Body size and age at maturity are indicative of the vulnerability of a species to extinction. However, they are both difficult to estimate for large animals that cannot be restrained for measurement. For very large species such as whale sharks, body size is commonly estimated visually, potentially resulting in the addition of errors and bias. Here, we investigate the errors and bias associated with total lengths of whale sharks estimated visually by comparing them with measurements collected using a stereo-video camera system at Ningaloo Reef, Western Australia. Using linear mixed-effects models, we found that visual lengths were biased towards underestimation with increasing size of the shark. When using the stereo-video camera, the number of larger individuals that were possibly mature (or close to maturity) that were detected increased by approximately 10%. Mean lengths calculated by each method were, however, comparable (5.002 ± 1.194 and 6.128 ± 1.609 m, s.d.), confirming that the population at Ningaloo is mostly composed of immature sharks based on published lengths at maturity. We then collated data sets of total lengths sampled from aggregations of whale sharks worldwide between 1995 and 2013. Except for locations in the East Pacific where large females have been reported, these aggregations also largely consisted of juveniles (mean lengths less than 7 m). Sightings of the largest individuals were limited and occurred mostly prior to 2006. This result highlights the urgent need to locate and quantify the numbers of mature male and female whale sharks in order to ascertain the conservation status and ensure persistence of the species.

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International trade and international flows of investment have mushroomed, and an extraordinary amount of the world's goods and services and annual investment capital flows cross international borders. The tax treatment of almost all of the income that results from these cross-border transactions is affected by tax treaties. Well over 2,000 bilateral tax treaties are now in force between the countries of the world. Canada alone has almost 100 tax treaties in force. Tax treaties have thus become a major interest to legislators, tax practitioners, and tax scholars and writing about them has become a cottage industry in large segments of the international tax community. As one indication of the interest they have generated, massive books are now being written about each article in these treaties; for example, a 415 page book has been published about Article 13 of OECD Model Convention, which deals with the taxation of capital gains and which is less than 20 lines of print long in the model treaty. 2 In part because they are so important, like substantive tax law itself, examining the design of the tax treaties a country enters into should tell us a good deal about the balance of interest group power in that country, the prevailing ideas, the ambitions of its politicians, the institutions of government, and the other variables that might influence public policy making in the country. Although the policy of tax treaties is thus multi-faceted and complex, this paper takes only one aspect of that larger picture and examines it in some detail; namely, Canada's evolving tax treaty policy toward low-income countries.This small slice of tax treaty policy is examined in this chapter for two reasons. First, this aspect of tax treaty policy is important in its own right. The revenue that low-income countries are able to raise from the income earned in their countries on cross border trade and investment flows is often significant and is critical for the development of their economy and for raising the standard of living of their impoverished residents. Second, and just as importantly for the purposes of a collection paying tribute to Alexander Easson, it was a subject that greatly interested Alex. Throughout much of his career he acted as a tax advisor to the governments of low-income countries and he was keenly aware of the importance of the design of tax treaties for them.

Age and growth data are central to management or conservation strategies for any species. Circumstantial evidence suggests that male whale sharks (Rhincodon typus) grow to asymptotic sizes much smaller than those predicted by age and growth studies and consequently, there may be sex-specific size and growth patterns in the species. We tested this hypothesis by using stereo-video and photo-identification studies to estimate the growth rates of 54 whale sharks that were resighted over a period of up to a decade at Ningaloo Reef. We found that male growth patterns were consistent with an average asymptotic total length (TL) of approximately 8-9 m, a size similar to direct observations of size at maturity at aggregation sites worldwide and much smaller than the sizes predicted by earlier modeling studies. Females were predicted to grow to an average asymptotic length of around 14.5 m. Males had growth coefficients of K = 0.088 year −1 , whereas limited resighting data suggested a growth coefficient of K = 0.035 year −1 for females. Other data including re-sightings of an individual male over two decades, records of sex-specific maximum sizes of individuals captured in fisheries and data from juveniles growing in aquaria were also consistent with the suggestion of sex-specific growth profiles for the species. We argue that selection for sex-specific growth patterns could explain many of the otherwise enigmatic patterns in the ecology of this species including the tendency of the species to form aggregations of juvenile males in coastal waters.