Post capture physiology and pathology of the Norway lobster, Nephrops norvegicus

This thesis describes a study into two post capture conditions, idiopathic muscle necrosis (IMN) and a post capture opportunistic bacterial infection, affecting the Norway lobster, Nephrops norvegicus, and a comprehensive analysis of the stressors involved in the capture and post capture periods of the fishery process. A multivariate approach was used to study progression in the post capture condition of trawl-caught N. norvegicus for the live transport market. Prolonged periods of aerial exposure resulted in large disruptions to the carbohydrate profile, increases in haemolymph L-lactate and crustacean hyperglycaemic hormone concentrations, and corresponding fluctuations in haemolymph pH. These disruptions increased with the increasing temperature of aerial exposure, which impacted the immunocompetence of the lobsters: circulating haemocytes and phenoloxidase levels were significantly reduced and the degree of bacteraemia increased. The health status of N. norvegicus captured during trials in spring and autumn by means of short trawl (1h duration), long trawl (5h duration) and creeling was assessed using a range of physiological (Haemolymph L-lactate, crustacean hyperglycaemic hormone (CHH), abdominal muscle glycogen concentrations), immunological (total haemocyte counts (THC)) and physical (mortality, damage indices) parameters. Increased duration of trawl did not significantly alter physiological parameters, while time of landing did have a significant effect on L-lactate, where animals landed in the morning exhibited higher concentrations. Seasonal variations in abdominal muscle glycogen concentrations were also apparent. Irrespective of season, individuals captured by short trawls in the morning suffered lowest mortalities. Damage assessment data revealed that a greater proportion of individuals were categorised as heavily damaged following longer trawls conducted in spring. The carbohydrate profile and immunocompetence of N. norvegicus was significantly affected following trawl capture and subsequent handling and aerial exposure post capture. The recovery period was investigated through a range of parameters (L-lactate, glycogen, glucose, THC) and the data suggested that animals should be submerged and unstressed for at least 24h following capture and handling to avoid further alterations to the carbohydrate profile and reduce the window of opportunity for invading bacteria to cause meat spoilage. The influence of air temperature on the condition of N. norvegicus caught for the live export market was assessed by correlating meteorological data with the percentage of catch accepted for live transport. Results illustrated a large degree of variability in the conditions of animals on arrival at the processing plant. Air temperature was the only meteorological factor that had an impact on the morbidity and mortality of the catch. In one instance in particular, mean air temperature on the day of capture had a significant negative impact on the health of the catch.EThOS - Electronic Theses Online ServiceGBUnited Kingdo