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Ocean Conditions (ocean + condition)
Selected AbstractsEstablishing climate,growth relationships for yelloweye rockfish (Sebastes ruberrimus) in the northeast Pacific using a dendrochronological approachFISHERIES OCEANOGRAPHY, Issue 5 2008BRYAN A. BLACK Abstract We applied dendrochronology (tree-ring) methods to develop multidecadal growth chronologies from the increment widths of yelloweye rockfish (Sebastes ruberrimus) otoliths. Chronologies were developed for the central California coast, a site just north of Vancouver Island, British Columbia, and at Bowie Seamount west of the Queen Charlotte Islands, British Columbia. At each site, synchronous growth patterns were matched among otoliths via the process of cross-dating, ensuring that the correct calendar year was assigned to all increments. Each time series of growth-increment measurements was divided by the values predicted by a best-fit negative exponential function, thereby removing age-related trends. These detrended time series were averaged into a master chronology for each site, and chronologies were correlated with monthly averages of sea surface temperatures, upwelling, the Northern Oscillation Index, and the Pacific Decadal Oscillation. The two northern growth chronologies positively correlated with indices of warm ocean conditions, especially from the prior summer through the spring of the current year. During the same period, the California chronology positively correlated with indices of cool ocean conditions, indicating an opposing productivity regime for yelloweye rockfish between the California Current and the Gulf of Alaska. Overall, this study demonstrates how tree-ring techniques can be applied to quickly develop annually resolved chronologies and establish climate,growth relationships across various temporal and spatial scales. [source] Tracking environmental processes in the coastal zone for understanding and predicting Oregon coho (Oncorhynchus kisutch) marine survivalFISHERIES OCEANOGRAPHY, Issue 6 2003E.A. Logerwell Abstract To better understand and predict Oregon coho (Oncorhynchus kisutch) marine survival, we developed a conceptual model of processes occurring during four sequential periods: (1) winter climate prior to smolt migration from freshwater to ocean, (2) spring transition from winter downwelling to spring/summer upwelling, (3) the spring upwelling season and (4) winter ocean conditions near the end of the maturing coho's first year at sea. We then parameterized a General Additive Model (GAM) with Oregon Production Index (OPI) coho smolt-to-adult survival estimates from 1970 to 2001 and environmental data representing processes occurring during each period (presmolt winter SST, spring transition date, spring sea level, and post-smolt winter SST). The model explained a high and significant proportion of the variation in coho survival (R2 = 0.75). The model forecast of 2002 adult survival rate ranged from 4 to 8%. Our forecast was higher than predictions based on the return of precocious males (,jacks'), and it won't be known until fall 2002 which forecast is most accurate. An advantage to our environmentally based predictive model is the potential for linkages with predictive climate models, which might allow for forecasts more than 1 year in advance. Relationships between the environmental variables in the GAM and others (such as the North Pacific Index and water column stratification) provided insight into the processes driving production in the Pacific Northwest coastal ocean. Thus, coho may be a bellwether for the coastal environment and models such as ours may apply to populations of other species in this habitat. [source] Retrospective growth analysis of Atlantic salmon Salmo salar and implications for abundance trendsJOURNAL OF FISH BIOLOGY, Issue 10 2010F. Hogan Scale archives of Atlantic salmon Salmo salar from Maine, U.S.A., were examined to determine whether ocean conditions affected the long-term trends in S. salar populations in the southern tier of the species' range in North America. To date, scale analyses of southern tier populations have been limited to hatchery fish; previous studies suggest that post-smolt growth does not influence recruitment, with the exception that winter growth may play a role in stock maturation rate. A time series of scales from the Machias and Narraguagus Rivers spanning the years 1946 to 1999 was analysed. Image analysis was used to measure intercirculi spacing, which provided proxy variables of growth rate. Post-smolt growth increment has increased since the early 1990s, as returns have decreased, suggesting that survival factors act on post-smolts independent of growth. The data support the hypothesis of a decoupling between freshwater size and early marine growth. Growth during the second sea winter was independent of post-smolt growth, suggesting that individuals are capable of significant compensatory growth. Southern tier North American stocks exhibit a similar pattern of independence between growth and survival as observed for northern tier North American stocks. These data support the inference that the recruitment of the North American and European subspecies is governed by fundamentally different mechanisms. [source] Different ocean and climate factors control the marine survival of wild and hatchery Atlantic salmon Salmo salar in the north-east Atlantic OceanJOURNAL OF FISH BIOLOGY, Issue 4 2008A. Peyronnet The influence of climate and ocean conditions on the marine survival of 1SW Irish Atlantic salmon Salmo salar was explored. Generalized additive models (GAM) explained c. 85% of the observed variations in survival and provided an insight into the mechanisms involved. A positive phase of the North Atlantic oscillation (NAO) and increasing sea surface temperatures (SST) were linked to a decrease in S. salar survival. The NAO in the winter before the smolts migration contributed to c. 70% of the deviance in marine survival of wild fish. The abundance of the copepod Calanus finmarchicus in the north-east Atlantic Ocean explained a further 25% of these variations in wild S. salar survival. By contrast, hatchery populations seem to be controlled by additional processes involving coastal SST. The marine recruitment of hatchery S. salar was largely explained (70% of the deviance) by SST close to the Irish coast in the spring before the year of the smolts migration. This study constitutes the first description of the processes controlling marine recruitment for these populations. [source] | ||||||||||