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Accurate identification of humpback whales from photographic identification data depends on the quality of the photographs and the distinctiveness of the flukes. Criteria for evaluating photographic quality and individual distinctiveness were developed involving judgments about overall quality or distinctiveness and about specific aspects of each. These criteria were tested for the level of agreement among judges. The distinctiveness scheme was tested for the independence of distinctiveness judgments and photographic quality. Our results show that judges could agree when evaluating specific and overall aspects of photographic quality and individual distinctiveness. The level of agreement varied for different pairs of judges, and less adept judges were identified. Ability to agree on evaluations of photographic quality was independent of the experience of the judges. Overall photographic quality and overall distinctiveness were successfully predicted from more specific variables, but the agreement between judges for these was not significantly greater than the agreement for the overall measures judged directly. There was no correlation between individual distinctiveness and photographic quality for four of the five judges, but the power of this rest may be low. Analyses of photographic identification data frequently require evaluations of photographic quality and individual distinctiveness. To obtain reliable results from such analyses, evaluation schemes and judges should be tested to ensure reliable and consistent evaluations.

We examined a suite of abiotic, biotic, and human metrics for the northeast U.S. continental shelf ecosystem at the aggregate, community, and system level (>30 different metrics) over three decades. Our primary goals were to describe ecosystem status, to improve understanding of the relationships between key ecosystem processes, and to evaluate potential reference points for ecosystem-based fisheries management (EBFM). To this end, empirical indicators of ecosystem status were examined and standard multivariate statistical methods were applied to describe changes in the system. We found that (i) a suite of metrics is required to accurately characterize ecosystem status and, conversely, that focusing on a few metrics may be misleading; (ii) assessment of ecosystem status is feasible for marine ecosystems; (iii) multivariate points of reference can be determined for EBFM; and (iv) the concept of reference directions could provide an ecosystem level analog to single-species reference points.

American whalemen sailed out of ports on the east coast of the United States and in California from the 18th to early 20th centuries, searching for whales throughout the world’s oceans. From an initial focus on sperm whales (Physeter macrocephalus) and right whales (Eubalaena spp.), the array of targeted whales expanded to include bowhead whales (Balaena mysticetus), humpback whales (Megaptera novaeangliae), and gray whales (Eschrichtius robustus). Extensive records of American whaling in the form of daily entries in whaling voyage logbooks contain a great deal of information about where and when the whalemen found whales. We plotted daily locations where the several species of whales were observed, both those caught and those sighted but not caught, on world maps to illustrate the spatial and temporal distribution of both American whaling activity and the whales. The patterns shown on the maps provide the basis for various inferences concerning the historical distribution of the target whales prior to and during this episode of global whaling.

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Population spatial structuring among North Atlantic humpback whales Megaptera novaeangliae on the summer feeding grounds was investigated using movement patterns of identified individuals. We analysed the results from an intensive 2-year ocean-basin-scale investigation resulting in 1658 individuals identified by natural markings and 751 individuals by genetic markers supplemented with data from a long-term collaborative study with 3063 individuals identified by natural markings. Re-sighting distances ranged from o1 km to 42200 km. The frequencies (F) of resighting distances (D) observed in consecutive years were best modelled by an inverse allometric function (F=6631D À1.24 , r 2 = 0.984), reflecting high levels of site fidelity (median re-sighting distance o40 km) with occasional long-distance movement (5% of re-sightings 4550 km). The distribution of re-sighting distances differed east and west of 451W, with more long-distance movement in the east. This difference is consistent with regional patterns of prey distribution and predictability. Four feeding aggregations were identified: the Gulf of Maine, eastern Canada, West Greenland and the eastern North Atlantic. There was an exchange rate of 0.98% between the western feeding aggregations. The prevalence of long-distance movement in the east made delineation of possible additional feeding aggregations less clear. Limited exchange between sites separated by as little as tens of kilometres produced lower-level structuring within all feeding aggregations. Regional and temporal differences in movement patterns reflected similar foraging responses to varying patterns of prey availability and predictability. A negative relationship was shown between relative abundance of herring and sand lance in the Gulf of Maine and humpback whale movement from the Gulf of Maine to eastern Canada.

The results of a double-marking experiment using natural markings and microsatellite genetic markers to identify humpback whales (Megaptera novaeangliae) confirm that natural markings are a reliable means of identifying individuals on a large scale. Of 1410 instances of double tagging, there were 414 resightings. No false positive and 14 false negative errors were identified. The rate of error increased with decreasing photographic quality; no errors were observed among photographs of the highest quality rating, whereas an error rate of 0.125 was identified in sightings for which only part of the area used for identification was visible. There was also a weaker relationship between error rate and the distinctiveness of markings, which may result from non-independence in coding for image quality and distinctiveness. A correction is developed for the Petersen two-sample abundance estimator to account for false negative errors in identification, and a parametric bootstrap procedure for estimation of variance is also developed. In application to abundance estimates from the North Atlantic, the correction reduces the bias in estimates made using poorer quality photographs to a negligible level while maintaining comparable precision.Résumé : Une expérience de marquage double à l'aide de marques corporelles et de marqueurs génétiques microsatellites confirme que l'utilisation des marques corporelles est une méthode fiable d'identification à grande échelle des individus du Rorqual à bosse (Megaptera novaeangliae). Des 1410 événements de double marquage, 414 impliquaient des animaux vus antérieurement. Aucun résultat faussement positif ou faussement négatif n'a été décelé. Le taux d'erreur augmentait avec la mauvaise qualité des photographies; aucune erreur ne s'est produite à l'utilisation des photographies de haute qualité et le taux d'erreur était de 0,125 lorsque seulement une partie de la surface de l'animal utilisée pour l'identification était visible. Il y avait aussi une relation plus faible entre le taux d'erreur et le caractère distinctif des marques corporelles, qui peut provenir du manque d'indépendance entre le codage de la qualité de l'image et le caractère distinctif de l'animal. On trouvera ici une correction de l'estimateur d'abondance à deux échantillons de Petersen pour tenir compte des résultats faussement négatifs dans l'identification, ainsi qu'une procédure bootstrap paramétrique pour estimer la variance. Appliquée à des estimations d'abondance provenant de l'Atlantique nord, la correction réduit à un niveau négligeable l'erreur due à l'utilisation de photographies de qualité inférieure dans les estimés, tout en maintenant un niveau de précision similaire.[Traduit par la Rédaction] 1870 Stevick et al.