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Our understanding of the biology of Atlantic bluefin tuna (Thunnus thynnus) has in-\ud creased profoundly in the last decade, and the progress is attributed to the development and application of a variety of novel tools. Here we provide a comprehensive examina-\ud tion of available data on the life history and stock structure of T. thynnus by re-examining current databases and literature and highlighting findings from recent studies using ap-\ud proaches such as archival tags and natural markers (e.g., genetics, otolith chemistry). The present review provides a detailed synthesis on the reproductive biology, feeding ecology, growth, mortality, migration, and stock structure of T. thynnus. In addition to\ud characterizing key life history attributes and discussing stock-specific (east versus west)differences, the implication of trans-Atlantic movement and mixing are addressed. We\ud also identify significant data needs that still exist and must be addressed to promote effective management and rapid recovery of T. thynnus populations

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In this paper, we address a recent article by Beck et al. (2001, Bioscience 51:633-641), in which it was proposed that the value of a juvenile fish habitat could be most efficiently measured as the production of adults from each juvenile habitat on a per area basis. Based upon retrospective microchemical analysis of otoliths, we calculated this metric (nursery value) for tidal freshwater and brackish littoral habitats of an estuarine fish, white perch Morone americana, in the Patuxent River estuary, Maryland (USA). In dominant year-classes of the population, brackish habitats had the highest nursery value, whereas in all other year-classes, freshwater habitats had the highest nursery value. This result highlights the importance of inter-annual variability in habitat use, and consequently presents a challenging trade-off for applying the nursery-role hypothesis to facilitate habitat conservation and management. Despite this limitation, the nursery-role hypothesis provides an enriched and much needed perspective on population connectivity.

24Thermoregulation is presumed to be a widespread determinant of behaviour in fishes, but has not 25 often been investigated as a mechanism shaping long-distance migrations. We used acoustic 26 telemetry and animal-borne thermal loggers to test the hypothesis that seasonal migration in 27 adult walleye in Lake Erie is size-and/or sex-specific and related to behavioural