Benjamin J. Laurel

INCREASED SPATIAL VARIANCE ACCOMPANIES REORGANIZATION OF TWO CONTINENTAL SHELF ECOSYSTEMS

Phase transitions between alternate stable states in marine ecosystems lead to disruptive changes in ecosystem services, especially fisheries productivity. We used trawl survey data spanning phase transitions in the North Pacific (Gulf of Alaska) and the North Atlantic (Scotian Shelf) to test for increases in ecosystem variability that might provide early warning of such transitions. In both time series, elevated spatial variability in a measure of community composition (ratio of cod [Gadus sp.] abundance to prey abundance) accompanied transitions between ecosystem states, and variability was negatively correlated with distance from the ecosystem transition point. In the Gulf of Alaska, where the phase transition was apparently the result of a sudden perturbation (climate regime shift), variance increased one year before the transition in mean state occurred. On the Scotian Shelf, where ecosystem reorganization was the result of persistent overfishing, a significant increase in variance occurred three years before the transition in mean state was detected. However, we could not reject the alternate explanation that increased variance may also have simply been inherent to the final stable state in that ecosystem. Increased variance has been previously observed around transition points in models, but rarely in real ecosystems, and our results demonstrate the possible management value in tracking the variance of key parameters in exploited ecosystems.

Temperature-dependent growth as a function of size and age in juvenile Arctic cod (Boreogadus saida)

Temperature-dependent growth as a function of size and age in juvenile Arctic cod (Boreogadus saida) Benjamin J. Laurel*, Louise A. Copeman, Mara Spencer, and Paul Iseri Resource Assessment and Conservation Engineering Division, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Hatfield Marine Science Center, 2030 SE Marine Science Drive, Newport, OR 97365, USA College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Hatfield Marine Science Center, Newport, OR 97365, USA *Corresponding author: tel: þ1 541 737 0197; fax: þ1 541 737 0186; e-mail: ben.laurel@noaa.gov

Impacts of temperature and food availability on the condition of larval Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus)

Original Article Impacts of temperature and food availability on the condition of larval Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus) Brittany L. Koenker, Louise A. Copeman*, and Benjamin J. Laurel College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 2030 SE Marine Science Drive, Newport, OR 97365, USA Cooperative Institute for Marine Resources Studies, Oregon State University, 2030 SE Marine Science Drive, Newport, OR 97365, USA Fisheries Behavioral Ecology Program, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2030 SE Marine Science Drive, Newport, OR 97365, USA *Corresponding author: tel: þ1 541 867 0165; fax: +1 541 867 0136; e-mail: lcopeman@coas.oregonstate.edu.

Effects of temperature and food availability on the survival and growth of larval Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus)

Original Article Effects of temperature and food availability on the survival and growth of larval Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus) Brittany L. Koenker, Benjamin J. Laurel*, Louise A. Copeman, and Lorenzo Ciannelli College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 2030 SE Marine Sciences Drive, Newport, OR 97365, USA Fisheries Behavioral Ecology Program, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2030 SE Marine Sciences Drive, Newport, OR 97365, USA Cooperative Institute for Marine Resources Studies, Oregon State University, 2030 SE Marine Science Drive, Newport, OR 97365, USA *Corresponding author: tel: þ1 541 737 0197; fax: þ1 541 737 0186; e-mail: ben.laurel@noaa.gov.