Bottom-Up Ecosystem Trophic Dynamics Determine Fish Production in the Northeast Pacific
by Daniel Ware and Richard Thomson in Science 27 May 2005 vol. 308 pg. 1280-1284

Journal abstract: We addressed the question of bottom-up versus top-down control of marine ecosystem trophic interactions by using annual fish catch data and satellite-derived (SeaWiFS) chlorophyll a measurements for the continental margin of western North America. Findings reveal a marked alongshore variation in retained primary production that is highly correlated with the alongshore variation in resident fish yield. The highest productivity occurs off the coasts of Washington and southern British Columbia. Zooplankton data for coastal British Columbia confirm strong bottom-up trophic linkages between phytoplankton, zooplankton, and resident fish, extending to regional areas as small as 10,000 square kilometers.

My commentary: Obviously humans are interested in the amount of fish caught each year. If you are a fisherman it defines your production, and thus your income (as the total catch goes lower the price per fish increases, but unfortunately the fisherman seldom shares enough of that increase to maintain a constant income). Most of the readers of this essay will be consumers, and a lower price is always better. This study doesn't provide a way to increase fish production. However, it attempts to identify factors that define, and thus predict the total amount of fish that grow in different regions of the ocean.

First I give you my translation of the title, which also states the conclusion of the paper.

Bottom-Up Ecosystem: Bottom of the food chain...
Trophic Dynamics: nutritional (amount of food) variations...
Determine Fish Production: determine the amount of fish caught by fishermen...
in the Northeast Pacific: along the coast, from Southern California to the State of Washington, across British Colombia, and out the Alaskan Aleutian Islands.

The West coast of the US and Canada was divided into 11 zones, starting at Pt. Conception CA and extending up the coast and out to end of the Aleutian Islands. The chlorophyll concentrations, averaged over the years 1998 to 2003 were then plotted against the average fish harvested over those same years, and a strong correlation (0.79) was observed.

It's not so clear (to me) why the fish harvest should be portional to the fish concentration. This assumes that the fishermen harvest a constant proportion of the total fish in an area. Maybe that has been shown?

The West coast of the US and Canada was divided into 11 zones, starting at Pt. Conception CA and extending up the coast and out to end of the Aleutian Islands. The chlorophyll concentrations, averaged over the years 1998 to 2003 were then plotted against the average fish harvested over those same years, and a strong correlation (0.79) was observed.

It's not so clear (to me) why the fish harvest should be portional to the fish concentration. This assumes that the fishermen harvest a constant proportion of the total fish in an area. Maybe that has been shown?

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