Regional variation in the annual feeding cycle of juvenile walleye pollock (Theragra chalcogramma) in the western Gulf of Alaska

• Main Authors: Wilson, Matthew T., Buchheister, Andre, Jump, Christina
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2011
• Subjects: Biology; Ecology; Fisheries; Gulf of Alaska; Kodiak; Theragra chalcogramma; Alaska
• Online Access: http://hdl.handle.net/1834/25360

Juvenile fish in temperate coastal oceans exhibit an annualcycle of feeding, and within this cycle, poor wintertime feeding can reduce body growth, condition, and perhapssurvival, especially in food-poor areas. We examined the stomach contents of juvenile walleye pollock (Theragrachalcogramma) to explain previously observed seasonal and regional variation in juvenile body condition. Juvenile walleye pollock (1732 fish, 37–250 mm standard length) of the 2000 year class were collected from three regions in the Gulf of Alaska (Kodiak, Semidi, and Shumagin) representing an area of the continental shelf of ca. 100,000 km2 during four seasons (August 2000 to September2001). Mean stomach content weight (SCW, 0.72% somatic body weight) decreased with fish body length except from winter to summer 2001. Euphausiids composed 61% of SCW and were the main determinant of seasonal change in the diets of fishin the Kodiak and Semidi regions. Before and during winter, SCW and the euphausiid dietary component were highest in the Kodiak region. Bioenergetics modeling indicated arelatively high growth rate for Kodiak juveniles during winter (0.33 mm standard length/d). After winter,Shumagin juveniles had relatively high SCW and, unlike the Kodiak and Semidi juveniles, exhibited no reduction in the euphausiid dietary component. These patterns explain previous seasonal and regional differences in body condition. We hypothesize that high-quality feeding locations (and perhaps nursery areas) shift seasonallyin response to the availability of euphausiid