from salmon producers are used to get closer to how various factors affect daily mortality. Three companies supplemented data from 41 farms with a total of 50 fishgroups. In this work, the number of dead fish per day is modeled as a function of various variables such as salinity, temperature, number of days since release, outbreaks of pancreatic disease and various sea lice treatments. Preliminary results show that mortality increases up to 9 times on the same day as thermal treatment, but decreases to 5 times increase the day after treatment. An increased mortality can be observed up to 15 days after treatment. Non-medicinal treatment results in an increased mortality the day after treatment of up to 6 times the usual mortality. The model is not complete, but these preliminary results show good agreement with the findings from the first part of the project. As a first step towards developing a system for warning of increased mortality, an application has been developed that shows mortality at various levels from 2015-2019. In this app, the user has the opportunity to see mortality over years, months, counties or production areas, and can compare mortality across these parameters: http://apps.vetinst.no/Laksetap/

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The ultimate goal of this project is to help producers, competent authorities and other stakeholders to understand drivers of mortality in aquaculture and provide them with tools to monitor and mitigate mortality in farmed fish. Low mortality can generally be regarded as a first indicator of good welfare, and minimizing mortality is a top-priority in an ethical, sustainable production of fish. The project will build on experience from producers, who have an extensive knowledge on individual factors driving mortality, but who have to adhere to regulations against specific diseases or environmental challenges that might be detrimental to the control of other adverse effects. The project will utilize extensive time series of 16 years of monthly data reported from all active Norwegian aquaculture farms for a model and a description of spatio-temporal differences in baseline mortality. The project will further develop a system that uses monthly reporting of production data to identify events of unusual mortality patterns in a syndrome-based surveillance system. Such events can be indicative of disease outbreaks or failures in management routines, and thus help stakeholders to activate prompt investigations and suitable responses. In order to reach a goal stated by the politicians of quintupling the aquaculture production by 2050 the producers are implementing new technologies, and changing their ways of producing. Measuring mortality and comparing to a baseline mortality will provide a robust tool to evaluate the impact on fish welfare due to these changes. High-resolution data from a subset of the producers will be used in a refined model that can calculate the effects of individual managemental factors on disease-driven mortality dependent on time and place of the application of these factors. Thus, the primary objective of the project is to disentangle the drivers for mortality and provide inputs for discussion on regulation of diseases.

Publications from Cristin

No publications found

Funding scheme:

HAVBRUK2-Stort program for havbruksforskning