ALBERT

Description: Time series (1965-1985) of Illex illecebrosus catch and morphometric data from the Northwest Atlantic were analysed to describe geographic variability in population structure. The areas studied were NAFO sub-areas 3 to 6, which range from Newfoundland to the northeastern USA shelf. Population components, reflecting seasonal spawning groups, were identified based on analysis of length frequency data. Components 3 and 4 represent two prominent life cycles: the summer spawners and winter spawners respectively. Components 1, 2, and 5 do not represent different life cycles, but result from the capacity to shift between life cycles by prolonging (or shortening) the life span. The presence of up to five components in the southern area illustrates a life history strategy involving protracted spawning and complex population structure. There was clear geographic variability in annual catch, with fluctuations being most extreme in the most northern area. Annual catch levels in all areas were significantly correlated with the abundance of the winter-spawning component, as represented by the number of squid within samples which belong to component 4. Population structure in the most northem area was simplest and catch levels therefore were most dependent on the highly migratory winter-spawning component. This leads to greater catch variability in the most northern area than in the other areas. The advantages of good feeding conditions may compensate for the risks associated with long-range migrations, especially recruitment failure. Life history strategies involving migratory and non-migratory population components limit the risk of recruitment failure. The overall resultant life history strategy for Illex illecebrosus is one that ensures survival of the species by stabilizing recruitment in at least one (southern) area through protracted spawning, complex population structure and interaction of spawning components. Time series (1965-1985) of Illex illecebrosus catch and morphometric data from the Northwest Atlantic were analysed to describe geographic variability in population structure. The areas studied were NAFO sub-areas 3 to 6, which range from Newfoundland to the northeastern USA shelf. Population components, reflecting seasonal spawning groups, were identified based on analysis of length frequency data. Components 3 and 4 represent two prominent life cycles: the summer spawners and winter spawners respectively. Components 1, 2, and 5 do not represent different life cycles, but result from the capacity to shift between life cycles by prolonging (or shortening) the life span. The presence of up to five components in the southern area illustrates a life history strategy involving protracted spawning and complex population structure. There was clear geographic variability in annual catch, with fluctuations being most extreme in the most northern area. Annual catch levels in all areas were significantly correlated with the abundance of the winter-spawning component, as represented by the number of squid within samples which belong to component 4. Population structure in the most northem area was simplest and catch levels therefore were most dependent on the highly migratory winter-spawning component. This leads to greater catch variability in the most northern area than in the other areas. The advantages of good feeding conditions may compensate for the risks associated with long-range migrations, especially recruitment failure. Life history strategies involving migratory and non-migratory population components limit the risk of recruitment failure. The overall resultant life history strategy for Illex illecebrosus is one that ensures survival of the species by stabilizing recruitment in at least one (southern) area through protracted spawning, complex population structure and interaction of spawning components.

Description: Illex illecebrosus squid appear to have a species‐typical and internally organized spatial arrangement of their groups. Squid maintained an average angle of 25° with respect to their nearest neighbour, and mostly had angular deviations between 5° and 20°. They maintained distances to nearest, second and third neighbours in a ratio of 1:1.5:2. The distances were strongly affected by group size (4, 20, or 38), with larger groups maintaining closer distances. Interindividual distances were not affected by two variables, day‐night and presence of a current in the large pool in which they were kept. The similarity of this organization to that of fish schools is discussed.

Description: Feeding strategies are different when adult Illex illecebrosus prey on large (trout) and small fish (mummichogs). Attacks on trout are characterized by (1) rotation as the squid changes from tail‐first to head‐first swimming; (2) an approach phase involving rapid acceleration towards the prey; (3) a tracking phase where the squid slowly follows the trout; (4) the capture phase. No tracking phase is present in attacks on mummichogs. These differences in feeding strategies can be explained by performance limitations of the squid jet propulsion system. Head‐first acceleration rates in Illex are low (max. = 12 m • s−2) and maneuverability poor compared to fish. A large fish could thus out‐perform an attacking squid if forced into evasive action. The tracking phase is a type of oceanic stalking strategy designed to bring the squid into close proximity to larger fish. The behaviour is not necessary when attacking small fish due to their low swimming speeds.

Description: The world's oceans are three‐dimensional habitats that support high diversity and biomass. Because the densities of most of the constituents of life are greater than that of seawater, planktonic and pelagic organisms had to evolve a host of mechanisms to occupy the third dimension. Some microscopic organisms survive at the surface by dividing rapidly in vertically well mixed zones, but most organisms, small and large, have antisinking strategies and structures that maintain vertical position and mobility. All of these mechanisms have energetic costs, ranging from the “foregone metabolic benefits” and increased drag of storing high‐energy, low‐density lipids to direct energy consumption for dynamic lift. Defining the niches in the mesopelagic zone, understanding evolution, and applying such ecological concepts as optimal foraging require good estimates of these costs. The extreme cases above are reasonably well quantified in fishes, but the energetic costs of dynamic physiological mechanisms like swim bladders are not; nor are the costs of maintaining vertical position for the chief invertebrate competitors, the cephalopods. This article evaluates a matrix of buoyancy mechanisms in different circumstances, including vacuum systems and ammonium storage, based on new data on the metabolic cost of creating buoyancy in Sepia officinalis.

Description: This report shares our experience of what worked and what did not while developing CephBase (www.cephbase.dal.ca). We share our triumphs and failures as well as our vision for the future to help and encourage those starting new database projects as well as outline ideas about collaboration between existing and yet to be developed databases. It also explains why we chose cephalopods and urges readers to share their enthusiasm for the groups of marine animals they investigate. Clearly, new Internet technologies offer a chance for substantial improvement in global distribution and sharing of information.

Description: The influence of salinity, temperature and prey availability on the marine migration of anadromous fishes was determined by describing the movements, habitat use and feeding behaviours of Arctic char (Salvelinus alpinus). The objectives were to determine whether char are restricted to the upper water column of the inter-/subtidal zones due to warmer temperatures. Twenty-seven char were tracked with acoustic temperature/pressure (depth) transmitters from June to September, 2008/2009, in inner Frobisher Bay, Canada. Most detections were in surface waters (0-3 m). Inter-/subtidal movements and consecutive repetitive dives (maximum 52.8 m) resulted in extreme body temperature shifts (-0.2-18.1 °C). Approximately half of intertidal and subtidal detections were between 9-13 °C and 1-3 °C, respectively. Stomach contents and deep diving suggested feeding in both inter-/subtidal zones. We suggest that char tolerate cold water at depth to capture prey in the subtidal zone, then seek warmer water to enhance feeding/digestion physiology.