The feeding habits of anadromous Arctic char (Salvelinus alpinus L.) in Frobisher Bay, Baffin Island in the eastern Canadian Arctic : diet, parasites and stable isotopes

Chapter One tested the hypothesis that there is trophic structuring (TS) among Arctic char populations feeding in the marine environment based on published data and the hypothesis was rejected.A comprehensive study was undertaken to test the hypothesis further, by collecting data on diet, parasites and using stable isotopes.Anadromous Arctic char consume diet items that occur in different trophic levels and their endohelminth parasite communìty, transmitted by a broad range of food items, is consists ofmostly non-host specific parasites.Based on 2002 data, char samples from several sites (Chapter Two) were similar with respect to length, weight age and sex and can be combined for statistical analyses-Moreover, male and female char diets were similar between sites and while diet varied among sample sites, char condition were comparable.chapter Three compared char samples collected during 2002,2004 and2005 and assessed diet, parasites and stable isotope ratios (SIR) to determine if TS occurs.Diet and parasite data were unable to show clear cut evidence for TS as char were infected by non-host specific parasite species which in turn is a reflection of their diet.By contrast, stable isotope data were able to show TS in specific diet species.Selection of diet items based on particle size suggested a potential for TS and the correlation was dependent on a specific food species and its size range during its life stages.Furthermore, char that fed on invertebrates had a higher nitrogen signal than char that fed on sculpins and Arctic cod.Char feeding on Arctic cod had more ôl3c enrichment than char that fed on invertebrates and sculpin, respectively.There was no trophic shift by char feeding on Arctic cod but this may be related to the amount of time feeding on cod.controlled feeding experiments ABSTRACT iii (Chapter Four) were designed to confirm if food particle size affected growth of char, if shifts in stable isotope values could be correlated with a diet shift and if the stable isotope halÊlifes (HLs) from experimentally fed and wild char were comparable.young-oÊthe- year (YoY) char were used because this is when char growth is considered the fastest and when the greatest shift in food particle size occurs in natural populations.char length was not correlated with diet particle size for experimentally fed char but there was correlation for wild char feedin g on Mysís spp., and onesimus littoralis.My calculations found that experimentally fed YoY char and the larger older wild char had comparable specific growth rate (sGR) at similar temperatures.I conclude that HL of stable isotopes of c and N is dependent on char growth rate and not fish size.stable isotopes HL were shorter for YoY but also relatively short for large wild char and can be contrasted with the much longer HLs reported in the literature for large old fish.clearly stable isotopes can be used to predict intra-annual shifts in diets.since sGR of char is high in the marine environment, at low temperatures, the quantity and quality of food plus the length of time food rernains in the intestine are needed to assess energy needs and possible shifts in diet preference (chapter Five).Bomb calorimetry and proximate analysis of diet items found that the major food items varied in their nutrient content and could lead to a diet item preference but not a trophic shift' The relationship describing rate of gastric evacuations in yoy char is linear and this is similar to the results obtained from wild char in chapter Three.Data from my experimental studies, in general, corroborates my findings from wild char and provides further evidence that even if quality of diet and particle size I thank you, Precious Holy Spirit for everything.I was nothing, had nothing and knew nothing, but your mercy, grace, guidance, strength and wisdom took over from my fears, frailties, weakness and dullness.I could not have made it without your continual Presence and teachings.I can never thank you enough!From the first day of our meeting to date, my supervisor, professor Terryr A. Dick, has not ceased to be a father.'when I freshly arrived from Nigeria, he granted me enough time to adjust to my new environment and that really helped me.I was not quick at understanding the details of my research and could not have been able to do anything meaningful without Prof.Dick's great patience and unwavering commitment to my study' His thoughtfulness, teachings, advice and sincere criticisms are greatly appreciated Professor Dick's motivation, stimulating scientific discussions, sincere excitement at new discoveries as well as exciting exha-curricular discussions are deeply appreciated and will be missed dearly.It is amazing that

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