Donald J. Noakes

Forecasting monthly riverflow time series

Abstract Mean monthly flows from thirty rivers in North and South America are used to test the short-term forecasting ability of seasonal ARIMA, deseasonalized ARMA, and periodic autoregressive models. The series were split into two sections and models were calibrated to the first portion of the data. The models were then used to generate one-step-ahead forecasts for the second portion of the data. The forecast performance is compared using various measures of accuracy. The results suggest that a periodic autoregressive model, identified by using the partial autocorrelation function, provided the most accurate forecasts

Early Marine Survival of Coho Salmon in the Strait of Georgia Declines to Very Low Levels

Abstract The marine survival of juvenile coho salmon Oncorhynchus kisutch from the time they enter the Strait of Georgia in mid-May to the time of our trawl survey in mid-September declined from an average of about 15% in 1998 to approximately 1% in 2007. Early marine survival rates for juvenile coho salmon have been consistently low (<5%) since 2002, and the rate of decline in early marine survival was greater for hatchery fish than for wild fish. This suggests that hatchery coho salmon are perhaps less able to survive than wild fish in the current marine ecosystem. The steady decline in total marine survival for coho salmon over the past four decades coincided with a warming of the Strait of Georgia, where both sea surface and sea bottom temperatures have increased by approximately 1°C since 1970. Another factor that appears to have contributed to the decline in early marine survival since the late 1990s is an increase in the number of days with an average sustained wind strength greater than 25 km/h. The linkage between wind strength and marine survival requires further study, but wind strength is known to affect the timing and level of primary productivity. The processes that caused the declining marine survival remain to be identified and may include factors associated with disease originating in both freshwater and salt water, metabolic stress, competition, and predation. The data suggest that coho salmon brood year strength is now mostly determined during the first 4 months spent in the Strait of Georgia. If the current low levels of marine survival continue, management initiatives to protect wild coho salmon will be urgently required, and it will be timely to critically evaluate the hatchery programs and policies.

Forecasting annual geophysical time series

Abstract An important test of the adequecy of a stochastic model is its ability to forecast accurately. In hydrology as in many other disciplines, the performance of the model in producing one step ahead forecasts is of particular interest. The ability of several stationary nonseasonal time series models to produce accurate forecasts is examined in this paper. Statistical tests are employed to determine if the forecasts generated by a particular model are better than the forecasts produced by an alternative procedure. The results of the study indicate that for the data sets examined, there is no significant difference in forecast performance between the nonseasonal autoregressive moving average model and a nonparametric regression model.

Synchrony of Marine Fish Catches and Climate and Ocean Regime Shifts in the North Pacific Ocean

Abstract Catches of 19 marine fish species from the eastern and western portions of the North Pacific Ocean during 1970–2004 were examined to determine whether there was synchrony in their responses to the generally accepted climate regime shifts that occurred during that period. Catches for these species represented approximately 55% of the total fish catch in the North Pacific in the 1990s. Five distinct groups were apparent in the data, and each group exhibited a different response to the climate regime shifts of 1977, 1989, and 1998. Some species appeared to have responded only to the regime shift in 1977, others responded only to the shift in 1989, and a few species responded to both. The trends in the time series of catches for these five groups were not random, and shifts in catch generally coincided with regime shifts as identified by the Pacific Decadal Oscillation and other indices of climate change. Although this study examined the relationship of fisheries to trends in climate, there is an obvious linkage to the population dynamics of a particular species. Understanding how climate affects these linkages may help improve our ability to reliably forecast population and fishery trends in the future.

Fitting Dynamic Models To Hydrological Time Series

Abstract Based upon the physical properties of the phenomena being modelled and valid statistical principles, techniques are presented for fitting dynamic models to hydrological time series. Procedures are devised for properly incorporating one or more covariate series into a dynamic model. Furthermore, when there are missing data points in the series, these can be estimated by including a special type of intervention component in the dynamic model. The efficacy of the model building techniques is clearly demonstrated by designing a transfer function-noise model to describe the dynamic relationships connecting a monthly river flow series in Canada to precipitation and temperature covariate series.