Narwhals (Monodon monoceros) are sentinel species in the Arctic environment and are a vital component for Inuit culture and subsistence. The Arctic is undergoing rapid changes in temperature and sea ice cover and relatively little is known about how this has and will change narwhal foraging behaviour. There are three narwhal populations in the world, the Baffin Bay (BB), Northern Hudson Bay (NHB), and East Greenland (EG) populations; however, foraging behaviour, in terms of dive behaviour and primary dietary components, has really only been investigated in the BB population. Using a combination of stable isotopes, fatty acids, genetic techniques, and satellite tracking technologies I evaluated foraging behaviour in all three of the world’s narwhal populations. I also investigated social structure in the BB population to determine how adaptable narwhals are to a changing and dynamic Arctic environment. Stable isotopes (δ13C and δ15N) and fatty acids are chemical signatures in the tissues of an organism that can provide long-term information on their diet over varying temporal scales depending upon the tissue. Stable isotope analysis in the three narwhal populations found they forage on different primary prey, suggesting narwhal are adaptable in their preferred prey and that there is potential for them to adjust foraging behavior in the face of changing climate. Dietary changes were also assessed over three decades to determine how sea ice changes have affected narwhal foraging for the NHB and BB populations. Dietary changes were evident and can be attributed to changes in sea ice patterns and an altered migratory pathway for narwhals. An understanding of narwhal social structure is also needed to determine how behaviourally flexible narwhal are in diet and site fidelity. Genetic relatedness and dietary signatures from fatty acids were assessed for an entrapped group to determine if individuals that are closely related forage together, which would support a matrilineally driven social structure where females teach their young foraging strategies, and/or travel and forage together. I found no evidence that narwhals form a matrilineal social group, but they may display a fission-fusion structure, which may be an adaptation to patchy prey distribution in the Arctic. Finally, narwhal dive behaviour in all three populations was investigated to determine if dive behaviour could be used to predict diet. Dive differences among populations did correspond with differences in diet, suggesting that narwhals employ specialized foraging strategies. This has repercussions for their ability to adapt to ecosystem changes. Overall, narwhals may be more flexible in terms of their foraging behaviour than previously believed. However, an increased resilience to changing food webs will not be the only predictor of how narwhals will fare in the face of a changing climate; how they respond to increased industrial activities in their preferred habitats, increased predation from southern predators, and increased competition from southern cetaceans and humans alike, will play an equally large role in how they cope with the future.

Biological and life history characteristics for a previously unstudied population of sailfish, Istiophorus platypterus, in the Arabian Gulf were investigated. Notable findings include temporal-spatial migration patterns for a genetically isolated population that is threatened by overexploitation. Conventional tagging resulted in 2053 releases and 114 recaptures (5.55%) inside the Gulf. Linear displacement ranged from 2.5 to 697 km, while days at liberty ranged from 17 to 818 days. Dead recoveries in Iranian gillnets account for 88.6% of recaptures. Modeling analyses produced a best estimate of annual survival probability (S) at 0.375 (slope = -0.101, SE = 0.324). Fifteen pop-up satellite archival tags were deployed on sailfish during 2001 - 2002 to track temporal and spatial movements. Extensive data from four tags showed 83.7% of time-at-depth was spent above 10 m with no significant difference (P &lt 0.05) in diel preference. Depth ranged from 0.0 m to 61.0 m, while temperature ranged from 19.7 ??C to 30.1 ??C. Small-scale movements of eight sailfish were measured using ultrasonic tracking for periods ranging from 3:33 to 53:06 hours. Track distances ranged from 5.5 to 78.5 km, while linear displacement ranged from 4.6 to 37.0 km. Average speed ranged from 0.29 to 0.75 m s-1. Vertical distributions showed 84.3% of time was spent above 10 m depth, even though water temperature showed negligible variation with depth. Mitochondrial DNA comparison of 147 sailfish produced 39 composite haplotypes using eight restriction enzymes. Significant differences occurred in the frequency between population groups inside and outside the Gulf (amova 34.8%, P &lt 0.01; FST = 0.356), along with evidence of restricted migration between them (average number of migrants, Nm = 0.903). Nine year classes (0-8) were determined from aging analysis of fin spines. Females (n = 50) ranged from 0 to 8 years, while males (n = 34) ranged from 0 to 6 years. Von Bertalanffy growth function indicated rapid growth during the first two years, after which males stabilized and females continued growing to a greater maximum mean length and weight. A comparison of allometric growth between sexes indicated no significant difference between length and other morphometric characters (P ranged 0.135 ??? 0.980).

Biological and life history characteristics for a previously unstudied population of sailfish, Istiophorus platypterus, in the Arabian Gulf were investigated. Notable findings include temporal-spatial migration patterns for a genetically isolated population that is threatened by overexploitation. Conventional tagging resulted in 2053 releases and 114 recaptures (5.55%) inside the Gulf. Linear displacement ranged from 2.5 to 697 km, while days at liberty ranged from 17 to 818 days. Dead recoveries in Iranian gillnets account for 88.6% of recaptures. Modeling analyses produced a best estimate of annual survival probability (S) at 0.375 (slope = -0.101, SE = 0.324). Fifteen pop-up satellite archival tags were deployed on sailfish during 2001 - 2002 to track temporal and spatial movements. Extensive data from four tags showed 83.7% of time-at-depth was spent above 10 m with no significant difference (P &lt 0.05) in diel preference. Depth ranged from 0.0 m to 61.0 m, while temperature ranged from 19.7 ??C to 30.1 ??C. Small-scale movements of eight sailfish were measured using ultrasonic tracking for periods ranging from 3:33 to 53:06 hours. Track distances ranged from 5.5 to 78.5 km, while linear displacement ranged from 4.6 to 37.0 km. Average speed ranged from 0.29 to 0.75 m s-1. Vertical distributions showed 84.3% of time was spent above 10 m depth, even though water temperature showed negligible variation with depth. Mitochondrial DNA comparison of 147 sailfish produced 39 composite haplotypes using eight restriction enzymes. Significant differences occurred in the frequency between population groups inside and outside the Gulf (amova 34.8%, P &lt 0.01; FST = 0.356), along with evidence of restricted migration between them (average number of migrants, Nm = 0.903). Nine year classes (0-8) were determined from aging analysis of fin spines. Females (n = 50) ranged from 0 to 8 years, while males (n = 34) ranged from 0 to 6 years. Von Bertalanffy growth function indicated rapid growth during the first two years, after which males stabilized and females continued growing to a greater maximum mean length and weight. A comparison of allometric growth between sexes indicated no significant difference between length and other morphometric characters (P ranged 0.135 ??? 0.980).