Impact of capture method and trawl duration on the health status of the Norway lobster, Nephrops norvegicus

For economic and logistical reasons, an increased proportion of landings from trawl caught Nephrops norvegicus is being used in the live export trade. This paper reports a series of trials that investigate the impact of capture method and trawl duration on the levels of stress, damage and mortality of N. norvegicus. The stress of N. norvegicus captured during trials in spring and autumn by means of short trawl (1 h duration), long trawl (5 h duration) and creeling was assessed using a range of physiological measures (for haemolymph l-lactate, crustacean hyperglycaemic hormone (CHH) and abdominal muscle glycogen concentrations), the immunological status (total haemocyte counts (THC)) and physical assessments (mortality, damage indices). N. norvegicus caught by creeling were generally less stressed (i.e. significantly lower haemolymph l-lactate and CHH concentrations) than their trawled counterparts. Increased duration of trawl did not significantly alter physiological parameters, while time of landing did have a significant effect on l-lactate concentrations, as individuals landed in the morning exhibited higher concentrations. Irrespective of the season in which trawling occurred, individuals captured by short trawls in the morning suffered lowest mortalities. Damage assessment data revealed that a greater proportion of individuals was categorised as heavily damaged following longer trawls conducted in spring.