The theory of recruitment in fishes and hypotheses pertaining to causes of recruitment fluctuation are summarized. In spite of considerable research effort over several decades there has been no significant improvement in identifying clear causal mechanisms of recruitment in marine fish stocks. Starvation has not been demonstrated to be a primary mechanism controlling survival of fish larvae. Studies matching food levels and year-class strength continue to provide indirect evidence that growth during the first year of life is dependent on food supply and may be important in determining survival. The hypothesis that survival is a direct function of growth provides a rational theoretical framework for recruitment research and is suggested as a basis for future work. Growth rate must be studied as a function of both ration and temperature. Studies examining the relationship of growth rate to survival should be specific to each life history stage and ideally integrated throughout the pre-recruit period. It remains to be demonstrated that survival is a direct function of growth, mediated through size-dependent predation.

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Anderson, J. T., Holliday, D. V., Kloser, R., Reid, D. G., and Simard, Y. 2008. Acoustic seabed classification: current practice and future directions. – ICES Journal of Marine Science, 65: 1004–1011. Acoustic remote sensing of the seabed using single-beam echosounders, multibeam echosounders, and sidescan sonars combined and individually are providing technological solutions to marine-habitat mapping initiatives. We believe the science of acoustic seabed classification (ASC) is at its nascence. A comprehensive review of ASC science was undertaken by an international group of scientists under the auspices of ICES. The review was prompted by the growing need to classify and map marine ecosystems across a range of spatial scales in support of ecosystem-based science for ocean management. A review of the theory of sound-scattering from seabeds emphasizes the variety of theoretical models currently in use and the ongoing evolution of our understanding. Acoustic-signal conditioning and data quality assurance before classification using objective, repeatable procedures are important technical considerations where standardization of methods is only just beginning. The issue of temporal and spatial scales is reviewed, with emphasis on matching observational scales to those of the natural world. It is emphasized throughout that the seabed is not static but changes over multiple time-scales as a consequence of natural physical and biological processes. A summary of existing commercial ASC systems provides an introduction to existing capabilities. Verification (ground-truthing) methods are reviewed, emphasizing the difficulties of matching observational scales with acoustic-backscatter data. Survey designs for ASC explore methods that extend beyond traditional oceanographic and fisheries survey techniques. Finally, future directions for acoustic seabed classification science were identified in the key areas requiring immediate attention by the international scientific community.

Abstract. We explored foraging strategies used by marine animals to search for prey by examining the relative importance of information exchange and memory in a cold ocean environment from 1998 to 2000. Recent technological advances have increased our knowledge of the foraging patterns of marine predators, but few of these studies have concurrently measured prey distribution and behavior. We quantified the arrival and departure behavior of a pursuit-diving, colonial seabird, the Common Murre, Uria aalge, at two colonies on the eastern Newfoundland Shelf through observational techniques. We also measured the distribution, abundance, and behavior of the capelin, Mallotus villosus, the main prey species of murres, within foraging ranges of each colony, using hydroacoustic, vessel-based techniques. Return and departure flight directions of murres did not match at either colony during the same period. This indicated that murres departing colonies did not use information on prey distributions outside of visual range of the colony provided by the flight paths of returning flocks of birds to the colony carrying fish. High-abundance aggregations of capelin were reliably found within specific 2.25-km areas (''hot spots'') for up to two weeks within the foraging ranges of murres from both colonies (ϳ100 km). This circumstance suggests that murres could use memory to locate hot spots on the coarse scale (1-100 km) of foraging ranges from both colonies. Specific commuting routes (regular flight paths) of murres toward and away from hot spots were obvious at sea, and feeding murres consistently marked the location of capelin schools within hot spots. These distributions provided excellent conditions for murres to locate capelin schools on both coarse and fine (1-1000 m) scales by cueing to the activities of conspecifics, known as local enhancement. While central-place foraging from breeding colonies, murres likely use a mixture of memory and local enhancement to locate prey, depending on the spatial and temporal resolution of search and current prey conditions. Uncovering such behavioral mechanisms responsible for predator-prey interactions increases our understanding of linkages among trophic levels and, ultimately, ecosystem dynamics.