Growth processes in the two Scottish populations of powan, Coregonus lavaretus (L.) (Eateleosteia, Salmonidae)

[摘要] The powan, Coregonus lavaretus (L.) is endemic to only twoBritish waters, Loch Lomond and Loch Eck, Scotland. Thisthesis describes the seasonal and longer term growthprocesses of the two populations, concentrating on growth inlength back-calculated from scales, factors affectingrecruitment and mortality, reproductive cycles, and seasonaldeposition and mobilisation of storage products,particularly lipid. The interrelationships of these cyclesis discussed. The populations differ in their diet andduration of feeding, and it is shown that most of the inter-population differences in seasonal cycles of growth relateto these feeding differences. The Loch Eck population is themore variable. In addition to adult and immature powan, athird category is identified, termed adolescents. These arefish which are entering their first reproductive cycle.Immature and adolescent fish are analysed separately andcompared with the adults. There are some differences inseasonal cycles between the juveniles and adults, mainly inrelation to the presence or absence of the reproductivecycle. A preliminary histological study of the ovaries ofadolescent females is carried out. Comparison of historicaldata with the results of the present study shows that therehas been little change in the Loch Lomond powan in the past200 years. Both lochs are coming under increasing humanpressure, and conservational measures urgently need to betaken if the powan populations are to survive.

[发布机构] University:University of St Andrews;Department:Biology (School of)

[效力级别] Powan

[关键词] Salmonidae;Powan