Ecology and demographics of Pacific sand lance, Ammodytes hexapterus Pallas, in Lower Cook Inlet, Alaska

Distinct sand lance populations occur within the relatively small geographic area of Lower Cook Inlet, Alaska. Marked meso-scale differences in abundance, growth, and mortality exist as a consequence of differing oceanographic regimes. Growth rate within populations (between years) was positively correlated with temperature. However, this did not extend to inter-population comparisons where differing growth rates were better correlated to marine productivity. Most sand lance reached maturity in their second year. Field observations and indices of maturity, gonad development, and ova-size distribution all indicated that sand lance spawn once each year. Sand lance spawned intertidally in late September and October on fine gravel/sandy beaches. Embryos developed over 67 days through periods of intertidal exposure and sub-freezing air temperatures. Mean dry-weight energy value of sand lance cycles seasonally, peaking in spring and early summer (20.91 kJg^-1 for males, 21.08 kJg^-1 for females), and subsequently declining by about 25% during late summer and fall (15.91 kJg^-1 for males, 15.74 kJg^-1 for females). Sand lance enter the winter with close to their minimum whole body energy content. Dry weight energy densities of juveniles increased from a minimum 16.67 kJg^-1 to a maximum of 19.68 kJg^-1 and are higher than adults in late summer.