Atlantic halibut (Hippoglossus hippoglossus L.) fry mortality after transportation with focus on biological and chemical aspects
Abstract
This thesis is a project finalizing Bachelor of Science degrees in the fields of biologicalchemistry and chemical- & environmental engineering. As the literature database for Atlantichalibut fish farming is scarce, the need for research is evident and potentially innovative. Theintention for this thesis was to show initiative contacting a company within the common fieldof interest that is fish farming and establish a mutually positive project. As a response toinquiry, Sterling White Halibut (SWH) presented a current problem that was very intriguingand relevant in an educative regard. The thesis project was designed in collaboration withSWH. The focus areas for monitoring were biological stress and water chemistry.Hippoglossus hippoglossus fry (6.70 ± 2.35 g) was transported approximately one thousandkilometers from Rørvik to Imsland. This thesis concerns one batch of 94 186 Atlantic halibutfry, with arrival at Imsland in March 2021. Measurements were made upon arrival and forone month after delivery. SWH reports that a late onset mortality occurs after transportationof small fry sent from the hatchery to the rearing facilities. Some fry batches have enduredsubstantial mortality which is considered caused by the transportation and transfer of fry. Thecomplex phenomenon of late onset mortality after transportation required investigation.Water sampling and chemical analysis were performed in two stages. First stage was atarrival. Analysis of transportation water compared to receiving water presented a relativelylarge difference in water quality. The second stage was comprised of daily analysis of thewater quality to monitor changes during the expected period of mortality. These differenceswere relatively minor. Biological parameters were measured at arrival and monitoredafterwards on each of the three field excursions to complement the water quality data. Thesedatasets served as the basis for the graphical- and statistical analysis. Mortality wasconsidered the prime biological parameter of which the other data were evaluated against.Correlation (r = -0.44) between pH and mortality was discovered and 19 % of the variationobserved is explained by the regression model of pH and mortality.Abrupt environmental differences in transportation water compared to receiving water wasrevealed, which contributes to additional stress after transportation. Stress levels wereindicated by elevated blood glucose concentration and increased red blood cell (RBC) count.Late onset mortality is suggested as a consequence of stress during and after transportation,including an unsuccessful adaptation to a new environment at the rearing facilities. This thesis is a project finalizing Bachelor of Science degrees in the fields of biologicalchemistry and chemical- & environmental engineering. As the literature database for Atlantichalibut fish farming is scarce, the need for research is evident and potentially innovative. Theintention for this thesis was to show initiative contacting a company within the common fieldof interest that is fish farming and establish a mutually positive project. As a response toinquiry, Sterling White Halibut (SWH) presented a current problem that was very intriguingand relevant in an educative regard. The thesis project was designed in collaboration withSWH. The focus areas for monitoring were biological stress and water chemistry.Hippoglossus hippoglossus fry (6.70 ± 2.35 g) was transported approximately one thousandkilometers from Rørvik to Imsland. This thesis concerns one batch of 94 186 Atlantic halibutfry, with arrival at Imsland in March 2021. Measurements were made upon arrival and forone month after delivery. SWH reports that a late onset mortality occurs after transportationof small fry sent from the hatchery to the rearing facilities. Some fry batches have enduredsubstantial mortality which is considered caused by the transportation and transfer of fry. Thecomplex phenomenon of late onset mortality after transportation required investigation.Water sampling and chemical analysis were performed in two stages. First stage was atarrival. Analysis of transportation water compared to receiving water presented a relativelylarge difference in water quality. The second stage was comprised of daily analysis of thewater quality to monitor changes during the expected period of mortality. These differenceswere relatively minor. Biological parameters were measured at arrival and monitoredafterwards on each of the three field excursions to complement the water quality data. Thesedatasets served as the basis for the graphical- and statistical analysis. Mortality wasconsidered the prime biological parameter of which the other data were evaluated against.Correlation (r = -0.44) between pH and mortality was discovered and 19 % of the variationobserved is explained by the regression model of pH and mortality.Abrupt environmental differences in transportation water compared to receiving water wasrevealed, which contributes to additional stress after transportation. Stress levels wereindicated by elevated blood glucose concentration and increased red blood cell (RBC) count.Late onset mortality is suggested as a consequence of stress during and after transportation,including an unsuccessful adaptation to a new environment at the rearing facilities.