Papers by Gregory T Ruggerone
Unprecedented biennial pattern of birth and mortality in an endangered apex predator, the southern resident killer whale, in the eastern North Pacific Ocean
Marine Ecology Progress Series, Jan 3, 2019
ICES Journal of Marine Science, 2019
Chinook salmon (Oncorhynchus tshawytscha, Salmonidae) returns to western Alaska were historically... more Chinook salmon (Oncorhynchus tshawytscha, Salmonidae) returns to western Alaska were historically high and variable but recently reached record lows. Understanding the differential influence of climatic and oceanic conditions on the growth of juvenile Chinook salmon in the north and south eastern Bering Sea is key to understanding mechanisms and factors affecting the production dynamics of Chinook salmon from western Alaska and the Arctic. Summer growth was lower and more variable among years for Chinook salmon in the south than the north eastern Bering Sea. Summer growth decreased with a rise in sea temperatures in the north and south and increased with more sea ice coverage and a later time of ice retreat in the south but not in the north. Capelin (Mallotus villosus), an important prey for juvenile Chinook salmon in the north and during cold years may link increased growth to cooler sea temperatures. Reduced and more variable summer growth of juvenile Chinook salmon from the easte...
Climate attribution time series track the evolution of human influence on North Pacific sea surface temperature
Environmental Research Letters, Nov 29, 2023
Canadian Journal of Fisheries and Aquatic Sciences, Dec 1, 2020
We recently became aware of an error in our calculation of sea surface temperature (SST) anomalie... more We recently became aware of an error in our calculation of sea surface temperature (SST) anomalies over the most recent decade (2005-2015), as well as an error in the equation used to estimate the influence of hatchery pink salmon (Oncorhynchus gorbuscha) production and SST on wild sockeye salmon (Oncorhynchus nerka) productivity. These errors quantitatively, but not qualitatively, affect our estimates of the effect of hatchery pink salmon abundance in the North Pacific on wild sockeye salmon productivity, and the influence of recent SST anomalies on these estimates, but do not otherwise affect any of the findings in the manuscript. The first error was in our calculation of average SST anomalies for each ocean region over the most recent decade. We calculated the
Chignik Salmon Studies: Investigations of Salmon Populations, Hydrology, and Limnology of the Chignik Lakes, Alaska, during 2003-2004
Selective predation by brown bears (Ursus arctos) foraging on spawning sockeye salmon (Oncorhynchus nerka)
Canadian Journal of Zoology, Jun 1, 2000
Investigations of Salmon Populations, Hydrology, Investigations of Salmon Populations, Hydrology, Investigations of Salmon Populations, Hydrology, Investigations of Salmon Populations, Hydrology, and Limnology of the Chignik Lakes, Alaska and Limnology of the Chignik Lakes, Alaska and Limnology o...
Density Dependence and Its Implications for Hatchery Supplementation and Habitat Restoration Programs in the Columbia River Basin
The Effects of Groundwater Pumping on Natural Spring Communities in Owens Valley
California Riparian Systems, 1984
Historical analysis of sockeye salmon growth among populations affected by the Exxon Valdez oil spill and large spawning escapements. Exxon Valdez oil spill restoration project 86048-BAA: Final report
Adult sockeye salmon scales, which provide an index of annual salmon growth in fresh and marine w... more Adult sockeye salmon scales, which provide an index of annual salmon growth in fresh and marine waters during 1965--1997, were measured to examine the effects on growth and adult returns of large spawning escapements influenced by the Exxon Valdez oil spill. Scale growth in freshwater was significantly reduced by the large 1989 spawning escapements in the Kenai River system, Red Lake, and Akalura Lake, but not in Chignik Lake. These data suggest that sockeye growth in freshwater may be less stable following the large escapement. Furthermore, the observations of large escapement adversely affecting growth of adjacent brood years of salmon has important implications for stock-recruitment modeling. In Prince William Sound, Coghill Lake sockeye salmon that migrated through oil-contaminated waters did not exhibit noticeably reduced marine growth, but a model was developed that might explain low adult returns in recent years.
Chignik sockeye studies
NMF
Linkages between climate, growth, competition at sea and production of sockeye salmon populations in Bristol Bay, 1955-2000
Non‐stationary and interactive effects of climate and competition on pink salmon productivity
Global Change Biology, 2021
Pacific salmon (Oncorhynchus spp.) are exposed to increased environmental change and multiple hum... more Pacific salmon (Oncorhynchus spp.) are exposed to increased environmental change and multiple human stressors. To anticipate future impacts of global change and to improve sustainable resource management, it is critical to understand how wild salmon populations respond to stressors associated with human-caused changes such as climate warming and ocean acidification, as well as competition in the ocean, which is intensified by the large-scale production and release of hatchery reared salmon. Pink salmon (O. gorbuscha) are a keystone species in the North Pacific Ocean and support highly valuable commercial fisheries. We investigated the joint effects of changes in ocean conditions and salmon abundances on the productivity of wild pink salmon. Our analysis focused on Prince William Sound in Alaska, because the region accounts for ~50% of the global production of hatchery pink salmon with local hatcheries releasing 600-700 million pink salmon fry annually. Using 60 years of data on wild pink salmon abundances, hatchery releases, and ecological conditions in the ocean, we find evidence that hatchery pink salmon releases negatively affect wild pink salmon productivity, likely through competition between wild and hatchery juveniles in nearshore marine habitats. We find no evidence for effects of ocean acidification on pink salmon productivity. However, a change in the leading mode of North Pacific climate in 1988/89 weakened the temperature-productivity relationship and altered the strength of intraspecific density dependence. Therefore, our results suggest non-stationary (i.e. time-varying) and interactive effects of ocean climate and competition on pink salmon productivity. Our findings further highlight the need for salmon management to consider potential adverse effects of large-scale hatchery production within the context of ocean change.
Chignik salmon studies: Evidence for morphological and behavioral responses by juvenile sockeye salmon to size-biased predation
NMF
Chignik salmon studies: Gastric evacuation rate and daily ration of juvenile coho salmon
NMF
Technical Report
Total abundance of Pacific salmon returning from the North Pacific Ocean increased following the ... more Total abundance of Pacific salmon returning from the North Pacific Ocean increased following the 1977 ocean regime shift, peaking in 2018 when approximately 950 million pink, chum, and sockeye salmon returned from the ocean (Fig. 1). In 2019, salmon abundance remained exceptionally high (~854 million salmon). Together the 2018/2019 period was the highest two-year period of salmon abundance on record since 1925, nearly 20% greater than the previous two-year high in 2009/2010, and more than 3.2 times higher than average abundance during relatively low salmon production years from 1960 to 1975.
Water temperature, water transparency, phytoplankton, and zooplankton samples were collected six ... more Water temperature, water transparency, phytoplankton, and zooplankton samples were collected six times on both Black Lake (three stations, Fig.1) and Chignik Lake (two stations, Fig. 2). Water clarity was estimated with a Secchi disk. Water temperatures were taken with a pocket thermometer on the lake's surface at Black Lake and from water taken at several depths with a van Dorn bottle at Chignik Lake. Additionally, data from automatic, year
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Papers by Gregory T Ruggerone