Table 1. Description of ‘core’ species (i.e., identified in similar clusters by both k-means and hierarchical clustering and in at least three out of four periods) found in each species assemblage defined for the northern and southern regions of the fall bottom trawl survey.

North: Gulf of Maine
Assemblage	Description
1: Alewife, American lobster, Atlantic mackerel, Blueback herring, Little skate, Longfin squid, Scup, Windowpane flounder, Winter flounder, Winter skate, Yellowtail flounder	Mid-trophic level species; mainly demersal; primarily in shallower, coastal inshore waters/protected bays and estuaries; some spawn in estuaries and rivers.
2: American plaice, American shad, Haddock, Red hake, Spiny dogfish, Wolffish	Mix of mid- and higher trophic level species; mix of pelagic and demersal species; found more frequently in coastal inshore waters.
3: Barndoor skate, Monkfish, Silver hake, White hake, Witch flounder	Mainly higher trophic level species; generally demersal, mid to deep waters and occasionally/soft bottom.
4: Blackbelly rosefish, Smooth skate	Mid-trophic level species; bathydemersal, found in very deep waters.
South: Mid-Atlantic Bight/Georges Bank
1: Atlantic croaker, Banded drum, Black sea bass, Bluefish, Bluntnose stingray, Bullnose stingray, Clearnose skate, Cownose ray, Cravelle jack, Northern kingfish, Northern puffer, Northern sea robin, Pig fish, Pin fish, Roughtail stingray, Scup, Sharpnose shark, Smooth dogfish, Southern stingray, Spiny butterfly ray, Spot, Striped burrfish, Striped sea robin, Summer flounder, Tautog, Weakfish, Windowpane flounder	Mix of mid- and higher trophic levels; mainly demersal and reef-associated; strongly tied to coastal inshore waters, bays, estuaries, etc. and warm waters.
2: Alewife, American shad, Atlantic cod, Atlantic herring, Barndoor skate, Butterfish, Fourspot flounder, Longhorn sculpin, Red hake, Sea raven, Sea scallop, Silver hake, Spiny dogfish, Yellowtail flounder	Mix of mid- and higher trophic level species; mainly demersal/benthic; Generally in coastal waters, or have the ability to migrate between deeper and shallower depths.
3: American lobster, American plaice, Monkfish, Rosette skate, Shortfin squid, Thorney skate, White hake	Mid- to high trophic levels; Found mostly around shelf edge over soft bottoms.
4: Blackbelly rosefish, Witch flounder	Mid-trophic level species; bathydemersal, found in very deep waters.