MEPS 391:1-12 (2009)  -  DOI:

Density-dependent, landscape, and climate effects on spawning distribution of walleye pollock Theragra chalcogramma

Nathan M. Bacheler1,4,*, Kevin M. Bailey2, Lorenzo Ciannelli1, Valerio Bartolino1, Kung-Sik Chan3

1College of Oceanic and Atmospheric Sciences, 104 COAS Administration Building, Oregon State University, Corvallis, Oregon 97331, USA
2Alaska Fisheries Science Center, NOAA-Fisheries, Seattle, Washington 98115, USA
3Department of Statistics and Actuarial Science, University of Iowa, Iowa City, Iowa 52242, USA
4Present address: University of Wisconsin Green Bay, Natural and Applied Sciences ES 317, 2420 Nicolet Drive, Green Bay, Wisconsin 54311, USA

ABSTRACT: Little is known about the ways in which density-dependent and density-independent factors influence the spatial dynamics of fish spawning, despite their importance for egg and larval development, survival, and, ultimately, recruitment. Using 2 novel approaches, we related the spatial and temporal patterns of 28 yr of walleye pollock Theragra chalcogramma egg data in Shelikof Strait, Alaska, USA, to density-dependent, landscape, and climate effects. First, we used a spatially explicit variable coefficient generalized additive model (GAM) to show that spawning biomass, water temperature, and ocean transport each had unique spatial effects on walleye pollock egg density. Specifically, increased spawning biomass had a positive effect on egg density at the periphery of the core spawning area, inferring spawning area expansion at high spawning biomass and contraction at low levels. Moreover, increased Shelikof Strait transport caused pollock egg density to increase at the downstream edge of the core spawning area and decrease at the upstream edge. To test the validity of the variable coefficient GAM we also used a geometric method that related the area and center of mass of the pollock spawning aggregation to spawning biomass, transport, and temperature in annual time steps. The area of the spawning aggregation was positively related to spawning biomass, but not to transport or temperature. Variable coefficient GAMs are a useful tool to disentangle the spatially explicit forces of density-dependent and density-independent processes on fish populations.

KEY WORDS: Reproduction · Spatial distribution · Generalized additive models · Gulf of Alaska · Density dependence · Recruitment

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Cite this article as: Bacheler NM, Bailey KM, Ciannelli L, Bartolino V, Chan KS (2009) Density-dependent, landscape, and climate effects on spawning distribution of walleye pollock Theragra chalcogramma. Mar Ecol Prog Ser 391:1-12.

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