Forecasting animal migration using SARIMAX: an efficient means of reducing silver eel mortality caused by turbines

Hydroelectric power plants are often considered a major cause of mortality for migra- tory fish. The endangered status of European eels Anguilla anguilla forces managers to make efforts to reduce this mortality. Among the mitigation measures used, turbine shutdowns appear to be an efficient method, but they involve a substantial financial loss for hydropower producers. To optimise the use of turbine shutdowns, the present study aimed to provide a precise but simple forecast of the migration peaks of migrant silver eels. We first developed a model to forecast silver eel migration using SARIMAX models and real biological data of silver eel migration from 2 fish- ing sites in Brittany (north-western France). This model combines exogenous covariates and past biological data to forecast future migrations. We then evaluated this model with several years of biological data from the same trap sites, based on the decision criterion that turbines should be shut down when the number of silver eels forecasted by our model represents >10% of the mean annual number of migrants. This model would have served to save 90 and 70% of eels on the Oir and Scorff Rivers, respectively, with only 3.3 to 5.6 turbine shutdowns per year on average. Initial shutdowns would have lasted 1 wk, but this study also showed that the duration of turbine shut- downs could be reduced to 2 d without a significant decrease in efficiency. SARIMAX models reduce the influence of exogenous factors in forecasting outcomes, these being the most variable factors in the current context of climate change. This model appears to be a powerful tool for eco- logical forecasting of endangered species in the context of global warming.

[1]  A. Haro.  Downstream migration of silver-phase anguillid eels , 2003 .

[2]  Alex Haro,et al.  Factors regulating the downstream migration of mature eels (Anguilla spp.) at Aniwhenua Dam, Bay of Plenty, New Zealand , 2001 .

[3]  R. McDowall,et al.  Diadromy in Fishes: Migrations between Freshwater and Marine Environments , 1988 .

[4]  F. Travade,et al.  Tests of two types of bypass for downstream migration of eels at a small hydroelectric power plant , 2005 .

[5]  H. Dingle.  Migration: The Biology of Life on the Move , 1996 .

[6]  B. Hau,et al.  Forecasting migration of cereal aphids (Hemiptera: Aphididae) in autumn and spring , 2009 .

[7]  S. Morris,et al.  Ecology and Behavior of Gecarcoidea natalis, the Christmas Island Red Crab, During the Annual Breeding Migration , 2001, The Biological Bulletin.

[8]  C. Durif,et al.  Behavioural study of downstream migrating eels by radiotelemetry at a small hydroelectric power plant , 2003 .

[9]  I. J. Russon,et al.  Response of downstream migrating adult European eels (Anguilla anguilla) to bar racks under experimental conditions , 2010 .

[10]  A. Haro,et al.  Simulated effects of hydroelectric project regulation on mortality of American eels , 2003 .

[11]  R. Eckmann,et al.  A preliminary telemetry study of the migration of silver European eel (Anguilla anguilla L.) in the River Mosel, Germany , 2003 .

[12]  Fred G. R. Watson,et al.  Predicting Bison Migration out of Yellowstone National Park Using Bayesian Models , 2011, PloS one.

[13]  J. Boubée,et al.  Selective opening of hydroelectric dam spillway gates for downstream migrant eels in New Zealand , 2005 .

[14]  H. V. Winter,et al.  Managing human impact on downstream migrating European eel in the River Meuse , 2009 .

[15]  M. Larinier,et al.  Downstream migration: problems and facilities , 2002 .

[16]  B. Jonsson,et al.  Descent of European silver eels, Anguilla anguilla L., in a Norwegian watercourse , 1985 .

[17]  Christopher Moriarty,et al.  Observations on the Silver Eel Migrations of the Burrishoole River System, Ireland, 1959 to 1988 , 1990 .

[18]  F. Ysnel,et al.  Habitat carrying capacity is reached for the European eel in a small coastal catchment: evidence and implications for managing eel stocks , 2011 .

[19]  Terence C. Mills,et al.  Time series techniques for economists , 1990 .

[20]  M. Blaszkowski,et al.  Long-term effects of hydropower installations and associated river regulation on River Shannon eel populations: mitigation and management , 2008, Hydrobiologia.

[21]  J. Inoue,et al.  Ecological Aspects of the Downstream Migration of Introduced European Eels in the Uono River, Japan , 2004, Environmental Biology of Fishes.

[22]  Thomas C. Cook,et al.  Development and evaluation of a new helical fish-friendly hydroturbine , 2005 .

[23]  Wendy D. Graham,et al.  Comparison of univariate and transfer function models of groundwater fluctuations , 1993 .

[24]  Harry Nyquist.  Certain Topics in Telegraph Transmission Theory , 1928 .

[25]  T. McCarthy,et al.  Hydrometric and Meteorological Factors Affecting the Seaward Migration of Silver eels (Anguilla anguilla, L.) in the Lower River Shannon , 2003, Environmental Biology of Fishes.

[26]  Lixin Zhu,et al.  Comparison of six statistical approaches in the selection of appropriate fish growth models , 2009 .

[27]  A. Burnet.  Migrating eels in a Canterbury river, New Zealand , 1969 .

[28]  R. Lowe.  The Influence of Light and Other Factors on the Seaward Migration of the Silver Eel (Anguilla anguilla L.) , 1952 .

[29]  G. Velde,et al.  Reaction of silver eels to artificial light sources and water currents: An experimental deflection study , 1999 .

[30]  A. Okamura,et al.  Exotic silver eels Anguilla anguilla in Japanese waters: seaward migration and environmental factors , 2002 .

[31]  B. Jonsson,et al.  Environmental Factors Regulating the Seaward Migration of European Silver Eels (Anguilla anguilla) , 1986 .

[32]  Willem Bouten,et al.  An operational model predicting autumn bird migration intensities for flight safety , 2007 .

[33]  A. Crivelli,et al.  Towards a standardized characterization of the potentially migrating silver European eel (Anguilla anguilla, L.) , 2005 .

[34]  A catch rate-environment time series approach to the prediction of catches taken from the Esperance southern rock lobster fishery , 2003 .

[35]  P. R. Todd.  Timing and periodicity of migrating New Zealand freshwater eels (Anguilla spp.) , 1981 .

[36]  J.B. Allen,et al.  A unified approach to short-time Fourier analysis and synthesis , 1977, Proceedings of the IEEE.

[37]  C. Durif,et al.  Predicting downstream migration of silver eels in a large river catchment based on commercial fishery data , 2008 .

[38]  Harold B. Dowse,et al.  The search for hidden periodicities in biological time series revisited , 1989 .

[39]  Sylvie Dufour,et al.  The silvering process of Anguilla anguilla: a new classification from the yellow resident to the silver migrating stage , 2005 .

[40]  Pascal Laffaille,et al.  Migration pattern of silver eel (Anguilla anguilla, L.) in an obstructed river system , 2008 .