Fish Morphology Data from Lower Cook Inlet, Alaska

FIELD: Fish schools were identified during hydroacoustic surveys in lower Cook Inlet between July and August from 2016-2019. Effort was focused around two seabird colony sites: Gull and Chisik Islands. Transects were established in both "nearshore" and "offshore" habitats. Nearshore transects followed the contours of mainland or island shorelines in a zig-zag pattern of 1.8 km legs, where waters were generally deeper than 10 m. Offshore transects cut across open water from one shore towards the other, over depths ranging from 10 m to >100 m. Offshore transects were parallel to latitude lines, and separated by 5 minutes of latitude (ca. 9.5 km). When we encountered significant hydroacoustic sign, a modified herring trawl was used to catch fish from the schools and to confirm species and length frequency of ensonified targets, to collect samples for measures of body condition, and to detect changes in overall community structure relative to habitat. The number of fish from trawl catch was determined by direct count or estimated by volume. A subsample of fish from each catch were weighted and measured. All fish were identified and enumerated by fisheries biologists in the field, or samples were frozen and identified in the lab once field work was complete. Large catches were sub-sampled by volume and total numbers were estimated from the proportion of fish in the sub-sample. Fish were measured with a standard ruler with millimeters and weighed with a calibrated Pesola or a Marel M2200 Marine Lab Scale.