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 biological chemistry and chemical- & environmental engineering. As the literature database for Atlantic halibut fish farming is scarce, the need for research is evident and potentially innovative. The intention for this thesis was to show initiative contacting a company within the common field of interest that is fish farming and establish a mutually positive project. As a response to inquiry, Sterling White Halibut (SWH) presented a current problem that was very intriguing and relevant in an educative regard. The thesis project was designed in collaboration with SWH. The focus areas for monitoring were biological stress and water chemistry. Hippoglossus hippoglossus fry (6.70 ± 2.35 g) was transported approximately one thousand kilometers from Rørvik to Imsland. This thesis concerns one batch of 94 186 Atlantic halibut fry, with arrival at Imsland in March 2021. Measurements were made upon arrival and for one month after delivery. SWH reports that a late onset mortality occurs after transportation of small fry sent from the hatchery to the rearing facilities. Some fry batches have endured substantial mortality which is considered caused by the transportation and transfer of fry. The complex phenomenon of late onset mortality after transportation required investigation. Water sampling and chemical analysis were performed in two stages. First stage was at arrival. Analysis of transportation water compared to receiving water presented a relatively large difference in water quality. The second stage was comprised of daily analysis of the water quality to monitor changes during the expected period of mortality. These differences were relatively minor. Biological parameters were measured at arrival and monitored afterwards on each of the three field excursions to complement the water quality data. These datasets served as the basis for the graphical- and statistical analysis. Mortality was considered 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 variation observed is explained by the regression model of pH and mortality. Abrupt environmental differences in transportation water compared to receiving water was revealed, which contributes to additional stress after transportation. Stress levels were indicated 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 biological chemistry and chemical- & environmental engineering. As the literature database for Atlantic halibut fish farming is scarce, the need for research is evident and potentially innovative. The intention for this thesis was to show initiative contacting a company within the common field of interest that is fish farming and establish a mutually positive project. As a response to inquiry, Sterling White Halibut (SWH) presented a current problem that was very intriguing and relevant in an educative regard. The thesis project was designed in collaboration with SWH. The focus areas for monitoring were biological stress and water chemistry. Hippoglossus hippoglossus fry (6.70 ± 2.35 g) was transported approximately one thousand kilometers from Rørvik to Imsland. This thesis concerns one batch of 94 186 Atlantic halibut fry, with arrival at Imsland in March 2021. Measurements were made upon arrival and for one month after delivery. SWH reports that a late onset mortality occurs after transportation of small fry sent from the hatchery to the rearing facilities. Some fry batches have endured substantial mortality which is considered caused by the transportation and transfer of fry. The complex phenomenon of late onset mortality after transportation required investigation. Water sampling and chemical analysis were performed in two stages. First stage was at arrival. Analysis of transportation water compared to receiving water presented a relatively large difference in water quality. The second stage was comprised of daily analysis of the water quality to monitor changes during the expected period of mortality. These differences were relatively minor. Biological parameters were measured at arrival and monitored afterwards on each of the three field excursions to complement the water quality data. These datasets served as the basis for the graphical- and statistical analysis. Mortality was considered 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 variation observed is explained by the regression model of pH and mortality. Abrupt environmental differences in transportation water compared to receiving water was revealed, which contributes to additional stress after transportation. Stress levels were indicated 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.