Marine Food Webs

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Ecosystems have a biological structure that is largely defined by feeding relationships — who eats whom.  A diagram of these relationships tends to look something like a spider web, thus the terminology food webs. Some ecosystems naturally have more intricate webs than others.  In highly productive fishery ecosystems, the webs tend to be less complex and often are seen more as chains; but regardless of its complexity, a healthy ecosystem is held together by its food webs.  Sadly many stressed ecosystems are mere ghosts of what they one were, and their food webs have become more like cobwebs.

Interruptions in food webs (or food chains) can occur when overfishing changes the balance of species or non-fishing stresses cause some species to decline or disappear.  When this happens, ecosystems become biologically impoverished and less stable.  Pressures on one species can cause others to decline as well, and the fabric of biodiversity changes color or fades.

We are particularly concerned about overfishing on species that form the base of critical food chains — forage fish, such as a variety of herring species upon which cod, tuna, and other valuable fish depend. Herring have long been fished at low levels with small scale gear to satisfy bait needs for lobster and recreational fisheries.  But now they are fished at industrial scales for industrial uses.  They are fished in a hit and run fashion that scoops up large schools and temporarily eliminates them from fished areas.  If other species need them for food, are they just supposed to wait until they rebound?  It doesn’t work that way. To restore healthy populations of the numerous commercial fisheries species that have declined, there must be a constant adequate supply of forage fish to support their increased growth.

NAMA is working for management policies that will rebuild and maintain food webs and recover healthy ecosystems that support healthy populations of commercially valuable fish.