Saffron Cod (Eleginus gracilis) in Shallow-Water Habitats of Prince William Sound, Alaska
Figure 1. Saffron cod (Eleginus gracilis) captured with a beach seine in western Prince William Sound, Alaska, in summer 2007.
ABL scientists have identified saffron cod (Eleginus gracilis) (Fig.1 above) as one of the dominant fish species in shallow-water habitats (<5 m deep) of western Prince William Sound (PWS), Alaska. Saffron cod have not been reported in PWS, and their appearance suggests changes have occurred in fish community structure in shallow-water habitats.
An estimated 15,910 saffron cod were captured in 49 of 95 beach seine hauls at eight locations in PWS in 2006 and 2007. Saffron cod accounted for 32% of the total fish catch (49,060 fish, 45 species). Abundance of saffron cod differed by season and habitat type; catch was greater in summer and fall than in spring, and fish were captured almost exclusively in eelgrass (Zostera marina).
Most saffron cod captured were age-0; based on age from otoliths, mean size of age-0 fish increased from 70 mm total length (TL) (n = 8) in July to 108 mm TL (n = 21) in September. Age≥1 saffron cod consumed larger and fewer varieties of prey than age-0 fish and targeted predominately epibenthic fauna, whereas age-0 fish consumed predominately pelagic fauna.
Most saffron cod leave shallow-water habitats by late summer or early fall; of 1,002 fish fin-clipped and released at one sampling location in July 2007, only 2 fish were recaptured in August 2007. The appearance of saffron cod in western PWS could be further evidence of community reorganization from an ocean climate regime shift in the late 1970s that favored other gadid populations in the northern Gulf of Alaska.
By Scott Johnson
Diel Use of Nearshore Habitats by Fishes in Late Summer in Prince William Sound, Alaska
To determine if there were differences in diel use of nearshore habitat, fishes were sampled diurnally and nocturnally at six locations in western Prince William Sound, Alaska in late August 2007. At each location, fish were sampled at low tide with a beach seine in one eelgrass and one understory kelp site; day and night sampling was separated by approximately 62 hours.
A total of 1,181 fish representing 31 species were captured; 629 fish representing 20 species during daytime sampling and 552 fish representing 30 species at night. Catches between the day and night were similar, but species composition and mean size of fish changed.
Species richness was similar in eelgrass during the day and night (mean = 6 species/site during the day and 7 at night), whereas in kelp, species richness was greater at night (mean = 8 species/site) than during the day (mean = 4 species/site). Mean length of fish was greater at night (112 mm) than during the day (101 mm) in eelgrass and was greater at night (114 mm) than during the day (58 mm) in kelp.
Saffron cod, tubesnout, crescent gunnel, manacled sculpin, bay pipefish, Pacific herring, and padded sculpin accounted for about 90% of both day and night catches in eelgrass and kelp. In eelgrass, saffron cod was the most abundant species during the day (57% of catch) and night (40% of catch). In kelp, herring was the most abundant species during the day (38% of catch), and saffron cod was the most abundant species at night (42% of catch).
Diel sampling indicates similar fish abundance in nearshore vegetated habitats during both day and night, but mean size of fish was greater, and number of fish species increased in kelp habitat at night.
